Pankyamma Viji

BACKGROUND: Asiatic hard clam (Meretrix meretrix) is an underutilized bivalve resource. This study discusses dried clam powders prepared from this resource to enhance its utilization and improve nutritional security in protein‐deficient populations. Dried clam powder was prepared from Asiatic hard clam and the effects of different pre‐cooking methods (boil‐dried clam powder, BDCP; steam‐dried clam powder, SDCP; and microwave‐dried clam powder, MDCP) on nutritional (proximate composition, amino acid profiling, mineral profiling, fatty acid profiling) and physicochemical qualities were investigated.RESULTS: Different pre‐cooking methods significantly influenced the characteristics of the clam powder. The MDCP sample showed the highest concentration of amino acids, polyunsaturated fatty acids, Na, K, Ca and Mg content compared to BDCP and SDCP. The boiling process led to a loss of nutritional quality in terms of amino acids and macrominerals. The MDCP displayed the highest solubility in water (30.10%) but its oil and water absorption characteristics were the lowest among all the samples. Boil‐cooked clam powder displayed the highest oil binding (2.03 mL g⁻¹ protein) capacity. Boiling and steaming processes resulted in malondialdehyde generation compared to microwaving. Different pre‐cooking processes did not influence the colour attributes significantly, but the control sample prepared without pre‐cooking (CCP) had a significantly lower L* value (32.34), resulting in a darker product. In vitro digestibility of the clam powder varied in the order MDCP > SDCP > BDCP > CCP.CONCLUSION: The study demonstrated that nutritionally rich protein powder can be prepared from Asiatic hard clam. Based on the results, microwave pre‐cooking is considered the best pre‐cooking method to preserve the nutritional qualities of clam powder. © 2024 Society of Chemical Industry.

Gravads were prepared from Nile tilapia (Oreochromis niloticus) and evaluated its shelf life during chilled (6 degrees C) and iced (0 degrees C) storage. For standardizing the gravading process, different salt:sugar combinations of gravad mix and two steaks to gravad mixture ratio (1:0.1 and 1:0.2) were selected. Gravads prepared using 1:2 salt-sugar in the gravad mix and a ratio of 1:0.1 steaks to gravad mix was found optimum combination. Gravads prepared using the standardized combination of salt and sugar were stored at 0 degrees C and 6 degrees C and evaluated for its biochemical and sensorial changes. Total volatile base nitrogen (TVB-N) increased from 10.25 mg/100 g to 29.85 and 30.66 mg/100 g on Day 41 and Day 49 for chilled and iced samples, respectively. The extend of secondary oxidation was low in both samples, registering an increase from 0.14 mg MDA/kg sample to 0.814 and 0.851 MDA/kg sample on 41st and 49th day, respectively, for chilled and iced samples. Water soluble and salt soluble nitrogen contents were reduced to 1.82 and 5.47 mg/100 g and 1.58 and 4.72 mg/100 g by the end of 41st and 49th day, respectively, for chilled and ice stored gravads. The shelf life of gravads was determined as 41 days under chilled storage and 45 days under iced storage. Practical applications Nile tilapia is widely cultured fish species in India after the Indian major carps. It is of great interest to the farmers and demand among the consumers because of its fast growth rate and good meat quality. Value addition is an effective approach to utilize this resource cost-effectively during excessive production periods. Conversion of Nile tilapia into gravads not only increases the value but also enhances the quality and shelf life of the product. The results of the present study provide an idea of appropriate process parameters for making gravads from Nile tilapia and information on its shelf life under refrigerated storage.

Preparation of bioactive hydrolysates is an efficient approach for developing high value industrially important products from fishery waste. In this study, gelatin hydrolysates were prepared from skin and scale of sole fish (Cynoglossus arel) and evaluated for functional and antioxidant properties. Hydrolysis of extracted gelatin solution with alcalase enzyme for 2 h yielded 16.42% (weight yield) skin gelatin hydrolysates (SGH) and 8.44% scale gelatin hydrolysates (SCGH) with 23.6 and 18.57% degree of hydrolysis, respectively. Quantity of proximate components including protein, fat, ash, and moisture of the two hydrolysates did not differ significantly (p > 0.05). SCGH displayed significantly higher (p < 0.05) foaming capacity (54%) and foam stability index (42%) compared to SGH (36 and 34%, respectively). Emulsion activity index was significantly higher with SGH (112.6 m²/g), whereas emulsion stability index was higher for SCGH (15.5 min). 2,2, diphenyl 2 picryl hydrazine (DPPH) free radical scavenging activity, metal reducing power, and metal chelating ability was found to be higher with SCGH than SGH; however, the values were not significantly different with respect to metal chelating activity and reducing power.

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.