Evaluation of lactic acid bacteria, isolated from lightly preserved fish products, as starter cultures for new fish-based food products

Comparative efficiency of native and non-native starter culture in the production of bio-silage using composite waste from fish and vegetables

The efficiency of native and non-native starter cultures in the production of bio-silage using composite waste from fish and vegetables was studied. An ensilage experiment was conducted in a natural way (without starter culture) of composite waste (fish to vegetable at 80 to 20%) to isolate the native fermentative microflora. An Enterococcus faecalis strain isolated from the natural ensilage of composite waste showed higher efficiency over other commercial LAB strains generally used for ensilation. A total of 60 isolates were screened and characterized biochemically from ensilaged composite waste. Among them, 12 proteolytic and lipolytic positive isolates were identified as Enterococcus faecalis, based on a BLAST search of the 16S rRNA gene sequences. Subsequently, composite bio-silage was prepared by inoculating starter cultures with three (3) treatments T1 (native-Enterococcus faecalis), T2 (non-native-Lactobacillus acidophilus), T3 (a mixture of E. faecalis and L. acidophilus) and compared with control (composite bio-silage without starter culture). The highest non-protein nitrogen (0.78 ± 0.01 mg of N /100 g) and degree of hydrolysis (70.00 ± 0.06% of protein/100 g) was seen in the T3 sample, and the lowest (0.67 ± 0.02 mg of N/100 g and 50.40 ± 0.04% of protein/100 g) was seen in the control. At the end of ensilation, the pH fell (5.95-3.88) in conjunction with the formation of lactic acid (0.23-2.05 g of lactic acid/100 g), and the lactic acid bacteria count nearly doubled (log 5.60-10.60). The lipid peroxidation products PV (0.11-0.41 milli equivalent of oxygen/kg of fat) and TBARs (1.64-6.95 mg of malonaldehyde/kg of silage) were changed within a reasonable range in the following pattern Control > T2 > T3 > T1, which led to oxidatively stable products. The findings revealed that native starter culture E. faecalis, which can be employed as a single or in combination with non-native L. acidophilus, performed better in the bio-ensilation process. Additionally, the finished composite bio-silage can be used as a novel, protein-carbohydrate rich feed component to help manage wastes from both sectors.

Starter inoculums assisted fermentation of Puntius sp. - role of Lactiplantibacillus plantarum and Staphylococcus piscifermentans to reduce fermentation time while increasing safety

AIMS

To evaluate the role of starter inoculums to reduce total fermentation time as well as improve safety and quality of Sheedal, a fermented fish-product of India.

METHODS AND RESULTS

Lactiplantibacillus plantarum and Staphylococcus piscifermentans were isolated from the Sheedal and used as starter inoculums. To justify fermenting and probiotic properties of the starter inoculums, characteristics like proteolytic and lipolytic activity, cell-surface hydrophobicity, cell auto-aggregation and co-aggregation, antibiotic susceptibility and antimicrobial assay were performed. Changes of the count of lactic acid bacteria, staphylococci and Enterobacteriaceae were studied periodically.

CONCLUSIONS

Higher increase of α-amino nitrogen and TCA-soluble peptides during fermentation was observed in treatment which was inoculated with both L. plantarum and S. piscifermentans. Poor competitiveness of staphylococci in presence of LAB was found. Inoculation of both L. plantarum and S. piscifermentans as starter showed positive effect to reduce significantly the fermentation period from usual 4-5 months to 75 days, whereas, same was achieved after 105^th and 120^th by the use of either L. plantarum or S. piscifermentans, respectively.

SIGNIFICANCE AND IMPACT OF STUDY

Reduction of the total fermentation period is considered as an additional advantage in Sheedal technology in addition to the safety of the product as evidenced by low pH and high titratable acidity.

Evaluation of Different Techniques, including Modified Atmosphere, under Vacuum Packaging, Washing, and Latilactobacillus sakei as a Bioprotective Agent, to Increase the Shelf-Life of Fresh Gutted Sea Bass (Dicentrarchus labrax) and Sea Bream (Sparus aurata) Stored at 6 ± 2 °C

Simple Summary

A method of increasing the shelf life of gutted sea bass and sea bream packaged under vacuum and stored at 6 ± 2 °C (simulating supermarkets and consumer fridges) through the use of bioprotective starter cultures was studied. An increase in the shelf life up until 14 days was observed by washing the gutted fish in water supplemented with a culture of Latilactobacillus sakei and dextrose (0.1%). L. sakei reduced the growth of specific spoilage microorganisms and consequently reduced the production of total volatile nitrogen and oxidized compounds.

Abstract

Fish meat is very perishable because of indigenous and microbial enzymes, which determine spoilage and shelf life. The deterioration processes, which lead to an important, sequential, and progressive modification of the initial state of freshness, are fast and depend on rearing, harvesting, slaughtering, handling, and storage conditions. Usually, the shelf life of gutted fish stored at 4 ± 2 °C under vacuum packaging (VP—1.0 bar) and modified atmosphere packaging (MAP, 70% N₂, <1% O₂, 30% CO₂) is approximately 9 days. The aim of this work was to improve the shelf life and preserve the microbiological and sensory quality of farmed gutted sea bass (Dicentrarchus labrax) and sea bream (Sparus aurata) using different methods, including VP, MAP, and bioprotective culture containing Latilactobacillus sakei, until 12–14 days. Microbiological, physicochemical, and sensory quality indices were monitored to confirm the effectiveness of biopreservation on product quality during proper refrigeration (4 ± 2 °C) or abuse (6 ± 2 °C, simulating supermarkets and consumer fridges) storage period. Considering the quality indexes represented by Enterobacteriaceae, total volatile nitrogen (TVB-N), and malonaldehyde concentrations (TBARS) and the sensorial analysis, the VP samples were more acceptable than the MAP fish, even though the shelf-life of the VP and MAP fish was similar at about 12 days. The second phase of the work was to evaluate the shelf-life of both VP fish stored at 6 ± 2 °C, which simulates the normal abuse temperature of supermarkets or consumer fridges. Data confirmed the previous results and demonstrated, despite the abuse temperature of storage, a shelf-life of about 12 days. Finally, the third phase consisted of prolonging the shelf life until 14 days of storage at 6 ± 2 °C by washing the gutted sea bass and sea bream in a suspension of bioprotective starter (7 log CFU/mL) with or without the addition of dextrose (0.1%) and by VP packaging. The bioprotective culture reduced the growth of spoilage microorganisms. Consequently, the total volatile nitrogen (TVB-N) concentration in both fish species was low (<35 mg N/100 g). Nonprofessional and untrained evaluators confirmed the acceptability of the inoculated samples by sensorial analysis.

Hydrolysis of raw fish proteins extracts by Carnobacterium maltaromaticum strains isolated from Argentinean freshwater fish

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Carnobacterium and Vagococcus genera were identified from Paraná River freshwater fishes.

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Low acidifying and antilisterial Carnobacterium strains were selected.

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Proteolysis of raw fish extract by C. maltaromaticum strains was confirmed.

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C. maltaromaticum strains may be used as functional cultures to develop novel LPFP.

Lactic acid bacteria (LAB) isolated from freshwater fish (hatcheries and captures) from Paraná river (Argentina) were analyzed by using culture-dependent approaches. The species belonging to Carnobacterium (C.) divergens, C. inhibens, C. maltaromaticum, C. viridans and Vagococcus (V.) salmoninarum were identify as predominant by RAPD-PCR and 16 s rRNA gene sequencing. C. maltaromaticum (H-17, S-30, B-42 and S-44) grew in raw fish extract and slightly reduced the medium pH (5.81–5.91). These strains exhibited moderate fish sarcoplasmic protein degradation (≤ 73 %) releasing small peptides and free amino acids, being alanine, glycine, asparagine and arginine concentrations increased in a higher extent (17.84, 1.47, 1.26 and 0.47 mg/100 mL, respectively) by S-44 strain at 96 h incubation. Interestingly C. maltaromaticum H-17 was able to inhibit Listeria monocytogenes. Results suggest that these strains would contribute to the development of new safe and healthy fishery products with improved nutritional and sensory characteristics.

Technological roles of microorganisms in fish fermentation: a review

Fermentation is an important way to process and preserve fish. It not only gives the product a unique flavor and texture, but it also contributes to increased nutritional value and better functional properties. The production of fermented fish relies on naturally occurring enzymes (in the muscle or the intestinal tract) as well as microbial metabolic activity. This review focuses on the role of microorganisms on texture change, flavor formation, and biogenic amines accumulation in fermented fish. In addition, the production conditions and the major biochemical changes in fermented fish products are also introduced to help understand the factors influencing the quality of fermented fish. Moreover, prospects for further research of fermented fish are discussed.

A comparison of endogenous and microbial proteolytic activities during fast fermentation of silver carp inoculated with Lactobacillus plantarum

The study was aimed to investigate different roles of endogenous and Lactobacillus plantarum proteases during fast fermentation of silver carp. The results show that endogenous proteases could degrade both sarcoplasmic and myofibrillar proteins. In contrast, L. plantarum had low proteinase activities and could only hydrolyze sarcoplasmic peptides. This indicates that gel properties could be mainly affected by endogenous proteolysis while microbial proteolysis contributed to the production of smaller peptides and free amino acids which may be related to flavor and taste. Texture and free amino acid analyses verified these hypotheses. It shows that endogenous lysosomal proteases were the major contributors for the decrease of gel strength while L. plantarum proteolytic activities could lead to the increase of aspartic acid, glutamic acid, and alanine, which may result in umami and sweet taste; and also lead to a rise in some amino acids which were volatile compounds precursors.

Study of the microbial ecology of wild and aquacultured Tunisian fresh fish

Eighty samples of fresh fish were collected in Tunisia and analyzed for microbial load. Quality and hygienic safety of the meat and intestines of wild and aquacultured fresh fish were determined. The mesophilic aerobic plate count and populations of psychrotrophic lactic acid bacteria (LAB) and other psychrotrophic bacteria ranged from 5.67 to 7.29, 4.51 to 6, and 5.07 to 6.21 log CFU/g, respectively. For all microbiological determinations, bacterial counts were lower in meat than in the intestines of fresh fish. For all samples lower microbial populations were found in most of the wild fish than in the aquacultured fish. No isolates of the pathogenic genera Salmonella and Listeria were detected in any sample. Among the 160 strains of biopreservative psychrotrophic LAB and the 150 strains of spoilage psychrotrophic gram-negative bacteria identified by biochemical and molecular methods, Lactobacillus (six species) and Pseudomonas (six species) predominated. Lactococcus, Leuconostoc, Carnobacterium (C. piscicola and C. divergens), Aeromonas, and Photobacterium were the most common genera, and Lactococcus lactis, Lactobacillus plantarum, Pseudomonas fluorescens, and Aeromonas hydrophila were the most common species. These findings indicate that the microbiological quality of fresh fish in Tunisia can be preserved by controlling pathogenic and psychrotrophic bacteria.

Biopreservation of Sardinella longiceps and Penaeus monodon Using Protective Culture Streptococcus phocae PI 80 Isolated from Marine Shrimp Penaeus indicus

The influence of Streptococcus phocae PI80 on the shelf life of Sardinella longiceps and Penaeus monodon was investigated by measurement of microbial and chemical analysis after appraising the safety of the protective probiotic culture in wistar rat's model. The results of this safety assessment indicate that oral administration of protective culture does not demonstrate any toxicological effects. Consumption of this LAB strain had no adverse effects on animal's general health status, hematology, blood biochemistry, histology parameters, or on the incidence of bacterial translocation. The effect of Streptococcus phocae is very evident with the reduction of Listeria monocytogenes, Vibrio parahemolyticus, and coliforms. During storage, a marked decline in total volatile base and peroxide value was observed in protective culture-treated samples than the control. This strain looks promising as a protective culture for the preservation of fish products.

Stabilizing smoked salmon (Oncorhynchus gorbuscha) tissue after extraction of oil

Alaska salmon oils are rich in n-3 polyunsaturated fatty acids and are highly valued by the food and pharmaceutical industries. However, the tissue that remains after oil extraction does not have an established market. Discarded pink salmon (Oncorhynchus gorbuscha) tissues were preserved using a combination of smoke-processing and acidification with lactic acid bacteria (LAB). All samples were analyzed for moisture, protein, ash, and lipid contents. Bacterial cell counts, pH, and lactic acid concentrations were recorded as a measure of LAB viability. Neither raw nor smoked salmon were free from spoilage during 60 d of storage. Only fermented samples successfully stabilized below pH 4.7, while retaining lactic acid concentrations over 15 g/L during storage. When smoked, fermented salmon head tissues were dried, the pH of the resulting high-protein "cracker" was significantly lower than when crackers were prepared only from the smoked (but not fermented) salmon material. Both cracker varieties retained valuable polyunsaturated fatty acids. This research suggests that salmon-head tissues discarded after oil extraction represent a good source of protein and high-value fatty acids in a shelf-stable form.

PRACTICAL APPLICATION

Alaska salmon oils are rich in n-3 polyunsaturated fatty acids and are highly valued by the food and pharmaceutical industries. However, the tissue that remains after oil extraction does not have an established market. Material produced from salmon tissue discarded after oil extraction may represent a valuable resource for preparing high-protein crackers and other fish-based food products. In addition to providing a unique smoke-flavoring, the smoked, fermented fish material may also impart antioxidant factors thereby extending the shelf life of the product.

Biopreservation of refrigerated and vacuum-packed Dicentrarchus labrax by lactic acid bacteria

Two lactic acid bacteria (LAB) were selected from 100 LAB isolated from various sea products to examine their use in Dicentrarchus labrax preservation. The isolates, tentatively named strain nr 3 and 7, were identified as Lactobacillus plantarum and L. pentosus, respectively. They showed antagonistic activity against psychrotroph, pathogenic, and coliform bacteria. The antagonistic activity of strain 3 was suggested to be by bacteriocins since activity was abolished by protease treatment, while that of strain 7 was due to the effect of pH decrease caused by the produced organic acids. Their use prevented total volatile basic nitrogen contents (TVB-N) and trimethylamine (TMA) to some extent, suggesting that inoculation could extend the period of storage.

Effect of controlled lactic acid bacterial fermentation on the microbiological and chemical qualities of Moroccan sardines (Sardina pilchardus)

Lactic acid bacteria (LAB) strains were assayed for the conservation of fresh sardine "Sardina pilchardus". Lactobacillus delbrueckii subsp. delbrueckii was used for inoculation of sardine fillets in a solution of NaCl (5%, w/w) and glucose (4%, w/w) concentration in water. Microbial counts including Standard Plate Count (SPC), LAB, yeasts, coliforms, Salmonella, staphylococci and Clostridium were followed during two weeks of storage at 30 degrees C. Determinations of chemical parameters including pH, dry matter, fat, ash, total nitrogen (NT), total volatile basic nitrogen (TVBN) and trimethylamine (TMA) were carried out under the same conditions. Chemical determinations showed a net pH decrease from an initial value of 6.05 in raw sardine fillets to 4.3 after 16 days of fermentation. Increases in TMA content and TBVN were observed. Microbiological control showed that LAB counts reached a level up to 3.10(9) cfu/g after 4 days of fermentation. After two weeks, fermented fish was free of coliforms and Salmonella. The inhibition of pathogenic microflora including staphylococci and Clostridium was also observed. The results indicated that controlled LAB fermentation could be used as a successful process for biopreservation of sardines produced in huge quantities in Morocco.