Experimental Investigation On High Pressure And Low Temperature Treatment Of Food

During the past decade, the high-pressure-low-temperature processes (HPLT) characterized by its keeping fresh, energy-saving and environmental protection have attracted attention of a number of food researchers. The high pressure low temperature treatment in the low-temperature storage, high pressure freezing and thawing can effectively keep the original flavor, color and quality of food, and decrease activity of enzymes or microorganisms, meanwhile shortens processing time of food. However the mechanism of high-pressure-low-temperature process is not clear right now. To enlarge industrialization of the high-pressure-low-temperature processes, a large amount of fundamental research has to be carried out. In this paper, high-pressure freezing and high-pressure thawing on typical creatural and botanic food samples are investigated with the HHP experimental equipment. The experiments of inactivation on anti-pressure enzymes and microorganisms are carried out. The main research work and results in this paper are as follows:(1) A set of high pressure low temperature equipment with pressure 0～600MPa and temperature -30°C～70°C is designed and setted up in this paper. The representative food of fish and potato are choosed to carry out lots of freezing ang thawing experiments.(2)The studies on micro-structure of freezing fish and potato treated by different freezing processes show the feasibility of high pressure freezing process. The high pressure freezing process not only shortens the process time but also effectively protects the texture of food.(3) The thawing investigations on potatos and fish show the feasibility of high pressure thawing process. The factors such as thawing time, rate of juice loss and microstructure are considered to investigate the thawing effect. The high pressure thawing preocess can effectively shorten thawing time, decrease juice loss and keep original texture of food comparing with the thawing process at atmospheric pressure; The main factor influencing the food quality processed by high pressure low temperature process is the size and shape of ice crystals during the freezing.(4)Escherichia coli and bacteria are chosen as typical anti-pressure microorganisms in the sample. The factors such as operate pressure, pressure holding time, pH and temperature are considered to investigate the effect on inactivation. The inactivation in high pressure freezing and thawing is studied by considering the phase transition. (5) The representative polyphenol oxidase is chosen to investigate the inactivation effect on enzyme. The factors such as operate pressure, pressure holding time, pH, temperature are considered to investigate the influence on the activity of enzyme.