The effect of delayed icing on the quality of Litopenaeus vannamei was assessed by chemical, microbiological and sensory evaluation. Shrimps were divided into three lots. One lot was immediately iced and the other two lots were subjected to delayed icing after keeping in ambient conditions (30 ± 2C) for 2 and 4 h, respectively. White shrimp had a moisture content of 77.21%, protein 18.80%, ash 1.47% and fat 1.30% on wet weight basis. Total volatile basic nitrogen, trimethylamine, thiobarbituric acid and K value showed increasing trend during chilled storage. It was observed that there is a significant (P < 0.05) decrease in the hardness of shrimp meat during storage. Sensory evaluation indicated that the shelf life of white shrimp iced immediately after catch and 2 h delayed iced was approximately 9 days, whereas 4 h delayed iced sample had shortened shelf life of 6 days. PRACTICAL APPLICATIONSShrimp is one of the most traded and consumed aquatic product worldwide. Shrimps are rich in protein, containing very little fat and have significant cholesterol content. Shrimp is more prone to deterioration because of its high content of free amino acids and other soluble nonprotein nitrogenous substances that can serve as easily digestible nutrients for microbial growth. Chilled or iced preservation helps in delaying or reducing the bacterial growth, preventing browning and prolonging the shelf life of shrimp. Delayed icing of the catch at the site results in downgrading of the shrimp. The present study provides information about a baseline investigation of the shelf life and quality of Pacific white shrimp due to delayed icing. It can be useful to quantify the quality and shelf life of fresh shrimp prior to the application of preservative treatments to extend the shelf life.

The antibacterial activity of essential oils (EOs) isolated from ginger (Zingiber officinale), eucalyptus (Eucalyptus camaldulensis) and sweet orange (Citrus sinensis) was evaluated against fish spoilage and fish‐borne pathogenic bacteria by agar well diffusion and microbroth dilution method. Chemical profiles of EOs by gas chromatography–mass spectrometer revealed that zingiberene, α‐phellandrene and limonene were the major components of ginger, eucalyptus, and sweet orange EOs, respectively. Among the three EOs evaluated, ginger oil had the best antibacterial activity against all the bacteria tested. Bacillus subtilis was found as the most sensitive bacterium against ginger EO. Vibrio parahaemolyticus and Aeromonas hydrophila were the most resistant to all the EOs. Antibiotic resistant Yersinia enterocolitica was found as the most sensitive bacteria among gram‐negative bacteria tested. PRACTICAL APPLICATIONS The results of the present study reveal the scope of the plant essential oils (EOs) in the shelf life extension of fish. The fresh fish after catching need to be ice‐preserved before undergoing further processing. In addition, the preservation during the postharvest handling and transportation of fish is important, during which there are chances for microbial contamination from the food contact surfaces, containers and transport vehicles. The use of plant EOs will definitely help in reducing the level of microbial contamination, preserving the fish and extending their shelf life. They are cheaper in economical terms as well and easy to use by dip or spray treatment. The fishermen can use the plant EOs onboard to preserve the fish. The retailers and vendors can use it for the quality maintenance of fish.

BACKGROUND Microwave vacuum drying is an innovative technology for drying fruits and vegetables. However, this technology has not been well explored for drying seafood. In the present study, the effects of microwave vacuum drying (MVD), hot air drying (HAD) and sun drying (SD) on the proximate composition, texture, rehydration, color and microstructure of squid shreds were investigated. RESULTS Proximate components of the samples dried by different methods were not significantly different, but the drying time was markedly lower for the MVD technique. The rehydration rate and water absorption index followed the order MVD > HAD > SD. The extent of browning as indicated by the b* value was significantly lower in MVD samples (14.38) compared with HAD (19.47) and SD (21.94) samples. MVD resulted in the lowest values for hardness, springiness and chewiness of both dried and rehydrated squid shreds, while SD recorded the highest values for the same. Scanning electron microscopy (SEM) images of the muscle fiber indicated muscle shrinkage and more toughness in SD samples, whereas Fourier transform infrared (FTIR) spectra revealed a small extent of protein degradation in MVD samples. CONCLUSION The study revealed that higher‐quality dried squid shreds can be prepared by microwave vacuum drying in a shorter time compared with the traditional methods of sun drying and hot air drying. Hence microwave vacuum drying can be used as an energy‐efficient and time‐saving technology to make dried seafood of superior quality. © 2019 Society of Chemical Industry

In the present study, Indian mackerel was dried by microwave vacuum drying (MVD) method and compared its physico chemical quality to mackerel dried by hot air drying (HAD) method. Antioxidant effects of thyme oil (TMO) and clove leaf oils (CLO) during storage were also evaluated. Brine salted mackerel was dried in hot air oven (50-55°C) and microwave vacuum dryer (600 W and 600 Hg mm). For essential oil treatment, mackerel was dipped in 0.75% TMO and CLO for 5 min. Moisture content of MVD and HAD samples was reduced to 30-32% in 1.2 h and 12 h, respectively. Rehydration ability and water absorption index of MVD samples were significantly higher to that of HAD samples. Mackerel dried by HAD showed significantly higher salt soluble and water soluble protein nitrogen fractions than that of MVD samples. Significantly higher hardness and chewiness values were observed for HAD samples. Color and appearance of uncooked MVD sample was superior to that of HAD samples. As per the results of PV and TBARS, TMO exhibited better antioxidant effect compared to CLO. The study demonstrated that fast drying can be achieved by microwave vacuum dryer and it can produce dried fish having better sensory and textural attributes.

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