Effect Of High Pressure Treatment On The Quality Of White Shrimp Meat

Shrimp is popular sea food for its delicious taste and rich nutrition. White shrimp (Penaeus Vannamei) is one of the top three high yield shrimp species in the world. It is also commonly cultured in South China. Shrimp meat is an excellent source of protein and minerals, so its post-harvest processing is of great interest to many researchers. High pressure processing (HPP), an alternative to traditional thermal processing, is considered a promising emerging technology for insuring food quality and safety. Recently, HPP is being increasingly used by the aquaculture as a post-processing technology.In this study, the effect of high pressure processing on the quality of white shrimp meat based on color, hardness, pH value, content of soluble-protein was studied. Low-field nuclear magnetic resonance (LF-NMR) technology was used to assay changes in water. Changes in protein and its crosslink was analyzed by electrophoresis technology. The differences of meat quality between HP-treated samples and heated ones were also compared. Shrimp samples were treated at different pressures (100-600 MPa) with various pressure holding time (3,5 or 10 min). The specific results are as follows:1. HP-treated samples had higher L* values but lower a* values compared to that of untreated samples. An increase in pressure resulted in an increase in whiteness (WI) and total color difference, more pronounced between 200-400 MPa. The hardness of shrimp meat presented an overall trend of increase with increasing pressures, while pH value decreased first and then increased. These results indicated that the variation of pressure holding time had less impact on the quality of shrimp meat than that of pressure.2. Analysis of the LF-NMR T2 relaxation data revealed that HP-treated sample has slower T2 relaxation time. Free water turning into bound water was also observed. These results indicated lower mobility of water due to enhanced interactions between water and protein molecules. HP induced a significant decrease (P<0.01) in protein solubility, while SDS has the power of solubilization for denatured protein. Electrophoresis analysis demonstrated that intermolecular cross-links by non-covalent bond enhanced with increasing pressures. Changes in water have a liner relationship with other qualities of shrimp meat. HP induced modification in water distribution and water phase existence, which had a compact on conformation of protein molecular. And protein denaturation will also influence physicochemical parameters, such as color and hardness.3. Temperature higher than 40℃gave the shrimp meat a brighter and less transparent appearance. Shrimp meat turned white at 50℃and the surface color turned red at 60℃.The whiteness (WI) and total color difference (ΔE) of shrimp meat showed an overall trend of increase with increasing temperature conditions. While the pH and hardness presented a change of inverted s-type. Immobilized water turned into bound water after heat treatment, indicating that the mobility of water become lower. Electrophoresis analysis demonstrated that intermolecular cross-links by non-covalent bond enhanced with increasing temperatures. Protein bands in low molecular weight area were more abundant in sample heated at 60℃. The aggregation of unfolded protein was induced by intermolecular disulfide bond at a higher temperature. 4. HPP and heat treatment caused quality changes in shrimp meat to different extent, while heat treatment resulted in a more sever impact. HPP can minimize the changes in color, water and protein denaturation, maintain pH value and texture. To obtain the same quality changes, energy consumption of high-pressure processing is much lower than that of conventional thermal processing. As an environment friendly technology, HPP has high potential for its application in post-harvest processing of shrimp meat.