by Chris Piotrowski, Director, Aunir, UK

NIR spectroscopy is an analytical technique that allows a rapid, non-destructive determination of a sample’s properties. It is used in various industries for identifying compounds and chemical structures which can then be accurately related to the nutritional, chemical and physical properties of the material.

How does it work?

Traditional ‘wet chemistry’ facilitates a greater level of understanding about the make-up of different materials. However, this technique requires heavy investment of time and money.
Organic molecules absorb infrared radiation at an energy that is characteristic of their composition. Every chemical compound is characterised by one of six types of molecular vibration; symmetrical stretching, asymmetrical stretching, scissoring, rocking, wagging or twisting. Each of these types of vibration absorbs light energy at a different frequency.
NIR spectroscopy measures the absorption of light energy shone at a material in order to produce a spectra. The resulting spectra can then be compared to other spectra of known materials to identify it.

In practice, a sample of material is placed on the reading pane of an NIR spectrometer, which will then take the measurement and produce a spectra file.
NIR analysis is very quick and simple, meaning that individuals operating the equipment do not need any special qualifications. Another benefit to NIR analysis is that there are no hazardous chemicals involved, allowing analysis to be carried out at various stages of production. And since NIR is non-destructive, it is perfect for use in plant breeding and raw material quality control since the sample can be used again.

Understanding NIR

Analysis of chemical compounds has rapidly evolved over the last century, but there are still many parameters measured which are not true compounds. For example, crude fibre is the material which remains after the action of acid and alkali on a sample of feed. There is no such compound in nature. Whereas reference chemistry on such compounds is not reliable, alternative techniques such as NIR remain pure.

Scanning a sample using NIR will only produce a spectra file. This then needs to be compared to a database of other spectra files of known substances in order to correctly determine the components in the material. Calibration databases are expensive to create in terms of both time and financial investment. Thus, a market in which the licensing of spectra databases for reference purposes has developed.

Licensing a set of calibrations cuts out the need for massive financial investment and eliminates any time delay in obtaining results since the predicted data is immediately available. Once an NIR machine is set up with calibrations, the technique for carrying out analysis is relatively simple and thus can be carried out by any member of staff, not necessarily a highly skilled technician. The results of NIR analysis are available instantly, allowing important decisions about quality control to be taken immediately. The future of NIR capability will allow further flexibility for analysis.

Who uses NIR?

Sample analysis can be carried out in the following three ways. Firstly, by an agreed standard method such as protein analysis (Dumas or kjeldahl). Secondly, by empirical methods such as those employed for oil or crude fibre analysis. Finally, there are subjective methods based on experience such as taste or smell, but these subjective methods are not an accurate measure for quality control purposes. Traditionally, quality control is carried out through wet chemistry analysis, but since this method is slow and expensive, alternatives such as NIR spectroscopy have been sought out.
NIR can be used across a wide range of industries. Animal feed and ingredients, flour and milling, wet and dried forage, animal proteins, pet food, aqua feed and plant breeding companies all utilise NIR analysis.

NIR in the pet food industry

NIR is a proven technique used by pet food manufacturers for the rapid, on-site multi-component analysis of raw materials and pet foods. Samples of pet food require little or no preparation, making NIR a quick, clean and chemical-free way of analysing for key quality parameters such as protein, oil, fibre, ash, moisture and even starch gelatinisation.
An NIR system is ideal for rapid analysis and it lowers the cost of achieving quality because it allows increased testing frequency at no extra cost. Analysis using NIR technology is employed by 90 percent of UK-based pet food manufacturers.

As part of the Premier Pet Nutrition complete pet nutrition package, pet food and raw material NIR calibration factors are provided. The NIR calibration factors help pet food brands to constantly improve standards for product quality, conformity, assurance and safety.
The impact NIR can have on a pet food manufacturers business is illustrated by one of Premier Nutrition’s clients who saved €100,000 in one year by using NIR as part of a complete pet nutrition package.

Premier Pet Nutrition also uses NIR innovatively at its own factory to test every incoming micro-ingredient (for example, vitamins, minerals, and nutraceuticals) to ensure identity and conformity. This adds another level of assurance in the final premix product.

NIR in determining corn quality

Feed represents around 70 percent of the cost of production of monogastric animals globally. Sourcing low cost ingredients is important for the economic success of companies involved in animal production, as is the quality of these ingredients. Ingredient quality will impact animal performance and consequently production costs. Cereals such as corn, sorghum and wheat are generally the major ingredients in animal feed formulations and so their quality will have a direct effect on animal performance.

The Corn Quality Service is a service provided by AB Vista, in association with Aunir. The service allows customers to automatically predict the quality of corn used in their feeds by determining the cereal composition and quality parameters such as vitreousness and protein solubility. The service allows monitoring of cereal quality, anticipating any variation, and assisting with decisions on dosing of additives such as feed enzymes. Adding an enzyme to the feed, for example, will maximise productivity and uniformity even when the cereal quality varies between batches and seasons. NIR spectroscopy is used by over 50 percent of animal feed manufacturers worldwide, confirming the value that can be gained from NIR in commercial applications.
1 If you are not profiting from Quality Control, Sampling and Analysis, why do any of it? Steven Tayfield, May 2012. Published in Feed Compounder, May 2012, p. 28-29.


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