Effect of modified atmosphere and vacuum packaging on some quality characteristics of sliced ‘sucuk’ produced using probiotics culture

The effects of probiotics (Lactobacillus acidophilus and Bifidobacterium lactis), packaging (vacuum, 50% N₂ + 50% CO₂ or 100% CO₂), storage temperature (4 and 10 °C) and storage time (90 d) on lipid oxidation, colour and microbial properties of sliced dry fermented sausage ‘sucuk’, which has a long storage time at low temperatures, was investigated. Probiotic‐added samples showed a significant reduction in the thiobarbituric acid‐reactive substances (TBARS) values compared with a control and starter culture groups. The analysis showed that control groups had the highest pH and that the pH was not affected by packaging or storage temperature. Probiotic use had a significant effect on total aerobic bacteria, lactic acid bacteria and Micrococcus/Staphylococcus counts, and bacterial counts decreased with storage time. The Enterobacteriaceae count was below detectable levels (<2.00 CFU g⁻¹) throughout the storage period. The storage temperatures had no effect on the microbial counts. Packaging had a significant effect on lactic acid bacteria, and the highest value was determined with 50% N₂ + 50% CO₂. The addition of probiotics and the storage time resulted in a significant decrease of colour values (L*, a* and b*). Copyright © 2005 Society of Chemical Industry     

Intestinal microbiota in rats fed with tofu (soy curd) treated under high pressure

The present study was carried out to assess the effect of intestinal microbiota in laboratory animals fed with tofu treated under high pressure. The counts of viable mesophilic bacteria and total enterobacteria in the three different groups assayed went down in the rats fed with a diet of untreated tofu. Significant differences (p0.05) for these microorganisms were found in the rats fed with untreated tofu when compared with the rats of the control group. However, when both tofu diets were compared the counts of mesophilic bacteria went up in the treated tofu and significant differences (p0.05) were found between treated and untreated tofu diets. Counts of lactic acid bacteria rose in both tofu diets and particularly in the treated tofu, but no significant differences (p0.05) were found in both tofu diets. Nevertheless significant differences were found with both tofu diets and the control. Some lactic acid bacteria have been identified in tofu diets, such as Lactobacillus plantarum, Lactobacillus acidophilus, Bifidobacterium infantis and also Streptococcus spp. The results for faecal enterococci, faecal coliforms and spores of sulphite-reducing clostridia showed similar values in the three diets. The treated tofu diet in each case presented higher values than the untreated tofu diet, especially for lactic acid bacteria, which means that high-pressure treatment produces a beneficial effect for tofu, owing to the increase of lactic acid bacteria. In conclusion, untreated and treated tofu diets act as functional food increasing the number of lactic acid bacteria and reducing the number of Enterobacteriaceae, especially those that are pathogenic, and opportunistic pathogenic bacteria.     

Microbiological survey of tofu sold in a rural Illinois county.

The purpose of this study was to determine the microbial status of tofu sold in a rural Illinois county and assess the factors contributing to the safety of tofu. Six brands of tofu from eight different stores (60 total samples) were purchased and analyzed for temperature, pH, total aerobic bacteria, and the presence of coliforms. Relationships between age, temperature, pH of tofu, and total aerobic bacteria were tested. An analysis of variance was also performed to test for differences in total bacterial counts among the brands. Mean aerobic bacterial counts ranged from 0 to 7.76 x 10(7) CFU/g. Fifty-five percent of the tofu tested fell within the excellent range for freshness as delineated by the standards developed by the Soyfoods Association of North America, 6.7% fell within the acceptable range, 6.7% within the marginal range, and 28% within the unacceptable range. Sixteen percent of the samples contained coliform bacteria. No significant correlation was found between variables, except pH with total aerobic bacterial counts (r = -0.51) and pH with eosin-methylene blue agar counts (r = -0.67). Most of the tofu was displayed at unsafe temperatures (>5 degrees C) for potentially hazardous foods. This study confirmed the concerns regarding safety of tofu sold in the grocery stores. Based on these results, special training on tofu storage and handling is recommended for grocery stores selling this food product.     

云南建水酸浆豆腐中乳酸菌的生长特性

为了筛选出优良的乳酸菌进行发酵制作酸浆,对分离自云南建水豆腐酸浆中的五株乳酸菌(SYG01、SYG02、SYG03、SYG04、SYG05)的生长曲线、产酸能力、耐酸能力和耐渗透压能力进行了比较。生长曲线实验表明在相同培养时间内,菌株SYG02繁殖能力最强,其次是菌株SYG03,而菌株SYG05、SYG04、SYG01的生长速率明显较慢;在产酸方面SYG02产酸能力最强,速度最快,SYG03、SYG05和SYG04次之,SYG01最弱。在耐酸方面,在pH4.0的环境下5株菌生长良好,在pH3.0的酸性环境下5株菌虽然能够存活,但活菌数的数量级仅在102~104 CFU/mL,其中菌株SYG02和SYG03比其它三株菌株表现出较好的耐酸能力。在耐渗透压方面,SYG02在8%(w/V)的NaCl中依然表现出较强的耐受性,活菌数的数量级达到107 CFU/mL,其余4株菌在NaCl含量大于6%(w/V)时生长受到明显抑制。并以发酵黄浆水的pH及产酸量为指标对菌株的产酸能力进行比较,发现混合菌株的产酸能力高于单菌株,其中菌株SYG02和菌株SYG03组合发酵的效果最好,在发酵72 h后黄浆水的pH为3.52,产酸量达到6.46 g/L。从而得出菌株SYG02具有良好的生长、产酸和耐渗透压能力,具有良好的应用潜力,对酸浆豆腐的工业化生产有重要的意义。     

Optimization of Fermentation Parameters for the Production of Concentrated Starters from Nonbitter Streptococcus lacti INIA 12

Streptococcus lactis INIA 12, a selected nonbitter strain, reached its maximum counts and its highest lactic acid production in a culture medium containing 125 g/L skim milk powder, fortified with 5 g/L yeast extract and digested with 10 ppm papain for 20 min at 65°C. Lactose added to the medium did not enhance growth rate or biomass production. A growth temperature of 32°C and the maintenance of pH at 6.80, with 10N NaOH as the neutralizer, were the optimum fermentation parameters in batch cultures. In ten 40-L fermentations carried out at 32°C and pH 6.80, with a 5% inoculum, a 0.2 kg/cm² nitrogen head space pressure and a stirring rate of 80 rpm, maximum counts of S. lactis (10¹⁰ CFU/mL) were reached after incubation for 6 hr at 32°C and pH 6.80.     

Author index

A survey of the microbiological quality of tofu was carried out in the summer and autumn of 1983. A total of 154 samples were examined. About 95% of the samples had an aerobic plate count above 10⁶ CFU/g, numbers of Enterobacteriaceae exceeded 10³ CFU/g in 86% of the samples and numbers of lactic acid bacteria exceeded 10⁴ CFU/g in 94% of the samples. Bacillus cereus was found in one sample and Staphylococcus aureus in another, at levels above 10⁵ CFU/g. Salmonella was not found in 25 g. 36% of the samples contained > 10² CFU/g Escherichia coli and Yersinia enterocolitica were detected in 11% of the samples (present in 0.2 g). The reasons for this poor microbiological quality are discussed and some recommendations made.     

Enhancement of Biological Properties of Soymilk by Fermentation

Soymilk has attracted much interest in the food industry because of its health- promoting properties. Fermentation with lactic acid bacteria is known to provide value addition to soymilk by reducing the beany flavor and content of indigestible oligosaccharides and by enhancing the bioavailability of isoflavones, resulting in a nutritious probiotic food product. In the present study, Soymilk fermentation was studied using Lactobacillus acidophilus strain isolated from ragi, and effect of soymilk supplementation on the fermentation characteristics was also investigated. Viable count of 1.99 × 10⁹ CFU/mL sample and 630.1 U/g of β-glucosidase activity were determined in soymilk after 12 h of fermentation. Soymilk supplementation with skimmed milk powder at 5% level gave best results with viable counts of 22.9 × 10⁹ CFU/ml sample or 212.9 × 10⁹ CFU/g solids; 764 U/g of β-glucosidase activity, 1.44% la titratable acidity and pH of 3.9. Daidzein and genistein profile in fermented soymilk showed that 45.8% and 57.5% of respective isoflavones existing as aglycone form, indicating enhancement of the biological property of soymilk through improvement of health-relevant bioactive forms.     

Complete Heterolactic Acid Fermentation of Green Beans by Lactobacillus cellobiosis

Only Lactobacillus cellobiosus, among eight strains of heterofermentative lactic acid bacteria, removed all fermentable sugars from green beans. Proper blanching of the beans was required to prevent growth by natural lactic acid bacteria. An inoculum of 10 CFU/ml Lactobacillus plantarum and 10⁶ CFU/ml L. cellobiosus resulted in the formation of twice as much lactic acid as inoculation with L. cellobiosus alone. A maximum of 3.74% sugar was metabolized by L. cellobiosus in bean juice containing 2.5% NaCI and 0.08% acetic acid. Fructose was nearly quantitatively reduced to mannitol with a concomitant accumulation of acetic acid. Ethanol was not observed until most of the fructose was metabolized. The L. cellobiosus-fermented beans had a more mild acid flavor than beans fermented with L plantarum.     

Fermentation of beet juice by beneficial lactic acid bacteria

Red beets were evaluated as a potential substrate for the production of probiotic beet juice by four species of lactic acid bacteria (Lactobacillus acidophilus, Lactobacillus casei, Lactobacillus delbrueckii, Lactobacillus plantarum). All the lactic cultures were found capable of rapidly utilizing beet juice for cell synthesis and lactic acid production. However, L. acidophilus and L. plantarum produced a greater amount of lactic acid than other cultures and reduced the pH of fermented beet juice from an initial value of 6.3 to below 4.5 after 48 h of fermentation at 30°C. Although the lactic cultures in fermented beet juice gradually lost their viability during cold storage, the viable cell counts of these lactic acid bacteria except for L. acidophilus in the fermented beet juice still remained at 10⁶–10⁸ CFU/ml after 4 weeks of cold storage at 4°C.     

Drying Temperature and Time Affect Quality of Chinese-style Sausage Inoculated with Lactic Acid Bacteria

Lactobacillus plantarum, Streptococcus thermophilus and a commercial culture (DS-66) were used as starter culture for manufacturing Chinese-style sausage. The influence of drying temperature and time on the growth of lactic acid bacteria (LAB) and on changes in quality were determined. After drying the sausage at 370 and 45°C for 12 hr, the population of LAB had increased from an initial 10⁶ CFU/g to 10⁸ and 10⁷ CFU/g, respectively. The pH value was the lowest for the sausage dried at 37°C. Nitrite residuals decreased rapidly with increased drying time. Starter cultures increased the amino nitrogen level and suppressed ammonia nitrogen production.     

MICROBIAL GROWTH IN PACKAGED FRESH ASPARAGUS

The effects of storage temperature and time on the microflora of fresh, vacuum packaged, and modified atmospheres packaged asparagus (Asparagus officinalis) were analyzed. Total aerobic mesophilic, psychrophilic, lactic acid bacteria, Enterobacteriaceae, and yeast and molds were determined as a function of time. The effect of washing on the original microflora of the asparagus and the growth of the different microbial groups during the storage time were checked. From day 8, a progressive increase in the mesophile and psychrophile counts in both types of packaging was observed. At the end of the experiment (day 21), the mesophile and psychrophile counts were all 10⁷ CFU/g, for both types of packaging. In the vacuum packaging, the final enterobacteria counts (2.5 × 10² CFU/g) and yeast and molds (10 CFU/g) were lower than in the polyethylene bag packaged asparagus, which showed enterobacteria counts of 7.3 × 10⁴ CFU/g) and yeast and mold counts of 2.3 × 10⁴ CFU/g. The non-packaged asparagus showed low counts from the fourth day due to their heavy dehydration caused by the low relative humidity in the storage chamber.     

Effect of storage temperatures and time on shelf‐life of sliced and modified atmosphere packaged Pastırma,a dried meat product,produced from beef

The effects of modified atmosphere on some physical, chemical and microbiological properties of sliced past?rma made from beef Longissimus dorsi muscle were investigated. Sliced‐past?rma samples (moisture 43.65 ± 0.15%, pH 5.71 ± 0.02) were stored in modified atmosphere packages (50% N₂ + 50% CO₂) at 4 and 10 °C for 150 days. The storage period had a significant effect (p < 0.01) on moisture, pH, thiobarbituric acid reactive substances, free fatty acid, non‐protein nitrogen, water‐soluble nitrogen, colour values and total aerobic bacteria, lactic acid bacteria and Micrococcus/Staphylococcus counts. The storage temperatures (4 and 10 °C) also had a significant effect (p < 0.01) on moisture, pH, thiobarbituric acid reactive subctances, free fatty acid, water soluble nitrogen, a* values, total aerobic bacteria lactic acid bacteria, and Micrococcus/Staphylococcus counts. It was determined that the storage period × the storage temperature interactions had a significant (p < 0.01) effect on the values of pH, a* and the counts of total aerobic bacteria, lactic acid bacteria, Micrococcus/Staphylococcus. It was also observed that the yeast and mold count was the highest in the first storage period and decreased throughout storage. Enterobacteriaceae count was also below the detectable level (<2.00 cfu g^?1) throughout the storage period. Copyright © 2005 Society of Chemical Industry     

Agar films containing green tea extract and probiotic bacteria for extending fish shelf-life

A bioactive film composed of agar, incorporating green tea extract and probiotic strains (Lactobacillus paracasei L26 and Bifidobacterium lactis B94) was applied on hake fillets in order to evaluate the effect of the films during 15 days of storage. Hake was previously inoculated with Shewanella putrefaciens and Photobacterium phosphoreum (10³–10⁴ CFU/g) to simulate a spoilage process. The green tea and/or probiotic film provoked a reduction, particularly of H₂S-producing bacteria counts and total viable bacteria throughout the storage period. The probiotic strains added to the film could pass to the fish producing an increment of lactic acid bacterial counts, even in the presence of green tea extract. The effect of the films also caused a decrease in the indexes of fish quality (total volatile basic nitrogen (TVB-N), trimethylamine nitrogen (TMA-N) and pH). The total viable counts, H₂S-producing microorganisms and TVB-N were maintained below the limits of acceptability during 15 days for the fillet covered with the green tea + probiotic film, compared to the rest of the samples. Films with green tea and probiotic were able to extend shelf-life of hake at least for a week and increase the beneficial lactic acid bacteria in fish.     

Probabilistic models for the prediction of target growth interfaces of Listeria monocytogenes on ham and turkey breast products

Abstract: This study developed growth/no growth models for predicting growth boundaries of Listeria monocytogenes on ready‐to‐eat cured ham and uncured turkey breast slices as a function of lactic acid concentration (0% to 4%), dipping time (0 to 4 min), and storage temperature (4 to 10 °C). A 10‐strain composite of L. monocytogenes was inoculated (2 to 3 log CFU/cm²) on slices, followed by dipping into lactic acid and storage in vacuum packages for up to 30 d. Total bacterial (tryptic soy agar plus 0.6% yeast extract) and L. monocytogenes (PALCAM agar) populations were determined on day 0 and at the endpoint of storage. The combinations of parameters that allowed increases in cell counts of L. monocytogenes of at least l log CFU/cm² were assigned the value of 1, while those limiting growth to <1 log CFU/cm² were given the value of 0. The binary data were used in logistic regression analysis for development of models to predict boundaries between growth and no growth of the pathogen at desired probabilities. Indices of model performance and validation with limited available data indicated that the models developed had acceptable goodness of fit. Thus, the described procedures using bacterial growth data from studies with food products may be appropriate in developing growth/no growth models to predict growth and to select lactic acid concentrations and dipping times for control of L. monocytogenes. Practical Application: The models developed in this study may be useful in selecting lactic acid concentrations and dipping times to control growth of Listeria monocytogenes on cured ham and uncured turkey breast during product storage, and in determining probabilities of growth under selected conditions. The modeling procedures followed may also be used for application in model development for other products, conditions, or pathogens.     

Application of Lactobacillus plantarum in Functional Products Based on Fermented Buckwheat

In this work, 12 plant‐based potential probiotic mashes were produced by fermenting buckwheat with lactic acid cocci of the Fresco DVS 1010 culture and the human‐derived isolate Lactobacillus plantarum HM1. The effect of single and coculture fermentation was studied at 30 and 37 ± 0.5 °C for 8 hr (5% CO₂), followed by a storage period of 21 days (6 ± 0.5 °C). Although milk is the typical growth medium for lactic acid bacteria (LAB), presumably viable counts of Fresco reached levels of 10⁸ to 10⁹ CFU/mL (specific growth rates ranging from 1.07 to 1.40 hr^?1) with higher counts in coculture fermentation (13%) that differed statistically significantly (P < 0.05). After storage, 194 to 4700 mg/kg lactic acid was found in the mashes, with significantly higher contents after cocultivation (11% to 96%). Based on the overall acceptance of the designed products, milk‐based mashes right after the fermentation were evaluated as the most satisfactory (3.3 to 3.6). Those after the storage period (21 days) exhibited an attractive sensory acceptability (2.2 to 3.2).     

Effect of different levels of fat and inulin on the microbial growth and metabolites in probiotic yogurt containing nonviable bacteria

Effects of different levels of fat and inulin on bacterial cell counts, degree of proteolysis and concentrations of organic acids in the yogurt containing inactivated cells of probiotic strains Bifidobacterium animalis and Lactobacillus acidophilus were investigated. Results showed that both L. acidophilus and B. animalis grew well in the yogurt samples reaching cell counts higher than 10⁶ CFU mL^?1 at the final pH of 4.5. Inulin at the concentration of 1% had no significant effects on the production of organic acids and cell counts of L. acidophilus, but promoted the growth of B. animalis with a reduction in the degree of proteolysis. Generally, different fat levels showed significant effects on the production of organic acids and nonsignificant effects on the cell counts of probiotic bacteria and degree of proteolysis. In case of lactic acid, the ratio of L‐ (+)to D‐ (?) isomer ranged from 50/50 to 80/20 in yogurt samples.     

Populations and potential association of Saccharomyces cerevisiae with lactic acid bacteria in naturally fermented Korean rice wine

The microbial populations focused on predominant yeast species and lactic acid bacteria (LAB) in 15 commercial makgeolli brands, where a fungal starter nuruk was used were examined. Viable yeast counts were obtained on yeast potato dextrose (YPD) and MRS agar containing sodium azide. MRS-C (0.1% cycloheximide supplemented) was used for selective counts of LAB. Saccharomyces cerevisiae was found to be predominant in the 15 samples tested, with an average count of 4.6×10⁷ CFU/mL. Contrary to the earlier studies, Lactobacillus plantarum and Weissella cibaria were shown as predominant LAB species with an average count of 1.7×10⁷ CFU/mL. Surprisingly, as many as 7 log viable cells/mL were present at the ethyl alcohol concentration of 6–7%. The data from real-time PCR also indicated that the yeast populations remains almost constant during the refrigerated storage of 12 days, while that of LAB decrease slightly first 9 days and increase after then, despite the overall increase in acidity. Data from the differential microbial counts suggest that yeast S. cerevisiae might be associated with 2 LAB species, L. plantarum and W. cibaria, under ethyl alcohol stress during the turbid rice wine fermentation.     

Changes in Numbers and Kinds of Lactic Acid Bacteria During Ripening of Kefalotyri Cheese

Changes in lactic acid bacteria in ripening Kefalotyri cheese were studied. Throughout ripening lactobacilli and enterococci counts were high (lactobacilli 10⁶-10⁹/g, enterococci 10⁴-10⁷/g). Leuconostocs, lactic streptococci and betabacteria disappeared early in ripening. Leuconostoc lactis and Streptococcus thermophilus prevailed intitially (23% and 13%, respectively). Enterococcus faecium, Lactobacillus casei and L. plantarum became predominant with ripening. After 4 months ripening, E. faecium were dominant (35.5%) followed by L. plantarum (18.4%) and L. casei subsp. casei (15.8%). Results suggested that a starter consisting of both lactic acid bacteria that disappeared early and lactic acid bacteria that survived throughout ripening should be preferable for the production of Kefalotyri cheese.     

Lactic acid production using waste generated from sweet potato processing

Organic waste generated from industrial sweet potato canning is estimated to be 30% of incoming raw material with significant residual carbohydrate content. The purpose of this study was to evaluate the potential of waste generated from sweet potato processing material to support the growth of lactic acid bacteria and the production of lactic acid. The waste was comprised of 16.5% solids consisting of 18.5% ash, 4.4% protein, 20.5% simple sugars and 19% soluble starch. Following a screening of three lactic acid bacteria strains, Lactobacillus rhamnosus was deemed the best candidate for lactic acid production. The potential of various dilutions of the enzyme‐hydrolysed waste, with and without pH control, as a fermentation substrate was evaluated. Lactic acid production was highest in hydrolysed waste (without dilution) at pH set point 5.0, yielding 10 g L^?1 in 72 h. Thus, lactic acid, a valuable organic compound, can be generated from sweet potato waste.     

Properties and acceptability of Som-fug, a Thai fermented fish mince, inoculated with lactic acid bacteria starters

Effect of inoculation of different lactic acid bacteria (LAB) on the fermentation and quality of Som-fug from bigeye snapper was investigated. Som-fug inoculated with Pediococcus acidilactici at 10⁴ CFU/g (PA104) had a greater acceptability than those inoculated with Lactobacillus plantarum and Pediococcus pentosaceus at either 10⁴ or 10⁶ CFU/g and the control (without inoculum). During fermentation, PA104 exhibited a higher rate of fermentation than the control as indicated by the greater rate of pH drop and lactic acid production (p<0.05). Based on pH desired (pH 4.5), the fermentation was completed within 48 and 36 h for the control and PA104, respectively. Due to higher acid production rate, the textural development of PA104 was more pronounced. Som-fug inoculated with LAB generally exhibited higher hardness and adhesiveness than the control (p<0.05), when assessed by texture profile analysis (TPA). From the result, inoculation with P. acidilactici resulted in a reduction of fermentation time and improved the quality of Som-fug. Therefore, P. acidilactici can be used as a potential starter for Som-fug fermentation.