Non-enzymatic browning path analysis of ready-to-eat crayfish(Promcambarus clarkii)tails during thermal treatment and storage

This study was carried out to reveal the browning path of ready-to-eat(RTE)crayfish tails during thermal treatment and storage using path analysis.Maillard reactions,lipid oxidation,and phenol oxidation were evaluated in combination with free radical content and FTIR analysis,and direct path coefficients as well as determination coefficients were obtained based on these parameters,such as the absorbance at 294 nm(A294),5-hydroxymethylfurfural(5-HMF),thiobarbituric acid-reactive substances(TBARS),and total phenols(TP).The result showed that the browning of seasoned RTE crayfish tails was ascribe to the synergistic effect of Maillard reaction and lipid oxidation by the order of determination coefficient.After the crayfish hepatopancreas were removed,the content of A294,5-HMF,TBARS,and TP declined more than 30%,specifically affecting the direct pathway from lipid oxidation to Maillard reaction and alleviating the browning.However,no significant change of color was observed in the group without thirteen-spices,while TBARS and free radical content increased by at least 16.7%.The removal of hepatopancreas and the control of Maillard reaction were deemed to be a good measure for inhibiting the non-enzymatic browning of RTE crayfish tails.

Co-inoculation of Lactiplantibacillus pentosus 1 and Saccharomyces cerevisiae 31 for a salt-free fish sauce production from channel catfish (Ietalurus punetaus) bone

The study aimed to evaluate the co-inoculation of non-fish sauce strains for a fish sauce production made from Ietalurus punetaus fish bone hydrolysate (FBH) without salt addition. Individual inoculation (Lactiplantibacillus pentosus 1, LP and Saccharomyces cerevisiae 31, SC), and co-inoculation of both strains (FS) were employed, including an uninoculated control. Both strains exhibited good growth in FBH without salt addition. Compared with individual inoculation and uninoculated control, co-inoculation (FS) produced acid and amino nitrogen more quickly, as well as displaying higher sugar consumption. No significant difference was observed in trichloroacetic acid (TCA)-soluble peptides among all groups (P > 0.05). Moreover, significantly lower levels of six bitter amino acids were observed after co-fermentation (P < 0.05). In addition, more alcohols, esters and acids with pleasant notes and fewer unsaturated aldehydes with fishy note were generated after co-inoculation, in the absence of traditional fish sauce off-odor notes. The study demonstrated that the co-inoculation of non-fish sauce strains were appropriate for producing a salt-free fish sauce with better flavor.

Profound changes of mitochondria during postmortem condition used as freshness indicator in grass carp(Ctenopharyngodon idella)muscle

Flesh quality changes during postmortem condition are involved with apoptosis initiation.Therefore,flesh quality evaluation based on the alteration of apoptosis process is quite important.Mitochondria,the regulation place of apoptosis,undergo profound changes in fish muscle during postmortem.Thus,this study aimed to investigate whether mitochondrial related parameters during apoptosis process constitutes a putative early fish freshness marker.Mitochondrial profound impairments during postmortem at 4◦C for 5 days demonstrated that the structural changes[double layer membranes and cristae,volume,swelling,membrane potential(ΔΨm),MPTP opening and membrane fluidity]and dysfunctional changes[energy deficiency and disharmony of Ca2+homeostasis]were occurred during postmortem alteration for energy deficiency and the oxidation by ROS accumulation.Study also investigated energy metabolism related products,TVB-N,lipid and protein oxidation.Compared with the insignificantly increased traditional freshness indicators(except K value)at the initial stage(day 1),the most sensitive parameters based on mitochondrial impairment were[mitochondrial swelling,depolarization ofΔΨm,and membrane fluidity].Therefore,these above parameters might be considered as suitable and early indicators for freshness evaluation.

The impact of pH and acid-activated proteases on the decrease of immunological properties of parvalbumin from freshwater fish

Fermentation has been found as an effective method to decrease the hypersensitive reactions of consumers by freshwater fish,but the reason is not clear.Therefore,the aim of this study was to investigate the impact of pH and acid-activated proteases on the decrease of immunological properties of parvalbumin from freshwater fish,by the indicators of SDS-polyacrylamide gel electrophoresis,western blotting,enzyme-linked immunosorbent assay,surface hydrophobicity and circular dichroism.The results showed that black carp(Mylopharyngodon piceus)had the highest level of immunological properties reflected by quantitation,the content of linear epitopes and conformational epitopes of parvalbumin,and IgE-binding rate.Afterwards,purified parvalbumin from black carp was obtained with purity higher than 95%.Then,for acidification and enzyme models,it indicated that acid-activated proteases were the reason for the decrease of immunological properties.Ulteriorly,the mechanism on the level of protein structure was provided,which showed the decrease ofα-helix and the increase ofβ-turn and random coil,as well as the decrease of surface hydrophobicity had joint contribution for the breaking of conformational epitopes.This study could provide a novel guidance for the decrease of immunological properties of fish and promote fish processing industry further.