Modifying textural and functional characteristics of fish (Nemipterus japonicus) mince using high pressure technology.

Effect of high pressure in inducing textural and functional modification has been investigated in pink perch (Nemipterus japonicus) mince. Fish mince undergone pressurization at 200, 400 and 600 MPa for a holding period of 10 min and was compared against cooked mince (90 °C; 40 min). The treated mince at 400 and 600 MPa lost its natural viscosity and behaved like cooked mince through denaturation and formation of protein aggregates. Textural characterisation showed the retention of tenderness in 200 MPa treated samples, but become harder on application of higher pressures. Unlike heat gels, pressure induced gels were more smooth, white and elastic in nature. A decreased in reactive SH groups was observed in 400 and 600 MPa treated samples due to the formation of disulfide bonds. Hydrophobic concentration was higher in cooked and 600 MPa treatments whereas Ca2+-ATPase activity decreased after pressurization. On application of different pressures microbial reduction of 2-3 log cycles was achieved in the mince samples. Hence pressure treatments at lower ranges cannot alter the texture and functionality of protein and the mince can undergo processing as required. Besides extending shelf life, the treatments above 400 MPa can make irreversible effect on texture quality and protein functionality which is similar to that of cooking.

Effect of high pressure and setting condition on physico-chemical, structural and functional characteristics of transglutaminase mediated fish gels.

Application of High pressure and low temperature setting condition on microbial transglutaminase (MTGase) mediated gelation was studied against conventional cooking in pink perch mince. A high pressure of 250 MPa was given to pink perch mince samples added with and without MTGase enzyme, for a holding time of 12 min and a setting condition of 25 °C for 30 min was given prior and after the treatments. Nine random experiments (T1 to T9) were made against high pressure and cooking and analysed its textural and functional properties. Addition of MTGase and setting conditions had significant effect on the textural properties of the both samples especially in inducing the gel strength. Reduction in total and reactive sulfhydryl groups observed was due to the formation of disulfide linkages, which was found more in T6 to T9. Setting condition had significant effect on protein hydrophobicity in both pressure and heat induced gels. No significant variation in the Ca2+-ATPase enzyme activity was observed among treatments. SEM images revealed more closed and dense fibrous network in samples with enzyme (T6 to T9), due to more protein polymerisation. So MTGase enzyme along with pressure treatment enhanced the conformational stability and produce stronger networks through the formation of non sulfide bonds between proteins and setting reinforced these networks. Hence the synergistic effect of high pressure and MTGase can enhance the textural and functional properties of fish gels, when compared with the conventional cooking.

Fortification of extruded snacks with chitosan: Effects on techno functional and sensory quality.

Chitosan is a dietary fibre that possesses numerous functional, technological and physiological properties useful in improving food quality. Owing to its fat absorbing ability, chitosan is widely consumed as a health supplement in the form of tablets and capsules. With a view to enhance it consumption and availability, the current work was taken up to evaluate techno-functional quality improvement of shrimp based extruded snacks fortified with chitosan. Chitosan powder at 1, 2 and 3% (w/w) level was added to the base material (corn flour and rice flour in the ratio of 70:30 and 15% Acetes powder) for extrusion. Addition of chitosan in acetes based snacks significantly reduced expansion ratio, porosity and crispiness and increased the hardness value of the product. Chitosan addition had a significant effect (p > 0.05) on the moisture retention and total protein contents of the products as well. Thiobarbituric acid reactive substances (TBARS) value of chitosan fortified extrudate showed a significantly lower value than the control sample. A higher level of chitosan also resulted in colour reduction of the final product. The FTIR spectra of extrudate confirmed the stability of chitosan during extrusion conditions. The sensory score revealed that extrudate fortified with 1% chitosan was comparable to control sample. From this study it is concluded that 1% chitosan can be incorporated in Acetes based extruded snacks for an increased level of functionality.

Development of functional extruded snacks by utilizing paste shrimp (Acetes spp.): process optimization and quality evaluation.

BACKGROUND: Functional extruded snacks were prepared using paste shrimp powder (Acetes spp.), which is rich in protein. The process variables required for the preparation of extruded snacks was optimized using response surface methodology. Extrusion temperature (130-144 °C), level of Acetes powder (100-200 g kg-1 ) and feed moisture (140-200 g kg-1 ) were selected as design variables, and expansion ratio, porosity, hardness, crispness and thiobarbituric acid reactive substance value were taken as the response variables. RESULTS: Extrusion temperature significantly influenced all the response variables, while Acetes inclusion influenced all variables except porosity. Feed moisture content showed a significant quadratic effect on all responses and an interactive effect on expansion ratio and hardness. Shrimp powder incorporation increased the protein and mineral content of the final product. The extruded snack made with the combination of extrusion temperature 144.59 °C, feed moisture 178.5 g kg-1 and Acetes inclusion level 146.7 g kg-1 was found to be the best one based on sensory evaluation. CONCLUSION: The study suggests that use of Acetes species for the development of extruded snacks will serve as a means of utilization of Acetes as well as being a rich source of proteins for human consumption, which would otherwise remain unexploited as a by-catch. © 2017 Society of Chemical Industry.

Functionality of chitosan in batter formulations for coating of fish sticks: Effect on physicochemical quality.

Chitosan is a natural polymer having diverse applications in food industry. The present study was undertaken to evaluate chitosan as a hydrocolloid in batter composition in developing enrobed fish sticks with better functional properties and improved quality. Different concentrations of chitosan gel were made in acetic acid medium and incorporated into batter for making enrobed fish sticks. Coating parameters, fat uptake, oil reduction, chemical quality parameters, instrumental texture analysis and colour were studied. Addition of chitosan gel had a significant effect (P<0.05) on the coating pickup, adhesion degree and cooking yield of the product. Total volatile basic nitrogen, pH, lipid oxidation parameters like peroxide value and thiobarbituric acid reactive substances of par-fried fish sticks also showed significant differences. The oil reduction in par-fried samples were 36.84, 65.05, 73.83, 77.65% respectively for 0.5, 1.0, 1.5, 2.0% chitosan added samples. Addition of chitosan significantly reduced crispness, gumminess, Warner-Bratzler shear force and toughness (P<0.05) of the product. The study clearly demonstrated that the inclusion of chitosan at 1.0% in batter can improve functional and other quality aspects of enrobed products.

Optimisation of gelatin extraction from Unicorn leatherjacket (Aluterus monoceros) skin waste: response surface approach.

Physical properties of gelatin extracted from Unicorn leatherjacket (Aluterus monoceros) skin, which is generated as a waste from fish processing industries, were optimised using Response Surface Methodology (RSM). A Box-Behnken design was used to study the combined effects of three independent variables, namely phosphoric acid (H3PO4) concentration (0.15-0.25 M), extraction temperature (40-50 °C) and extraction time (4-12 h) on different responses like yield, gel strength and melting point of gelatin. The optimum conditions derived by RSM for the yield (10.58%) were 0.2 M H3PO4 for 9.01 h of extraction time and hot water extraction of 45.83 °C. The maximum achieved gel strength and melting point was 138.54 g and 22.61 °C respectively. Extraction time was found to be most influencing variable and had a positive coefficient on yield and negative coefficient on gel strength and melting point. The results indicated that Unicorn leatherjacket skins can be a source of gelatin having mild gel strength and melting point.

Optimization of process parameters for gelatin extraction from the skin of Blackspotted croaker using response surface methodology.

Utilization of waste from fish processing industry for production of value added products has attracted substantial attention. Blackspotted croaker (Protonibea diacanthus) is a marine fish having the potential of abundant supply of raw skins for production of gelatin. This study was aimed to optimize the extraction conditions for gelatin production from skin of Blackspotted croaker. Response surface methodology (RSM) was adopted by following central composite design to determine the optimal conditions of four independent variables namely concentration of NaOH (X1), soaking time (X2), extraction temperature (X3) and extraction time (X4) for three response variables namely yield, gel strength and melting point. The models obtained by RSM produced a satisfactory fit to the data with respect to gelatin extraction (for gelatin yield, R (2) = 0.867, P = 0.0003; for gel strength, R (2) = 0.837, P = 0.007; for melting point, R (2) = 0.765, P = 0.01). Based on these models, the optimum conditions to achieve the predicted maximum values were: yield of 17.21 % at X1 = 0.23 %, X2 = 46.19 min, X3 = 55.29 °C and X4 = 17.29 h; gel strength of 422.69 g at X1 = 0.22 %, X2 = 44.56 min, X3 = 59.02 °C and X4 = 15.35 h and melting point of 23.48 °C at X1 = 0.20 %, X2 = 46.68 min, X3 = 56.23 °C and X4 = 15.21 h. It can be concluded from the present study that Blackspotted croaker skin is a prospective source to produce gelatin in good yield with desirable quality attributes comparable to commercially available mammalian gelatins.

Improvement of gel strength and melting point of fish gelatin by addition of coenhancers using response surface methodology.

UNLABELLED: Fish gelatin is a potential alternative to mammalian gelatin. However, poor gel strength and low melting point limit its applications. The study was aimed at improving these properties by adding coenhancers in the range obtained from response surface methodology (RSM) by using Box-Behnken design. Three different coenhancers, MgSO4, sucrose, and transglutaminase were used as the independent variables for improving the gel strength and melting point of gelatin extracted from Tiger-toothed croaker (Otolithes ruber). Addition of coenhancers at different combinations resulted gel strength and melting point in the range of 150.5 to 240.5 g and 19.5 to 22.5 °C, respectively. The optimal concentrations of coenhancers for predicted maximum gel strength (242.8 g) obtained by RSM were 0.23 M MgSO4, 12.60% sucrose (w/v), and 5.92 mg/g transglutaminase and for predicted maximum melting point (22.57 °C), the values were 0.24 M MgSO4, 10.44% sucrose (w/v), and 5.72 mg/g transglutaminase. By addition of coenhancers at these optimal concentrations in verification experiments, the gel strength and melting point were improved from 170 to 240.89 g and 20.3 to 22.7 °C, respectively. These experimental values agreed well with the predicted values demonstrating the fitness of the models. Results from the present study clearly revealed that the addition of coenhancers at a particular combination can improve the gel strength and melting point of fish gelatin to enhance its range of applications. PRACTICAL APPLICATION: There is a growing interest in the use of fish gelatin as an alternative to mammalian gelatin. However, poor gel strength and low melting point of fish gelatin have limited its commercial applications. The gel strength and melting point of fish gelatin can be increased by incorporation of coenhancers such as magnesium sulphate, sucrose, and transglutaminase. Results of this work help to produce the fish gelatin suitable for wide range of applications in the food industry.

Oxidative stability and in vitro digestibility of fish oil-in-water emulsions containing multilayered membranes.

The oxidative stability and lipid digestibility of fish oil-in-water emulsions (d(43); 5.26-5.71 microm) laminated by primary, secondary, and/or tertiary layers of interfacial membranes have been investigated. The primary emulsion (5 and 0.5% wt % of fish oil and Citrem in acetate buffer) was produced through a membrane homogenizer. The second and tertiary emulsions were prepared by electrostatic deposition of chitosan and sodium alginate on the surfaces of the oil droplets, respectively. The lamination of biopolymers was measured by zeta potential. The lipid oxidative stability was assessed with peroxide value, thiobabituric acid reactive substances, and headspace aldehydes of the emulsions stored at 20 degrees C for 40 days. The positively charged secondary emulsions (+56.27 +/- 2.5 mV) were more stable to lipid oxidation compared to negatively charged primary (-45.13 +/- 1.7 mV) and tertiary emulsions (-24.8 +/- 1.2 mV). An in vitro digestion model was used to study the impact of different layers on the digestibility of oil droplets. Lipid digestion was decreased with multilayer coating, and chitosan coating further reduced the digestion. These findings have implications for the design of structured emulsions to achieve better oxidative stability with more controlled digestibility of lipids.