Effects of frozen storage on texture,chemical quality indices and sensory properties of crisp Nile tilapia fillets

Crisp Nile tilapia(Oreochromis niloticus)is a kind of valuable fish product with high muscle firmness and crispiness texture.However,with the change of physicochemical in crisp Nile tilapia,the frozen storage parameters and quality would be different comparing to normal Nile tilapia.Thus,the aim of this study was to analyze the changes in texture,chemical quality indices and volatile compounds of Nile tilapia fillets during frozen storage.The remaining storage time of the crisp Nile tilapia fillets could be estimated within 120 days.During frozen storage,fillets resulted in softer started at 90-day,and 36.75%,45.74%,48.81%and 20.37%reduction of hardness,springiness,gumminess and chewiness were observed at 120-day.Thiobarbituric acid reactive substances(TBARS)for frozen samples showed similar with fresh fillets within 60 days,while the TBARS was 1.97 folds higher than fresh one at 120-day.Low-field nuclear magnetic resonance(LF-NMR)indicated that the water loss of Nile tilapia fillets was significant changed at 120-day,which reduced more than 12.5%water out of weight.The volatile compound analysis showed that more free fatty acid will be detected at 120-day comparing to the fresh fillets.The combined results demonstrated that the crisp Nile tilapia fillets had the best quality before 60 days frozen storage then loss of some quality properties in longer freezing.Thus,these results identified the ideal storage strategy for the preservation of crisp Nile tilapia without affecting sensory appeal and commercial value.

Physicochemical properties of silver carp(Hypophthalmichthys molitrix)mince sausages as influenced by washing and frozen storage

Frozen storage of emulsion-type sausages may be one approach to avoid or reduce the use of sodium nitrite,which is associated with health risks.Silver carp(Hypophthalmichthys molitrix)mince(M_(0))was washed for 1(M_(1))or 3(M_(3))times and the impact of washing on the properties frozen storage(−18℃)during 4 months were determined and results were compared to those of conventional silver carp sausages(Mt).Lipid oxidation,as evidenced by changes in thiobarbituric acid reactive substances and FFAs,took place during storage in the order of M_(0)>M_(1)=M_(3)=Mt with M_(0)being highly oxidized(P≤0.05).Total volatile base nitrogen formed during storage and the ranking for the quality loss was as follows M_(0)>M_(1)>M_(3)=Mt.Washing(M_(1)=M_(3))led to less hardness(P≤0.05).Mt had better redness,while M_(1)and M_(3)led to higher expressible moisture,water release and lightness(P≤0.05).Results indicated the lower sensory and consumer-liking properties of frozen M_(1)and M_(3)sausages.Therefore,washing and frozen storage influenced silver carp mince sausages.

Biquinho pepper(Capsium chinense):Bioactive compounds,in vivo and in vitro antioxidant capacities and anti-cholesterol oxidation kinetics in fish balls during frozen storage

The present study reports bioactive constituents from biquinho pepper,such as carotenoids,capsaicinoids,and capsinoids,identified by UHPLC-MS.Biquinho pepper extract showed an antioxidant potential by DPPH(33.17±0.08%),ORAC(32.35±0.02μM TE/g),β-carotene/linoleic acid(55.80±1.30%),and FRAP(315.88±4.23μmol TE/g)assays.Additionally,in vivo antioxidant analyses demonstrated that the pepper extract(170μg/mL)decreased the damage promoted by H_(2)O_(2) in Saccharomyces cerevisiae cells.Fish balls were prepared using different concentrations of pepper(0.0%,0.5%,0.75%,1.0%)to investigate its antioxidant effect during frozen storage.Biquinho pepper effectively reduced the formation of cholesterol oxides and preserved essential fatty acids,mainly in samples containing 1.0%of pepper.Moreover,this treatment was more efficient than sodium erythorbate(p<0.05),which was used as standard.The kinetics of cholesterol oxidation was also determined,showing that both cholesterol degradation and cholesterol oxides formation fit a first-order kinetic model(R^(2)>0.8).

Effect of Glutathione and Storage Time on Rheological Properties of Per-proofed Frozen Dough

The effect of reduced glutathione (GSH) on fresh and pre-proofed frozen dough rheological properties were investigated using dynamic stress rheometry and small scale extensibility with the addition of three levels (80×10-6, 160× 10-6 and 240×10-6 GSH) and six storage times (0 and 1 day, 2, 4, 6 and 8 weeks). Three relaxation times (1, 13 and 26min) after loading the dough in the rheometer were used to determine storage (G’) and loss (G”) moduli. Correlations for G’ (r=0.678 and 0.622 at 0.05, and 10Hz, respectively) and G” (r=0.699, and 0.690 at 0.05, and 10Hz, respectively) were observed with the area under the extension curve at 26 min relaxation time. The addition of GSH to fresh dough reduced G’ (16.4% to 55.9%) and G” (13.7% to 52.2%). Freezing and frozen storage caused increase in G’ and G”. The addition of GSH reduced dough strength indicated by the reduction in maximum resistance to extension (Rmax) and the ratio of maximum resistance to extensibility (Rmax/E). The reduction in Rmax across all relaxation times ranged from 16.2% to 59.4%. An increase in dough extension (E) was observed with 240×10-6 GSH at all frozen storage and rest period times. Addition of GSH caused an increase of liquid phase (30.6% to 35.3%) in fresh dough and frozen dough (10.3% to 20.7%) after one day frozen storage. Negative correlations of water content in the solid phase with dough extensibility and area under the extensibility curve were found (r=-0.594 and-0.563, respectively, p<0.001). This suggests a loss of dough extensibility and strength as the water holding capacity of the dough components changes during frozen storage.

Quality Assessment of Frozen Solenocera crassicornis Treated with Sodium Metabisulphite by Soaking or Spraying

The present work was carried out to evaluate the safety of shrimp(Solenocera crassicornis)treated with different concentrations of sodium metabisulfite(SMB)by soaking or spraying during frozen storage.Shrimps soaked in higher concentrations of SMB showed higher sensory scores,lower total color differences,and better anti-melanosis effects than shrimps in the control and other treatment groups throughout frozen storage(−18℃).Lower total volatile basic nitrogen and thiobarbituric acid reactive substances and higher salt soluble protein contents were detected in shrimp soaked with high doses of SMB compared with other samples.In addition,lower counts of total aerobic plates and psychrotrophic bacteria were observed in shrimp treated by soaking with higher doses of SMB than those in control shrimp and shrimp treated with other methods during frozen storage(−18℃).However,the SO2 content of 5%SMB-soaked samples exceeded the maximum allowable limit of 100mgkg−1.Overall,the use of 1.5%SMB soaking to treat shrimp results in good antioxidant and antimicrobial effects and,thus,may be suggested to preserve S.crassicornis under frozen conditions.The results of this study present important guidance on the use of SMB to maintain the quality of marine-trawling shrimp from manufacturing to consumption.