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Blood tofu, or cooked duck blood curd, is a Chinese delicacy in East Asia. Its quality and shelf-life are low due to microorganism contamination during production. Therefore, the present study was performed to investigate the role of sodium diacetate (SD), sodium chloride (NaCl), and polyethylene glycol 400 (PEG) combinations in increasing the quality of blood tofu. A total of 45 cooked duck blood curd samples were randomly divided into 3 groups with 3 replicates per group. The first two groups were used to investigate the effect of SD, NaCl, and PEG combinations on microbiological and physical analyses for non-inoculated samples. Another group was used to determine the effect of antimicrobial combinations on Lactobacillus plantarum, Pseudomonas fluorescens, Salmonella typhimurium, Escherichia coli, and Staphylococcus aureus in inoculated samples that were inoculated with these bacteria. All groups were treated with control-sterilized water, 0.15% SD (w/v) + 1.25% NaCl (w/v), 0.30% SD (w/v) + 1.25% NaCl (w/v), 0.15% SD (w/v) + 0.15% PEG (w/v), and 0.15% SD (w/v) + 1.25% NaCl (w/v) + 0.15% PEG (w/v). The results indicated that soaking cooked duck blood curd samples in antimicrobial agent combinations could reduce mesophile and psychrophile bacteria counts in non-inoculated samples. Additionally, 0.15% SD + 1.25% NaCl + 0.15% PEG combination had a higher reduction in mesophile and psychrophile counts, compared to soaking the samples in 0.30% SD + 1.25% NaCl, 0.15% SD + 1.25% NaCl and 0.15% SD + 0.15% PEG combinations. Similarly, this combination showed a significant decrease in lactic acid bacteria, Pseudomonas, Salmonella, Escherichia coli, and Staphylococcus aureus counts in inoculated samples. Furthermore, soaking the samples in 0.15% SD + 1.25% NaCl + 0.15% PEG combination did not negatively affect the samples’ physical quality. Soaking the samples in 0.15% SD + 1.25% NaCl + 0.15% PEG combination inhibited the growth of mesophile, psychrophile, and Pseudomonas in non-inoculated samples after storage for 10, 6, 10, and 8 days in a slaughter warehouse at 7℃, respectively, and extended shelf-life of samples for 16 days. Regarding physical quality changes, this treatment delayed the reduction of pH, hue, hardness, and chewiness of the samples after storage for 10, 8, 12, and 10 days, respectively. Thus, SD, NaCl, and PEG combination had a high preservative potential for cooked duck blood curd used in industrial slaughterhouses. Keywords: Blood curd, Duck, Organic acid salt, Polyethylene glycol, Quality changes

The thermal-death times of Listeria monocytogenes were determined in inoculated restructured goat steak at 60°C, 65°C, and 70°C of sous-vide temperatures. D-values of L. monocytogenes in inoculated restructured goat steak ranged from 7.27 min at 60°C to 0.46 min at 70°C. Times need to yield at least a 6 log reduction of L. monocytogenes at their temperatures for this product were 47, 12, and 3 min, respectively. After sous-vide, all microbial counts in non-inoculated samples were not detectable, except the aerobic and anaerobic mesophilie and lactic acid bacteria counts were lower than 2 Log CFU/g. For sous-vided and grilled sous-vided samples, sous-vide loss and surface shrinkage were the lowest in samples sous-vided at 60°C for 47 min (p

Objective The influence of konjac gel level on fermentation process and product qualities were assessed to evaluate the feasibility of using it as fat analog in Northeastern Thai fermented sausage (Sai Krok E-san). Methods Five treatments of fermented sausages were formulated by replacing pork backfat with 0%, 7.5%, 22.5%, and 30% konjac gel. The changes in lactic acid bacteria (LAB) and important physicochemical properties of samples were assessed during 3 days of fermentation. After the end of fermentation at day 3, water activity (aw), instrumental texture, color, microbial counts, and sensory evaluation were compared. The best product formulation using konjac for replacing pork back fat were selected and used to compare proximate composition and energy value with control sample (30% pork backfat). Results An increase in konjac gel resulted in higher values of LAB, total acidity, and proteolysis index with lower pH and lipid oxidation during 3 days of product fermentation (p< 0.05). It was noted that larger weight loss and product shrinkage during fermentation was observed with higher levels of konjac gel (p

Current Applied Science and Technology, 19, 3, 306-312

To obtain proteases with high collagenolytic activity, 400 bacteria isolates were screened. The secreted proteases from Bacillus subtilis subsp. subtilis B13 (isolated from beef butchery) and B. siamemsis S6 (isolated from soil) which showed the two highest activity to hydrolyze collagen from bovine Achilles tendon were partially characterized. After enzyme fractionation, both enzymes had the optimum pH for the collagenolytic activity at pH 7.5. However, the optimum temperature of enzyme produced by S6 (60 °C) was higher than B13 (50 °C). The inhibitor study revealed that these proteases were mainly a member of serine proteases and some metalloproteases. Both enzymes were able to degrade collagen with multiple cleavage sites as observed by electrophoretic patterns. In contrast to papain and bromelain, these collagenolytic proteases showed strong hydrolysis toward collagen and elastin as well as beef intramuscular collagen with low beef myofibrillar protein degradation. Moreover, the lower digestion of myofibrillar protein and casein by these enzymes as compared with collagenase from Clostridium histolyticum were observed. These proteases could be applied as a meat tenderizer when collagen or connective tissue protein was responsible for the meat toughness.

The effects of different strains of lactic acid bacteria (LAB) inoculation on the fermentation rates and qualities of moo som, a traditional Thai fermented pork, were evaluated. Lactobacillus plantarum KL102 (spontaneous starter) and L. plantarum TISIR543 (commercial starter) were used as starter cultures in the production of moo som. The decreased amounts of Staphylococcus aureus and coliforms in moo som inoculated with L. plantarum KL102 were at faster rates than those in Moo som inoculated with L. plantarum TISIR543. However, the final products of moo som inoculated with both LAB starters did not find S. aureus or and coliform loadings. Inoculation of both LAB starters could control growth of yeast in samples during fermentation. Furthermore, both starter cultures exhibited a higher rate of fermentation than the control (without inoculum), as demonstrated by the faster rate pH drop and acid production (p < 0.05) during fermentation, while the fermentation of all samples were completed within 3 d. Due to higher acid production rate, texture, and especially hardness, gumminess and chewiness of inoculated moo som were higher than control moo som in the final products (p < 0.05). From the results, the inoculation of LAB starter was more beneficial in color and in overall sensory evaluation (p < 0.05). The overall quality was positively correlated with the color, odor, and texture of moo som (p < 0.01). Based on microbiological and physicochemical qualities and sensory evaluation, KL102 is a potential LAB starter for moo som production.

Objective The aims of this study were to select one strain of Lactobacillus platarum for a potential indigenous safe starter culture with low level antibiotic resistant and low biogenic amine production and evaluate its effect on biogenic amines reduction in Moo som. Methods Three strains of indigenous L. plantarum starter cultures (KL101, KL102 and KL103) were selected on the basis of their safety including antibiotic resistance and decarboxylase activity, and fermentation property as compared with a commercial starter culture (L. plantarum TISIR543). Subsequently, the effect of the selected indigenous safe starter culture on biogenic amines formation during Moo som fermentation was studied. Results KL102 and TISIR 543 were susceptible to penicillin G, tetracycline, chloramphenicol, erythromycin, gentamycin, streptomycin, vancomycin, ciprofloxacin and trimethoprim (MIC90 ranging from 0.25 to 4 μg/ml). All strains were negative amino acid-decarboxylase for lysis of biogenic amines in screening medium. For fermentation in Moo som broth, a relatively high maximum growth rate of KL102 and TISIR543 resulted in lower their generation times than other strains (p < 0.05). These strain counts were constant during the end of fermentation. Similarly, KL102 or TISIR543 addition supported increases of lactic acid bacterial count and total acidity in Moo som fermentation. For biogenic amine reduction tyramine, putrescine, histamine and spermine contents in Moo som decreased significantly by the addition KL102 during 1 d of fermentation (p < 0.05). In final product, histamine, spermine and tryptamine contents in Moom-Moo som inoculated with KL102 were lower amount those with TISIR543 (p < 0.05). Conclusion The results focused on selection of an indigenous safe starter culture, KL102, for using in production of Moo som and composition of this suitable starter culture to reduce the biogenic amine formation in Moo som.

Under conditions of stress, cells of Campylobacter assume a coccoid shape that may be an evolutionary strategy evolved by the organism to enable survival between hosts. However, the physiology of Campylobacter as it devolves from spiral to coccoid-shaped morphology is poorly understood. In this study, conditions influencing the survival of Campylobacter jejuni ATCC 35921 in broth were determined. Cells in late log phase were resuspended in broth at 4 or 60 degrees C. The culturability of these cold- or heat-stressed cell suspensions was determined by spread plate counts and the activity of cells by the direct viable count technique and 5-cyano-2,3-ditolyltetrazolium chloride staining. C. jejuni changed form completely from culturable to viable but nonculturable cells (VBNC) within 25 days at 4 degrees C, and 15 min at 60 degrees C. Light microscopy of C. jejuni VBNC cells showed that the spiral-shaped cells became coccoid, and transmission electron microscopy of C. jejuni VBNC cells showed that the outer membrane was lost in aging cell suspensions. Furthermore, a limited proteomic study was carried out to compare C. jejuni proteins that exhibited increased or decreased synthesis on exposure to 60 degrees C.

The objective of this study was to investigate the in vitro activities of virgin coconut oil, lauric acid and monolaurin in combination with lactic acid against two strains of Staphylococcus aureus, ATCC 25923 and an isolate from a pig carcass, by determination of Fractional Bactericidal Concentration Index (FBCI), time-kill method, as well as scanning and transmission electron microscopy. Minimum bactericidal concentrations (MBC) of lauric acid, monolaurin and lactic acid were 3.2 mg/ml, 0.1 mg/ml and 0.4% (v/v), respectively. The effects of lauric acid + lactic acid and monolaurin + lactic acid combinations were synergistic against both strains, exhibiting FBCIs of 0.25 and 0.63, respectively. In time-kill studies, lauric acid and monolaurin + lactic acid combinations added at their minimum inhibitory concentrations produced a bactericidal effect. The induction of stress in non-stressed cells was dependent on the type and concentration of antimicrobial. This resulted in a loss and change of the cytoplasm and membrane in cells of the bacterium. In contrast, virgin coconut oil (10%) was not active against S. aureus. The bacterial counts found in pork loin treated with lauric acid and monolaurin alone were significantly higher (p0.05) than those treated with both lipids in combination with lactic acid at sub-inhibitory concentrations. The color, odor and overall acceptability of the pork loins were adversely affected by treatment with the three lipids and lactic acid alone but when combinations of the agents were used the sensory quality was acceptable.