• Journal of the Korean Society of Food Science and Nutrition
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• v.46 no.3
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• pp.327-334
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• 2017

Water and 75% ethanol extracts were prepared from defatted green tea seeds and evaluated for their anti-yeast activities. The antimicrobial activities of defatted green tea seed extracts (DGTSEs) were tested against food-spoilage bacteria, yeasts, and molds. DGTSEs exhibited antimicrobial activities with minimum inhibitory concentrations of $39{\sim}1,250{\mu}g/mL$ against three bacteria, two molds, and all tested yeast strains. Ethanol extract showed higher antimicrobial activity than water extract. The stability of anti-yeast activities of DGTSEs was examined under different conditions of temperature, pH, and NaCl concentrations. The anti-yeast activities of DGTSEs were stable at pH 3~9, 0~20% NaCl, and $100^{\circ}C$ for 30 min. However, anti-yeast activities of DGTSEs decreased upon heating at $70^{\circ}C$ for 24 h or $121^{\circ}C$ for 15 min. DGTSEs were applied to food models to determine their inhibitory effects on yeast film formation. Water and 75% ethanol extracts were effective in preventing yeast film formation at concentrations more than 156 and $39{\mu}g/mL$ in soy sauce, 156 and $78{\mu}g/mL$ in pickle sauce, and 78 and $39{\mu}g/mL$ in kimchi, respectively.

• Animal Bioscience
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• v.34 no.6
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• pp.1029-1037
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• 2021

Objective: This study was conducted to investigate effects of antifungal substance and carboxylesterase-producing inoculant on fermentation indices and rumen degradation kinetics of whole crop rice (WCR) silage ensiled at different dry matter (DM) contents. Methods: Dual-purpose inoculants, Lactobacillus brevis 5M2 and Lactobacillus buchneri 6M1, confirmed both activities of antifungal and carboxylesterase in the previous study. The WCR at mature stage was chopped, and then wilted to obtain three different DM contents consisting of 35.4%, 43.6%, and 51.5%. All WCR forages were applied distilled water (CON) or mixed inoculants with 1:1 ratio at 1×105 colony forming unit/g (INO), and ensiled into 20 L mini silo (5 kg) in quadruplicates for 108 d. Results: The INO silages had lower lactate (p<0.001) and butyrate (p = 0.022) with higher acetate (p<0.001) and propionate (p<0.001) than those of CON silages. Ammonia-N (p<0.001), lactate (tendency; p = 0.068), acetate (p = 0.030), and butyrate (p<0.001) concentrations of INO silages decreased linearly with increasing DM content of WCR forage. The INO silages presented higher lactic acid bacteria (p<0.001) with lower molds (p<0.001) than those of CON silages. Yeasts (p = 0.042) and molds (p = 0.046) of WCR silages decreased linearly with increasing DM content of WCR forage. In the rumen, INO silages had higher the total degradable fraction (p<0.001), total volatile fatty acid (tendency; p = 0.097), and acetate (p = 0.007), but lower the fractional degradation rate (p = 0.011) and propionate (p<0.001) than those of CON silage. The total degradable fraction (p<0.001), total volatile fatty acid (p = 0.001), iso-butyrate (p = 0.036), and valerate (p = 0.008) decreased linearly with increasing DM content of WCR forage, while the lag phase (p<0.001) was increased linearly. Conclusion: This study concluded that application of dual-purpose inoculants on WCR silage confirmed antifungal and carboxylesterase activities by inhibiting mold and improving rumen digestibility, while increase of wilting times decreased organic acids production and rumen digestibility.

• Food Science and Preservation
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• v.13 no.3
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• pp.292-298
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• 2006

Effect of gamma irradiation on the microbiological and physicochemical characteristics of steamed waxy corns was determined in order to develop preservation techniques to enhance shelf-life during storage at room or low temperature. The initial total microbial count, and yeast & molds steamed waxy corns before irradiation were $2.1{\times}10^3CFU/g,\;1.9{\times}10^3CFU/g$, respectively. However, the total microbial count were completely inactivated and the count of yeast and molds were only 34 CFU/g at 3 kGy treatment When non-irradiated steamed waxy corns were stored at $25^{\circ}C$ for 7 months, the growth of total microbial counts and yeasts & molds were rapidly increased up to $7.1{\times}10^6CFU/g\;and\;1.9{\times}10^7CFU/g$, respectively. However, the total microbial counts at 3 kGy treatment and yeast & molds at 5 kGy treatment for 7 month storage were completely inactivated Similar result was observed at $15^{\circ}C$ and $4^{\circ}C$ storage. The Hardness of the irradiated steamed waxy corns and irradiation dose were not significantly different from those of the non-irradiated steamed waxy corns before storage, but the hardness of non-irradiated steamed waxy corns was significantly increased during the storage, compared to those of irradiated corns. The water content of both irradiated and non-irradiated steamed waxy corns after 7 month storage were significantly decreased from $65{\sim}60%$ to 30% but the changes of water content among treatments or irradiation doses were not significantly different during storage. Sugar contents in the irradiated steamed waxy corns were less free than those of non-irradiated samples and the amount of free sugar slowly increased as storage temperature increased. Sensory evaluation result showed that total sensory scores in irradiated steamed waxy corns were better than those of non-irradiated samples and total sensory scores were increased as irradiation doses increased.

• Food Science and Biotechnology
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• v.17 no.1
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• pp.212-215
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• 2008

The effect of gamma irradiation on the Hunter color values, microbiological quality, and sensory attributes of frozen ground beef, pork, and chicken was investigated. Fresh meat samples were purchased from local markets, packed and frozen in polyethylene bags, and irradiated at 5 kGy. The Hunter's L-values (lightness) were not significantly different in all the meat samples after irradiation, but the a-values (redness) were higher in the irradiated beef and pork than the non-irradiated ones. After 6 months of storage at $-6^{\circ}C$, the L-values increased in all the meat samples and the a-value in chicken was lower in the irradiated sample than that of the control. The microbial counts decreased in all the samples right after irradiation, but the coliforms and yeasts & molds increased by 1-2 log cycles after 6 months even under frozen state. The overall acceptability of the meat was not affected by irradiation. Panelists had a higher likeness for the increased redness in irradiated beef. In general, only the color changes in meat as a result of irradiation were found to be species-dependent.

• Journal of Microbiology and Biotechnology
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• v.28 no.1
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• pp.105-108
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• 2018

Beef was dry aged for 40-60 days under controlled environmental conditions in a refrigerated room with a relative humidity of 75%-80% and air-flow. To date, there is little information on the microbial diversity and characteristics of dry aged beef. In this study, we explored the effect of change in meat microorganisms on dry aged beef. Initially, the total bacteria and LAB were significantly increased for 50 days during all dry aging periods. There was an absence of representative foodborne pathogens as well as coliforms. Interestingly, fungi including yeast and mold that possess specific features were observed during the dry aging period. The 5.8S rRNA sequencing results showed that potentially harmful yeasts/molds (Candida sp., Cladosporium sp., Rhodotorula sp.) were present at the initial point of dry aging and they disappeared with increasing dry aging time. Interestingly, Penicillium camemberti and Debaryomyces hansenii used for cheese manufacturing were observed with an increase in the dry aging period. Taken together, our results showed that the change in microorganisms exerts an influence on the quality and safety of dry aged beef, and our study identified that fungi may play an important role in the palatability and flavor development of dry aged beef.

• Asian-Australasian Journal of Animal Sciences
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• v.30 no.6
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• pp.804-810
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• 2017

Objective: The objective of this study was to evaluate the effect of sodium diacetate (SDA) on fermentation profile, chemical composition and aerobic stability of alfalfa (Medicago sativa L.) silage. Methods: Fresh alfalfa was ensiled with various concentrations of SDA (0, 3, 5, 7, and 9 g/kg of fresh forage). After 60 days of the ensiling, the samples were collected to examine the fermentative quality, chemical composition and aerobic stability. Results: The application of SDA significantly (p<0.05) decreased silage pH with the lowest value in silage with 7 g/kg of SDA. The proliferations of enterobacteria, yeasts, molds and clostridia were inhibited by SDA, resulted in lower ethanol, propionic and butyric acid concentrations and dry matter loss in SDA treated silages than control. The increasing SDA linearly decreased free amino acid N (p<0.001), ammonia N (p = 0.018) and non-protein N (p<0.001), while linearly increased water soluble carbohydrate (p<0.001) and peptide N (p<0.001). It is speculated that SDA accelerated the shift from homofermentative to heterofermentative lactic acid bacteria during the silage fermentation, indicated by lower lactic acid production in SDA-9 than SDA-7 silages after 60 days of ensiling. Alfalfa silages treated with SDA at 7 g/kg had highest Flieg's point and remained stable more than 9 d during aerobic exposure under humid and hot conditions in southern China. Conclusion: SDA may be used as an additive for alfalfa silages at a level of 7 g/kg.

• Korean Journal of Food Science and Technology
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• v.47 no.1
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• pp.70-74
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• 2015

Inactivation of microorganisms in grains used for saengshik, a formulated health food, was attempted by corona discharge plasma jet (CDPJ). The initial microbial counts of the grains were in the range of $1.7{\times}10^3-9.9{\times}10^5CFU/g$. The CDPJ-inactivation effect was increased with electric current in the range of 1-1.5 A. Regarding span length between the tips of the electrodes and the treatment surface, the highest inactivation effect was observed at 25 mm. The inactivation pattern fitted well to the Singh-Heldman model. Bacteria were more labile to the CDPJ inactivation than yeasts and molds. Among tested grains, white rice showed the highest sterility followed by pressed barley and brown rice. Despite the inactivation by plasma, the thiobarbituric acid content of the grains remained unchanged over 10 min of treatment. Our results indicated the potential of the CDPJ treatment to improve the hygiene of saengshik products with no remarkable changes in lipid quality.

• Food Science of Animal Resources
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• v.37 no.2
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• pp.297-304
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• 2017

Animal-origin food products pose serious threat to public food safety due to high microbial loads. The microbial and radioactive contaminations in commercial cold duck meat products were evaluated. Ten different lots of commercial samples ($C_1-C_{10}$) were classified based on type and smoking process. All samples were highly contaminated (< 4-7 Log CFU/g) with total aerobic bacteria (TAB), yeasts and molds (Y&M), and 7 samples ($C_1-C_7$) were positive for coliforms. Furthermore, three samples were contaminated with Listeria monocytogenes ($C_4-C_6$) and one with Salmonella typhimurium ($C_6$). No radionuclides ($^{131}I$, $^{137}Cs$, and $^{134}Cs$) were detected in any sample. The results of DEFT (direct epifluorescent filter technique)/APC (aerobic plate count), employed to screen pre-pasteurization treatments of products, indicated that smoked samples were positive showing DEFT/APC ratios higher than 4. Notably, the samples showed a serious threat to microbial safety, thus were irradiated with electron-beam (e-beam). The $D_{10}$ values for S. typhimurium and L. monocytogenes were 0.65 and 0.42 kGy, respectively. E-beam application at 3 and 7 kGy resulted in reduction of initial TAB, Y&M, and coliform populations by 3 and 6 log cycles, respectively. Thus, e-beam was proven to be a good decontamination approach to improve the hygiene of cold duck meat.

• Korean Journal of Food Science and Technology
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• v.47 no.6
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• pp.687-697
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• 2015

With the shortage of edible fats and oils and depletion of fossil fuels in many countries, microbial lipids is emerging as one of the most promising sources of fats and oils in the global market. Oleaginous microorganisms, also called single cell oils (SCOs), can accumulate lipids more than 25% in the cell volume. Triacylglycerols are the major storage lipids. SCOs offer several advantages for lipid production as follows: SCOs have short life span which would shorten production time, cultivation conditions are not affected by climate and place; the production process is easy to control. There are a number of oleaginous yeasts, molds, and microalgae. Furthermore, the lipid productivity of SCOs can be enhanced through strain improvement and the optimization of cultivation conditions. The new strains developed using recent advanced biotechnical methods showed greatly improved oleaginicity. Further, hydrolysates of lignocellulosic materials can be used as carbon sources for economic production of SCO.

• Journal of Microbiology and Biotechnology
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• v.24 no.8
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• pp.1088-1095
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• 2014

A systematic investigation was performed on the bacterial, Bacillus, fungal, and yeast communities of the three types of Daqu (mechanically prepared, manually prepared, and mixed prepared) used in Baiyunbian Company by reconditioning PCR-denaturing gradient gel electrophoresis (PCR-DGGE). The DGGE results showed that the microbes in the three types of Daqu were mainly thermotolerant and thermophilic microbes, and the most dominant bacterial species were Bacillus and Virgibacillus, followed by Lactobacillus and Trichococcus. Furthermore, the dominant fungi were found to be molds, such as Rasamsonia, Penicillium, Aspergillus, and Monascus, and the dominant yeasts were Saccharomyces cerevisiae, Saccharomycopsis fibuligera, Pichia anomala, and Debaryomyces hansenii. In general, the three types of Daqu showed slight differences in microbial communities, and the Shannon indexes (H') of the manually prepared and mechanically prepared Daqu were similar. The results suggest that mechanically prepared Daqu can replace manually prepared Daqu in liquor production, and this research provides useful information for liquor production and process improvement.