Synergistic anti-oxidative and antimicrobial effects of oat phenolic compounds and ascorbate palmitoyl on fish balls during cold storage

Fermentation of Lactobacillus fermentum NB02 with feruloyl esterase production increases the phenolic compounds content and antioxidant properties of oat bran

In this study, strains producing feruloyl esterase were screened by Oxford Cup clear zones method and by evaluating the ability to decompose hydroxycinnamoyl esters. The strain was identified by 16S rDNA molecular biology. The contents of dietary fiber, reducing sugar, water-extractable arabinoxylans, phytic acid, total phenolics, total flavonoid, phenolic compounds composition, microstructure and antioxidant activity in bran before and after fermentation were studied. Eight strains producing feruloyl esterase were screened, among which strain P1 had the strongest ability to decompose hydroxycinnamoyl esters. The strain was identified and named L. fermentum NB02. Compared with unfermented bran, fermented bran exhibited higher contents of soluble dietary fiber, reducing sugar, water-extractable arabinoxylans, total phenolics, total flavonoid, and lower insoluble dietary fiber and phytic acid content. The dense surface structure of bran was destroyed, forming a porous structure. The release of phenolic compounds increased significantly. L. fermentum NB02 fermentation improved the antioxidant capacity of bran.

Food-grade silica-loaded gallic acid nanocomposites: Synthesis and mechanism for enhancing water-based biological activity

As the low water solubility of gallic acid (GA), its biological activities such as water-based antioxidant effect may be greatly reduced. Therefore, GA-loaded nanocomposites (F-SiO2@GA) with high water solubility were synthesized via solvent evaporation using food-grade silica (F-SiO2) as carriers in this work. The assessment of antioxidant capacity revealed that F-SiO2@GA exhibited considerably greater free-radical scavenging ability than free GA and the physical mixture of F-SiO2 and GA. In the photooxidation experiment of food-grade gardenia yellow pigment (GYP), F-SiO2@GA showed a notable antioxidant effect on GYP solution. Additionally, in the storage experiment on chilled whiteleg shrimp (Litopenaeus vannamei) treated with F-SiO2@GA, pH, total volatile basic nitrogen (TVBN), and thiobarbituric acid reactive substance (TBARS) values were effectively inhibited. In conclusion, the internal encapsulation of GA effectively prevented the self-aggregation phenomenon, thereby facilitating the exposure of its active phenolic hydroxyl group and significantly enhancing its water-based biological activity.

Effect of sodium alginate ice glazing on the quality of the freeze-thawed fish balls

The effect of 1.0 % (w/v) sodium alginate (SA) glazing on surface frost formation and the quality of frozen fish balls in repeated freeze-thaw (F-T) cycles was studied. The optimal glazing property of 1.0 % SA solution was manifested by high transmittance, excellent water resistance, and high ice glazing rate. After seven F-T cycles, compared with the control, the ice production, thawing loss, and total volatile base nitrogen (TVB-N) value of samples with 1.0 % ice glazing decreased by 28.30 %, 21.02 %, and 27.35 %, while the chewiness and whiteness were increased by 15.02 % and 10.40 %, respectively. Moreover, compared to the control, the microstructure of fish balls glazed with 1.0 % SA was smoother and more uniform, and the ice crystal diameter was smaller. Therefore, 1.0 % SA glazing effectively inhibits the formation of ice crystals, reducing water migration and loss while minimizing damage to the meat structure, thus enhancing the quality of meat products.

Changes in the characteristic volatile aromatic compounds in tuna cooking liquid during fermentation and deodorization by Lactobacillus plantarum RP26 and Cyberlindnera fabianii JGM9-1

Tuna cooking liquid has unpleasant aroma. In our previous studies, Cyberlindnera fabianii JGM9-1 and Lactobacillus plantarum RP26 demonstrated the ability to degrade this unpleasant aroma. However, the mechanism of microbial deodorization remains unclear. In this study, tuna cooking liquid was fermented using JGM9-1 alone, RP26 alone, and a combination of both strains. Changes in volatile aromatic compounds during fermentation were analyzed using HS-SPME-GC/MS. The unpleasant aroma of tuna cooking liquid were nine characteristic aromatic compounds associated with fishy, stinky, and greasy aromas. Furthermore, we found that the fermentation of microbes removed these unpleasant aromatic compounds and replaced them with pleasant aromatic compounds that contributed to fruity, grassy, and floral aromas. Finally, we screened 21 strong pairwise correlations between the production and consumption of characteristic volatile aromatic compounds by RP26 and JGM9-1, through HCA, VIP, OAV and Spearman's pairwise correlation analysis. These results help to clarify the metabolic mechanisms of microbial deodorization in tuna cooking liquid.

Integrated volatile compounds and non-targeted metabolomics analysis reveal the characteristic flavor formation of proteins in grouper (Epinephelus coioides) during cold storage

Microorganisms, lipids, and proteins always interact in a complex way in the fish matrix, which becomes a hindrance to evaluate the quality of the individual factors affecting them. In order to investigate the relationship between protein deterioration and volatile compounds (VOCs) in grouper during cold storage, the myofibril protein (MP) was used as a single-factor study to exclude microorganisms and lipids effects. The oxidation and degradation of MP during storage at 4 ℃ were evaluated, including MP content, total sulfhydryl content, carbonyl content, spatial structure and microstructure. Headspace-solid phase microextraction- gas chromatography-mass spectrometry (HS-SPME-GC-MS) was used to analyze the VOCs of grouper MP, and a total of 7 key VOCs were selected, including three ketones (2-nonanone, 2-undecanone and 2-tridecanone), three esters (methyl butyrate, methyl palmitate and methyl ester 9-octadecenoic acid) and one alcohol (3-methyl-1-butanol). At the same time, a non-targeted metabolomics method based on UPLC-Q-Extractive Orbitrap was used to investigate the changes in metabolites during MP storage. A total of 107 up-regulated differential metabolites and 7 down-regulated metabolites were annotated, and 6 metabolic pathways highly related to proteins were screened. Spearman correlation analysis showed that 7 key VOCs are associated with the biosynthesis and metabolism of ornithine and lysine. And a possible solution to protein deterioration in grouper was proposed, which provided a reference for improving protein quality and regulating flavor formation during cold storage of grouper at source.

Effects of various logistics packaging on the quality and microbial variation of bigeye tuna (Thunnus obesus)

Bigeye tuna (Thunnus obesus) is an economically valuable ocean fish species. It is susceptible to contamination during storage and transportation. Having proper transportation packaging and stable temperature during transportation are critical to prevent quality deterioration. However, the influence of packaging on retaining freshness in transit remains unknown. Here, the impact of different transportation packaging on the quality and microbiological variation of bigeye tuna during the logistics process was investigated by measuring physical-chemical indexes and microbial diversity. It turned out that aluminum foil paper (AFP) group had minimum temperature fluctuation, exhibited preferable water retaining capacity and color protection effect. AFP packaging could efficiently prevent TVB-N increase and microbial growth. After 40 h, the TVB-N value was 21.28 mg/100 g and microbial total plate count was 3.53 lg CFU/g, which was within the acceptable range. Temperature fluctuations and packaging materials had a major effect on the microbial community structure of bigeye tuna. Chitinophagaceae, Acinetobacter, and Knoellia were dominant in the AFP group, while Pseudomonas, Acinetobacter, and Macrococcus were dominant in the expanded polystyrene foam (EPSF) and European logistics (EUL) groups. AFP packaging could effectively slow down the growth and reproduction of Pseudomonas, restraining the growth of microorganisms and preserve the quality of bigeye tuna. This study provides insights into understanding the effects of packaging material on maintaining quality during logistics transportation.