Effects Of Ultra-high Pressure Treatment On Food Quality

Ultra-high pressure processing (UHPP), as a non-thermal food technology has attracted more and more attention in the food industry. Unlike traditional thermal processing, high pressure treatment can maintain the nutritional value of fresh foods due to its limited effects on covalent bonds of low molecular compounds such as amino acids, vitamins, aroma components, etc.Ultra-high pressure processing has been commercialized in some food processing. UHPP causes destruction or formation of hydrogen bonds, ionic bonds, hydrophobic bonds and other non-covalent bonds, resulting in the effect of "protein denaturation","enzyme inactivation" and "sterilization", thus affect the quality of food.In addition, freezing temperature of water changes with pressure. This phenomenon allows the achievement of novel methods for freezing and thawing foods. This high pressure low temperature process is currently difficult and hot.Based on the considerations above, the main research contents and results are as follows:(1) Using pilot scale UHPP device to study the effects of high pressure treatment on shrimp quality within the scope of the pressure up to300MPa. Analyze the advantages of UHPP on seafood preservation by monitoring changes of pH and the Total Volatile Base Nitrogen (TVB-N) value during chill storage. The results show that UHPP can be used for shrimp shucking and high pressure shucking can effectively improve the yield and integrity of the product. UHPP can help reduce the drip loss, the drip loss of shrimp treated by150-200MPa range is less than1%. Texture of the shrimp undergone significant changes after high pressure treatment, hardness, springness, chewiness increase and shear strength decrease with the increase of pressure. The pH and the TVB-N value can be suppressed during chill storage after UHPP. TVB-N value is still maintained at below30mg/100g after refrigerated for15days for shrimp treated by300MPa.(2) Build a numerical model by using COMSOL Multiphysics to simulate high pressure thawing processing and study the effect of pressure and sample size on thawing time. Experimental study changes in quality after air thawing, liquid thawing and pressure-assisted thawing changes. The results showed that pressure-assisted thawing can significantly shorten thawing time, particularly for the large-size samples.Shorten ratio increases with the increase of pressure and has little relationship with sample size. Thawing time is reduced by about22.9%,34.3%,42.9%and51.4%under50,100,150and200MPa.Pressure-assisted thawing helps to reduce the drip loss and improve the texture of the product compared with traditional thawing methods.(3) Study the effects of UHPP on carrot texture, peroxidase (POD) activity and vitamin C by using pilot scale UHPP device and compared with the thermal processing. The results show that product texture parameters change significantly after UHPP. The hardness decreased by35%,48%and61%after treated by100,200, and300MPa.Compared with thermal processing, UHPP can better keep its texture, the hardness of the sample treated by100MPa for10min is3.9times of the sample treated by100℃for10min. POD inactivation rate increases as the temperature rises. Pressure will activate the POD activity in the range of300MPa. Vitamin C will pyrolysis at a high temperature, vitamin C loss is nearly70%after treatment by100℃for10min, while the high pressure treatment almost has no impact on vitamin C content.