s2fieldsofstudy:
Agricultural And Food Sciences
Environmental Science

text:
LUCC impact on water quality change in Xingyun Lake basin

Basin ecological environment and water quality are seriously threatened by development around the lake. The thesis intends to assess basin Land Use and land Cover Changes (here after abbreviated as LUCC) impact on water quality change in Xingyun Lake basin. To achieve this purpose, land use information was interpreted from six periods high-resolution images in the past 30 years, which were classified into seven land use types. The water quality data was obtained by investigation and collection. SPSS software was used to celebrate the correlation coefficient between water quality and LUCC. The results revealed that, in the study area construction land, transportation land and farm land were underwent an increase with the region development; grassland and bare land were gradually reduced, forest land had become fragmented. In addition, the water pollution index gradually increased since 2000, the water deteriorated significantly. Furthermore, there was a strong positive correlation between water pollution indicator and farmland, construction land and transportation land, which indicated that the deterioration of water quality may be the result of the combined effects of agriculture non-point source pollution, domestic and industrial pollution; there was a significant negative correlation between water pollution indicator and grassland and bare land, which indicated that permeable underlying mat had significant interception and absorption effects on pollutants.

Introduction
Lake is an important resource for regional economic and social development [1]. The development within the lake basin will cause land use and land cover changes (LUCC) [2][3][4], and the water quality will affect the ecological environment and people's living quality in the Lake basin. The present research is motivated by the facts that Lake Basin is exploited quickly on the basis of social development projects, leaded to land use tyeps have been changed greatly, and received a serious threat to water quality. Therefore, research and assess the relationship between LUCC and water quality change have the important research significance.
A lot of studies have shown that LUCC had a significant impact on water quality in Lake Basin [5][6], but there were many differences between different regions. Therefore, it is necessary to carry out research on the influence of LUCC on water quality change in Xingyun Lake basin, and it also has regional characteristics.
As one of the important freshwater lakes in central Yunnan Plateau, Xingyun Lake has played a vital role in local economic and tourism development. The lake water and basin ecosystem are under serious threat because of urbanization around the lake. Finding out the relationship between LUCC and water quality change can provide useful information for lake water conservation and land use management in Lake Basin.
This paper is divided into three parts. The first part is an introduction about LUCC, study area status and water quality. Part 2 introduces the research methods of the correlation analysis about LUCC with water quality. In the last part, it analyzes the land use and land cover changes, water quality changes, and discusses the impact of LUCC on water quality.

A Brief Description of Correlation Analysis
Correlation analysis can be used to measure the degree of correlation between two variables. Correlation analysis has been applied to study the impact of LUCC on water quality in different regions. Jiang Chang and Liu Hongyan in the 2018s took correlation analysis method to study the response relationship between Land use change and water quality in Hongfeng Lake basin [6]. Yang Yanan also used this method to study the relationship between Land use pattern and water quality change in Fuxian Lake bain [7].
There are three common correlation coefficients: Spearman, Kendall, and Pearson. In this study, Pearson correlation coefficient was selected to analyse the correlation between water quality and LUCC. Pearson correlation coefficient reflects two variables linear correlation degree.

(1) Land Use and land Cover Changes
The LUCC information of Xingyun Lake basin can be obtained by using RS and GIS technologies. First of all, it needs to get high-resolution remote sensing image data in different times. In this study it obtained 6 frames remote sensing images from 1990 to 2016. Secondly, the land use information of Xingyun Lake basin can be extracted by processing remote sensing images. In the end, LUCC can be obtained through land use information in different periods.
(2) Water Quality In this study, the data of Xingyun Lake water quality in 1990,1995,2000,2005,2010, and 2016 were obtained by using references and downloading from the official website. Chemical oxygen demand (COD), total phosphorus (TP) and total nitrogen (TN) were selected for water quality analysis. Phosphorus (P) and nitrogen (N) are the main factors leading to water eutrophication, and chemical oxygen demand (COD) can reflect the degree of organic pollution in water.

Application of Correlation Analysis to study LUCC impact on Water Quality
It is reasonable to select the correlation analysis in the research of the response relationship between LUCC and water quality, first of all, there is a clear correlation between LUCC and water quality, and the basin land use change has a significant impact on water quality; the second, the response relationship between LUCC and water quality can be explained clearly and accurately with the correlation coefficient; in the end, the degree of linear correlation between LUCC and water quality can be clearly reflected by Pearson correlation coefficient. In this study, the software of SPSS19.0 was used for Pearson correlation analysis to explore the response relationship between LUCC and water quality change in the past 26 years.

Analysis and Discussion on the Basin Land use and land Cover Changes
Based to the regulations of the Third National Land Investigation and Classification, combined with the actual situation of the basin and research purpose, the land use types in Xingyun Lake basin were determined, which included: farmland, forest land, grassland, construction land, transportation land, water and bare land. Land use monitoring results of Xingyun Lake basin from 1990 to 2016 can be seen that (1) all the land use types had the obvious changes; (2) construction land and transportation land showed a gradual upward trend, the areas increased significantly, the construction land area increased from 15.12 km 2 to 31.61 km 2 , and the transportation land area increased from 0.62 km 2 to4.31 km 2 , this situation was consistent with the development of regional economy and the promotion of urbanization; (3) the area of grassland and bare land had been gradually reduced, the grassland area had been reduced by more than half; (4) the water area fluctuated in a small range, the forestland cover area became fragmentation; (5) the area of farmland was gradually decreasing before 2005, and increased significantly between 2005 and 2010. All these data implied that business actives around the basin had intensified, water quality had been threatened.

Analysis and Discussion Based on Water Quality
The water quality of Xingyun Lake was Grade III before 1995. With the development of the regional economy, the water quality fell to Grade IV in 2000, and to Grade V since 2005. The water quality was in a moderate to severe eutrophication state. Before 2000, the changes of various water pollution indexes were not obvious, but after 2000, the water pollution indexes gradually increased. From 2005 to 2010, the water pollution index changed significantly and the water quality deteriorated significantly. The rate of deterioration has slowed since 2010. Xingyun Lake is adjacent to Jiangchuan City, where aquaculture is developed and the surrounding terrain is gentle. Discharge of domestic sewage, unreasonable aquaculture and agricultural non-point source pollution may be the main reasons for the deterioration of water quality. The water pollution indices from1990 to 2016 shows that chemical oxygen demand was gradually increasing, the other two indexes had increased before 2010, and decreased between 2010 and 2016. All these data means water quality had changed significant in the past 26 years.

Analysis and Discussion in Light with
Correlation between LUCC and Water Quality SPSS software was used to calculate the correlation coefficient between LUCC and water quality. This may mean that (1) there was a significant positive correlation between farmland and water pollution index, and the correlation coefficients of COD, TP and TN reaching 0.976, 0.866 and 0.669 respectively. Farmland was significantly positively correlation with COD, and there was also a strong positive correlation with TP. This may indicate that agricultural non-point source pollution represented by farmland has a strong influence on the water pollution of Xingyun Lake. (2) There was a strong positive correlation between construction land and transportation land and water pollution index, which may indicate that industrial and domestic pollution sources have an important contribution to the introduction of nitrogen and phosphorus in lake water. (3) Both grassland and bare land showed a very strong negative correlation with water pollution index, which may indicate that grassland and bare land had a strong interception effect on surface sewage.

Conclusions
Through the above analyses and discussion, three conclusions may be drawn that, firstly, there is a significant changes of land use in the Xingyun lake basin in the past 30 years. With the development of the basin construction land, transportation land and farm land increased obviously, but bare land and grassland were gradually reduced. Secondly, the water pollution index gradually increased since 2000. Finally, there was a significant positive correlation between water pollution indicator and farmland, construction land and transportation land, which indicated that the deterioration of water quality may be the result of the combined effects of agriculture non-point source pollution, domestic and industrial pollution; there was a strong negative correlation between water pollution indicator and grassland and bare land, which may indicate that grassland and bare land had a strong interception effect on surface sewage.
The study of the response relationship between LUCC and water quality proves to be inadequate in that the water quality data is annual average, which is inconsistent with land use information in time. Therefore, it is recommended to increase funding for water quality data collection, and detailed research the response relationship between LUCC and water quality in different months or seasons.


extfieldsofstudy: Chemistry Medicine

provenance: AgriculturalAndFoodSciences,2019-2020-Agricultural And Food Sciences-2020.jsonl.gz.gz

text:
Effects of Storage Conditions on Degradation of Chlorophyll and Emulsifying Capacity of Thylakoid Powders Produced by Different Drying Methods †

Thylakoid membranes isolated from spinach have previously been shown to inhibit lipase/co-lipase and prolong satiety in vivo. There is a need to develop thylakoid products that not only have the desired characteristics and functionality after processing, but also are stable and provide equivalent effect on appetite over the promised shelf life. The aim of the present study was therefore to evaluate how the thylakoid powders’ characteristics and functionality were affected by moisture during storage. Thylakoids produced by drum-drying, spray-drying, and freeze-drying were incubated in controlled atmosphere with different relative humidity (10 RH%, 32 RH%, 48 RH% and 61 RH%) for 8 months. The water content in all powders was increased during storage. The water absorption was moisture-dependent, and the powders were considered hygroscopic. Relative humidity showed a definite influence on the rate of chlorophyll degradation and loss of green color in thylakoid powders after storage which correlated with impaired emulsifying capacity. Spray-dried powder had the overall highest chlorophyll content and emulsifying capacity at all RH-levels investigated. Spray drying was therefore considered the most suitable drying method yielding a powder with best-maintained functionality after storage. The results can be applied towards quality control of high-quality functional foods with appetite suppressing abilities.

Introduction
Dehydrated foods are subjected to physical, chemical and biological deterioration processes during storage such as loss of nutritional substances, color, and aroma compounds [1]. Water activity is a key parameter that determines storage stability of dry products. Lipid oxidation is accelerated in materials with very low water activity [2] and enzymatic reactions and growth of undesirable microorganisms are accelerated at high water activity during storage [3]. For functional foods containing active ingredients, it is important to control these processes during storage to ensure both microbial safety and the proposed function over the products' shelf life.
Thylakoid membranes isolated from spinach can be used as an appetite-reducing ingredient promoting weight loss due to increased satiety between meals [4]. Thylakoids are the photosynthetic membrane in the chloroplast and is responsible for the conversion of solar energy into adenosine triphosphate (ATP) and nicotinamide adenine dinucleotide phosphate (NADPH), used in the production

Isolation of Thylakoid Membranes and Powder Production
Thylakoids were isolated as previously described by Östbring et al. [18]. Frozen spinach leaves (Spinacia oleracea) were homogenized with water in a blender (Robot Coupe Blixer 4 Robot Coupe SA, Bourgogne, France). The slurry was further homogenized at 60 Hz for three minutes (Ytron-Y Jet Stream, Ytron, Bad Endorf, Germany) and filtered through four layers of 20 µm polyester mesh filter. The filtrate was centrifuged at 5000× g, 4 • C, for 30 min (Beckman Coulter Allegra X-15 R Centrifuge, Fullerton, CA, USA). The sediment was collected and re-suspended in water (0.011 kg dry solids/kg water), and was thereafter homogenized (Ystral D-79282, Ballrechten-Dottingen, Germany) until a homogenous slurry was obtained. The pH was adjusted to 7.0 with NaOH.
Thylakoid slurry was either spray-dried or freeze-dried. Spray drying was performed using a lab scale Büchi spray drier (B-290, Büch Labortechnik AG, Flawil, Switzerland). Drying conditions during spray drying were inlet air temperature was 120 • C, outlet temperature 72-75 • C and feed flow rate 0.6 L/h. Freeze drying was carried out using a laboratory freeze dryer (Hetosicc freeze dryer CD 12, Birkerod, Denmark). The sample were frozen in −18 • C for 24 h prior to drying. The plate temperature was 20 • C, the condenser −50 • C and the pressure in the freeze dryer was 0.02 mbar. Residence time in the freeze-dryer was seven days. The freeze-dried powder was grinded in an electrical coffee grinder (OBH Nordica) to reduce the particle size. The resulting powders were stored dark and in sealed containers in −18 • C until storage incubated in controlled atmosphere. Spray-dried powders are hereafter referred to as SD w and freeze-dried powders as FD w .

Commercial Thylakoid Samples
Two types of commercial thylakoid samples were received from Green Leaf Medicals and the isolation process was essentially as described by Emek et al. 2009 [6]. Hot air-dried spinach leaves (Spinacia oleracea) were homogenized with water (1:1 w/w) followed by filtration. The filtrate was diluted with water (1:9 w/w) and the pH was adjusted to the thylakoid membranes isoelectric point 4.7. The filtrate was incubated at 4 • C for four hours. The sediment was collected and once again diluted with water (1:9 w/w), pH was adjusted to 4.7 and the dispersion was incubated as described above. The sediment was collected, and pH was adjusted to 7.0 with NaOH. Thylakoids were thereafter drum dried under industrial conditions. Typical drum drying conditions have a drum surface temperature of 105 • C with drying completed within 30 s. One of the received samples was produced with maltodextrin (1:3 w/w dry base) and are hereafter referred to as drum-dried thylakoids produced by the pH method with addition of maltodextrin (DD pH+M ). The other sample was produced under similar conditions but without the addition of maltodextrin and are hereafter referred to as drum-dried thylakoids produced by the pH method (DD pH ).

Incubation in Controlled Atmosphere
Saturated salt solutions of LiCl, MgCl 2 , Mg(NO 3 ) 2 and KI were prepared and put in desiccators to achieve a relative humidity of 10 RH%, 32 RH%, 48 RH% and 61 RH% respectively. The desiccators were left for at least one week to reach equilibrium. All powders (DD pH , DD pH+M , SD w , FD w ) were freeze-dried prior to incubation in the desiccators to assure a low initial water activity (see above for details). After freeze-drying, three grams of each powder were put in open Petri dishes in the different desiccators, four dishes in each desiccator in total. The powders were incubated dark in 20.0 • C for a total of eight months.

Evaluation of Powder Characteristics
A series of analysis was performed to evaluate the effect of thylakoid powder during storage in controlled atmosphere. Analysis was performed both prior to incubation and after incubation for eight months in desiccators with specific humidity.

Water Activity
Water activity was analyzed using a water activity meter (AquaLab Ver 3TE, Decagon Devises, Pullman, WA, USA). The equipment was calibrated with standard salt solutions (13.41 (0.25 a w ) or 8.57 (0.50 a w ) mol/kg LiCl). Analysis was performed in triplicates.

Dry Matter Analysis
Dry matter content was determined according to the official method of analysis (AOAC) by drying in a convective oven at 102 • C for 24 h or longer until a constant weight was obtained. Analysis was performed in duplicates.

Color Analysis
The color attributes (Hunter L, a and b values) of each powder were measured with a portable spectrophotometer (CM-700d, Konica Minolta, Osaka, Japan). Each sample was randomly measured at three locations and the average was reported.

Chlorophyll Content
Chlorophyll content in the thylakoid powders were determined by photo spectroscopy according to Porra et al. [22]. Powders (0.04-0.08 g) were homogenized with 2 mL deionized water in a Potter-Elvehjelm homogenizer until a homogenous slurry was obtained. 10-100 µL thylakoid slurry was added to 1 mL ice-cold acetone (80 vol%) depending on color intensity of the powder. The samples were vortexed and incubated dark and on ice for 20 min followed by centrifugation (Eppendorf Mini Spin, Eppendorf AG, Hamburg, Germany) at 13,400× g for 4 min, at 25 • C before spectrophotometric analysis was carried out. Spectra were obtained over the wavelength range 200-800 nm against a blank of acetone (80 vol%). Absorbance at λ = 646.6 nm and λ = 663.6 nm was used to quantify the chlorophyll content. Chlorophyll a and total chlorophyll concentration were analyzed in triplicate and determined according to Porra

Evaluation of Powder Functionality
Thylakoids are known to adsorb to the oil-water interface due to exposure of hydrophobic, hydrophilic and charged side groups. In previous studies close correlations were found between thylakoids' interfacial properties, lipase-inhibiting capacity and chlorophyll content (R 2 = 0.80 for interfacial properties vs. lipase-inhibiting capacity, R 2 = 0.81 for interfacial properties vs. chlorophyll content, R 2 = 0.95 for chlorophyll content vs. lipase/inhibiting capacity) [23,24]. Due to the close correlation, the thylakoids ability to stabilize the oil-water interface of oil-in-water emulsions was used as a functional endpoint in the present study. To examine whether exposure to varying humidity affected the thylakoid powders interfacial properties, the thylakoids' ability to stabilize the oil-water interface were analyzed both prior to incubation in controlled atmosphere and after 8 months storage.

Preparation of Thylakoid-Stabilized Emulsions
Emulsions were prepared in glass test tubes by adding 64 mg thylakoid powders (dry basis) dried by either drum drying, spray drying or freeze drying to 2 mL continuous phase (5 mM phosphate buffer with 0.2 M NaCl, pH 7.0) and 1 mL lipid phase (Miglyol 812, Asaaol AG, Germany). The mixture was homogenized by a high shear mixer with a 6 mm dispersing head (Ystral D-79282, Ballrechten-Dottingen, Germany) operated at 22,000 rpm for 60 s. The emulsions were prepared in triplicates and were incubated dark in 4 • C for 60 min prior to particle size distribution analysis.

Particle Size Measurements of Thylakoid-Stabilized Emulsions
Particle size distribution of the emulsions stabilized by thylakoid powder were analyzed with a laser diffraction particle analyzer (Malvern Mastersizer 2000 Ver 5.60, Malvern, Worcestershire, UK). The dispersing unit (Hydro 2000S) was filled with 100 mL MilliQ water and the pump was operated at 2000 rpm. The glass test tubes were turned upside down three times before a small volume was added to the flow system and pumped through the optical chamber for measurements. Obscuration was between 10% and 20%. The RI of the sample was set to 1.45 (miglyol) and the RI of the continuous phase was set to 1.33 (water). The emulsifying capacity (EC) of the thylakoid membranes i.e., the maximum surface that can be created and stabilized by a unit emulsifier (m 2 /mg) was calculated as where φ is the disperse phase volume fraction, C a is the initial concentration of emulsifying agent (assumed that all emulsifier is adsorbed at the oil-water interface) and d 32 is the volume-surface mean droplet diameter.

Statistical Analysis
All statistical analyses were performed using SPSS software version 22 (IBM). For parametric datasets (L-, a-, and b values, total chlorophyll and emulsifying capacity), the univariate general linear model with Tukey's test was performed to investigate significant differences. For non-parametric datasets (dry matter, water content and water activity), a Kruskal-Wallis test with Bonferroni-adjusted pairwise comparison was performed. Differences were considered significant if p < 0.05

Results and Discussion
The present work investigates the effect of storage conditions in varying relative humidity on appetite reducing thylakoid powders produced and dried in different ways. Powder characteristics and functionality, i.e., dry matter, water activity, chlorophyll content, color and emulsifying capacity were evaluated after 8 months storage.

Water Content and Water Activity
The water content for the majority of the powders (DD pH+M , SD w and FD w ) increased during 8 months of storage in controlled atmospheres with different relative humidity. The commercial sample DD pH had a higher water content prior incubation compared with the other powders and was instead subjected to desorption when incubated in 11 RH%, 32 RH% and 48 RH% but after incubation in the highest relative humidity (61 RH%), absorption was taking place in these samples as well. Increase in water content during storage can either depend on absorption or chemical or biological reactions in the material. In the present study, the weight of the samples increased over time indicating that water absorption was the dominating reaction.
During the storage period of 8 months, equilibrium was reached for the drum-dried powder with addition of maltodextrin (1:3 w/w dry basis) but not for the other powders. Drum-dried thylakoid powders (DD pH ) displayed a sigmoidal shape with the highest increase in water content between 32 RH% and 48 RH%. The water content varied from 0.0494 kg water/kg solids at 10 RH% to 0.1017 kg water/kg solids at 61 RH% and the change was significant. DD pH+M had lower water content compared to the other powders with 0.0322 kg water/kg solids at RH 10% to 0.1025 kg water kg water/kg solids at 61 RH% although not significantly compared with other samples incubated under the same conditions, and the sorption isotherm followed the characteristic behavior of maltodextrin. Spray-dried and freeze-dried powders had higher water content at higher relative humidity levels, compared to the drum-dried powders, although not significant. Water content varied from 0.0528 kg water/kg solids (10 RH%) to 0.1173 kg water/kg solids (61 RH%) for spray-dried powders and 0.0548 kg water/kg solids (10 RH%) to 0.1291 kg water/kg solids (61 RH%) for freeze-dried powders.
All powders, independent on drying method displayed higher water activity when exposed for higher relative humidity ( Figure 1). Spray-dried and freeze-dried powders appeared to display water activities in a narrower range compared to drum-dried powders. There was a trend towards higher water activities for spray-dried and freeze-dried powders (a w = 0.30 and 0.29) compared to drum-dried powders (a w = 0.24 for both) after exposure for the lowest relative humidity (RH 10%) investigated, but the difference was not significant. At the highest relative humidity (RH 61%) the trend was reversed with spray-dried and freeze-dried powders displaying lower water activities (a w = 0.38 and 0.46) compared to drum-dried powders (a w = 0.51 for DD pH and 0.58 for DD pH+M ), although not significant. The differences may be explained by different morphology and porosity of the powders, although the mentioned parameters were outside the scope of the present study. All powders, independent on drying method displayed higher water activity when exposed for higher relative humidity ( Figure 1). Spray-dried and freeze-dried powders appeared to display water activities in a narrower range compared to drum-dried powders. There was a trend towards higher water activities for spray-dried and freeze-dried powders (aw = 0.30 and 0.29) compared to drumdried powders (aw = 0.24 for both) after exposure for the lowest relative humidity (RH 10%) investigated, but the difference was not significant. At the highest relative humidity (RH 61%) the trend was reversed with spray-dried and freeze-dried powders displaying lower water activities (aw = 0.38 and 0.46) compared to drum-dried powders (aw = 0.51 for DDpH and 0.58 for DDpH+M), although not significant. The differences may be explained by different morphology and porosity of the powders, although the mentioned parameters were outside the scope of the present study.

Color Loss During Storage Are Related to Specific Relative Humidity
Storage for 8 months affected the lightness and green color of the powders (Table 1, Figure 2). The L-value was significantly decreased (indicating darker color) for DDpH and SDw when the lightness prior incubation was compared with lightness after incubation in 48 RH% (SDw) and 61 RH% (both DDpH and SDw). When the lightness between powders in similar relative humidity was compared, FDw had in general lower L-values compared to the other powders in all relative humidity's investigated and additionally SDw was significantly darker compared to DDpH and DDpH+M in the lowest relative humidity's. Water content for thylakoid powders produced in different ways as a function of water activity in the powders after 8 months of storage in controlled atmosphere with different relative humidity. DD pH = drum-dried powder produced by the pH method, DD pH+M = drum-dried powder produced by the pH method with addition of maltodextrin, SD w = spray-dried powder produced by the water method, FD w = freeze-dried powder produced by the water method.

Color Loss During Storage Are Related to Specific Relative Humidity
Storage for 8 months affected the lightness and green color of the powders (Table 1, Figure 2). The L-value was significantly decreased (indicating darker color) for DD pH and SD w when the lightness prior incubation was compared with lightness after incubation in 48 RH% (SD w ) and 61 RH% (both DD pH and SD w ). When the lightness between powders in similar relative humidity was compared, FD w had in general lower L-values compared to the other powders in all relative humidity's investigated and additionally SD w was significantly darker compared to DD pH and DD pH+M in the lowest relative humidity's. L, a and b are Hunters color coordinates. Labels: DD pH = drum-dried powder produced by the pH method. DD pH+M = drum-dried powder produced by the pH method with addition of maltodextrin. SD w = spray-dried powder produced by the water method. FD w = freeze-dried powder produced by the water method. Different uppercase letters indicate significant difference between incubation conditions within each powder formulation, p < 0.05. Different lowercase letters indicate significant difference within each incubation condition between powder formulations, p < 0.05. Foods 2020, 9, x FOR PEER REVIEW 8 of 16 Figure 2. Photography of thylakoid powders produced in different ways after 8 months storage in controlled atmosphere with different relative humidity. DDpH = drum-dried powder produced by the pH method, DDpH+M = drum-dried powder produced by the pH method with addition of maltodextrin, SDw = spray-dried powder produced by the water method, FDw = freeze-dried powder produced by the water method.

Chlorophyllase Catalyze Degradation of Chlorophyll
In dehydrated foods, deteriorative reactions depend on the state of water present [21]. At very low water activities (aw = 0-0.2), a monolayer of water is tightly bound to ionic groups of the food material such as anion and carboxyl groups [25]. At slightly higher water activities (aw = 0.2-0.4) the water exists as multimolecular layers, the fraction being less firmly bound compared to the DD pH+M DD pH FD w SD w 61 RH% 48 RH% 32 RH% 10 RH% Figure 2. Photography of thylakoid powders produced in different ways after 8 months storage in controlled atmosphere with different relative humidity. DD pH = drum-dried powder produced by the pH method, DD pH+M = drum-dried powder produced by the pH method with addition of maltodextrin, SD w = spray-dried powder produced by the water method, FD w = freeze-dried powder produced by the water method.
All powders displayed an increased a-value (indicating loss of green color) after incubation and the changes were dependent on the specific relative humidity, with a greater loss of green color when exposed for higher relative humidity. For DD pH and DD pH+M the loss of green colour was only significant for samples incubated in 61 RH% whereas for SD w both incubation in 48 RH% and 61 RH% resulted in a significant loss of green color. For FD w , incubation in all relative humidity's resulted in significant differences where incubation in higher relative humidity's was associated to greater loss. The spray-dried and freeze-dried powders had initial lower a-values (indicating more intense green color) compared to drum-dried powders and were consequently displaying a larger reduction in green color at all relative humidity levels investigated. The effect was more pronounced for powders exposed to higher relative humidity. The b-value was changed after incubation and the powders significantly lost yellow color after incubation in 61 RH% except for DD pH+M where there was no difference.

Chlorophyllase Catalyze Degradation of Chlorophyll
In dehydrated foods, deteriorative reactions depend on the state of water present [21]. At very low water activities (a w = 0-0.2), a monolayer of water is tightly bound to ionic groups of the food material such as anion and carboxyl groups [25]. At slightly higher water activities (a w = 0.2-0.4) the water exists as multimolecular layers, the fraction being less firmly bound compared to the monolayer at very low water activities. At high water activity (a w = 0.4 and above), water exists as free molecules resulting in accelerated undesirable enzyme reactions and microbial growth [3].
Chlorophyllase, the enzyme catalyzing the conversion of chlorophyll to its degradation product chlorophillide has been reported to be accelerated by high water activity [21]. Chlorophyllase activity has also been reported to be temperature dependent with a maximum at 23 • C [26]. Many efforts have been invested in controlling chlorophyllase to prevent discoloration and prolong the shelf life of green vegetables. Chlorophyllase is known to be accelerated by mild heat treatment (50 • C), however the activity has been reported to be seriously reduced upon heating above 80 • C [27]. Ihl et al. reported that blanching for a few minutes in boiling water inactivated the chlorophyllase in artichokes [20].
Relative humidity showed a definite influence on the rate of chlorophyll degradation in thylakoid powders stored for 8 months (Figure 3). Chlorophyll content was dramatically degraded in spray-dried and freeze-dried powders after storage with a greater chlorophyll loss at exposure for higher relative humidity. For spray-dried powders, there were no significant change at low relative humidity (10 RH% and 32 RH%), but at higher relative humidity, the chlorophyll content significantly decreased from 68 mg/g prior incubation to 42 mg/g (−38%) and 32 mg/g (−52%) after incubation in 49 RH% and 61 RH%. Freeze-dried powders displayed the overall largest chlorophyll degradation of the powders investigated. The chlorophyll content decreased from 76 mg/g prior incubation to 58 mg/g and 54 mg/g (11 RH% and 33 RH%, no significant difference between the two) and when powders was incubated in 49 RH% and 61 RH%, the concentrations was even lower: 39 mg/g (−48%) and 27 mg/g (−63%) after incubation in 49 RH% and 61 RH%.
The drum-dried powder did not have a significant amount of chlorophyll prior to incubation, hence no significant chlorophyll degradation.
The spray-dried and freeze-dried powders displayed absorption spectra with a shift of maximum in the blue spectrum to shorter wavelengths after storage. The height of the peak corresponding to chlorophyll a (at 436 nm [19]) was reduced with increased relative humidity, and the peak corresponding to the degradation products pheophorbide a and pheophytin a (both displaying absorption maximum at 409-415 nm [19]) was present independent of relative humidity during storage (Figure 4). The height of the peak corresponding to chlorophyll a was decreased to some extent for the drum dried powders (Figure 4). These findings are in accordance with Dutton et al., where chlorophyll degradation in dehydrated spinach was reported to be dependent on relative humidity during storage [28]. Dutton et al. reported a shifted absorbance maxima towards the blue region and decreased maximum at 665 nm after storage in high relative humidity [28]. The changes were attributed to chlorophyll degradation. Chlorophyll can be degraded via two different routes: chemical degradation or enzymatic degradation. Chlorophyll is degraded to pheophytin by heat or acid by replacement of the central Mg 2+ ion by two H + , which induce a color shift from bright green to olive brown [29]. The mechanism is not clear but magnesium dechelatase are proposed to be involved in the ion replacement [30]. The enzymatic degradation route involves chlorophyllase catalyzed removal of the chlorophyll's phytol chain producing chlorophillide with a bright green color displaying the same absorption maximum as chlorophyll (436 nm). Chlorophillide is rapidly degraded by heat or acid to the olive brown pheophorbide by replacement of the central Mg 2+ ion by two H + [31]. The two degradation products pheophytin and pheophorbide cannot be separated by photo spectrometric analysis [32]. Degradation products (pheophorbide and/or pheophytin) were detected in the present study (Figure 4). Heat or acid is required for formation of these products. Dutton et al. reported the pH in dehydrated spinach to be lowered during storage in high humidity [28]. Since no heat was applied in the system in the present study, the degradation is suggested to be driven by protons probably provided from dissociated molecules like carotenoids in the system.  The spray-dried and freeze-dried powders displayed absorption spectra with a shift of maximum in the blue spectrum to shorter wavelengths after storage. The height of the peak corresponding to chlorophyll a (at 436 nm [19]) was reduced with increased relative humidity, and the peak corresponding to the degradation products pheophorbide a and pheophytin a (both displaying absorption maximum at 409-415 nm [19]) was present independent of relative humidity during storage (Figure 4). The height of the peak corresponding to chlorophyll a was decreased to some extent for the drum dried powders (Figure 4). These findings are in accordance with Dutton et al., where chlorophyll degradation in dehydrated spinach was reported to be dependent on relative humidity during storage [28]. Dutton et al. reported a shifted absorbance maxima towards the blue region and decreased maximum at 665 nm after storage in high relative humidity [28]. The changes were attributed to chlorophyll degradation. Chlorophyll can be degraded via two different routes: chemical degradation or enzymatic degradation. Chlorophyll is degraded to pheophytin by heat or acid by replacement of the central Mg 2+ ion by two H + , which induce a color shift from bright green to olive brown [29]. The mechanism is not clear but magnesium dechelatase are proposed to be involved in the ion replacement [30]. The enzymatic degradation route involves chlorophyllase catalyzed removal of the chlorophyll's phytol chain producing chlorophillide with a bright green color displaying the same absorption maximum as chlorophyll (436 nm). Chlorophillide is rapidly degraded by heat or acid to the olive brown pheophorbide by replacement of the central Mg 2+ ion by two H + [31]. The two degradation products pheophytin and pheophorbide cannot be separated by photo spectrometric analysis [32]. Degradation products (pheophorbide and/or pheophytin) were  . Total chlorophyll content of thylakoid powders produced in different ways after 8 months storage in controlled atmosphere with different relative humidity. DD pH = drum-dried powder produced by the pH method, DD pH+M = drum-dried powder produced by the pH method with addition of maltodextrin, SD w = spray-dried powder produced by the water method, FD w = freeze-dried powder produced by the water method. Different letters indicate significant difference (p < 0.05).

Heat Treatment During Drying Affects Chlorophyll Loss During Storage
The thylakoid powders investigated in the present study had been subjected to different heat treatments during drying prior to storage. Drum-dried powders was dried at 105 • C for several seconds. Spray-dried powders was exposed for air at 72 • C for a few seconds in the drying chamber, whereas the freeze-dried powders were not exposed to any heat treatment at all. The chlorophyll degradation rate was different among the investigated powders during storage, with powders dried at high temperatures displayed limited absolute chlorophyll degradation. We suggest that the drum-dried powders did not had substantial amount of chlorophyll left after drying and the chlorophyllase were close to inactivated by the substantial heat treatment during drum-drying. Drum-dried powders were therefore omitted to one single degradation route of chlorophyll, the chemical degradation, which explains the limited chlorophyll degradation rate. . Absorption spectra for thylakoid powders produced in different ways after 8 months storage in controlled atmosphere with different relative humidity. Non-treated thylakoids in aqueous solution is provided for comparison. Due to limitations in the method, the absolute values cannot be compared. DDpH = drum-dried powder produced by the pH method, DDpH+M = drum-dried powder produced by the pH method with addition of maltodextrin, SDw = spray-dried powder produced by the water method, FDw = freeze-dried powder produced by the water method.

Heat Treatment During Drying Affects Chlorophyll Loss During Storage
The thylakoid powders investigated in the present study had been subjected to different heat treatments during drying prior to storage. Drum-dried powders was dried at 105 °C for several seconds. Spray-dried powders was exposed for air at 72 °C for a few seconds in the drying chamber, whereas the freeze-dried powders were not exposed to any heat treatment at all. The chlorophyll degradation rate was different among the investigated powders during storage, with powders dried at high temperatures displayed limited absolute chlorophyll degradation. We suggest that the drum- . Absorption spectra for thylakoid powders produced in different ways after 8 months storage in controlled atmosphere with different relative humidity. Non-treated thylakoids in aqueous solution is provided for comparison. Due to limitations in the method, the absolute values cannot be compared. DD pH = drum-dried powder produced by the pH method, DD pH+M = drum-dried powder produced by the pH method with addition of maltodextrin, SD w = spray-dried powder produced by the water method, FD w = freeze-dried powder produced by the water method.
Freeze-dried powders were not exposed to heat during drying and displayed the highest chlorophyll degradation of the powders investigated. Chlorophyllase was intact and powder storage in 20 • C was a temperature close to optimal for the enzymatic activity [26], allowing a significant enzymatic reduction of chlorophyll. The degradation was more pronounced for higher water activities which is in accordance with Lajollo et al. [21]. Spray-dried powders were exposed for moderate heat during drying and displayed limited chlorophyll degradation at low relative humidity. At higher relative humidity the degradation rate was higher. We suggest that the moderate thermal treatment during spray-drying (72 • C for a few seconds) inactivated chlorophyllase to some extent. At low water activity, the enzymatic activity was inhibited but at higher water activities, the remaining chlorophyllase was accelerated by the free available water, causing significant chlorophyll degradation. Weemaes et al. reported that heat treatment at 50 • C accelerated the enzymatic activity in broccoli juice [27] but in the present study we found that dry thermal treatment at 72 • C for a few seconds instead resulted in limited chlorophyll degradation at low water activities and that the degradation was moisture dependent. We therefore suggest that the heat treatment during spray drying was harsh enough to partially inactivate chlorophyllase, rather than accelerate the enzymatic activity. Spray-dried powder displayed, at each relative humidity level investigated, the highest chlorophyll content of all powders. This may be due to the partial inactivation of chlorophyllase. We suggest that the chlorophyll in the spray-dried and freeze-dried powder was degraded via two routes: enzymatic catalyzed degradation known to be accelerated at higher relative humidity, and chemical acid-induced degradation. This can be the reason why spray-dried and freeze-dried powders were subjected to larger absolute chlorophyll degradation compared to drum-dried powders, although the chlorophyll content in spray-dried and freeze-dried powders was higher than the drum-dried powders at all relative humidity levels investigated.

Effect of Storage on Thylakoids' Interfacial Properties
Thylakoids' emulsifying capacity of the all thylakoid powders was generally reduced after 8 months storage ( Figure 5), and the loss was positively correlated to relative humidity. The effect was more pronounced for the spray-dried and freeze-dried powders compared to the drum-dried powders. Freeze-dried powders showed the most dramatic reduction in emulsifying capacity. Prior to incubation, the emulsifying capacity was 0.0116 m 2 /mg for freeze-dried powder and after 8 months storage in 61 RH% the emulsifying capacity was reduced to 0.00294 m 2 /mg, which corresponds to −75% loss.
Foods 2020, 9, x FOR PEER REVIEW 12 of 16 Figure 5. Emulsifying capacity of thylakoid powders produced in different ways after 8 months storage in controlled atmosphere with different relative humidity. DDpH = drum-dried powder produced by the pH method, DDpH+M = drum-dried powder produced by the pH method with addition of maltodextrin, SDw = spray-dried powder produced by the water method, FDw = freezedried powder produced by the water method. Different letters indicate significant difference (p < 0.05).
The particle size of lipid droplets stabilized by thylakoid powder stored at 8 months in 61 RH% was increased compared to lipid droplets stabilized by thylakoid powders prior incubation ( Figure  6). This indicates reduced emulsifying capacity of the membranes during storage in high relative humidity. The increase in emulsion droplet size was larger for spray-dried and freeze-dried powders compared with drum-dried powders. All powders except the spray-dried powder displayed one dominating peak. The spray-dried powder displayed two peaks, one corresponding to the same particle size as stabilized by thylakoids prior to incubation, and an additional peak with larger particle size. Emulsifying capacity of the thylakoids have previously been reported to be closely linked to chlorophyll content and lipase/co-lipase inhibiting effect [18]. Prolongation of lipolysis is in Emulsifying capacity of thylakoid powders produced in different ways after 8 months storage in controlled atmosphere with different relative humidity. DD pH = drum-dried powder produced by the pH method, DD pH+M = drum-dried powder produced by the pH method with addition of maltodextrin, SD w = spray-dried powder produced by the water method, FD w = freeze-dried powder produced by the water method. Different letters indicate significant difference (p < 0.05).
The particle size of lipid droplets stabilized by thylakoid powder stored at 8 months in 61 RH% was increased compared to lipid droplets stabilized by thylakoid powders prior incubation ( Figure 6). This indicates reduced emulsifying capacity of the membranes during storage in high relative humidity. The increase in emulsion droplet size was larger for spray-dried and freeze-dried powders compared with drum-dried powders. All powders except the spray-dried powder displayed one dominating peak. The spray-dried powder displayed two peaks, one corresponding to the same particle size as stabilized by thylakoids prior to incubation, and an additional peak with larger particle size. Emulsifying capacity of the thylakoids have previously been reported to be closely linked to chlorophyll content and lipase/co-lipase inhibiting effect [18]. Prolongation of lipolysis is in turn correlated to prolonged satiety in animal and human models demonstrated by   [13,15]. Emulsifying capacity was therefore used as marker for the thylakoids' functionality in the present study.
Foods 2020, 9, x FOR PEER REVIEW 13 of 16 Figure 6. Particle size distribution of oil-in-water emulsions stabilized by thylakoid powder produced in different ways prior incubation and after 8 months storage in 61 RH%. DDpH = drum-dried powder produced by the pH method, DDpH+M = drum-dried powder produced by the pH method with addition of maltodextrin, SDw = spray-dried powder produced by the water method, FDw = freezedried powder produced by the water method.

Chlorophyll Is Important for the Thylakoids' Functional Properties
Chlorophyll has been suggested to play an important role in facilitating steric stabilization of hydrophobic alpha helices within the light harvesting complexes in the thylakoid membrane [33]. In a series of previous experiments, alpha helices have been identified as the surface-active parts [9], enable thylakoids to associate to the oil-water interface of lipid droplets, hindering lipase/co-lipase from reaching their substrate. When chlorophyll is degraded either by replacement of Mg 2+ with 2 H + or removal of the phytol chain, the polarity of the molecule is altered [29]. This could lead to reduced stability inside the thylakoid membrane, promoting association between hydrophobic domains [34]. Heat treatment of thylakoids induced chlorophyll degradation and reduced the lipase/co-lipase inhibiting capacity as well as the thylakoids' emulsifying capacity as demonstrated in previous studies [18,23,24]. Aggregation of heat-treated thylakoids was observed in the previous studies, but it could not be concluded if the reason to the aggregation was chlorophyll degradation causing structural reorganization inside the membrane, or heat-induced aggregation of the thylakoid membranes. Degradation of chlorophyll may cause aggregation within the alpha helices known to play a decisive role in inhibition of lipase/co-lipase. Thylakoid membranes are also known to form inverted vesicles over 55 °C [35], with hydrophobic parts turned outside which facilitate aggregation due to minimization of free energy. The heat-induced aggregation can reduce the available thylakoid surface thereby reducing lipase/co-lipase inhibition.
In the present study, chlorophyll was degraded not by heat, but by enzymatic degradation with Prior% incuba+on% A-er% storage% DD pH DD pH+M SD w FD w Figure 6. Particle size distribution of oil-in-water emulsions stabilized by thylakoid powder produced in different ways prior incubation and after 8 months storage in 61 RH%. DD pH = drum-dried powder produced by the pH method, DD pH+M = drum-dried powder produced by the pH method with addition of maltodextrin, SD w = spray-dried powder produced by the water method, FD w = freeze-dried powder produced by the water method.

Chlorophyll Is Important for the Thylakoids' Functional Properties
Chlorophyll has been suggested to play an important role in facilitating steric stabilization of hydrophobic alpha helices within the light harvesting complexes in the thylakoid membrane [33]. In a series of previous experiments, alpha helices have been identified as the surface-active parts [9], enable thylakoids to associate to the oil-water interface of lipid droplets, hindering lipase/co-lipase from reaching their substrate. When chlorophyll is degraded either by replacement of Mg 2+ with 2 H + or removal of the phytol chain, the polarity of the molecule is altered [29]. This could lead to reduced stability inside the thylakoid membrane, promoting association between hydrophobic domains [34]. Heat treatment of thylakoids induced chlorophyll degradation and reduced the lipase/co-lipase inhibiting capacity as well as the thylakoids' emulsifying capacity as demonstrated in previous studies [18,23,24]. Aggregation of heat-treated thylakoids was observed in the previous studies, but it could not be concluded if the reason to the aggregation was chlorophyll degradation causing structural reorganization inside the membrane, or heat-induced aggregation of the thylakoid membranes. Degradation of chlorophyll may cause aggregation within the alpha helices known to play a decisive role in inhibition of lipase/co-lipase. Thylakoid membranes are also known to form inverted vesicles over 55 • C [35], with hydrophobic parts turned outside which facilitate aggregation due to minimization of free energy. The heat-induced aggregation can reduce the available thylakoid surface thereby reducing lipase/co-lipase inhibition.
In the present study, chlorophyll was degraded not by heat, but by enzymatic degradation with decreased emulsifying capacity as consequence. Thus, the present study indicates that chlorophyll is important for the internal structure of the thylakoid membranes. When chlorophyll was degraded, either by heat or enzymatic degradation, association between the hydrophobic alpha helices was suggested to be promoted, causing reduced surface activity of the thylakoid membranes, thus reduced emulsifying capacity.
Drum-dried thylakoids with low amount remaining chlorophyll were still able to stabilize the oil-water interface to a limited extent. It is therefore suggested that the thylakoids interfacial properties are determined by both a minor chlorophyll-independent factor and a major chlorophyll-dependent factor.
The results from the present study demonstrate that chlorophyll is important for the thylakoids function in terms of interfacial properties. Chlorophyll is known to be degraded by light, acid, heat, and by enzymes accelerated at higher relative humidity. To assure the interfacial properties of the thylakoids essential for lipase/co-lipase inhibition hence increased satiety, the chlorophyll content must be maintained to as great extent as possible during both processing and storage. For powders produced by drum drying, the chlorophyll was degraded by heat during drying and chlorophyllase was inactivated due to exposure to high temperatures, hence less degradation during storage. Thylakoid powders produced by the gentler drying methods freeze-drying and spray-drying had high chlorophyll levels after drying and were therefore sensitive for enzymatic chlorophyll degradation accelerated at higher relative humidity. The heat exposure during spray drying induced partial inactivation of chlorophyllase in the spray-dried powder. Therefore spray-dried powders had the highest levels of chlorophyll and highest emulsifying capacity at all relative humidity levels investigated, compared to the other powders.

Conclusions
The effect of 8 months storage in varying relative humidity on thylakoid powders dried by drum-drying, spray-drying or freeze-drying was evaluated. All powders were considered hygroscopic and absorbed moisture from the surrounding air. Addition of maltodextrin decreased the hygroscopicity of the drum-dried powder. The green color, chlorophyll content and emulsifying capacity of the powders were decreased during storage. The effect was moisture-dependent with a greater loss at higher relative humidity. The effect was more pronounced for the spray-dried and freeze-dried powders, which contained higher initial levels of green color and chlorophyll. These powders were therefore more susceptible to chlorophyll degradation during storage. The thylakoid powder should be stored dark in air-tight packages, preferably single dose sachets, to control the powders' total exposure for moisture during the shelf life. The suggested packaging would ensure the thylakoid powders' function as appetite-reducing ingredient after storage. The results provide knowledge regarding standardization and quality control of a functional food ingredient with appetite-reducing properties.


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Performance analysis of the process of combine harvesting of grain crops

The effectiveness of combine harvesting processes is one of the most important indicators of planting enterprises, as it largely determines the efficiency of the entire organization. One of the problems in assessing the effectiveness of combine harvesters is the determination of the planned performance of machines with rated productivity. The paper considers approaches to determining the planned and actual performance of the processes of combine harvesting of grain crops. The factors affecting the decrease in the performance of combines have been studied. The analysis of data on the wheat harvesting process in local organizations of the South of Russia during 2014-2019 has been carried out. The results of calculating the planned and actual performance of wheat harvesting processes in these farms are presented.

Introduction
Combine harvesters (CH) are one of the most complex and expensive means of mechanization in crop production. Moreover, the result of the annual production cycle is largely determined by the quality of the harvesting process (in particular, grain crops). The main work in the process of harvesting of grain crops is performed using a combine harvester and means of transporting the crop to storage sites. The purchase and maintenance of combine harvesters suggests significant costs and the maximum use of each unit of equipment becomes very important for agricultural producers. On the one hand, the harvesting time from the stage of the full maturity of the grain until the end of harvesting leads to an increase in biological losses of the crop. On the other hand, incomplete loading of equipment leads to unnecessary (sometimes excessive) costs for the purchase, maintenance, salaries, etc. To assess the state of the processes of combine harvesting of grain crops, it is necessary to determine the indicators of their performance and effectiveness.
Existing approaches to assessing the performance and effectiveness of combine harvesters usage consider only some aspects of the harvesting processes and do not provide grounds for determining the potential of agricultural producers. For instance, the effectiveness of the work is estimated by the actual threshing or actually harvested area per machine during the harvesting period, the duration of harvesting. Such estimates do not allow to evaluate how this corresponds to the real equipment capabilities claimed by the manufacturer.
If the performance of the process of mechanized harvesting of grain crops is defined as the ratio of planned and actually achieved results, the productivity indicator is always close to 100 percent (it is very rare that not all sown areas are harvested with a satisfactory yield). Moreover, the quality of the process is estimated only by the amount of costs (grain loss, fuel consumption, purchase of spare parts, depreciation, wages, etc.) associated with its implementation.
Such an approach to assessing the processes of mechanized harvesting of grain crops makes it difficult to find ways to increase the performance and efficiency of this process, therefore, alternative options for evaluating the performance should be considered.

Research status and work relevance
To assess the processes in management systems, two groups of indicators have been taken into considerationeffectiveness indicators and performance indicators: -effectiveness is the ratio between the achieved result and used resources; -performance is the degree of implementation of the planned activity and achievement of the planned results.
The presented definitions show that the evaluation of the effectiveness is directly related to the assessment of the performance, since both of these indicators require determining the actually achieved result, however, to determine the effectiveness it should be attributed to the expenses on achieving this result, and to determine the performance -to the planned results.
Effectiveness and performance indicators can be described by the following formulas, (1) and (2) respectively.
where: Рaan indicator (assessment) of the actually achieved results; ∑Erassessment of the total expenses on achieving the results.
where: Рaan indicator (estimation) of the actually achieved results; Ppplanned results.
At evaluating complex systems, the calculation of effectiveness and performance indicators, of course, cannot be reduced to such a simple formula, since both the dividend and the divisor in formulas (1) and (2) are themselves complex integrated estimates.
At evaluating the effectiveness of using the combine harvester fleet, the assessment of the achieved results is natural, reflecting the purpose of the combine harvesting process. The actual performance estimates this. The performance of combine harvesters is usually expressed through the capacity (kg/s), the productivity of the main product (tons/h;), or the harvested area (ha/h). These indicators are correlated and can be expressed through each other.
Considering the fact that the main load during combine harvesting of grain crops falls on the threshing and separating device (thresher), the productivity of the combine harvester is limited by its capacity. The threshing capacity means the maximum amount of grain mass that the combine can process per unit of time in compliance with agrotechnical requirements.
Then the correlation between the capacity of the harvester and the size of the harvested area can be described by the following dependence: where: Sthe area harvested by the combine harvester, ha; qthe capacity of the combine harvester, kg/s; Ythe yield capacity, kg/ha; Krthe ratio of straw and grain by weight (standard value of 1.5:1); Kscrop stand by weight,%; thoperating time, sec. The planned performance should be determined on the basis of the need to fully load the combine harvester, that is, as the multiplication of the combine harvester productivity and the calendar time of the harvesting duration. To determine the planned (ideal) performance, it is necessary to equate the harvesting time (th) in expression (3) with the calendar time from the beginning to the end of harvesting: where: Р , the planned performance expressed in terms of the planned number of the harvested areas; ℎis the planned harvesting time corresponding to the calendar time from the beginning to the end of harvesting.
The planned value of the performance of the combine harvesting processes cannot be achieved due to the influence of a number of reasons, among which the main ones are [1][2][3]: -reduced performance due to technical condition; -reduced performance due to technological adjustment; -reduced performance for organizational reasons; -decrease in performance due to weather (climatic) conditions. The influence of the above mentioned reasons on the actual performance of the harvesting processes is presented in Figure 1.
availability factor; coefficient of technical use; Кcoefficient of technological adjustment (setting); coefficient of organizational downtime; load factor of the CH; coefficient of weather conditions; planned harvested area; ℎplanned harvesting time; qthe productivity of the combine harvester. Weather (climatic) conditions significantly affect the efficiency of the combine harvesting processes. Precipitation and daily fluctuations in air humidity lead to the fact that it is impossible to harvest crops daily and around the clock.
It is reasonable to correct the planned value of the performance of the combine harvesting processes by the value of the coefficient of weather conditions, reflecting a decrease in the available harvesting time due to weather (climatic) conditions: where: weather coefficient: where: the average time during which weather and climatic conditions did not impede the implementation of mechanized harvesting; is the average time during which weather and climatic conditions did not allow mechanized harvesting.
Among the technical reasons for reducing the performance of technological processes of combine harvesting, it is possible to single out the indicators related to the aspects of managing the technical condition of combine harvesters -repair and maintenance of machines [4][5][6]. Maintenance is an integral part of the operation system of machines, without which it is impossible to ensure their proper functioning throughout the service life of the machine.
Implementation of a set of maintenance activities reduces the operating time of combine harvesters, thereby reducing the total threshing and harvested area, that is, the actual performance of the grain harvesting process [7].
The decrease in performance associated with the technical condition of the machines should be evaluated using the availability factor or the technical utilization rate of the equipment. These concepts are defined in [8][9][10].
Availability factor is the probability that the object will be in working order at a given time: where: availability factor; Т ̅average failure interval; Т ̅average recovery time.
The coefficient of technical use is the ratio of the mathematical expectation of the total time the object is in working order for a certain period of operation to the mathematical expectation of the total time the object is in working order and downtime due to maintenance and repair during the same period: where: coefficient of technical use; Т ̅average maintenance time.
The coefficient of technical use seems to be more suitable for assessing downtime associated with the technical condition of the machines, since it takes into account scheduled maintenance [11][12]. However, if scheduled maintenance of combines is carried out during periods of time when harvesting cannot be performed (for example, due to increased humidity in the morning), it is preferable to use the availability factor.
Another reason for the decrease in the actual performance of the processes of combine harvesting of grain crops is the need to find the optimal values of the regulated parameters of the work of the combine harvesters. Non-optimal solutions for setting the combines can lead to long downtime of the equipment, an increase in grain losses and a decrease in its quality.
The quality of the processes of setting and technological adjustment of combine harvesters can be characterized by the following indicators: -time of presetting; -time of setting technological adjustments; -optimality of the settings. The optimality of the setting of the combine harvester is determined by the totality of the values of the parameters of the working devices, environmental conditions and the correlations between them. The optimality of the setting can be estimated by the level of losses, the quality of the threshed grain and threshing per unit time [13][14][15].
The time for setting and adjusting the technological configurations of the CH affects the actual performance of the harvesting process in the same way as the technical indicators mentioned above, reducing the available working time. The time spent on technological adjustment and setting of technological configurations of the combine harvesters leads to the decrease in shift productivity of the combines.
The need for operations for the technological adjustment of the combine harvesters is confirmed by the assessment of the third indicator highlighted in the group of the technological reasons for the decrease in the performance -the optimal setting of the combine harvesters. Non-optimal settings of the combine harvester lead to the increase in grain losses, to the decrease in the combine harvester productivity (work with incomplete loading), or to both of these consequences.
If the increase in grain losses does not affect the performance of the mechanized harvesting of grain crops (although, undoubtedly, significantly affects its effectiveness), then the decrease in productivity due to incomplete loading reduces the actual performance of the combine.
It is proposed to evaluate the influence of factors associated with the technological adjustment of the combine using two coefficients: the coefficient of technological adjustment (setting) ( ) and the load factor of the CH ( ).
The coefficient of technological adjustment (setting) ( ) characterizes the time spent on setting up and adjusting the operating modes of the working devices of the CH: where: Т ̅ average time spent on useful work; Т ̅the average time spent on setting up the combine; Т ̅the average time spent on the adjustment of technological configurations.
The load factor ( ) shows how fully the claimed combine capacity is used: where:the claimed capacity of the combine harvester, kg/s; the actual capacity of the combine harvester, kg/s.
where:area (ha), actually harvested during continuous operation; ℎ (hours); Ycrop yield, tons/ha; Кthe ratio of straw and grain by weight (standard value of 1,5:1); contamination of the crop stand by weight. However, determining the load factor of the combine harvester using formulas (10), (11) under the real conditions of the combine harvesting of grain crops is very inconvenient, since the time ℎ , used to calculate the , is very difficult to define accurately. During operation, the combine performs turns and other maneuvers, during which the supply of grain mass stops, but there is no countdown. It is easy to take into account such breaks only in test conditions.
For a simpler assessment of the load factor of the combine ( ) it is possible to rely on the ratio of the speeds of the combine during the harvesting process. In the Russian standards for testing the combine harvesters, the concept of working speed is established, which corresponds to the estimated productivity: where: is the estimated productivity of the combine, t/h (can be calculated by the formula (3)); preliminary crop yield excluding losses after the combine, tons/ha; Lestructural width of the reaper grab, m Preliminary yield is determined by manual harvesting and threshing of wheat from several random fields.
The load factor of the combine harvester can be calculated as the ratio of the actual harvesting speed to the speed corresponding to the design capacity ( ): where: the actual speed of the harvester during harvesting, km/h. Such an approach to determining the load factor seems justified, since the speed of the combine is set as the result of the adjustment and is the value that is functionally related to both the number of losses and the performance of the combine.
The decrease in the time of use of combines and, accordingly, the shift productivity, is possible due to a number of organizational reasons: downtime due to the change of machine operators (including the inability to work around the clock); stops for refuelling; downtime due to waiting for machines for unloading grain; transportation, etc.
It is proposed to evaluate the organizational and logistic component of the reasons for the decrease in the performance of the CH using the coefficient of organizational downtime ( ): where: Т ̅ average time to complete useful work; Т ̅ average downtime for organizational reasons: where: is the average downtime associated with the operator (lunch break, shift, including the time of possible harvesting, but work is not carried out due to excess workload for the operator, etc.); average downtime due to refuelling; average downtime associated with waiting for machines for unloading grain; average time of equipment transportation from field to field and to places of permanent location (brigades, field camps, machine parks, garages, etc.).
The actual performance of the processes of combine harvesting of grain crops can be described by the expression: Evaluation of the performance of the process, in this case, can be calculated by the formula (2), as the ratio of Р to Р .

Results and discussion
To increase the performance of the process of mechanized harvesting of grain crops, all the components presented in expression (16) should be considered. The choice of priority areas for improvement must be carried out based on the values of the coefficients KTU, KS, KO, KL and the capabilities of planting enterprises.
In recent years, we have accumulated a significant amount of statistical data on the processes of combine harvesting of grain crops in planting enterprises of the Myasnikovsky District of the Rostov Region (Russian Federation), which together operate more than 60 machines of various manufacturers.
As a result of the analysis of indicators recorded at these farms in the period from 2014 to 2019, the following generalized data have been obtained (table 1): The capacity of the combine harvester, kg/s 11 14 The ratio of straw and grain by weight (Kr), 1. 5 15 Contamination of the grain mass (Kc), 0.05 Based on the data in table 1, the values of the coefficients given in formulas (4) -(16) are calculated (table 2). The value of the performance indicator of the processes of combine harvesting of grain crops can be determined by the formula (2). For the data given in tables 1, 2, the performance indicator is 0.34. The resulting assessment of the performance of the mechanized harvesting of grain crops indicates a very low degree of use of the potential of mechanization means. It is possible to judge the contribution of various reasons for the decrease in the harvesting performance by the value of the indicators presented in table 2 ( Figure 2). The analysis of the reasons for the decrease in the performance of the harvesting processes has shown that the most significant reason is weather conditions, organizational and logistical reasons. Weather conditions are uncontrollable, so there are practically no ways to reduce their impact. The reasons for downtime associated with logistics and the organization of work seem to be the most significant for the considered agricultural enterprises.

Conclusions
1. Presented in the paper approach to assessing the performance of the processes of the mechanized harvesting of grain crops allows not only to present the actual performance of the work, but also to determine the most promising ways of its increase.
2. The application of the presented methodology for assessing the performance of the processes of combine harvesting of grain crops requires the development of reliable procedures for the collection and management of documented information on various aspects of the agricultural company activities.
3. To develop a strategy of improving the harvesting processes, it is necessary to consider not only their performance, but also effectiveness, since the increase in performance may require unreasonably high expenses (for example, reducing downtime due to logistical reasons by involvement additional means of grain transportation will increase the below-cost per the kilogram of grain, with a slight increase in threshing).