Microorganisms associated with Maari, a Baobab seed fermented product

A microbiological study was carried out on Baobab fermented seeds (Maari) obtained from 4 different production sites in Burkina Faso (Mansila, Toulfé, Ouagadougou and Gorgadji).A total of 390 representative isolates comprising 251 aerobic mesophilic bacteria (AMB) and 139 lactic acid bacteria (LAB) were isolated and identified to species level using a combination of pheno- and genotypic methods including conventional morphological analysis, carbohydrate fermentation profiling, rep-PCR ((GTG)₅-fingerprinting) and 16S rRNA gene sequencing.The fermentation of Baobab seeds was initiated by the AMB identified as Bacillus subtilis (82% of AMB isolates) and Staphylococcus sciuri (18% of AMB isolates). No lactic acid bacteria were isolated at the beginning of the process. After 24 h fermentation time, Enterococcus faecium appeared in the fermenting seeds and remained until the end of the fermentation, as the predominant LAB.In Maari collected from retail outlets the AMB count ranged from 6.7 log10 CFU/g to 10 log10 CFU/g while the LAB load ranged from 4.4 log10 CFU/g to 9.9 log10 CFU/g. The AMB were identified as belonging to genus Bacillus (12 species), Staphylococcus (3 species) and one species of Aerococcus, Macrococcus, Leifsonia, Kurthia, Proteus, Acinetobacter and Globicatella, respectively. A putatively novel, previously undescribed Corynebacterium sp. was also found. E. faecium was the dominant LAB in all investigated retail samples except one sample dominated by Pediococcus acidilactici.     

Histamine formation by histamine-forming bacteria in douchi,a Chinese traditional fermented soybean product

Seven soybean and 19 black bean douchi products sold in the supermarkets in southern Taiwan were purchased and tested to determine the occurrence of histamine and histamine-forming bacteria. The levels of pH, salt content, water content, yeast and mold, and aerobic plate count (APC) in all samples ranged from 4.7 to 5.9, 4.4% to 14.0%, 6.8% to 51.6%, 3.0 to 5.1 log CFU/g, and 5.2 to 9.2 log CFU/g, respectively. None of these samples contained total coliform and Escherichia coli. Although black bean douchi products had an average histamine content of 29.0 mg/100 g, 18 of them had histamine contents greater than 5 mg/100 g, the allowable level set by the US Food and Drug Administration (FDA) for scombroid fish and/or products. In contrast, only four soybean douchi products had histamine levels greater than 5 mg/100 g. Among the black bean samples, four contained histamine at 56.3, 62.1, 80.2 and 80.8 mg/100 g, that are above the 50 mg/100 g hazard action level. Eight histamine-forming bacterial strains, capable of producing 11.7–601 ppm of histamine in trypticase soy broth (TSB) supplemented with 1% l-histidine (TSBH), were identified as Bacillus subtilis (four strains) Staphylococcus pasteuri (one strain) and Staphylocuccus capitis (three strains) by 16S rDNA sequencing with PCR amplification. S. capitis, which was previously reported to be halotolerant, was a potent histamine-former capable of producing more than 500 ppm of histamine in TSBH in the presence of 0.5–10% NaCl.     

Angiotensin I-converting enzyme inhibitory peptides in douchi,a Chinese traditional fermented soybean product

Douchi, a soybean product originating in China, produces angiotensin I-converting enzyme (ACE) inhibitors with the potential to lower blood pressure. The ACE inhibitory activities of douchi qu pure-cultured by Aspergillus Egyptiacus for 48 h, and 72 h were compared with douchi secondary-fermented for 15 d. The results showed that ACE inhibitory activities were improved following the fermentation. ACE inhibitory activities of 48 h-primary-fermented douchi qu did not change dramatically after preincubation with ACE, but increased greatly after preincubation with gastrointestinal proteases. The results suggest they were pro-drug-type or a mixture of pro-drug-type and inhibitor-type inhibitors. The ACE inhibitors in 48 h-fermented douchi qu were fractionated into four major peaks by gel filtration chromatography on Sephadex G-25. Peak 2, which had the highest activity, had only one peptide, composed of phenylalanine, isoleucine and glycine with a ratio of 1:2:5.     

Probiotic monocultures in fermented goat milk beverages – sensory quality of final product

The aim of our study was to conduct a selection of the monocultures capable of providing the most attractive sensory features of the final product. Four fermented goat's milk beverages were produced with probiotic monocultures containing Lactobacillus (Lb. acidophilus La‐5, Lb. rhamnosus K3 and Lb. plantarum O20) and Bifidobacterium (Bif. animalis subsp. lactisBB‐12). A sensory analysis and microbiological assessment of fermented goat's milk beverages were made at the beginning of the study and after 3, 7, 10 and 14 days of refrigerated storage (5 ± 1 °C). We found that samples including monocultures Lb. plantarum O20 and Bif. animalis subsp. lactisBB‐12 were differentiated from other goat's milk beverages.     

Isolation,characterisation and identification of lactic acid bacteria from bushera: a Ugandan traditional fermented beverage

One hundred and thirteen strains of lactic acid bacteria (LAB) were selected from 351 isolates from 15 samples of traditionally fermented household bushera from Uganda and also from laboratory-prepared bushera. Isolates were phenotypically characterised by their ability to ferment 49 carbohydrates using API 50 CHL kits and additional biochemical tests. Coliforms, yeasts and LAB were enumerated in bushera. The pH, volatile organic compounds and organic acids were also determined.

The LAB counts in household bushera varied between 7.1 and 9.4 log cfu ml⁻¹. The coliform counts varied between <1 and 5.2 log cfu ml⁻¹. The pH of bushera ranged from 3.7 to 4.5. Ethanol (max, 0.27%) was the major volatile organic compound while lactic acid (max, 0.52%) was identified as the dominant organic acid in household bushera.

The initial numbers of LAB and coliforms in laboratory-fermented bushera were similar; however, the LAB numbers increased faster during the first 24 h. LAB counts increased from 5.5 to 9.0 log cfu ml⁻¹ during the laboratory fermentation. Coliform counts increased from 5.9 to 7.8 log cfu ml⁻¹ at 24 h, but after 48 h, counts were less 4 log cfu ml⁻¹. Yeasts increased from 4.3 to 7.7 log cfu ml⁻¹ at 48 h, but thereafter decreased slightly. The pH declined from 7.0 to around 4.0. Lactic acid and ethanol increased from zero to 0.75% and 0.20%, respectively.

Lactic acid bacteria isolated from household bushera belonged to Lactobacillus, Streptococcus and Enterococcus genera. Tentatively, Lactobacillus isolates were identified as Lactobacillus plantarum, L. paracasei subsp. paracasei, L. fermentum, L. brevis and L. delbrueckii subsp. delbrueckii. Streptococcus thermophilus strains were also identified in household bushera. LAB isolated from bushera produced in the laboratory belonged to five genera (Lactococcus, Leuconostoc, Lactobacillus, Weissella and Enterococcus. Eight isolates were able to produce acid from starch and were identified as Lactococcus lactis subsp. lactis (four strains), Leuconostoc mesenteroides subsp. mesenteroides (one strain), Leuconostoc mesenteroides subsp. dextranicum (one strain), Weissella confusa (one strain) and L. plantarum (one strain).     

Proteolytic and lipolytic modifications during the manufacture of dry-cured lacón,a Spanish traditional meat product: Effect of some additives

The extractability of sarcoplasmic and myofibrillar proteins, the myofibrillar proteins and their degradation products, classical nitrogen fractions, free amino acids, acidity of the fat, and free fatty acids were determined throughout the manufacturing process of dry-cured lacón, a traditional dry-salted and ripened meat product made in the northwest of Spain from the foreleg of the pig, following a similar technological process to that of dry-cured ham. The effect of the use of additives (glucose, sodium nitrite, sodium nitrate, sodium ascorbate and sodium citrate) on the proteolytic and lipolytic changes was also studied.     

Volatile components of the enzyme-ripened sufu, a Chinese traditional fermented product of soy bean

In the present study, sufu, a soft cheese-like oriental fermented food, was prepared by ripening the salted-tofu cubes in Aspergillus oryzae-fermented soybean-rice koji at 37°C for 16 days (16-day sufu). Sufu was further held at room temperature for another 30 days (46-day sufu). The volatile components of the non-fermented tofu cubes and the sufu products were identified and quantified by GC and GC-MS. A total of 70 volatile compounds including 20 aldehydes, 18 alcohols, 16 esters, 5 ketones, 5 acids and 6 other compounds were identified. Sufu products contained more volatile compounds than non-fermented tofu cubes qualitatively and quantitatively. After 16-days of ripening, fatty acid, aldehyde and ester were noted to be the dominant volatile fractions. In contrast, the 46-day sufu contained ester, and alcohol as the major volatile fractions. They comprise approximately 63.9% of the total volatile components.     

Proteolytic and lipolytic starter cultures and their effect on traditional fermented sausages ripening and sensory traits

In this study, three starter formulations including Lactobacillus curvatus and Staphylococcus xylosus strains selected in vitro on the basis of their lipolytic and proteolytic activities were employed for the manufacture of traditional fermented sausages of southern Italy. Microbial population, proteolysis, lipolysis, changes in free amino acids (FAA) and free fatty acids (FFA) and development of characteristic taste and flavor of the final product were investigated. Proteolysis and lipolysis were observed in sausages inoculated with proteolytic and lipolytic S. xylosus coupled with L. curvatus, while the sausage started with only S. xylosus without lactobacilli was identical to the non-inoculated control, indicating that the proteolysis could be due to both microbial activity and endogenous proteases activated by the decrease in pH. The statistical analysis applied to the instrumental and sensory data showed that there was an effect of the starter used on the characteristics of the sausage obtained. In particular, the control samples showed very close features different from the sausages obtained by adding starter cultures. Finally, analyzing the sensory parameters the sausages ripened without starter addition and those started without the L. curvatus AVL3 showed similar features indicating an influence of the presence of the lactobacilli on the final organoleptic quality of the sausages. An appropriate choice of a combination of strains in a starter formulation is fundamental to obtain products of the expected quality.     

Lipolysis and lipid oxidation caused by Staphylococcus xylosus 135 and Saccharomyces cerevisiae 31 isolated from Suan yu,a traditional Chinese low‐salt fermented fish

The aim of this study was to investigate the lipolysis and lipid oxidation of Staphylococcus xylosus 135 and Saccharomyces cerevisiae 31 in Suan yu. Suan yu were made inoculated with and without two strains at different stages, and model systems of emulsions were also established. Lipolysis and lipid oxidation were evaluated by determining the changes in free fatty acid (FFA) content and composition, conjugated diene (CD) value and thiobarbituric acid reactive substances (TBARS) value. The total FFA of the sample without cultures increased from 476.61 mg/100 g fat to 1413.89 mg/100 g fat after 5 weeks fermentation, while those of samples with cultures declined to 258.98 and 452.89 mg/100 g fat, respectively. On the other hand, CD and TBARS values of samples with inoculation markedly increased. In the model system, higher FFA, CD and TBARS values for the samples added with CFE were observed. This study showed that Staphylococcus xylosus 135 and Saccharomyces cerevisiae 31 made a significant contribution to lipolysis and lipid oxidation during the processing of Suan yu.     

Quality,functionality, and microbiology of fermented fish: a review

Abstract

Fermentation is a traditional food preservation method and is widely used for improving food safety, shelf life, and organoleptic and nutritional attributes. Fermented fish are produced and consumed in different parts of the world and are an integral part of many food cultures. Furthermore, fermented fish are a source of interesting microbes and are an important industry in many countries. This review tries to update the types and manufacturing processes for fermented fish around the world. The emphasis is on this work related to fermented fish and their health benefits, as well as the contribution of microorganisms to their fermentation. A variety of different approaches have been used to determine and understand microbial composition and functionality. Moreover, some challenges and future research directions regarding fermented fish are also discussed in this review. Further research into fermented fish products is of crucial importance not only for the food industry but also for human health. However, extensive in vivo and toxicological studies are essential before the application of bioactive-rich fermented fish products for human health benefits.     

A newly isolated strain Pediococcus parvulus from Xuanwei ham, a traditional Chinese fermented meat product

A comparative study on technological suitability for fermented dry sausages of Pediococcus parvulus , a newly isolated strain from Xuanwei ham, a traditional Chinese fermented meat product, was carried out. One type of fermented dry sausage was produced with P. parvulus and the other without starter culture, using the same formulation and technological conditions. Thus, the evolutions of microbiological and physicochemical parameters during ripening, as well as colour, texture and sensory quality of end products, were measured and assessed. The results indicated that P. parvulus had an inhibitory effect on non-lactic acid bacteria, especially Enterobacteriaceae . It was thought that the use of P. parvulus could enhance the hygienic quality of fermented sausages, which could mainly be attributed to its acidification of fermented sausages. Differences in colour parameters, with higher value in lightness (L*) and lower in redness (a*), were also found ( P  < 0.05). The most significant differences were observed in texture, informing the influence of P. parvulus on texture profile analysis characteristics of fermented sausages ( P  < 0.05). However, the evolutions of total nitrogen, fat and ash were the same. That meant the starter had no effects on these parameters during ripening of sausages. Free amino acid analysis showed that P. parvulus might have some proteolytic activity and more intense odour detected by our sensory judges. Our panelists also gave a higher score to the sausage with starter in terms of overall acceptability, indicating their preference of this product to the control. For all these results, we concluded that the newly isolated strain P. parvulus was a good starter for the production of fermented sausages.     

Fructooligosaccharides as a fat replacer in fermented cooked sausages

Fermented cooked sausages with a 50% reduction in pork back fat and addition of 0%, 3%, 6% or 9% of fructooligosaccharides (FOS) were produced and studied during manufacturing and storage. Their production was monitored by physicochemical (pH, water activity, weight loss, proximate composition, colour and texture profiles) and microbiological analysis (aerobic mesophiles, lactic acid bacteria, and total and faecal coliforms). During storage, it was evaluated the sensory properties, stability to lipid oxidation and microbiological safety. The final fat content of the control was 27.54%. F0, F3, F6 and F9 treatments had final fat contents of 17.63%, 17.55%, 17.91% and 17.59%, respectively, representing an approximately 40% reduction in the fat content. The simple reduction in pork back fat without fat substitute adversely affected the technological and sensory properties of the fermented cooked sausages, but the addition of FOS suppressed the defects caused by the fat reduction. The content of FOS did not changed during storage, indicating that this functional prebiotic compound can be used for developing of reduced fat fermented meat products.