| Acidic electrolyzed water ice(AEW ice) is a novel and nonthermal technology for inactivating bacteria and preserving the freshness of foods developed in food industry in recent years. AEW ice, with low pH, high oxidation reduction potential(ORP), contains some available chlorine concentration(ACC), has the advantages of tap water ice, importantly, possesses the good ability of AEW on rapidly inactivating bacteria and keeping freshness of seafood, and can be reducible to no toxic and no residual water after use and therefore to be pollution free for environment. With the wider application of AEW in food industry and constantly goes deeper of related studies, widespread attention has been found in researches of AEW ice. So far, many researchers have investigated the effects of AEW ice on keeping the freshness of food by examining some quality indices, and indicating that AEW ice has a good capability to preserve the quality and safety of food and hence to meet consumers′ demands.At present, the mechanism of AEW ice on preserving the quality of seafood is not clear, due to the related studies mainly focused on investigating the food preservation and inactivating bacteria of AEW ice. Thus, shrimp, which is a typical representative of seafood and consumed widely in China, was chosen as the experimental subject in this study. The objective of this study, compared to tap water ice(TW ice), was to ⑴ investigate the effect of AEW ice treatment on the quality and safety of shrimp, and changes in secondary structure of its muscle protein by using Fourier transform-infrared spectroscopy(FT-IR); ⑵ characterize secondary structure components of muscle protein in shrimp during acidic electrolyzed water ice storage examined by Fourier transform infrared spectroscopy; ⑶ study the effect of AEW ice treatment on protein changes in shrimp muscle, and expect to found the differential protein in shrimp between these two treatments and the protein of potential freshness markers by using proteome. Thus, this study will provide theoretical research foundation on applying AEW ice to improve quality safety of other seafood in food industry in the future. The main content of this study were summarized as follows: 1. Effect of acidic electrolyzed water ice in preserving the quality of shrimpAcidic electrolyzed water(AEW) ice has been perceived as a novel and effective technology for inactivating bacteria and preserving the freshness of foods in food industry in recent years. The objective of this study was to investigate comprehensively the effect of acidic electrolyzed water(AEW) ice in preserving the quality of shrimp(Litopenaeus vannamei) by examining the sensory, physical, chemical, and microbiological changes during storage for 8 days. The results showed that compared with traditional tap water(TW) ice, AEW ice had an obvious(p < 0.05) capability in retarding the changes of color difference and pH, and no adverse effects on the sensory quality of shrimp. And the formation of thiobarbituric acid(TBA) was limited when treated with AEW ice. Additionally, traditional plate counts and PCR-DGGE demonstrated that the bands of DGGE profile and Shannon index(H′) of bacterial diversity were greatly decreased under AEW ice treatment, indicating that AEW ice had a stronger efficacy on inhibiting the growth of bacteria on shrimp. Therefore, AEW ice can serve as a promising technology for improving the quality and shelf life of aquatic products in food industry. 2. Secondary structure components of muscle protein in shrimp during acidic electrolyzed water ice storage characterized by Fourier transform infrared spectroscopyTo reveal the preliminary mechanism of acidic electrolyzed water(AEW) ice in preserving the quality of shrimp, Fourier transform infrared spectroscopy(FT-IR) was used firstly to characterize secondary structure components of muscle protein in shrimp stored in AEW ice for 8 days. The results showed that good stability was found in all of spectra profile. Faint characteristic peak of lipids at 1745 cm-1 were appeared in all of sample, indicating that shrimp had relatively low content of lipids. The results of second derivative infrared(SD-IR) spectra indicated that intensity of absorption peak in muscle protein of shrimp was enhanced with the storage period advancing and that of AEW ice treatment showed a stronger one at about 1612 cm-1, 1618 cm-1, 1630 cm-1 and 1649 cm-1, while decreased and that of AEW ice treatment showed a lighter one at about 1667 cm-1, 1674 cm-1, 1682 cm-1, 1688 cm-1 and 1693 cm-1. Based on Gauss formula curve-fitting, AEW ice treatment showed a lower ratio of random coils/α-helices and a higher ratio of β-sheets/ β-turns when compared with tap water(TW) ice treatment. Based on above analysis, AEW ice has a potential use of inhibiting/ retarding the destruction of secondary structure of muscle protein in shrimp, and hence to facilitate the preservation of shrimp quality. 3. Proteomic analysis of acidic electrolyzed water ice in improving the quality of shrimpTo reveal the mechanism of acidic electrolyzed water(AEW) ice in preserving the quality of shrimp, proteomic analysis was used firstly to characterize muscle protein profile changes of shrimp stored in AEW ice for 8 days. The results showed that a total of 182 protein spots with abundance changes(> two-fold) in response to AEW ice were observed, and 60 of them were chose for further MALDI-TOF-TOF analysis and 52 spots were successfully abtained. The analysis of 2-DE showed that three proteins of interest, including Projectin, fructose 1, 6-biphosphate-aldolase(Ec 4.1.2.13), and myosin heavy chain type 2, had a gradually change(up- or down-regulated) under TW ice treatment with storage period increasing when compared with control at day zero. By bioinformatics analysis, AEW ice could inhibit abundant increase of some enzymes involved in energy metabolism, especially in fructose 1, 6-biphosphate-aldolase(Ec 4.1.2.13) and Triose-phosphateisomerase(Ec 5.3.1.1), and tropomyosin as well as some structural components proteins including β-Actin, and hence to possess a good ability on preserving the quality of shrimp. Moreover, these two pathway have aslo interrelations, which worked by interaction of enolase(Ec 4.2.1.11) andβ-Actin. Based on above analysis, this study can provide basic evidence to elucidate the mechanism of AEW ice on improving the quality of shrimp. |
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