Effects of low concentration of salt and sucrose on the quality of bighead carp (Aristichthys nobilis) fillets stored at 4°C

Biogenic Amines and Predictive Models of Quality of Rainbow Trout ( Oncorhynchus mykiss ) Fillets during Storage

To estimate biogenic amines and changes in quality of rainbow trout ( Oncorhynchus mykiss ) fillets at different temperatures, we determined the sensory attributes, total volatile basic nitrogen (TVB-N), total viable counts (TVC), and biogenic amines (BAs) of samples that were untreated (CK) or dry cured with 1.8% salt (T). There was no significant difference between CK and T samples in terms of TVB-N, TVC, and BAs. TVB-N and TVC increased significantly (P < 0.05) with storage time at 3, 9, and 15°C. Putrescine (PUT) and cadaverine (CAD) increased significantly (P < 0.05) at -3, 3, 9, and 15°C during storage. Histamine formed more easily when storage temperatures were higher. The kinetic models of sensory scores for TVB-N, TVC, PUT, CAD, and the sum of PUT and CAD (PUT+CAD) in T samples versus storage time and temperature were developed based on the Arrhenius equation. High regression coefficients (R² > 0.9) indicated the acceptability of the kinetic model for predicting changes in the quality of the rainbow trout fillets. Relative errors between predicted and experimental values of TVB-N, TVC, and PUT+CAD were all within 10% except for TVB-N on day 6. The prediction model based on TVB-N, TVC, and PUT+CAD can be applied to evaluate changes in quality of rainbow trout fillets from -3 to 15°C (270 to 288 K).

Bacterial diversity analysis of pork longissimus lumborum following long term ohmic cooking and water bath cooking by amplicon sequencing of 16S rRNA gene

The bacterial ecology of long term ohmic- (LTOH) and water bath- (WB) cooked pork longissimus lumborum during refrigerated storage was investigated by culture-dependent and amplicon sequencing of 16S rRNA gene. High bacterial diversity was observed in both LTOH- and WB-cooked meat, and the diversity decreased with prolonged storage, however, it was more complex in LTOH-cooked meat compared with WB treated ones. Bacillus, Pseudomonas, Enterococcus and Lactococcus were the most prevalent genera in the first two weeks and were replaced by Carnobacterium by the end of storage. Brevundimonas, Bacteroidaceae, Lactobacillaceae, uncultured Clostridiales Family_XIII, Alcaligenaceae and Micrococcales were more abundant in LTOH-cooked meat, while only Moraxellaceae were more abundant in WB-cooked samples. The different abundances may have resulted from the reaction of bacteria to different heating mechanisms. Overall, LTOH-cooked meat has a similar shelf-life with shorter processing time compared to WB treated ones.

Effect of Sugar on the Changes in Quality of Lightly Salted Grass Carp (Ctenopharyngodon idellus) Fillets under Vacuum Packaging at 4°C

To estimate the effect of a low concentration of sugar on the changes in quality of lightly salted grass carp (Ctenopharyngodon idellus) during storage under vacuum packaging at 4°C, we determined the sensory score, total viable counts, biochemical quality, and physical quality of fish fillets. Fish samples were left untreated, dry cured with 1.3% salt, or dry cured with 1.3% salt plus 1.0% sugar. Compared with untreated samples, curing treatments reduced chemical changes reflected in pH, inosine monophosphate, hypoxanthine riboside, hypoxanthine, and total volatile base nitrogen; decreased the formation of phenylethylamine, putrescine, cadaverine, and histamine; and increased the overall sensory quality of fillets (P < 0.05). Compared to dry cured with 1.3% salt samples, sugar treatment significantly inhibited (P < 0.05) the increase in pH and total volatile base nitrogen value, but it promoted microbial growth and the formation of phenylethylamine and tyramine at later stages of storage. By considering each indicator, the addition of sugar, which can improve the taste of fillets, has no significant effect on the shelf life of vacuum-packaged grass carp fillets.

Quality changes and predictive models of radial basis function neural networks for brined common carp (Cyprinus carpio) fillets during frozen storage

To investigate and predict quality of 2% brined common carp (Cyprinus carpio) fillets during frozen storage, free fatty acids (FFA), salt extractable protein (SEP), total sulfhydryl (SH) content, and Ca(2+)-ATPase activity were determined at 261 K, 253 K, and 245 K, respectively. There was a dramatic increase (P<0.05) in FFA and a sharp decrease (P<0.05) in SH at 261 K during the first 3 weeks. SEP decreased to 67.31% after 17 weeks at 245 K, whereas it took about 7 weeks and 13 weeks to decrease to the same extent at 261 K and 253 K, respectively. Ca(2+)-ATPase activity kept decreasing to 18.28% after 7 weeks at 261 K. Furthermore, radial basis function neural networks (RBFNNs) were developed to predict quality (FFA, SEP, SH, and Ca(2+)-ATPase activity) of brined carp fillets during frozen storage with relative errors all within ±5%. Thus, RBFNN is a promising method to predict quality of carp fillets during storage at 245-261 K.

Changes in Biogenic Amines and ATP-Related Compounds and Their Relation to Other Quality Changes in Common Carp (Cyprinus carpio var. Jian) Stored at 20 and 0°C

Biogenic amines, ATP-related compounds, sensory attributes, total volatile basic nitrogen, microbial flora (total viable bacteria, Pseudomonas, Aeromonas, and H2S-producing bacteria), and free amino acids were determined in common carp (Cyprinus carpio var. Jian) stored at 20 and 0°C. Pseudomonas and H2S-producing bacteria became the dominant bacteria in carp stored at 20 and 0°C, whereas Aeromonas rapidly increased only in carp stored at 0°C. Inosine monophosphate, which is responsible for flavor and freshness, increased to a maximum of 2.37 l mol/g after 12 h at 20°C and to 4.72 l mol/g after 3 days at 0°C. Putrescine and cadaverine were the dominant amines in carp and their concentrations were significantly correlated (P < 0.05) with total volatile basic nitrogen and sensory scores in all samples during the storage. Significant correlations also were observed between histamine and total volatile basic nitrogen and sensory scores only in samples stored at 20°C. Arginine decreased while putrescine increased in all samples. A significant decrease (P < 0.05) in histidine was observed after 24 h of storage, which coincided with an increase in histamine after 36 h in samples stored at 20°C. Hypoxanthine concentrations were significantly correlated with the microbial species (P < 0.01) and sensory scores (P < 0.05) and seems to be a reliable marker for quality of carp fillets stored at 20 and 0°C.

Effects of different concentrations of salt and sugar on biogenic amines and quality changes of carp (Cyprinus carpio) during chilled storage

BACKGROUND

Biogenic amines have gained a great deal of attention due to their toxic potential in humans. Carp is one of the most important freshwater fish species in China. Salt and sugar are capable of preserving food. There is a limited amount of information on the changes of biogenic amines in freshwater fish influenced by salt and sugar. This study aimed to detect the changes in biogenic amines, sensory attributes, total volatile basic nitrogen (TVB-N) and total viable counts (TVC) of carp influenced by different concentrations of salt and sugar stored at 4 °C.

RESULTS

TVB-N and TVC increased with storage time, which was in accordance with the changes of sensory scores. The eight biogenic amines were detected in fresh carp. Putrescine and cadaverine were the main biogenic amines found in carp fillets stored at 4 °C; they had a significant (P < 0.05) correlation with TVB-N.

CONCLUSION

Salt processing was found to inhibit the increase of TVB-N, TVC, putrescine and cadaverine in carp. High salt concentration had a positive effect on extending the shelf-life of the carp, compared to low salt concentration.

Quality assessment of rainbow trout (Oncorhynchus mykiss) fillets during super chilling and chilled storage

In order to evaluate the effect of super chilling (-3 °C) and chilled (3 °C) storage on the quality of rainbow trout fillets, total volatile base nitrogen (TVB-N), drip loss, pH, electric conductivity (EC), total aerobic count (TAC), K and related values, adenosine triphosphate (ATP) and related compounds, color and sensory score were determined and correlation between these indicators were analyzed. According to the comprehensive evaluation of TAC, K value and sensory score, the limit for acceptability of rainbow trout fillets was 5 days at 3 °C and 11 days at -3 °C. Additionally, the correlation coefficients between TVB-N and other freshness indicators (TAC, K value, sensory score) were relatively low. TVB-N may be inadequate for evaluating freshness changes of rainbow trout fillets compared with other indicators. Among the K and related values, H value was a better freshness indicator in rainbow trout fillets during chilled and super chilling storage for its better correlation coefficients with other freshness indicators. Super chilling storage could extend the shelf life of rainbow trout fillets by 6 days compared to chilled storage.

Effects of salt concentration on biogenic amine formation and quality changes in grass carp (Ctenopharyngodon idellus) fillets stored at 4 and 20 °C

The effects of different salt concentrations on the quality changes of grass carp (Ctenopharyngodon idella) fillets were evaluated in terms of biogenic amines, adenosine triphosphate and its related compounds, sensory attributes, total volatile basic nitrogen (TVB-N), and total viable counts during 4 and 20 °C storage. Grass carp fillets were brined in solutions of 2% NaCl (T1) and 10% NaCl (T2), and unsalted carp fillets were used as controls (CK). T1 and T2 showed higher sensory scores than CK. According to the TVB-N values, CK, T1, and T2 could maintain the freshness of carp for approximately 9, 12, and 27 days, respectively, when stored at 4 °C. The higher salt concentration had better inhibitory effect on the accumulation of some biogenic amines, such as tryptamine (TRM), 2-phenylethylamine (PHE), putrescine (PUT), and cadaverine (CAD). TVB-N of untreated grass carp fillets showed a significant (P < 0.05) correlation with TRM, PHE, PUT, and CAD during storage. PUT and CAD showed a significant (P < 0.05) correlation with TVB-N for T2 at 20 °C and T1 at 4 °C.

The polysaccharides from porphyra yezoensis suppress the denaturation of bighead carp myofibrillar protein

In this study, investigated was the effect of the porphyra yezoensis polysaccharides (PPs) on the denaturation of bighead carp (Aristichthys nobilis) myofibrillar protein (Mf) during frozen storage at -18°C for 90d. The PPs (2.5%, 5%, and 7.5%, respectively) was added to 100g of Mf. The changes in the Ca-adenylpyrophosphatase (ATPase) activity and unfrozen water content in Mf were examined to evaluate he denaturation of Mf during frozen storage. Ca-ATPase activity decreased gradually during frozen storage at -18°C upon addition of PPs. By contrast, Ca-ATPase activity in the control group dropped drastically during the first 45d of storage and then further decreased gradually for up to 90d of storage, indicating a biphasic denaturation pattern. PPs addition significantly increased sulfhydryl contents in the Mf of the treatment groups compared with that of the control group (p<0.05) during frozen storage at -18°C.

Biogenic amine and quality changes in lightly salt- and sugar-salted black carp (Mylopharyngodon piceus) fillets stored at 4°C

The effects of low salt and sugar dry-curing on the quality changes of black carp (Mylopharyngodon piceus) fillets stored at 4°C were evaluated by sensory, physical, chemical, and microbiological methods. Fish samples were left untreated (control), or were dry-cured with 1.5% salt (T1) or 1.5% salt+1.2% sugar (T2). Curing treatments reduced chemical changes reflected in HxR, Hx, pH, and total volatile base nitrogen (TVB-N); decreased cooking loss; and increased overall sensory quality of fish (p<0.05) compared to untreated samples. Significantly lower values of cadaverine and putrescine were observed in T1 and T2 compared to the control after the 2nd and 4th day, respectively (p<0.05). There were significant differences (p<0.05) between T1 and T2 for pH, TVB-N, total aerobic counts (TAC), and sensory characteristics. Sensory characteristics were significantly correlated with TAC, TVB-N, putrescine, and cadaverine in all samples (p<0.01).

Chitooligosaccharides suppress the freeze-denaturation of actomyosin in Aristichthys nobilis surimi protein

Effect of chitooligosaccharides on the denaturation of bighead carp (Aristichthys nobilis) surimi protein during frozen storage at -18 °C was investigated. The addition of 4 g of chitooligosaccharides to 100 g of the bighead carp (A. nobilis) surimi effectively inhibited the inactivation of the Ca(2+)-ATPase during frozen storage at -18 °C for 15 days compared to the control group (p<0.05), while excessive chitooligosaccharides decreased the inhibition effect. The Ca(2+)-ATPase activity of actomyosin for the treatment group decreased gradually during frozen storage at -18 °C, while that of the control dropped drastically and could not be detected after 30 days of storage. On the other hand, the addition of chitooligosaccharides also significantly increased the solubility of actomyosin compared to the control group (p<0.05) during frozen storage at -18 °C up to 120 days.