Effects of inoculating Lactobacillus sakei starter cultures on the microbiological quality and nitrite depletion of Chinese fermented sausages

In order to improving the food safety of Chinese fermented sausages, Lactobacillus sakei as starter cultures was inoculated into sausages and effects on qualities of sausages were studied. The results clearly demonstrated that due to L. sakei inoculation, lactic acid bacteria rapidly dominated the total of microflora and the growth of food-borne pathogens, such as Escherichia coli and Enterobacteriaceae, was completely inhibited during sausages fermentation. The pH of sausages fermented by L. sakei significantly decreased from6.31 at to 4.52, whereas that of spontaneous fermentation dropped from 6.41 to 5.42. Furthermore, the nitrite content of sausages fermented by L. sakei dropped rapidly from 100 ppm to 9.6 ppm. Accordingly, for spontaneous fermentation, the nitrite content dropped slowly from 100 ppm to 32.1 ppm. After sensory evaluation, sausages fermented by L. sakei was more likely accepted and enjoyed by consumers. L. sakei inoculation was beneficial for microbiological quality against the growth of food-borne pathogens and contributed to nitrite depletion as well as to improving sensorial characteristics.     

Effect of the use of selected starter cultures on some quality,safety and sensorial properties of Dacia sausage,a traditional Romanian dry-sausage variety

The effect of selected starter cultures (Lactobacillus sakei CECT5764 + Staphylococcus equorum SA25 or L. sakei CECT5764 + S. equorum SA25 + Lactobacillus acidophilus CECT903) on some quality, safety and sensorial characteristics of Dacia sausage, a Romanian traditional variety, was investigated. Physico-chemical parameters, microbial counts and biogenic amines during manufacture as well as the sensorial characteristics of the final products were determined both in control and in inoculated sausages.The use of starter cultures significantly (P <0.05) increased he counts of LAB and Micrococcaceae + Staphylococcaceae, and provoked an earlier drop of the pH values and the fall, even the disappearance, of the Enterobacteriaceae. The inoculated batches showed significantly (P < 0.05) lower contents of tyramine, putrescine and cadaverine and of total biogenic amines, and they received higher scores for overall acceptability when they were sensory analyzed.Results obtained in this work indicated that starter culture consisting of L. sakei CECT5764 + S. equorum SA25 + L. acidophilus CECT903 was the best culture for this type of sausage.     

Effect of inoculation of selected Staphylococcus xylosus and Lactobacillus plantarum strains on biochemical,microbiological and textural characteristics of a Tunisian dry fermented sausage

In this study, a selected starter culture of Lactobacillus plantarum and Staphylococcus xylosus was used for the manufacture of a traditional Tunisian dry fermented sausage. Changes of microbiological, biochemical, sensorial and textural characteristics during the ripening of sausages were investigated.Counts of lactic acid bacteria and staphylococci were significantly higher in inoculated sausages than in control ones. Moreover, the acidifying activity of the selective L. plantarum strains improved the hygienic quality of fermented sausages by reducing counts of Enterobacteriaceae. Both a significant decrease in pH and a significant increase in nitrite contents were observed in inoculated sausages compared to control ones. The loss of moisture during the ripening of sausages was not affected by the use of starters. Proteolysis and lipolysis were observed both in control and in inoculated sausages; however, these activities during ripening could be due to the activity of starter culture enzymes or the activity of meat endogenous enzymes. The Factorial Discriminative Analyze (FDA) of sensorial parameters (aroma, color, taste and firmness) discriminate clearly inoculated sausages from non-inoculated ones. In fact, inoculated sausages showed a more intensive red color, related to the production of nitrosomyoglobin pigment, and an acid flavor. Finally, textural parameters of sausages were not affected by the use of the selective starters.     

Anti-listeria activity of Pediococcus pentosaceus BCC 3772 and application as starter culture for Nham, a traditional fermented pork sausage

Lactic acid bacteria forming bacteriocin active against Listeria monocytogenes were screened for potential use in controlling growth of L. monocytogenes in Nham, a Thai traditional fermented pork sausage. Based on the spot-on-lawn assay, Pediococcus pentosaceus BCC 3772 was found to produce the highest anti-listeria activity. Through a series of chromatographic techniques, Edman N-terminal sequencing and mass spectrometry, this anti-listeria compound showed a complete homology to pediocin PA-1/AcH. Inoculation of P. pentosaceus BCC 3772 in Nham caused a significant decrease of 3.2 log in population of spiked L. monocytogenes within 18-24 h of fermentation, in comparison with the initial count with no significant changes in sensory properties and consumer acceptability on the overall characteristics of the final fermented Nham products. These results indicate that the P. pentosaceus BCC 3772 should be useful as a functional starter culture for control of L. monocytogenes without compromising the unique quality of Nham.     

Effect of commercial starter cultures on physicochemical characteristics,microbial counts and free fatty acid composition of dry-cured foal sausage

The need for high-quality safe products has resulted in the use of starter cultures for the production of dry-cured sausages. The aim of this work was to evaluate the effect of commercial starter cultures on the physicochemical properties, microbiological counts and free fatty acid composition during the ripening of dry fermented foal sausages. Microbial counts revealed that, although initial counts of Enterobacteriaceae were similar in the four batches (3.48 log CFU/g), this microbial group exhibited a strong decrease during the ripening of inoculated sausages, and reached values below 1 log CFU/g in the final product, whereas the counts of Enterobacteriaceae in the control sausages were 2.41 log CFU/g at the end of the ripening. In general, physicochemical parameters were not affected by the use of starter cultures, but by the ripening time, with the exception of pH values, since the inoculation of starter cultures resulted in a stronger acidification during the first two weeks of production, with pH values below 5 in inoculated batches. Finally, statistical analysis revealed that free fatty acid (FFA) profile was not significantly affected by starter cultures and it might therefore be considered that the major release of FFA was probably due to endogenous lipases. In conclusion, it seems that the inclusion of starter cultures contributes to improve the hygienic quality of foal sausages without significant effect on lipolysis, texture and appearance.     

General patterns of background microbiota and selected bacterial pathogens during production of fermented sausages in Serbia

The presence of Salmonella spp. or Escherichia coli O157 and background microbiota, pH and a_w were determined in raw fermented sausages produced from pork or beef and without lactic acid bacteria starters. The investigation was conducted at five meat processing plants, and the sampling was done at five steps of the production process at each plant. In meat trimmings, total viable count (TVC) ranged around 6 log CFU/g and around 5–6 log CFU/g in the pork and the beef sausages, respectively. Enterobacteriaceae count (EBC) ranged in the vicinity of 3–4 log CFU/g, whilst E. coli count (ECC) ranges were comparably lower (by 1–2 logs). During chopping of both the pork and the beef trimmings, the levels of TVC, EBC and ECC increased by 1–1.5 logs. After the additives and the spices were added, background microbiota tended to slightly decrease, generally more noticeably in pork sausages and with ECC. During the fermentation-drying stage, in both pork and beef sausages, initial TVC levels (6–7 log CFU/g) increased by the mid-process (by approximately 1.5–2 logs) and remained at those levels in finished products. During the same period, lactic acid bacteria (LAB) increased from initial levels of 5.5–6 log CFU/g to around 7–8 log CFU/g in pork and around 8–9 log CFU/g in beef sausages, and became the predominant microbial group. Salmonella spp. was found in the first three stages of the production process (trimmings, trimmings chopping, mixing with additives/spices), in two of three meat processing plants, but not at later stages of the production process. E. coli O157 was found only in one sample of chopped trimmings in one meat processing plant. The background microbiota patterns and levels were, generally, similar to those commonly reported for raw fermented sausages in other published studies. The initial presence of foodborne pathogens in raw fermented sausage production may be considered as a potential meat safety risk, because in the case of high initial pathogen counts, their total elimination cannot be assumed.     

Lactobacillus sakei 1 and its bacteriocin influence adhesion of Listeria monocytogenes on stainless steel surface

Listeria monocytogenes is of particular concern for the food industry due to its psychrotolerant and ubiquitous nature. In this work, the ability of L. monocytogenes culturable cells to adhere to stainless steel coupons was studied in co-culture with the bacteriocin-producing food isolate Lactobacillus sakei 1 as well as in the presence of the cell-free neutralized supernatant of L. sakei 1 (CFSN-S1) containing sakacin 1. Results were compared with counts obtained using a non bacteriocin-producing strain (L. sakei ATCC 15521) and its bacteriocin free supernatant (CFSN-SA). Culturable adherent L. monocytogenes and lactobacilli cells were enumerated respectively on PALCAM and MRS agars at 3-h intervals for up to 12 h and after 24 and 48 h of incubation. Bacteriocin activity was evaluated by critical dilution method. After 6 h of incubation, the number of adhered L. monocytogenes cells in pure culture increased from 3.8 to 5.3 log CFU/cm² (48h). Co-culture with L. sakei 1 decreased the number of adhered L. monocytogenes cells (P < 0.001) during all sampling times with counts lower than 3.0 log CFU/cm². The CFNS-S1 also led to a significant and similar reduction in culturable adhered L. monocytogenes counts for up to 24 h of incubation, however after 48 h of incubation, re-growth of L. monocytogenes number of adhered cells was observed, likely due to lack of competition for nutrients. L. sakei ATCC 15521 or its supernatant (CFNS-SA) did not reduce the number of adhered L. monocytogenes cells on stainless steel surface and from 6 h of incubation, listerial counts were between 4.3 and 4.5 log CFU/cm². These results indicate that L. sakei 1 and its bacteriocin sakacin 1 may be useful to inhibit early stages of L. monocytogenes adherence to abiotic surface.     

Pathogen reductions associated with traditional processing of landjäger

To determine if traditional processing would reduce Escherichia coli O157:H7 (EC), Listeria monocytogenes (LM), and Salmonella spp. (S) in landjäger, beef and pork trim (95% lean) and pork fat was experimentally-inoculated to obtain a pathogen population of ca. 8 log₁₀ CFU/g. The trim was spray-treated with 4.5% lactic acid (30 min, 25 °C), ground, mixed with seasonings, and a starter culture added. Sausages were stuffed, pressed, fermented (to pH 4.8), cold smoked, and dried to a water activity of 0.88. Sausages were vacuum packaged, stored (20 days, ca. 23 °C), and evaluated for microbial populations, pH, and water activity. Lactic acid treatment of beef trim reduced EC, S, and LM 0.23, 0.42, and 0.22 log₁₀ CFU/g, respectively. Subsequent fermentation and drying reduced EC, LM, and S 3.94, 4.11, and 4.29 log₁₀ CFU/g respectively. Average log reductions of 7.83, 6.19, and 7.21 log₁₀ CFU/g were observed for EC, LM and S, respectively, for the duration of the study. This study demonstrates that traditional processing of landjäger may result in a ca. 5 log reduction of foodborne pathogens.     

Improvement of the food safety of low acid fermented sausages by enterocins A and B and high pressure

Fermented sausage technology involves a sequence of hurdles that appear along the ripening process. A wide variety of fermented sausages are manufactured worldwide based on the concept of reduction of pH and/or water activity. In low acid fermented sausages the absence of high acidification can be balanced by the application of additional hurdles such as bacteriocins and/or high hydrostatic pressure (HHP). The addition of enterocins A and B to raw-sausages spiked with 3 log CFU/g of Salmonella, Listeria monocytogenes and Staphylococcus aureus showed an immediate reduction in the counts of L. monocytogenes due to the enterocins, while Salmonella was more affected by the endogenous hurdles associated with the ripening process. The application of an HHP treatment of 400 MPa at the end of ripening produced an immediate reduction in the counts of Salmonella but not in L. monocytogenes or S. aureus. During storage of the low acid sausages (fuets) at room temperature and at 7 °C, counts of Salmonella and L. monocytogenes progressively decreased in all batches although the decrease was faster in the pressurized ones stored at room temperature. At the end of storage, Salmonella was <1 log CFU/g in all the batches but only the combination of enterocins and HHP could reduce the counts of L. monocytogenes to this level. Neither the ripening process, the enterocins nor the pressurization could control the levels of S. aureus.     

Technological properties and bacteriocins production by Lactobacillus curvatus 54M16 and its use as starter culture for fermented sausage manufacture

Lactobacillus curvatus 54M16 was isolated from traditional fermented sausages of Campania region (Italy) and identified by 16S rRNA and hsp60 gene sequencing and by SDS-PAGE of whole cell proteins. The strain produced more than one bacteriocin, carrying the genes for sakacin X, T and P as demonstrated by PCR studies. The ability of L. curvatus 54M16 to produce multiple bacteriocins is confirmed by molecular mass spectrometry analysis and N-terminal amino acid sequencing. Among the bacteria tested, the pathogens Listeria monocytogenes and Bacillus cereus and the meat spoilage Brochotrix thermosphacta were sensitive to the bacteriocins. No inhibition of tested Gram-negative bacteria, some strains of Lactobacillus and of strains of Staphylococcus aureus was observed.All the in vitro conditions tested for the production of the bacteriocins (temperature, pH and NaCl), indicate that the strain of L. curvatus 54M16 is able to grow and to produce the antagonistic substances at pH 4.5 and in the presence of 4% NaCl. The strain has good acidifier capability and it is able to hydrolyse sarcoplasmic but not myofibrillar proteins, lipids and to reduce nitrates. Moreover it shown high values of SOD, while the aminopeptidase activity is restricted to whole cells that hydrolyse at high rates the amino acids l-arginine, l-valine, l-phenylalanine and l-lysine. The suitability of L. curvatus 54M16 as starter culture was assayed during sausage fermentation. Its use can improve the quality and safety of the traditional fermented sausages prepared without antimicrobial additives.     

Microbiological quality of raw-fermented sausages with Lactobacillus casei LOCK 0900 probiotic strain

The objective of this study was to evaluate the microbiological quality, defined as health safety, microbiological stability, sensory acceptability and dietary value, of raw-fermented sausages with Lactobacillus casei LOCK 0900 probiotic strain. The study assessed the impact of the number of probiotic starter culture suspension (Lc1 ≈ 6 log cfu/g; Lc2 ≈ 7.3 log cfu/g) on the microbiological quality of sausages after the fermentation and following 6 months' storage. The number of used probiotic in the examined raw-fermented sausages was approx. 9 log cfu/g after the fermentation and following 6 months' storage. The number of lactic acid bacteria in the Lc1 and Lc2 samples after the fermentation was similar, however, the smaller number of Staphylococcus aureus, Escherichia coli and Enterobacteriaceae in the Lc2 sample shows that a greater addition of the starter culture suspension is more beneficial. The sensory evaluation results showed that the overall quality was positively correlated with the aroma of cured meat, the taste of dried meat and muscle tissue fragmentation following the fermentation. Negative evaluation of the product was based on such parameters as bitter or other taste, acrid odour, fatty taste. The environment of raw-fermented sausages is suitable for the growth and survival of probiotic.     

Quantification of persistence of the food-borne pathogens Listeria monocytogenes and Salmonella enterica during manufacture of Italian fermented sausages

The objective was to evaluate the survival capability and quantify the persistence of the food-borne pathogens Listeria monocytogenes and Salmonella enterica in the Cacciatore, Felino and Milano type salami preparation. The batter of each sausage was inoculated with a five-strain cocktail of L. monocytogenes or S. enterica (ca. 10⁴–10⁵ CFU/g) and their progression was monitored at specific time intervals during preparation of the sausages. Four different batches were prepared at different times for each sausage/pathogen combination. Different models were used to fit the experimental data and to calculate the kinetic parameters. The best model was chosen based on statistical comparisons. S. enterica proved to be more sensitive susceptible to fermentation and ripening processes than L. monocytogenes. Both pathogens, however, survived relatively well as the result of the conditions (pH, a_w and fermentation temperature) prevailing during fermentation and ripening of the sausages. Water activity proved to be a key factor in the survival of the microorganisms. The statistical analysis of quantitative data gathered from challenge tests is useful for the food business operators as it can provide practical information on the process parameters combinations that could lead to a better control of the pathogens.     

Microbial composition of turbid rice wine (Makgeolli) at different stages of production in a real processing line

The aim of this study was to examine for changes in microbial populations during the production of turbid rice wine (also known as Makgeolli) at different production plants and to identify critical points for the control of microbial quality. Samples from raw ingredients (water, rice and wheat flour), materials from different production stages (steamed ingredients, the base of fermentation, primary and secondary fermentation stages at different time points), and the final rice wine products (non–sterilized and sterilized) were analyzed. The microbiological content of samples was assessed by quantitative (aerobic plate counts, lactic acid bacteria, fungi, acetic acid bacteria, coliforms and Bacillus cereus) and qualitative (Escherichia coli and eight foodborne pathogens) analyses. Aerobic plate counts for rice and wheat flour were relatively low (3.1 and 1.9 log CFU/g, respectively), as were those for lactic acid bacteria (1.6 and 2.1 log CFU/g), and fungi counts (2.2 and 0.7 log CFU/g). All counts increased to 7.8–7.9 log CFU/ml in the base of fermentation after the addition of Nuruk and Koji, and these counts were maintained at 8–9 log CFU/ml during fermentation. Acetic acid bacteria were not detected in the ingredients, but were isolated from the base of fermentation (1.2–2.8 log CFU/ml). Heat sterilization reduced aerobic pate counts significantly from 8.4 to 2.1 log CFF/ml, and lactic acid bacteria, fungi and acetic acid bacteria were reduced to non-detectable or negligible levels. Isolated microorganisms were considered as autochthonous to the environment or were artificially introduced with the starter culture. B. cereus was widely distributed throughout the manufacturing process, and may have been introduced from the raw material (present in 100% rice and 41.7% wheat flour samples). B. cereus counts were not significantly affected by sterilization, suggesting that it may exist at low levels as spores in the final products. No coliforms and other pathogens were detected in any samples. The raw materials, the base of fermentation, and sterilization stage were identified as important points for the control of microbial quality during the fermentation process.     

Whole soybean as probiotic lactic acid bacteria carrier food in solid-state fermentation

For the purpose of preparing lactic acid bacteria (LAB) carrier food, the solid-state fermentation of whole soybean was performed using Bifidobacterium animalis 937, Lactobacillus casei Zhang and Lactobacillus plantarum P-8 mixed with Bacillus subtilis natto, respectively. The physicochemical properties, the amino nitrogen content and peptide molecular weight distribution of the fermented whole soybean products were examined during this process. After 48 h of fermentation, the viable counts of the three samples were 1.41 × 10⁸ CFU/g (B. animalis 937), 1.74 × 10¹⁰ CFU/g (L. casei Zhang) and 2.19 × 10¹⁰ CFU/g (L. plantarum P-8), with the pH declined rapidly from 6.32 to 5.78, 5.60 and 5.44 at the early stage of the fermentation and increased to 6.71, 6.47 and 6.60 at the later stage of the fermentation. The fermentation caused a sharply increase in the content of the free amino nitrogen from 99.7 μmol/g to 301.9 μmol/g, 390.1 μmol/g and 529.1 μmol/g in the solid fermented soybean products, due to the multiplication of microorganism and the effect of enzyme system. Furthermore, the levels of soybean peptide with molecular weight less than 1000 Da increased 30.7%, 71.2% and 81.3% relative to that of the control group at 48 h. The result of the present work implied that whole soybean fermented by LAB can provide the different probiotics for the host, and there is potential to develope nutritious fermented soybean products.     

Effect of starter cultures on microbial ecosystem and biogenic amines in fermented sausage

The microbial ecology of fermented sausages inoculated with different starter cultures (Pediococcus pentosaceus + Staphylococcus xylosus, batch A; Lactobacillus farciminis + Staphylococcus saprophyticus, batch B) was studied by culture-dependent and independent methods. The concentration of biogenic amines, pH and a_w (water activity) were followed. The starter B can inhibit indigenous bacteria effectively judged by traditional microbiological method and PCR-DGGE fingerprint. There was no statistical difference in pH between batches A and B at 2 days when substantial amounts of BAs were produced, while the amounts of histamine, putrescine, cadaverine and tyramine in batch B was lower than in batch A significantly (P < 0.001). As a result, the starter cultures which can complete, grow well and inhibit amine-positive bacteria play an important role in reducing the production of BAs during ripening of fermented sausage.     

Biogenic amine inhibition and quality protection of Harbin dry sausages by inoculation with Staphylococcus xylosus and Lactobacillus plantarum

This study was conducted to evaluate the effects of inoculation with Staphylococcus xylosus, Lactobacillus plantarum, or a mixture of strains (L. plantarum + S. xylosus) on the formation of biogenic amines (BAs) and quality characteristics in Harbin dry sausage. Microbial analysis shows that total aerobic bacteria and lactic acid bacteria (LAB) counts were higher in the inoculated sausages, especially in those inoculated with a mixture of strains, but the growth of enterobacteriaceae was inhibited (P < 0.05). A sharp decrease in the pH value of the sausages was observed, and the moisture content and water activity were significantly decreased during fermentation. Sausages inoculated with a mixture of bacterial strains had the lowest pH, moisture content and water activity (P < 0.05). Inoculation of dry sausages with S. xylosus or L. plantarum, especially a mixture of strains (L. plantarum + S. xylosus), significantly delayed lipid oxidation, improved sensory characteristics, and inhibited BA accumulation. Six types of BAs (cadaverine, putrescine, tryptamine, 2-phenylethylamine, histamine, and tyramine) were inhibited by the presence of L. plantarum and S. xylosus, and a mixture of them had the most inhibitive effect. Correlation analysis showed that the BA concentrations correlated well with enterobacteriaceae counts, and some BAs were negatively correlated with LAB counts. These results demonstrate that S. xylosus and L. plantarum could be used as starter cultures in Harbin dry sausage production to inhibit BA accumulation and improve quality characteristics.     

Microbial profile of buffalo sausage during processing and storage

A study was made on the microbial levels of buffalo sausage during preparation and storage at 4 ± 1 °C. Microbial counts in raw minced meat were, total plate count (TPC) (log cfu/g) 5.41 ± 0.25; coliforms (MPN/g) 23.2; Staphylococcus aureus (log cfu/g) 1.57 ± 0.11; yeasts and molds (log cfu/g) 2.29 ± 0.07 and lactic acid bacteria (LAB) (log cfu/g) 0.60 ± 0.20. Sausage emulsion showed similar trend in microbial counts with minimal microbial contamination during the preparation of emulsion. Cooked buffalo sausage gave the following microbial counts: TPC (log cfu/g) 3.75 ± 0.31; coliforms (MPN/g) 0.2; LAB (log cfu/g) 0.07 ± 0.01; yeast and molds (log cfu/g) 0.72 ± 0.07. S. aureus, Clostridium perfringens and Bacillus cereus were not detected in cooked sausages. These results indicate that steam cooking for 45 min followed in the study was effective in reducing the microbial counts substantially. The investigation revealed that shelf life of cooked buffalo sausage was 31 days in either vacuum or CO₂ at 4 ± 1 °C. The results indicated that spoilage of vacuum packed cooked buffalo sausage was likely due to LAB while microflora other than LAB may be responsible for spoilage of CO₂ packed cooked buffalo sausage. The study suggests that measures such as low initial microbial counts, hygienic precautions during preparation of sausage, steam cooking for 45 min, vacuum or CO₂ packing and storage at 4 ± 1 °C would control the microbial growth and provide wholesomeness and safety to the buffalo sausage.     

Effect of starter culture on growth of Staphylococcus aureus in sucuk

The effects of starter cultures, starter A (Pediococcus acidilactici + Lactobacillus curvatus + Staphylococcus xylosus), starter B (Lactobacillus sakei + Staphylococcus carnosus) and ripening period on growth of S. aureus were investigated in sucuk (Turkish dry-fermented sausage) production. Sucuk batters were inoculated with S. aureus (10⁶/g). S. aureus, Micrococcus/Staphylococcus, lactic acid bacteria and Enterobacteriaceae counts were determined during ripening, and pH and a_w were analyzed. Both starter cultures and ripening period had significant effects on the S. aureus, lactic acid bacteria, Micrococcus/Staphylococcus, Enterobacteriaceae counts and pH value (P < 0.01). The numbers of S. aureus increased by 1 log on the 3rd day in the control group, whereas a reduction was observed during ripening period in sucuk with starter cultures.     

Characterization and selection of Lactobacillus brevis starter for nitrite degradation of Chinese pickle

To improve the safety of Chinese pickles, lactic acid bacteria were isolated from traditional fermented foods to test for nitrite degradation during the pickling process. Lactobacillus brevis AR123 was screened out as a starter culture for pickle fermentation. L. brevis AR123 has a high tolerance to nitrite and salt. During pickle fermentation, the nitrite peak appeared from 12 to 24 h in the pickle juice and was delayed to 24–48 h in the pickles. In 6% salt, L. brevis AR123 and a commercial starter could rapidly lower the pH of the pickles, and the nitrite contents were 0.83 mg kg⁻¹ and 3.05 mg kg⁻¹, respectively, in pickles at 72 h. Meanwhile, no obvious nitrite peak was observed for the pickle inoculated with a mixed starter; it had a low nitrite level (0.88 mg kg⁻¹ at 72 h). However, the concentration of nitrite was as high as 17.92 mg kg⁻¹ in the spontaneous fermentation group. During pickle fermentation, Lactic acid bacteria (LAB) population increased significantly when salt concentration was 4%–8%, and sensory analysis shown that the L. brevis AR123 inoculated pickle exhibited better sensory evaluation results than spontaneous fermentation pickle. In conclusion, inoculation with L. brevis AR123 alone or combined with a commercial starter (mixed starter) is effective in removing nitrites and enhancing the sensory properties of pickle. LAB could accelerate degradation of nitrite significantly and shorten the fermentation time for pickle process.     

The potentials of Bacillus licheniformis strains for inhibition of B. cereus growth and reduction of biogenic amines in cheonggukjang (Korean fermented unsalted soybean paste)

The aim of this study was to control Bacillus cereus growth and biogenic amines formation by using a starter in cheonggukjang fermentation. We used the four selected B. licheniformis strains for cheonggukjang fermentation and investigated whether the strains are effective in reducing both B. cereus level and biogenic amines content. We confirmed that the selected strains are able to reduce B. cereus level to below l log CFU/g after cheonggukjang fermentation from the initial level of 3–4 log CFU/g (artificial contamination). Tryptamine, β-phenylethylamine, putrescine, cadaverine, tyramine, spermidine, and spermine were detected whereas histamine, serotonin, noradrenaline, and dopamine were not detected in the cheonggukjang samples. Most of biogenic amines contents were lower than those of previous studies, indicating that the strains produced the low level of biogenic amines in cheonggukjang fermentation. The acceptable levels of amino-type nitrogen, free amino acids, and isoflavones were contained in the cheonggukjang samples. These results demonstrate that the selected strains are not only effective for reduction of both B. cereus contamination and biogenic amines but also suitable for preparation of cheonggukjang with good quality.