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Summary: Litopenaeus vannamei heads were autolysed at a constant temperature of 50 °C, pH 7.0 for a maximum duration of 5 h, and the antifreeze activity and physicochemical properties of the head autolysates were determined. Thermal hysteresis (TH) was used as an index for determining the antifreeze activity of the shrimp head autolysates. The highest thermal hysteresis activity was 1.82 °C which was measured in the 5 h‐shrimp head autolysate. The highest negative zeta potential value (−41.06 ± 2.08 mV) and surface hydrophobicity (295.575 ± 9.7819) were in the 5 and 1.5 h autolysate groups, respectively. Generally, <2000 Da components accounted for over 85% of the total molecular weight in all shrimp head autolysate groups. Pearson correlation analysis was used to investigate how physicochemical properties influenced the thermal hysteresis index. Although at varying degrees, the analysis confirmed that a positive correlation existed between TH activity and molecular weight, hydrophobic amino acid content, and surface hydrophobicity. A negative correlation existed between TH activity and zeta potential, and hydrophilic amino acids. The findings of our study suggest that Litopenaeus vannamei head autolysate has a potential antifreeze effect and that the physicochemical properties influence its thermal hysteresis. [ABSTRACT FROM AUTHOR]

The increasing threat posed by antibiotic-resistant pathogens has prompted a shift to the use of naturally-derived antimicrobial peptides (AMPs) in place of chemical preservatives in controlling foodborne pathogens. In this study, ten peptides were identified from salt-fermented shrimps (Penaeus vannamei) using ultra-performance liquid chromatography-mass spectrometry. One of the peptides, designated PV-Q5 (QVRNFPRGSAASPSALASPR), with most features of an AMP, was further explored and found to possess strong antibacterial activity against Vibrio parahaemolyticus and Escherichia coli, with a minimum inhibitory concentration of 31.25 μg/mL. Moreover, PV-Q5 increased bacterial cell membrane permeability and ruptured bacteria cell membranes, as revealed by transmission electron microscopy. Circular dichroism analysis showed that the conformation of PV-Q5 was a random coil in phosphate-buffered saline and α-helical in sodium dodecyl sulfate, which is conducive for interaction with bacteria cell membranes. These findings indicated that PV-Q5 could find potential use in food preservation to control foodborne pathogenic bacteria. [ABSTRACT FROM AUTHOR]

Summary: Previous studies have found that UV‐C irradiation activated endogenous acid protease (EAP) in shrimp heads. Aiming at understanding the effect of UV‐C irradiation on the activation of EAP and improving the utilisation of EAP, the effect of UV‐C irradiation on the enzymatic properties and conformation of EAP was investigated. The enzymatic properties of EAP were unaltered after UV‐C irradiation, and the optimum pH, temperature, and NaCl concentration were 3, 60°C, and 0.5 mol/L, respectively. Ca2+ and Mg2+ activated the enzyme. The molecular weight of the purified endogenous acid protease (P‐EAP) was 32 kDa. UV–Vis, FTIR, circular dichroism, and fluorescence spectroscopy indicated that the increase in enzyme activity by UV‐C irradiation was related to an increase in tryptophan and hydrogen bonding, implying that it may be the change in the spatial structure of the protein that caused the activation of the enzyme. Results revealed that UV‐C irradiation can be used to activate proteases and provide a reference for enhancing the enzymatic activity of other enzymes from shrimp heads. [ABSTRACT FROM AUTHOR]

The effect of fully deacetylated chitosan (FDCH) edible coating combined with kojic acid (KA) and clove essential oil (CEO) as natural preservatives was investigated on the shelf-life of white prawn shrimp (Litopenaeus vannamei) during 15 days at cold storage. The results indicated that FDCH 1 :KA 0.25 :CEO 0.25 coating significantly inhibited the increase in total aerobic plate count, total volatile basic nitrogen content and pH of shrimp in comparison with the control. Moreover, compared with the control, the changes of total color difference (ΔE values) and melanosis were significantly retarded, and the texture parameters and sensory scores were significantly improved in shrimp treated by FDCH 1 :KA 0.25 :CEO 0.25, suggesting that there is a synergistic effect between FDCH, KA, and CEO. In addition, a significant (P < 0.05) reduction in weight loss was observed for coated shrimp during the storage. The results suggested that FDCH 1 :KA 0.25 :CEO 0.25 coating may be promising to be used as active packaging for extending the shelf life, and incorporation of KA and CEO may enhance the efficacy of the coating. [ABSTRACT FROM AUTHOR]

Pigment-binding proteins play important roles in crustacean shell colour change. In this study, a red colour-related pigment-binding protein, designated LvPBP75, was purified from the shell of Litopenaeus vannamei . HPLC and PAGE analysis showed that LvPBP75 was a homogeneous monomer with molecular mass of 75 kDa. Peptide mass fingerprint analysis revealed that LvPBP75 belonged to hemocyanin, and the released pigment from heated LvPBP75 showed a λ max at 481 nm in acetone. The significant red-colour change temperatures were detected at 30 and 80 °C, respectively. Based on the determined amino acid fragments, a full-length cDNA of LvPBP75 was cloned and sequenced. The ORF encodes a protein of 662 amino acids having 80% identity with penaeidae hemocyanin. These results strongly suggest a novel function of hemocyanin, namely binding with pigment, and its involvement in L. vannamei shell colour change. [ABSTRACT FROM AUTHOR]

Abstract: Microbial inactivation of Litopenaeus vannamei by dense phase carbon dioxide (DPCD) treatment was investigated and neural network was used to optimize the process parameters of microbial inactivation. The results showed that DPCD treatment had a remarkable bactericidal effect on microorganism of shrimp. A 3×5×2 three-layer neural network model was established. According to the neural network model, the inactivation effect was enhanced with pressure, temperature and exposure time increasing and temperature was the most important factor affecting microbial inactivation of shrimp. Cooked appearance of shrimp by DPCD treatment was observed and seemed to be more positively acceptable by Chinese diet custom. Therefore, color change of shrimp by DPCD treatment could have a positive effect on quality attributes. Moderate temperature 55°C with 15MPa for 26min treatment time achieved a 3.5-log reduction of total aerobic plate counts (TPC). The parameters combination might be appropriate for shrimp process by DPCD. [Copyright &y& Elsevier]

Abstract: The inactivation of polyphenol oxidase (PPO) from Pacific white shrimp exposed to dense phase carbon dioxide (DPCD) treatment was investigated. PPO activity showed a dramatic loss at 4–25MPa and 37°C. At the lower pressure (4–15MPa), the experimental data of inactivation followed the first-order reaction kinetic model, the pressure sensitivity (Z P ) of the kinetic parameters was 49.02MPa and the activation volume (△ V ≠) was −120.88cm3/mol. At the higher pressure (20 and 25MPa), the experimental data of inactivation followed the biexponential kinetic model. The kinetic rate constant k F and k S of fast and stable fractions were 2.45 and 0.08min− 1, respectively. The decimal reduction time D F and D S were 0.94 and 29.43min at 25MPa and 37°C, respectively. After DPCD treatment, the loss activity of PPO had no restoration storing for 6days at 4°C. The results of SDS-PAGE and activity staining also showed that DPCD treatment had the obvious inhibitory effect on PPO from Pacific white shrimp. The PPO activity in vivo was easier to be inactivated than that in crude PPO extracts under the same DPCD treatment conditions. Industrial relevance: There is a growing interest in non-thermal pasteurization methods, which could retain food''s freshlike physical, nutritional, and sensory qualities. Pacific white shrimp accounts for 90% of the global aquaculture shrimp production, they are becoming increasingly popular. However, enzymatic browning of shrimp has been of great concern to food scientists and food processors. Dense phase carbon dioxide (DPCD) may be an adequate tool to obtain high quality since PPO activity could not be inactivated totally by high pressure under 400MPa yet. The present work deals with the inactivation of PPO from Pacific white shrimp exposed to DPCD treatment in order to explore the feasibility of shrimp by DPCD process. [Copyright &y& Elsevier]