• Journal of Microbiology and Biotechnology
• /
• v.27 no.10
• /
• pp.1778-1782
• /
• 2017

To identify and discriminate the bacterial species at the subspecific level, rep-PCR is a reliable genomic fingerprinting tool. Fourteen strains of bacteria were isolated from different food sources, identified as Leuconostoc citreum using 16S rRNA gene sequencing, and amplified using rep-primers (REP, ERIC, and $(GTG)_5$). Fingerprinting patterns generated bands in the range of 300-6,000 bp with REP, 150-6,000 bp with ERIC, and 200-1,700 bp with $(GTG)_5$ primers. In UPGMA dendrogram analysis, 14 strains were clustered into three clades (I, II, and III) with all the primers, thus differentiating them at the molecular level. The present study revealed the differentiation of L. citreum strains using rep-PCR.

• Journal of the Korean Society of Food Science and Nutrition
• /
• v.1 no.1
• /
• pp.51-62
• /
• 1972

In Korea, fermented fish has been playing an important role as a preserved and flavor rich food. It is said that the digestion of fish protein is due to both action of intrinsic (autolytic enzymes) and bacterial enzymes in fish. The mass production of fermented fish has been impeded since traditional method of fermentation requires a long duration for a complete digestion. A high concentration of salt and unsanitary condition are also considered disadvantages of the old method. To improve the quality of the product and to develop mechanized process of fermentation, fermentors which have such control device as temperature, pH and agitation control system have been urgently needed. In this study, a model design of a fermentor is studied. The calculation was based on the optimum conditions for enzymatic hydrolysis of fish protein which involve temperature, pH, viscosity and other factors.

• Food Science and Preservation
• /
• v.20 no.3
• /
• pp.323-329
• /
• 2013

Strawberries are among the leading ready-to-eat agricultural products that have superior taste and nutrition. Thus, consumer concerns about the safety of eating strawberries are growing. To evaluate the contamination levels of strawberries according to their cultivation methods (nutriculture, pesticide-free culture and organic farming) and parts [fruit (flesh), stalk (pedunle) and leaf (calyx)], 1,020 parts of strawberry samples were collected at 12 farms in Nonsan-si and quantitatively or qualitatively examined for the indicators of food safety and food poisoning bacteria. The total aerobic bacteria count in the whole samples was 2.3~6.8 ${\log}_{10}$ CFU/g, and coliform bacteria were detected in 14.2% of the whole samples with a contamination level range of 2.1~4.5 log CFU/g. E. coli were detected in 0.9% of the whole samples with a contamination level range of 2.1~2.8 log CFU/g. The analysis of the bacterial levels according to the cultivation methods showed that the total aerobic bacteria and coliform counts were higher in the strawberries that were grown via organic farming than in those that were grown via nutriculture and pesticide-free culture. However, the E. coli counts of the strawberries that were grown via organic farming and via pesticide-free culture were similar and differed from that of the strawberries that were grown via nutriculture. The analysis of the contamination levels according to the parts of the strawberries showed that the total aerobic bacteria, coliform and E. coli counts of the fruits, stalks and leaves of the strawberries did not significantly differ. Staphylococcus aureus was detected in two organically grown strawberries, but Salmonella spp., Listeria monocytogenes and E. coli O157:H7 were not detected in the whole samples. These results show that the bacterial contamination levels of the strawberries differed based on their cultivation methods. Thus, a suitable method of reducing the bacterial contamination levels of strawberries according to their farming methods is needed.

• Korean Journal of Food Science and Technology
• /
• v.29 no.5
• /
• pp.919-924
• /
• 1997

The changes in physicochemical properties of cooked rice stored in an electric rice cooker at different temperature (63, 66, 69 and $72^{\circ}C$) were investigated. The growth of thermophilic bacteria was gradually increased in all samples with storage time up to 6 hours and increased rapidly afterward. The bacterial growth rate was higher during storage at low temperature than at high temperature, and the bacterial number generally reached the maximum at 18 hours of the storage. The number of bacteria in sample stored at $63^{\circ}C$ was increased to $10^6$ CFU/g after storage for 6 hours. The heat treatment at 6 hours of storage decreased the bacterial number to $10^5 $ CFU/g at 8 hours of storage. Bacterial number was gradually increased with storage time after the first heat treatment. When the sample was reheated after 8 hours of storage, the bacterial number was reduced to the level at which off-odor was not detected after storage for 24 hours. During the storage, moisture content of heat-treated sample was lower than that of sample stored at $63^{\circ}C$ but higher than that of sample stored at $72^{\circ}C$. The L value of heat-treated sample was higher than that of the sample stored at $72^{\circ}C$, but lower than that of the sample stored at $63^{\circ}C$. The b value showed an opposite trend to the L value with regard to the storage temperature. Changes in texture were not remarkable during the storage for the sample heat-treated and stored at low temperature. The occurrence of off-odor and browning was depressed in the heat-treated sample, and the texture and overall eating quality were more acceptable than the samples stored at low temperature.

• Journal of Microbiology
• /
• v.39 no.3
• /
• pp.202-205
• /
• 2001

The EF-18 agar/hydrophobic grid membrane filter (EF18/HGMF) method was evaluated for the isolation of Salmonella in naturally contaminated chicken carcasses, chicken parts (legs, wings and giblets) and processed chicken products (sausages and hamburgers). Percentages of false positive results for Salmonella (colonies with a similar morphology to those of Salmonella) were 78.75, 81.67 and 80% for carcasses, chicken parts and processed chicken products, respectively. The bacterial isolates that caused false positive reactions using this method were identified as Proteus mirabilis (70.85%), Citrobacter freundii (15.25%), Klebsiella ozaenae (5.83%), Hafnia alvei (4.48%), Escherichia coli (2.69%) and Enterobacter aerogenes (0.90%). The data obtained in this study suggest that the EF-18/HGMF method is not sufficiently selective or specific far isolating Salmonella from meat and chicken products.

• Korean Journal of Food Science and Technology
• /
• v.15 no.2
• /
• pp.118-122
• /
• 1983

The whole eggs with of without added 1% of glucose, lactose and sucrose respectively were pasteurized at $58^{\circ}C$ for 30min and then incubated for 24 hrs after inoculating with S. lactis, L. casei and S. faecalis to investigate the changes in lactic acid bacterial cell counts, titable acidity and pH. Fresh eggs were not contaminated with common bacteria and Salmonella, Proliferation of L. casei was the best among those microorganisms in pasteurized whole egg without sugar added, and titrable acidity was the highst and pH the lowest in the eggs fermented with L. casei. However, lactic acid bacterial cell counts, titrable acidity and pH were changed significantly by the addition of sugar, especially the growth of S. faecalis was better than two other organisms, and lactic acid bacterial cell counts, titrable acidity and pH of the eggs fermented with S. faecalis were $2.5{\times}10^{10}$, 0.70 and 4.8 respectively after 24 hrs fermentation.

• Food Science and Preservation
• /
• v.18 no.1
• /
• pp.7-12
• /
• 2011

Paprika is a major export of Korea, but biosafety is important if exports are to grow. To date, few paprika biosafety data are available. We evaluated microbiological contamination of paprika, and determined bacterial levels with respect to storage temperature. Mean counts of total aerobic bacteria were $2.3{\pm}0.3\;log_{10}\;CFU/g$, but coliforms were not isolated. Staphylococcus aureus, Salmonella spp., Listeria spp., and Escherichia coli O157 were also not detected. When bacterial contamination of paprika stored at room temperature or $4^{\circ}C$ for 20 days was evaluated, the numbers of total aerobic bacteria peaked at 14-16 days at room temperature (4 times more than those of $4^{\circ}C$). However, aerobic bacteria grew slowly at $4^{\circ}C$. Coliforms were also detected twice at room temperature, but not upon storage at $4^{\circ}C$. The results indicate that the paprika exported from Korea is relatively biosafe. However, food hygiene issues must be addressed to reduce contamination during storage and distribution.

• Microbiology and Biotechnology Letters
• /
• v.41 no.1
• /
• pp.119-127
• /
• 2013

Twenty-three strains of Leuconostoc species and 45 strains of Weissella species inhibiting the growth of Lactobacillus sakei, one of the most populous lactic acid bacteria in over-ripened kimchi, were isolated from kimchi in our previous study. Among these hetero-fermentative 68 strains, Leuconostoc mesenteroides CK0128, Weissella cibaria CK0633, and W. cibaria KK0797 exhibited a relatively high survival rate in MRS medium, which was adjusted to pH 4.3 using an acid mixture consisting of acetic and lactic acids, and produced a large amount of exopolysaccharides. The culture supernatants of 3 strains were fractionated by a molecular weight cutter and lyophilized. The fractions with a molecular weight smaller than 3,000 Da showed antagonistic activity against Staphylococcus aureus and Lb. sakei. The anti-bacterial substances were very stable to heat treatments ($121^{\circ}C$, 15 min) and active at acidic conditions below pH 5. ${\alpha}$-Amylase, lipase, and proteolytic enzymes (proteinase K and pepsin) did not affect their activities. These non-proteinaceous anti-bacterial substances inhibited the growth of several food pathogens.

• Journal of Life Science
• /
• v.19 no.8
• /
• pp.1132-1138
• /
• 2009

We investigated the physicochemical stabilities and biological activities of ethanol- extracted pigment from marine bacterium Pseudoalteromonas psicida TA20. This bacterial pigment was very stable at a pH range of between 4.0 and 8.0 at a temperature below $40^{\circ}C$. In the presence of light, the pigment was also very stable, showing more than 90 percent remaining absorbance during 14 days at $25^{\circ}C$. The stability of the pigment, when metal ions were present, showed higher stability in all examined metal ions except for $Al^{3+}$ and $Cu^{2+}$, especially in the presence of $Fe^{2+}$. This pigment showed higher stability than other pigment extracts reported. The pigment has free-radical scavenging (3,495 ${\mu}g/ml$) activity and 44% antioxidant protective effect against DNA damage of human lymphocyte cells at a concentration of 10 ${\mu}g/ml$. The results indicate that the bacterial pigment produced a significant reduction in oxidative DNA damage. The pigment also showed antimicrobial activity against major food poisoning bacteria. Therefore, these results suggest that this bacterial pigment could be used as a natural colorant in the food industry, having the advantages of antioxidant and antimicrobial activities.

• Journal of Applied Biological Chemistry
• /
• v.62 no.2
• /
• pp.181-186
• /
• 2019

The optimum design of LED device for irradiation of 460 nm blue light on extruded rice cake using simulation and the effect of the blue light on the inactivation of Bacillus cereus (B. cereus) group on the rice cake were investigated. The irradiated light intensity patterns on the surface area of the sample were simulated with three different LED arrays (centered, cross, and evenly spaced) and at various distances (22, 32, 42 mm) between the LED modules and the sample. In addition, the uniformity was calculated as Petri factor. The evenly spaced array resulted the most uniform light intensity pattern in the simulation, and the Petri factor of 32 and 42 mm of the distances showed higher than 0.9, which represents the ideal uniformity of LED device. The bacterial population of the rice cake decreased to less than the initial bacterial population during exposure to LED blue light, whereas the bacterial population of the control sample increased. The bacterial count of the rice cake after blue light irradiation for 24 h was 1.21 log CFU/g lower than the control sample. Petri factor increased with increase of the distance between the light source and sample, however, the reduction rate of B. cereus group decreased. Therefore, the design of LED device, that represented the Petri factor higher than 0.9 and inactivated the population of B. cereus group, with evenly spaced and 32 mm of distance between the light source and sample was suitable for extending shelf-life of rice cake.