Quality Improvement of Zhayu, a Fermented Fish Product in China: Effects of Inoculated Fermentation with Three Kinds of Lactic Acid Bacteria

Comprehensive insights into the mechanism of flavor formation in mandarin fish (Siniperca chuatsi) with inoculated fermentation

The inoculated fermentation is an effective way to shorten fermentation time and improve the flavor quality in fermented food. Therefore, this work aims to analyze the difference between traditional and inoculated fermentation, and explore the mechanism of flavor formation in mandarin fish during fermentation. Results showed that a total of 67 volatile compounds were detected, and 13 key flavor compounds were identified in fermented mandarin fish. Inoculation promotes the oxidation and hydrolysis of fatty acids, thus forming more aldehydes and alcohols. Moreover, inoculated fermentation inhibited the growth of Enterococcus, Carnobacterium and Morganella, thereby reducing indole content. In addition, inoculation increased the taste activity values of Glu, Gly and Ala, which improved umami taste and sweet taste of fermented mandarin fish. In short, the mixed inoculation shortened the fermentation time from 12d to 8d, which improved the flavor quality of fermented mandarin fish.

Regulation of the quality, flavour, and microbial community of industrially fermented split red sour soup by Lentilactobacillus buchneri and Pediococcus ethanolidurans

In order to study the changes in physicochemical properties, microbial diversity, and flavour substances during the industrial fermentation of split red sour soup (RSS) inoculated with lactic acid bacteria (LAB), two groups of samples from natural and inoculated fermentation were analyzed. The physicochemical properties in inoculated fermentation group were better than those of natural fermentation group. Compared to natural fermentation, inoculated fermentation led to rapid acidification, and the increased contents of key volatile compounds (isoamyl acetate, ethyl acetate, phenylethanol, acetic acid, etc.) in sour soup. The dominant bacterial genera in the inoculation group included Lentilactobacillus, Pediococcus, Lactobacillus and Lactiplantibacillus. The dominant bacterial genera in the natural fermentation group were Pediococcus, Lentilactobacillus, Levilactobacillus, and Weissella. The dominant fungal genera in the inoculated fermentation samples of tomato sour soup were Pichia and Hanseniaspora. The dominant genera in the remaining sour soup samples were Kazachstania. Spearman correlation analysis showed that Lentilactobacillus, Levilactobacillus, and other bacterial genera were positively correlated with phenylethanol, isoamyl acetate, and terpenoids in tomato sour soup, whereas Kazachstania, Pichia, Hanseniaspora, Candida, and other fungal spp. were positively correlated with alcohols 2-undecanol, cis-3-hexenyl acetate, etc. In chilli sour soup, most of the bacterial genera were negatively correlated with volatile flavour compounds. Acetic acid was positively correlated with Hanseniaspora and negatively correlated with Candida. This study revealed the effects of LAB fermentation on the flavour quality and microbial community of split RSS and laid the basis for the industrial production of split RSS.

Effect of glycine and Pediococcus pentosaceus R1 combined application on the physicochemical properties, oxidative stability, and taste profile of Harbin dry sausages

This study investigated the effects of the application of glycine (Gly) and Pediococcus pentosaceus R1(Pp), alone or in combination, on the physicochemical properties, oxidative stability, and taste quality of Harbin dry sausages. The results demonstrated that after nine days of fermentation, the Gly + Pp group exhibited significantly (P < 0.05) lower moisture content (19.04%), water activity (0.686), and pH (4.78) values, alongside notably (P < 0.05) higher lactic acid bacteria count (8.11 log CFU/g sausage) and redness value (17.2), compared to the other three groups (P < 0.05). In addition, the dry sausages in the Gly + Pp group exhibited the lowest peroxide value (0.34 meq/kg sausage), thiobarbituric acid reactive substances (0.46 MAD/kg sausage), and protein carbonyl content (1.26 nmol/kg protein) during fermentation, followed by the Gly group, Pp group, and control group. Electronic tongue (e-tongue) and sensory evaluations revealed that the combined treatment with P. pentosaceus R1 and Gly resulted in superior taste characteristics. Besides, partial least squares regression (PLSR) analysis illustrated that the taste qualities characterized using the e-tongue were accordant with the sensory evaluation consequences, and total free amino acids (FAAs) and organic acids contributed to the dry sausages' taste properties. In conclusion, the combined application of Gly and P. pentosaceus R1 enhanced the physicochemical properties, oxidative stability, and taste profile of Harbin dry sausages.

Red Yeast Rice and Optimal Fermentation Periods Improve the Quality of Esan Fermented Fish Sausage

Esan fermented fish sausage (EFFS) has an unappealing off-white color. The incorporation of an appropriate amount of red yeast rice (RYR) and the selection of an optimal fermentation period may yield visually appealing, high-quality sausages. This study is aimed at investigating the effects of different RYR levels (0, 0.35, and 0.7%) and fermentation periods (0, 2, 4, and 6 days) on the quality parameters of EFFS. The following parameters were examined for raw EFFS: CIE color values (L∗, a∗, and b∗), microbial analyses (total viable count, lactic acid bacteria, and yeast and mold counts), titratable acidity (TA), pH, weight loss, cooking loss, texture profile analysis (TPA), and sensory evaluation (color, odor, hand-feel texture, overall acceptability, and overall preference ranking). The quality parameters of the cooked EFFS were CIE color values and sensory evaluation (color, odor, mouthfeel, texture, flavor, overall acceptability, and overall preference ranking). The results showed that 0.35 and 0.7% RYR increased the a∗ (red/green) values of raw and cooked EFFS but decreased the L∗ (lightness) and b∗ (yellow/blue) values. These RYR levels significantly improved the sensory color, overall acceptability, and overall preference ranking of the raw and cooked EFFSs. However, no statistical differences were observed between the effects of 0.35 and 0.7% RYR. RYR levels did not affect the microbial analyses, TA, pH, weight loss, cooking loss, or TPA. Moreover, they had no effect on the odor and hand-feel texture of raw EFFS, or the odor, mouthfeel texture, or flavor of cooked EFFS. Therefore, RYR supplementation improved the color quality of the EFFSs without altering the other quality parameters, with 0.35% RYR deemed optimal. Moreover, the fermentation period significantly influenced most quality parameters, except CIE color values and sensory color perception of raw and cooked EFFSs. Most sensory parameters improved by day 2, remained unchanged until day 4, and then deteriorated on day 6.

Processing and Preservation of Aquatic Products

Aquatic products represent an important food source; they include products such as fish, shrimp, shellfish, crab, and seaweed, and provide high-quality proteins, fatty acids, minerals, and other nutritional elements [...].

Application and Effect of Pediococcus pentosaceus and Lactiplantibacillus plantarum as Starter Cultures on Bacterial Communities and Volatile Flavor Compounds of Zhayu, a Chinese Traditional Fermented Fish Product

Zhayu is a type of traditional fermented fish product in China that is made through the fermentation of salted fish with a mixture of cereals and spices. Inoculation fermentation was performed using Pediococcus pentosaceus P1, Lactiplantibacillus plantarum L1, and a mixture of two strains, which were isolated from cured fish in Hunan Province. Compared with the natural fermentation, inoculation with lactic acid bacteria (LAB) accelerated the degradation of myosin and actin in Zhayu, increased the trichloroacetic acid (TCA)-soluble peptide content by about 1.3-fold, reduced the colony counts of Enterobacteriaceae and Staphylococcus aureus by about 40%, and inhibited their lipid oxidation. In the texture profile analysis performed, higher levels of hardness and chewiness were observed in the inoculation groups. In this study, the bacterial community and volatile flavor compounds were detected through 16S high-throughput sequencing and headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS). Inoculation with L. plantarum L1 reduced around 75% abundance of Klebsiella compared with the natural fermentation group, which was positively correlated with 2,3-Butanediol, resulting in a less pungent alcohol odor in Zhayu products. The abundances of 2-pentylfuran and 2-butyl-3-methylpyrazine were increased over threefold in the L1 group, which may give Zhayu its unique flavor and aroma.

Changes of Physicochemical Characteristics and Flavor during Suanyu Fermentation with Lactiplantibacillus plantarum and Saccharomyces cerevisiae

This study investigates the changes of the physicochemical characteristics and flavor of fermented Suanyu (Chinese fermented fish) during fermentation with Lactiplantibacillus plantarum (L. plantarum) and Saccharomyces cerevisiae (S. cerevisiae). The related indicators, including pH, water activity (Aw), volatile base nitrogen (TVB-N), thiobarbituric acid (TBA), free amino acids (FAAs), microbial community, and volatile compounds were determined. L. plantarum fermentation samples (LP) and natural fermentation samples (NF) were used as controls. The pH and Aw of three groups of Suanyu samples decreased continuously through the entire fermentation process. Meanwhile, the TVB-N of three groups of samples increased gradually, while TBA first increased and then decreased. Notably, the pH, Aw, TVB-N, and TBA of MF group samples (inoculated L. plantarum and S. cerevisiae) were significantly lower than the NF group samples. In addition, both TVB-N and TBA of the MF group samples were lower than those of the LP group samples during fermentation, suggesting that combined fermentation could inhibit the growth of undesirable microorganisms more effectively. Lactobacillus were the main bacterial genus of the three group fermented samples during fermentation, and combined fermentation could promote the growth of Lactobacillus more significantly. In addition, the highest content of umami (145.16 mg/100 g), sweet amino acids (405.75 mg/100 g), and volatile compounds (especially alcohols and esters) were found in MF group samples, followed by the NF and LP group samples, indicating that combined fermentation could give Suanyu a better flavor quality. This study may provide a theoretical basis for the industrial production of fermented fish products and the improvement of fermentation technology.