Selection of Autochthonous Strains as Starter Cultures for Fermented Fish Products

Role of Microorganisms in the Development of Quality during the Fermentation of Salted White Herring (Ilisha elongata)

Salted white herring (Ilisha elongata) is a popular fish product in the coastal region of China. The complex endogenous enzymes and microbial action determine the quality of a traditionally salted herring. In order to investigate the role of microorganisms in the quality formation of salted herring, three groups for different salting processes were established: traditional salted (TS), non-starter salted (NS), and starter culture salted (SS). The predominant microorganism in each processing group was Staphylococcus spp., as inferred by next-generation sequencing data. Different physicochemical parameters were obtained in each of the three processing groups (TCA-soluble peptide (trichloroacetic acid-soluble peptide), TVB-N (Total volatile basic nitrogen), and TBA values (thiobarbituric acid-reactive substance)). The TS group had the maximum level of total biogenic amines, while the SS group had the lowest. A strong positive correlation was found between Staphylococcus and 14 aromatic compounds, of which 5 were odor-active compounds that created fishy, grassy, fatty, and fruity flavors. Shewanella may produce trimethylamine, which is responsible for the salted herrings’ fishy, salty, and deteriorating flavor. The findings demonstrated that autochthonous strains of Staphylococcus saprophyticus M90−61 were useful in improving product quality because they adapted quickly to the high osmotic environment.

The Effects of Garlic and Red Chilli Pepper Powder on Physicochemical, Microbiological, and Sensory Properties of Cincalok

Cincalok, a traditional fermented shrimp, is prepared by mixing rebon shrimps (Acetes sp) with coarse salt and granulated sugar in a certain ratio. This research was aimed at studying the effect of adding garlic and red chilli pepper powder on the physicochemical, microbiological, and sensory properties of cincalok. Cincalok was made to be three recipes, namely, original cincalok, A, consists of 2 kg of rebon shrimp, 400 g of granulated sugar, and 100 g of coarse salt; B (A ingredients plus 20 g of red chilli pepper powder); and C (A ingredients plus 20 g of garlic powder). Sensory analysis was conducted on recipe A, and the colour was observed by the naked eye on days 0, 2, 4, 6, 8, 13, 18, 23, 28, 33, 43, 60, 90, 120, 150, and 180. According to the highest criterion score on sensory results, the panellists chose day 6 as the best fermentation for recipe A. The colour of recipe A started changing from pink to a light brown colour on the surface on day 28. Therefore, the physicochemical, microbiological, and sensory properties of each recipe were analyzed for 28 days. Overall, the water, ash, and fat content; titratable acid (TA); total volatile base nitrogen (TVBN); and amino acid nitrogen (AAN) showed insignificant differences (p > 0.05) among the recipes during 28 days of the same observation. The crude protein, pH, and free fatty acid (FFA) of recipe C were significantly different (p < 0.05) from recipes A and B. All recipes contained the total count of mesophilic anaerobic bacteria (TMABs) and the lactic acid bacteria (LABs) except Bacillus cereus, Clostridium perfringens, Staphylococcus aureus, and Enterobacteriaceae for all observation times. The highest criterion score for consumer acceptability was awarded for recipe C followed by recipes B and A. The addition of garlic and red chilli pepper powder affected the physicochemical, microbiological, and sensory properties of cincalok.

Marinated Sea Bream Fillets Enriched with Lactiplantibacillus plantarum and Bifidobacterium animalis subsp. lactis: Brine Optimization and Product Design

This study aimed to design marinated sea bream fillets, inoculated with either Lactiplantibacillus plantarum (strains 11, 68, 69) or Bifidobacterium animalis subsp. lactis DSM 10140. In the first step, the optimization of brine composition was performed through a centroid; the factors of the design were citric acid, vinegar, and salt. As a result of optimization, the optimal composition of brine was set to 0.75% citric acid, 55% vinegar, and 3% NaCl. In the second step, sea bream fillets were inoculated with L. plantarum strain 69 and B. animalis subsp. lactis, marinated and then packed in a conditioning solution (oil or diluted brine); the samples were stored at 4 °C for 21 days. The viability of the strains and sensory scores were assessed. The bacteria retained a high viability throughout storage (21 days); however, the sensory scores were at their highest level for 4 days. In particular, sensory assessment suggested a preference for a conditioning solution with oil, rather than with a diluted brine. In addition, a slightly higher preference was found for B. animalis subsp. lactis.

Use of Autochthonous Lactiplantibacillus plantarum Strains to Produce Fermented Fish Products

The present research was aimed to the optimization of the production of a fish fermented salami-like product using autochthonous Lactiplantibacillus plantarum starters. The activity was performed through two phases: (1) Optimization of fermented fish product composition by using a 2^k-p Fractional Factorial Design: the variables tested were nitrites (0–150 ppm), salt (2.5–7.5%), sucrose (0–4%), white pepper (0–0.10%), and fermentation temperature (10–30°C); (2) Product realization and evaluation of its microbiological profile [aerobic microbiota (APC), Pseudomonadaceae (PSE), Enterobacteriaceae (E), and lactic acid bacteria (LAB) populations], chemico-physical parameters (pH and a_w), and sensorial quality (odor, texture, color, and overall acceptability) during its storage at 4°C for 21 days. In the first step, the fish pulp was mixed with the appropriate amounts of ingredients, according to the experimental design; each batch was individually inoculated with the studied starter (L. plantarum 11, L. plantarum 69, and L. plantarum DSM1055) at 10⁷ cfu/g and incubated at 10, 20, or 30°C for 7 days. The lowest fermentation time (time to reach pH 4.4) was obtained with 4% sucrose, 100 ppm nitrite and a process temperature of 30°C. In the second step, salami-like were produced according to the individuated formulation and inoculated with the studied starters (10⁷ cfu/g); the fish mixture was stuffed into a natural casing and left to ferment at 30°C for 7 days. The use of the selected strains not only assured a correct fermentation but reduced the process time at only 2 days; during refrigerated storage, a good microbiological, chemico-physical and sensorial quality of the final product was recorded for at least 21 days.

Virgibacillus halodenitrificans ST-1 for fermentation of shrimp paste and hydrolysates of its protease

The nutrition and flavor of shrimp paste came from hydrolyzation by enzymes that were produced by microorganisms. The salt-tolerant strain Virgibacillus halodenitrificans ST-1 isolated from shrimp paste was studied and used in the fermentation of shrimp paste. The strain and the protease produced by ST-1 were investigated. The optimum pH of the protease was 8.0, and the reaction temperature was 30°C. The protease showed high activity in the range of pH (5.0-11.0) and NaCl concentration (1%-15%). Divalent cations such as Ba2+, Ca2+, Mg2+, Mn2+, and Si2+ could enhance the protease activity. Residual activity of protease was more than 90% when it was incubated with PMSF and H2O2. Also, the enzyme retained more than 90% of initial activity after it was incubated with organic solvents. Variety of natural proteins could be substrates of the protease. By analyzing the release rate of free amino acids, it was predicted that the cleavage sites of the protease were mainly Glu, Asp, Gly, Leu, and Lys. Moreover, the hydrolysates of the protease had antioxidant activity, especially for DPPH and superoxide anion radical scavenging. The strain ST-1 and the protease both were excellent candidates for food industries.

Discovering microbiota and volatile compounds of surströmming, the traditional Swedish sour herring

In this study, the microbiota of ready-to-eat surströmming from three Swedish producers were studied using a combined approach. The pH values of the samples ranged between 6.67 ± 0.01 and 6.98 ± 0.01, whereas their a_w values were between 0.911 ± 0.001 and 0.940 ± 0.001. The acetic acid concentration was between 0.289 ± 0.009 g/100 g and 0.556 ± 0.036 g/100 g. Very low concentrations of lactic acid were measured. Viable counting revealed the presence of mesophilic aerobes, mesophilic lactobacilli and lactococci as well as halophilic lactobacilli and lactococci, coagulase-negative staphylococci, halophilic aerobes and anaerobes. Negligible counts for Enterobacteriaceae, Pseudomonadaceae and total eumycetes were observed, whereas no sulfite-reducing anaerobes were detected. Listeria monocytogenes and Salmonella spp. were absent in all samples. Multiplex real-time PCR revealed the absence of the bont/A, bont/B, bont/E, bont/F, and 4gyrB (CP) genes, which encode botulinic toxins, in all the samples analyzed. Metagenomic sequencing revealed the presence of a core microbiota dominated by Halanaerobium praevalens, Alkalibacterium gilvum, Carnobacterium spp., Tetragenococcus halophilus, Clostridiisalibacter spp. and Porphyromonadaceae. Psychrobacter celer, Ruminococcaceae, Marinilactibacillus psychrotolerans, Streptococcus infantis and Salinivibrio costicola were detected as minor OTUs. GC-MS analysis of volatile components revealed the massive presence of trimethylamine and sulphur compounds. Moreover, 1,2,4-trithiolane, phenols, ketones, aldehydes, alcohols, esters and long chain aliphatic hydrocarbons were also detected. The data obtained allowed pro-technological bacteria, which are well-adapted to saline environments, to be discovered for the first time. Further analyses are needed to better clarify the extent of the contribution of either the microbiota or autolytic enzymes of the fish flesh in the aroma definition.