Using High Pressure Treatment for Research in Food Processing and Development of Cooked Rice

Until recently, the factor that has played a predominant role in food processing was not "pressure" but "heat, " although both factors are independently responsible for transforming the state of a substance. In food processing, high pressure treatment produces no aberrant matter that puts the safety of food at risk because the food processing can be achieved without any cleavage of covalent bond contained in the ingredients of food. Moreover, high pressure treatment is considered to be very promising for food processing of the future. This is because decomposition of nutrients and production of stench can be minimized more effectively and energy consumption can be reduced more efficiently when compared with heat treatment. Further, whena food product in a container is subjected to high pressure treatment, uniform processing throughout the food can be guaranteed. It has been confirmed that pressure treatment exhibits the following effects, which are useful to improve the quality of food to create new added value . 1) Removal of air bubbles: Air bubbles trapped in a solid substance can be removed therefrom by placing it in a solvent . Then a relatively low pressure ranging between about 10 to 100 MPa is applied and then rapidly reduced . By using this method, we have succeeded in developing food products, for example "rice cakes whose dispersion rate is decreased to one sixth" and "low-salt pickles prepared in 10 min." 2) Impregnation of a solid substance with a liquid and extraction of an ingredient from the solid substance: The sequential operation of applying a pressure of about 50 to 300 MPa to a solid substance and reducing the applied pressure can form a flow path for liquids in the solid substance. The solid substance can be thus impregnated with a liquid and a predetermined ingredient can be extracted from the solid substance effectively through the path. More specifically, we have completed the development of "low allergenic rice" by extracting an allergen-containing protein from rice, and "unpolished rice that can be cooked by normal procedures" by improving the water absorption properties of unpolished rice. 3) Control of enzyme reaction and destruction of cell wall and cell membrane: By the application of a pressure of 200 to 600 MPa to a living organism, the cell wall and the nuclear membrane in the cell are destroyed to cause the leakage of cell sap and halt the activity of some enzymes . By taking advantage of the above-mentioned effect, we ha