Vacuum frying technology originated from a patent on closed fryer in the United States, which can be said to be the earliest prototype of vacuum frying equipment. Subsequently, Japan conducted extensive research on this technology, the research focus was mainly on the improvement of frying equipment, and thus invented a number of patented technologies.

Until 1977, the publication of a research paper on vacuum frying banana crisps equipment and technology by a Japanese scholar officially marked the beginning of the exploration of vacuum frying equipment. Subsequently, West Germany, the United States, the Netherlands, Canada and other countries have set off. The research and development of vacuum frying equipment is booming. Especially in the two patent studies in 1983 and 1985, vacuum technology was used for the first time in the frying process, and the vacuum frying equipment truly opened the "vacuum era" from the initial closed frying mode.

Although the research on vacuum frying equipment has started, vacuum frying equipment still faces many research problems, such as high fat content, long frying time and product deformation. In order to solve this technical problem, two patented technologies in the United States Invented and conquered both the pre-treatment of frying ingredients and the modification of the frying machine, which effectively improved the quality of vacuum frying products and the efficiency of vacuum frying equipment, thereby promoting vacuum frying technology Industrialization.

At present, foreign countries have been quite mature in using vacuum frying equipment to produce fruit and vegetable chips. However, my country's research on vacuum frying equipment started late. At present, it is mainly to absorb and innovate vacuum frying equipment in various directions on the basis of introduction. Among them, the most concentrated research and application is in the field of fruit and vegetable chips technology.

The principle of vacuum frying equipment

The basic principle of vacuum frying equipment is to reduce the vaporization temperature of oil and water under vacuum negative pressure, and then use oil as a medium to quickly remove water from food, so as to reduce food moisture and improve food under low temperature conditions. The role of flavor, improving food texture, etc. Because under normal pressure conditions, the boiling point of water is 100°C, and vacuum frying works under negative pressure. The so-called negative pressure refers to pressure conditions lower than standard atmospheric pressure. At this time, the boiling point of water decreases, and the moisture can be reduced. At a lower temperature, it reaches its boiling point and evaporates quickly, so as to achieve the purpose of dehydrating and drying food. Therefore, the temperature of vacuum frying is usually lower than that of normal pressure frying. Lower oil temperature can effectively avoid a series of technologies such as browning of food, deterioration of fats, Maillard reactions, and loss of nutrients. problem.

Five advantages of vacuum frying equipment

1. With good brittleness, vacuum frying gives the product a loose and porous structure, ensuring its good sensory quality. Under negative pressure conditions, the water in the intercellular spaces of food tissues is heated to evaporate and spray out, so that the food has a loose and porous structure and a crispy taste.

2. Reduce the loss of nutritional active ingredients in food. Vacuum frying equipment is usually carried out at low temperature (100°C), which can effectively reduce the temperature's destructive effect on the nutritional active ingredients in food, and is especially suitable for the retention of heat-sensitive nutrients.

3. It slows down the deterioration of grease and reduces fuel consumption. Compared with normal pressure frying, vacuum frying oil temperature is lower, and the frying system is closed, the oxygen content is less, the fat and the oxygen are less contacted, it is not easy to oxidize, and its polymerization decomposition and other degradation reactions are slow, and the grease cycle utilization rate high.

4. Greatly reduce the oil absorption of fried products, reduce or even prevent the production of harmful substances. Starch-containing foods usually produce acrylamide, which is harmful to the human body, under high temperature conditions. Vacuum frying equipment is carried out at relatively low temperature conditions, so it can effectively reduce the amount of acrylamide produced.

5. It better retains the original color and flavor of the food. Under a closed vacuum condition, its oxygen content is low, which helps processed foods to be less prone to fading, discoloration or browning, thereby maintaining the color of the food itself. In addition, in a closed vacuum frying system, the water-soluble taste substances in the raw materials are dehydrated and concentrated and are not easily dissolved out, so the original flavor of the raw materials is better retained.

Application of vacuum frying equipment

Nutrition, convenience, safety, and greenness are the current trends in food production and research. In the future, food processing and production will inevitably promote products with natural, nutritious and convenient characteristics in terms of raw materials, production technology, and equipment. Vacuum frying equipment has these characteristics, and can be widely used in fruit and vegetable chips, dried fruits, meat products, convenience dishes, soy products, etc. For example, vegetables and fruits made by vacuum frying mainly include potatoes, pumpkins, winter melons, sweet potatoes, carrots, green peppers, garlic, bananas, peaches, pears, cantaloupe, persimmons, strawberries, etc. At the same time, the application of vacuum frying equipment in the preservation of fresh fruits and vegetables is also worthy of our future focus and research. At present, the main technical problems in this field are high fat content, poor storage quality, high cost, single variety, etc. New operational model analysis and mechanism discussion are urgently needed to solve practical problems in application.