Keeping vegetables fresh (an essay from China)


This excerpt is the fourth essay of the 1972 edition of “Serving the People with Dialectics”, which tells the story of agricultural workers in their daily application of materialist dialectics to socialist construction. Enjoy!

Keeping Vegetables Fresh, by the Peking Chungwen District Vegetable Station Scientific Experiment Group

As fresh vegetables of increasing variety have occupied a greater place in the Chinese people’s diet the contradiction between the seasonal nature of the vegetables and the steady demand of the market became marked. During the height of the season, vegetables often went bad, while in off seasons the supply could not meet the demand. To solve this contradiction, it became necessary to store surplus vegetables, keep them fresh and supply the market in off seasons.

We tackled the problem from two sides: one was to work in close co-operation with vegetable-producing communes and brigades in the suburbs; the other was to mobilize the comrades of our station to solve certain problems in storing perishable vegetables. In 1968we formed a three-in-one scientific experiment group of cadres, workers and technical personnel, with workers as the main force, and set out to use the philosophic teachings of Chairman Mao to help solve these problems through scientific experiment.

Three tomatoes

We focused on tomatoes, known among truck gardeners as the “overnight headache”, because of their perishability. We tried storing them, and one day discovered three of our tomatoes still well preserved after more than a month. Why had the rest spoiled? Here, Chairman Mao’s teaching that it is “in the particularity of contradiction that the universality of contradiction resides” gave the clue. If three tomatoes could be preserved for over a month, it should be possible to preserve all of them. The conditions under which the three tomatoes had been stored were: low temperature, a certain humidity and good ventilation. These conditions had slowed down metabolism in the tomatoes and prolonged their period of wholesomeness.

In other words, controlled temperature, humidity and ventilation kept the tomatoes living longer. High temperature and humidity caused rot, while too low a temperature spoiled them by freezing. Too brisk ventilation dried them and made them lose their freshness. What was needed was to handle the relations among the three conditions well. We turned to Chairman Mao’s teaching that “in studying any complex process in which threre are two or more contradictions, we must devote every effort to finding its principal contradiction. Once this principal contradiction is grasped, all problems can be readily solved”. We analyzed the three basic conditions of temperature, humidity and ventilation and experimented with different relationships. The contradiction between temperature and ventilation was apparently the principal one. Therefore, we took measures to maintain the correct temperature in the storage cellar. Then we turned to the problems of humidity and ventilation. By correctly handling the relation between the principal contradiction and others, that year we succeeded in storing four hundred tons of tomatoes in July for sale in late months. Thus we took a first step in solving the contradiction between the seasonal nature of tomatoes and the constant demand of the market. Though we had some success in preserving tomatoes, we did not know much about their metabolism, that is, the laws of the inner contradiction of tomatoes. We realized that it was not enough to pay attention to external conditions such as temperature, humidity and ventilation. More important was to master the laws of the inner changes taking place in the tomatoes under storage, so that we could preserve large quantities and popularize our methods. Guided by Chairman Mao’s philosophic thinking, we further explored the laws governing these inner contradictions. We noted that even in the same basket, tomatoes underwent different changes. Those on top ripened quickly and couldn’t be stored long, while those beneath ripened slowly and could be stored longer. Nothing this, we understood better the metabolism that went on in the tomatoes for a certain period after they were picked, that is, they went on giving off carbon dioxide and taking in oxygen. Basing on this, we continued our experiments, using new methods to control the respiration and metabolism of tomatoes, to make them take a turn favorable to lengthening the time we could preserve them and improving their quality. The result was that we turned the “overnight headache” into a “one-hundred-day-fresh”.

Solving the particular contradiction of onions


Our success in preserving tomatoes gave us confidence and inspiration to tackle the problem of storing other perishable vegetables. We experimented with onions. They are a bulb, very nutritious but apt to sprout, become hollow and rot when stored for a long time.

To prevent sprouting, we first tried the same method as for preserving tomatoes, that is, by controlling temperature, humidity and ventilation. It didn’t work. The onions were all right as long as they were in cold storage, but they sprouted all the quicker when they were taken out. We studied Chairman Mao’s teaching: “Unless we study the particularity of contradiction, we have no way of determining the particular essence of a thing which differentiates it from other things, no way of discovering the particular cause or particular basis for the movement or development of a thing, and no way of distinguishing one thing from another or of demarcating the fields of science”. With this as our guide, we specifically analyzed the characteristics of onions’ changes after they were picked and found that, different from tomatoes, they sprouted only after undergoing a dormant period. While a low temperature could prevent them from sprouting temporarily, it didn’t solve the contradictions fundamentally. They sprouted as soon as they were out of the cold storage and in a suitable temperature.

We tried something else. Instead of storing at a controlled temperature in the cellar, we sprayed a chemical on the shoots in the field before harvest. Onions thus treated did not sprout, and storage time could be extended. Our success with experiments on a small scale was popularized in the communes and brigades in the suburbs. But unexpected problems arose. Some of the chemically-treated onions still sprouted. The chemical strength of the solution, and amount were all the same, why were the results different? We went to the fields to do careful investigation and analysis and found that dryness prevented absorption of the chemical, while rain washed it out. Besides harvesting time and cultivating methods, many factors affected the chemical treatment. With this understanding of how to use the chemical, we co-operated with the communes and brigades in overcoming the unfavorable factors affecting the chemical. We succeeded in solving the problem of onion sprouting, and supplied the market the whole year round.

Storing cabbage

Chinese cabbage, a leafy vegetable, is stored in large quantities by the state, collectives and households every year. But some leaves fall off or go bad before being stored very long. Spoilage sometimes reached 40 per cent.

At first we didn’t know why cabbage kept or spoiled and could only take routine measures of sorting and turning. Later, we went to a suburban production brigade and learned that experienced farmers estimated the temperature of the storage cellars according to how it felt on their ears, while they tested the ventilation by smelling. The brigade was thus able to maintain optimum storage conditions. Enlightened by their experience, we found that Chinese cabbage is a live organic whole. Though stored, the cabbages went on giving off carbon dioxide and taking in oxygen, that is, their metabolism continued. Insufficient ventilation caused rot. We set about experimenting and collecting data. At the beginning of the storage period, the end of November, when the relatively high temperature caused rot, we turned the cabbages often and opened the door to lower the cabbages often and opened the door to lower the temperature of the storage cellar. At the middle of the storage period, in freezing weather, the lowest temperature would freeze them, so we ventilated and turned them during the warmest part of the day so as to keep the temperature around zero. At the end of the storage period, after the cabbages had been kept for a long time, and as the temperature in the storage cellar gradually rose, they sprouted readily. Then we kept the temperature down. We also used a chemical to prevent them from sprouting. In this way we reduced the damage.

Chairman Mao says: “Processes change, old processes and old contradiction disappear, new processes and new contradictions emerge, and the methods of resolving contradictions differ accordingly”. After solving the primary problem of rot, the secondary problem, that of leaf shedding, became the principal contradiction. We again used chemical treatment and solved this contradiction, but we noticed that the cabbages treated with the chemical were easily damaged. Analysis showed that the chemical increased their ability to hold water. The treated cabbages were fresh but delicate, so that damage and resulting contamination were apt to occur. The old ways of turning, piling up and ventilating would not do for chemically-treated cabbage. We adjusted the amount of the chemical, and changed the way of piling up and the turning time, according to the length of storage time. The result was that rot was decreased, preserving time considerably lengthened, and the popular demand for fresh cabbage in winter was met.

After our successful experiments in keeping tomatoes, onions and Chinese cabbage fresh, we worked with other vegetables such as sweet peppers, cauliflower, potatoes and garlic. Some common rules for storing succulent and leafy vegetables, and tubers, were arrived at and we thus solved some of the problems involved in bringing fresh vegetables to the tables of more people in all seasons.

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