With the improvement of living standards, people’s concept of food consumption is no longer limited to safety and hygiene, but the color, aroma, taste, nutrients and other aspects of food put forward higher requirements.

Ultra-high pressure technology to deal with food can not only sterilize, but also maximize the maintenance of the original functional composition of food and nutrients, while also overcoming the irradiation, microwave and electromagnetic fields and other processing technology deficiencies, can save resources, reduce pollution.

Although the application of UHP technology in food processing in China is still in its infancy, there are enterprises using domestic UHP equipment and technology to process fresh oysters, fresh sea cucumbers, fresh fruit juices and other food products successfully and have been on the market. This means that China has made a breakthrough in the manufacturing of UHP equipment, which is of great significance in promoting the industrial development of UHP technology in China’s food field.

The concept of ultrahigh pressure technology

Ultra-high pressure technology, also called ultra-high pressure sterilization technology, refers to the use of more than 100MPa pressure, at room temperature or lower temperature conditions, so that the food enzymes, proteins and starch and other biological macromolecules to change the activity, denaturation or paste, and at the same time to kill bacteria and other microorganisms of a food treatment method.

Ultra-high pressure technology in the field of food sterilization, processing technology has unique advantages:

(1) Uniform, instantaneous and high efficiency;

(2) easy to control, safe operation, low energy consumption, less pollution;

3) can maintain the inherent nutritional quality and flavor of food;

(4) Improve the structure of biopolymer, adjust the food texture;

(5) Different pressure effects affect the nature of different.

Processing principle of ultrahigh pressure technology

The principle of ultrahigh-pressure processing of food is: when the food in the ultrahigh-pressure state, which the distance between the small molecules (such as water molecules) will be reduced, while the food protein and other large molecules in the composition of the material is still in its original state.

At this time, water molecules will produce infiltration and filling effect, enter and adhere to the amino acids around the protein and other macromolecules, thus changing the nature of proteins, when the pressure drops to atmospheric pressure, “denaturation” of the macromolecular chain will be elongated, so that part of the three-dimensional structure has been destroyed, thus making the protein coagulation, starch denaturation, enzyme inactivation or activation, bacteria and other microorganisms. This results in the coagulation of proteins, denaturation of starch, inactivation or activation of enzymes, killing of bacteria and other microorganisms, and improvement of the organization of the foodstuff, leading to the generation of new foodstuffs.

Only act on the non-covalent bond is a unique property of ultrahigh pressure technology, so it has no obvious effect on the covalent bond of low molecular substances such as vitamins, pigments and flavor substances, so it can better maintain the original nutritional value of food, color and natural flavor.

The application of ultrahigh pressure in food processing

Ultra-high pressure processing technology can not only be used for food sterilization, inactivation of enzymes and texture improvement, but also on the nutritional value of food, color and natural flavor also has a unique protective effect.

At present, ultrahigh pressure technology has been widely used in meat products, dairy products, egg food, fruit and vegetable products, aquatic products processing and extraction of active ingredients.

(1) the application of ultrahigh pressure in fruit and vegetable processing
Sterilization of fruit and vegetable products is the most successful application of ultrahigh pressure technology in food processing. Compared with the traditional thermal sterilization, ultrahigh pressure technology can achieve the effect of sterilization, enzyme inhibition and improvement of food properties at room temperature or lower temperatures, without destroying the freshness and nutrients of fruit and vegetable products, in line with the requirements of consumers on the nutrition and flavor of fruit and vegetable products.

Fresh fruit juice is rich in protein, vitamins, amino acids and reducing sugar and other nutrients, the traditional heat sterilization treatment will make these nutrients loss is very large, ultra-high-pressure sterilization technology can be effectively avoided in the juice of the nutrients in a large number of losses.

The use of high-pressure sterilization technology can not only kill the microorganisms in the fruit, but also reduce the enzyme activity.

The sensory quality of fruit juice includes color, aroma, taste and other aspects. Ultra-high pressure sterilization belongs to the cold sterilization technology, the operation process is carried out at room temperature, and ultra-high pressure only acts on the non-covalent bond, does not affect the covalent bond, so it can better maintain the original taste, flavor and color of fruit juice.

(2) the application of ultrahigh pressure in meat processing
The use of ultrahigh pressure technology to deal with meat products, can effectively improve the tenderness of meat products, flavor, color and maturity and other characteristics, but also to extend the shelf life of meat products. The tenderness of meat reflects the texture and eating quality of meat, which refers to the old and young taste of meat when eating, and it is a common indicator for consumers to evaluate the quality of meat.

(3) ultra-high pressure in aquatic products processing applications
The processing of aquatic products requires the original flavor, color, texture and texture of aquatic products. Commonly used dry processing, heat treatment can not meet the requirements. And ultrahigh pressure treatment of aquatic products can better maintain the original fresh flavor.

(4) Application of ultrahigh pressure in liquor processing
The natural aging of wine in the production of liquor is a time-consuming and energy-consuming process. UHP technology can play an important role in the aging of wine. In addition, ultrahigh pressure technology also has a good sterilization effect in beer.

(5) The application of ultrahigh pressure in the processing of egg products
When the pressure of 600MPa is applied to the egg, the egg is already solidified although it is cold. Compared with hard-boiled eggs, the flavor of eggs treated with ultra-high pressure is very delicious, the yolk is bright yellow and has good elasticity.

Studies have shown that the protein denaturation gel of ultra-high pressure treatment is softer and more elastic than heated gel, with higher digestibility, in addition, there is no loss of amino acids and vitamins, retaining the natural flavor of the egg, and does not generate other substances.

6）Ultra-high pressure in dairy processing applications
Heat treatment is the most common processing treatment method in modern dairy production. Although it can kill some or all of the microorganisms in dairy products, destroy enzymes, and extend the shelf life of the product. But at the same time will also bring negative aspects to the product, and ultra-high pressure technology can ensure the safety of dairy products in terms of microorganisms, but also better maintain the inherent nutritional quality, flavor and color of dairy products.

Casein is the main protein in milk, ultrahigh-pressure treatment makes the diameter of casein gels smaller, the surface of milk proteins exposed hydrophobic groups increase, causing the whey protein denaturation, so that it clumps.

(7) The application of ultrahigh pressure technology in the extraction of active ingredients
Compared with traditional extraction methods, UHP technology has the advantages of short extraction time, high extraction rate and low energy consumption in the extraction of active ingredients. Ultra-high pressure extraction can be carried out at room temperature, avoiding structural changes, loss of active ingredients and reduction of physiological activity caused by thermal effects.

At present, UHP technology has been applied in the extraction of polysaccharide components, flavonoids, saponins, alkaloids, terpenes and volatile oils, phenols and easy to oxidize components, organic acids and other components.

Conclusion

UHP technology is one of the cutting-edge technologies in the 21st century, which is known as the current hot spot of science and technology and a revolution in the food industry. UHP food better maintains the original color, aroma, taste and nutrients, this advantage meets the modern human nature, the pursuit of natural, low-processed food consumer psychology, in line with the current requirements of green food.

However, UHP technology also has shortcomings, such as high investment cost of UHP equipment, high requirements for equipment sealing and strength, and short life of equipment consumables. The basic theoretical system and standards of UHP technology need to be improved, and the main limiting factors of UHP sterilization need to be further studied as the conditions are strict.

In addition, the changes of food components after ultrahigh-pressure treatment and the relationship between the interaction of the components are not yet clear. China is still in the initial stage of high pressure technology, compared with the world’s advanced level, there is still a big gap, and the domestic market requirements are not compatible, for this reason, China should speed up the research and application of ultrahigh pressure technology.