Gelling properties and microstructure of the silver carp surimi treated with pomegranate (Punica granatum L.) peel extract.

Effects of ethanolic extracts of pomegranate peel (PPE) on the gelling and textural characteristics of silver carp surimi gel was investigated. The peels extracted with 100% ethanol exhibited highest total phenolics, tannin and flavonoid contents. The change of the gelling properties of surimi was explained using infrared spectroscopy, chemical interactions, and scanning electronic microscopy images. Greater number of hydrogen bonds and hydrophobic interactions were found in surimi gel fortified with 0.45% PPE. Amongst all the concentrations of PPE, 0.45% level exhibited the lowest sulfhydryl and primary amino groups and this was concurrent with the highest gel strength. The FT-IR analysis showed a gradual reduction of intensity of the amide I band with the increase of PPE concentration, and also shifting to lower value from control to surimi with PPE 0.90%. Absorption bands like C-N stretching from amide II and N-H deformation from amide III were also detected. The SEM images showed that surimi with 0.45% PPE had most ordered, finest and denser gel network, and was closely integrated with higher breaking force, hardness, and WHC. This study showed the potential of functional components of fruit wastes for improving gelling properties of surimi with additional health benefits for the consumers.

Influence of the extent of enzymatic hydrolysis on the functional properties of protein hydrolysates from visceral waste of Labeo rohita.

The study aimed to evaluate the extent of hydrolysis on the functional properties of fish protein hydrolysates from fish wastes. Fish protein hydrolysate (FPH) was prepared from the visceral waste of Rohu (Labeo rohita) using Alcalase®. Independent variables of the hydrolysis conditions, namely, time, temperature and enzyme-substrate ratio were optimized through response surface methodology using a completely randomized factorial design. Functional properties of FPH, such as antioxidant activity, metal chelating activity, emulsifying and foaming capacity were studied. Pre-heating of the raw viscera resulted 83% reduction of lipid content in the FPH. The DH was found to be significantly influenced by the hydrolysis conditions studied. The gel electrophoretic study showed that FPH contained peptides in the range of < 10-25 kDa. Optimum degree of hydrolysis (DH) was obtained as 34.7% at 87.5 min, 48.64 °C and enzyme concentration of 0.99%. The results demonstrated that the antioxidant and metal chelating properties of FPH increased with the increase of DH. The surface active properties like emulsifying and foaming capacity were found to be decreased with the increased levels of hydrolysis. These results suggest that hydrolysates from visceral waste of Rohu could find potential use as supplement in animal feed.

Chemical and microbial properties of shidal, a traditional fermented fish of Northeast India.

Like Southeast Asian countries fermented fish is a well known strategy of food preservation in the Northeast region of India. Shidals are mostly preferred salt-free fermented fish product amongst all. Chemical and microbial composition, antioxidative potential, fatty acid profile and proteins profile in gel electrophoresis of shidals were studied. pH and total titratable acidity (TTA) have been found as 5.86 ± 0.11, 0.115 ± 0.01 and 6.62 ± 0.07, 0.092 ± 0.01 in punti and phasa shidal respectively. DPPH (·) radical scavenging activity of punti and phasa shidal was determined as 80.15 ± 5.67 and 68.30 ± 3.22 respectively. Presence of eicosapentaenoic, docosahexaenoic, arachidonic, linolenic and linoleic acid indicate the nutritional significance of shidal. However, the result showed that punti shidal was rich in omega-3 but poor in omega-6 fatty acid, whereas, reverse was observed in respect of phasa shidal. Poly acrylamide gel electrophoretic study of protein revealed disappearance of myosin head chain (MHC) in the dry puntius fish (raw material of shidal). Proteins or peptides with low molecular weight between 45 and 29 kDa and between 45 and 66 kDa were noticed in both the shidals and indicative of intensive protein degradation during fermentation. Therefore, fermented fish product, shidal could be used as a potential source of nutrients and natural antioxidants.

Gel properties of sutchi catfish (Pangasius hypophthalmus) surimi as affected by selected washing process and number of washing cycles.

The gel properties of sutchi catfish surimi prepared by conventional washing and alkaline-saline washing method were studied for four washing cycles. Decrease (p < 0.05) in myoglobin content was found in alkaline washing process compared to conventional washing at each washing cycle. The highest hardness, breaking force and deformation was observed in gels prepared from alkaline-saline washing method. Whiteness in conventional washed surimi gels increased non-significantly (p < 0.05) compared to alkaline-saline-washed surimi gels. Protein bands on Sodium dodecyl sulfate polyacrylamide gel electrophoresis indicated that the protein extractability was more in alkaline-saline washing and disappearance of bands in conventional washing method was observed between 116 and 45 kDa indicating less yield of protein.

Effect of garlic extract on physical, oxidative and microbial changes during refrigerated storage of restructured product from Thai pangas (pangasianodon hypophthalmus) surimi.

The effect of garlic's aqueous extract (GAE) during refrigerated storage of the restructured products from Pangasius (Pangasianodon hypophthalmus) was evaluated. Protein and lipid oxidation, protein pattern on SDS-PAGE, TPC as well as WHC, gelling properties, texture profiles and whiteness of the surimi gel was evaluated periodically during a refrigerated storage period of 20 days. Increase of water holding capacity in GAE added gels indicated stronger protein network formation, whereas, decrease of protein solubility suggested formation of protein aggregates during gelation process. Lipid oxidation decreased in treated samples but the rate of increase varied, depending upon the concentration of GAE. Protein carbonyl content increased during storage, but slow increase in treated samples. Gel strength in treated samples increased and accompanied by thickening of myofibrillar head chain. Hardness, adhesiveness and gumminess parameters affected most due to addition of GAE. Sensory analysis revealed that the RP with 1 % GAE preferred most and control was acceptable upto 12 days.

Biochemical and microbial characterization of Ngari and Hentaak - traditional fermented fish products of India.

Ngari and hentaak are the two most preferred traditional salt-free fermented fish products of North-Eastern (NE) states of India. Chemical and microbial composition, antioxidative potential, fatty acid profile and electrophoretic pattern of protein in ngari and hentaak were studied. pH and total titratable acidity (TTA) of the products justified their stability at ambient temperature. Both ngari and hentaak showed higher contents of calcium (362.79 ± 26.89, 472.11 ± 62.7); sodium (199.66 ± 24.92, 94.0 ± 12.78); potassium (58.20 ± 7.36, 75.74 ± 6.62) and magnesium (16.056 ± 3.89, 21.125 ± 3.78) respectively. Iron, copper and zinc were found in lesser amount. DPPH (·) radical scavenging activity was close to 87 % in both the products and the ferric chloride reducing power assay was dose dependent in both the products. Both omega-3 and omega-6 fatty acids were found in ngari; whereas, only omega-3 fatty acids were observed in hentaak. Linoleic acid (11.68 %) and arachidonic acid (0.65 %) were the n-6 PUFA in ngari; while, in hentaak, it was only arachidonic acid (8.54 %). Apart from essential fatty acids, essential amino acids were also found in considerable quantity in both the products. Micrococcus sp. and Staphylococcus sp. were found to be the dominant bacterial genus in both the products; while Ngari also had lactic acid bacteria group. The nutritional properties afforded by these products justify their preference by the population.

Optimization of process conditions for Rohu fish in curry medium in retortable pouches using instrumental and sensory characteristics.

'Kalia', a popular preparation of Rohu fish, packed in four-layered laminated retort pouch was processed in a steam/air mixture over-pressure retort at 121.1 °C to three different F 0 values of 7, 8 and 9 min. Time-temperature data were collected during heat processing using an Ellab Sterilization Monitoring System. Texture profile such as hardness, springiness, gumminess and chewiness decreased as the F 0 value increased. The L* values decreased whereas a* and b* values increased with increasing F 0 value. Based on the commercial sterility, sensory evaluation, colour and texture profile analysis, F 0 value of 8 min and cook value of 66 min, with a total process time of 41.7 min at 121.1 °C was found satisfactory for the preparation of Rohu fish curry (Kalia) in retort pouches.

Optimum extrusion-cooking conditions for improving physical properties of fish-cereal based snacks by response surface methodology.

To establish the effect of barrel temperature, screw speed, total moisture and fish flour content on the expansion ratio and bulk density of the fish based extrudates, response surface methodology was adopted in this study. The experiments were optimized using five-levels, four factors central composite design. Analysis of Variance was carried to study the effects of main factors and interaction effects of various factors and regression analysis was carried out to explain the variability. The fitting was done to a second order model with the coded variables for each response. The response surface plots were developed as a function of two independent variables while keeping the other two independent variables at optimal values. Based on the ANOVA, the fitted model confirmed the model fitness for both the dependent variables. Organoleptically highest score was obtained with the combination of temperature-110(0) C, screw speed-480 rpm, moisture-18 % and fish flour-20 %.