• Journal of the Korean Society of Food Science and Nutrition
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• v.33 no.8
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• pp.1343-1347
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• 2004

Conjugated linoleic acid (CLA) concentrations of commercial yoghurts and the ability of dairy starter cultures to produce CLA were investigated. The CLA contents of yoghurts were in the range of 4.1~14.8 mg/l00 g. CLA contents in yoghurts depended on the amount of milk used for raw material. Regression test showed positive correlations between CLA concentrations and selected fatty acids (stearic acid, oleic acid, linoleic acid and linolenic acid) of lipids in yoghurts. Among the 67 commercial dairy starter cultures tested, one of Lactobacillus acidophilus, one of Lactobacillus casei and three of Streptococcus thermophilus were found to be capable of converting free linloeic acid to CLA and cis-9, trans-11 octadecadienoic acid presented more than 70% of the total CLA formed. The CLA conversion rate of the screened strains ranged from 6.1% to 8.6% in whole milk for 24 hours at 37$^{\circ}C$.

• Korean Journal of Food Science and Technology
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• v.38 no.2
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• pp.313-316
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• 2006

To obtain antibiotic resistant profiles of Bifidobacterium, minimum inhibitory concentrations (MIC) of 14 antibiotics for 93 Bifidobacterium isolates from Korean intestine origin were determined. All strains tested were sensitive to chloramphenicol, rifampicin, and amoxicillin, whereas resistant to aminoglycoside family, nalidixic acid, and vancomycin. Among vancomycin-resistant strains, 34% were resistant at more than $100\;{\mu}g/mL$, and showed variant resistances toward tetracycline, erythromycin, and penicillin. Their resistances against penicillin, cephalothin, and tetracycline were higher than ten years ago. MIC of ten isolates from commercial yoghurt products were very similar to those of strains from Korean intestine origin, and 20% strains showed resistance at higher than $100\;{\mu}g/mL$ vancomycin. These results indicated patterns of antibiotic resistance against Bifidobacterium from Korean intestine origin and commercial yoghurts were very similar,and prevalence of vancomycin resistance for Bifidobacterium was 20%. To develop new probiotic, antibiotic resistance of vancomycin and risks involved should be evaluated.

• Korean Journal of Food Science and Technology
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• v.25 no.3
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• pp.258-263
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• 1993

New type yoghurts were prepared by fermenting milk containing puffed rice flour(PRF) with some commercial lactic acid bacterial starters. The yoghurts were evaluated for pH, tillable acidity, viscosity and color with sensory evaluation for final quality. The optimum moisture content of rice for puffing was over or less 14%. Increasing addition level of PRF, lightness decreased and, redness and yellowness increased with increasing viscosity greatly. There was no quality difference among commercial starters but pH, acidity and viscosity of yoghurt were affected. During the storage at $5^{\circ}C$, pH dropped, acidity and viscosity increased gradually. The number of lactic acid bacteria was increased until 6 days storage to $3{\times}10^8$ and dropped after on. The yoghurt containing PRF was inferior in flavor texture and taste comparing with commercial yoghurt.

• Korean Journal of Food Science and Technology
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• v.21 no.6
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• pp.795-799
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• 1989

This study was carried out to hydrolyze lactose in commercial milk by ${\beta}-galactosidase$ from Kluyveromyces fragilis and to compare some physicochemical properties of yoghurts made from control and lactase-treated commercial milks. Quantitative analysis of sugars was performed by gas liquid chromatograph (GLC) on trimethylsilyl (TMS) derivatives. In commercial milk, 94.6% of lactose was hydrolyzed after 2 hours incubation at $40^{\circ}C$ with 6.0 units/ml of ${\beta}-galactosidase$. pH, titratable acidity and viable cell number of yoghurt made from lactase-hydrolyzed (LH) commercial milk were 4.1, 1.04% and $6.5{\times}10^8/ml$ of Str. thermophilus, $8.9{\times}10^8/ml$ of L. bulgaricus after 8 hours incubation at $40^{\circ}C$, respectively, The total contents of amino acid were 2.63% in control and 2.19%. in LH yoghurt. The total contents of free amino acid were 26.95 mg% in control and 17.55mg% in LH yoghurt. Analysis of free fatty acids resulted in that the contents of short chain fatty acids in LH yoghurt were a little higher than those in control. Both in control and LH yoghurt, the palmitic acid content was highest and that was followed by oleic and myristic acid.

• Korean Journal of Food Science and Technology
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• v.25 no.4
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• pp.340-344
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• 1993

Gel type yoghurts from 5 representative manufacturers were collected at market and evaluated their physico-chemical properties during storage at $5^{\circ}C$. The range of pH, acidity, Brix and viscosity of each product were $3.87{\sim}4.19,\;0.97{\sim}1.42%,\;16.2{\sim}22.2\;and\;7,850{\sim}21,000 cp$ respectively. The pH of each product decreased gradually during storage time and reached around pH 4.1 after 16 days with proportional acidity increasing. The viscosity of all test products showed increasing trend by lactic acid bacterial action. Total lactic acid bacteria were $10^8{\sim}10^9\;CFU/ml$ at the beginning storage and increased or decreased depending upon each product. But all product maintained over than $10^8 CFU/ml$ which meets regulatory level after 16 days storage.

• Food Science of Animal Resources
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• v.29 no.4
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• pp.437-444
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• 2009

${\gamma}-Aminobutyric$ acid (GABA) producing lactic acid bacteria, Lactobacillus acidophilus RMK567 was cultivated in 50 L of sterilized MRS broth using a fermenter at $40^{\circ}C$ for 24 h. The cell number was increased to $10.04{\pm}0.13$ Log CFU/mL with a growth rate constant (k) of 0.454 generation/h and a generation time (g) of 2.303 h after a lapse of a lag phase (L) of 5.16 h. A total of 487 g of cell paste with 40.5% moisture was harvested with viable cell number of 12.48 Log CFU/g cell paste. The cell pastes after preparation with glycerol, glucose, and polydextrose as cryo-protectants were lyophilized under a vacuum of 84 m torr. A total of 408 g of freeze dried (FD) cell powders were mixed with a commercial strain of Streptococcus thermophilus to prepare of three types FD starter cultures with the viable cell numbers of 12.42 (FDA-GY), 12.60 (FDBGG) and 12.91 (FDC-GP) Log CFU/g. During preservation the FD cultures at -$18^{\circ}C$, the cell viability of the FD starter cultures were rapidly dropped to below 3.24% of the day of storage. No significant difference was found in the cell viabilities among three types of FD starters cultures, but significant difference (p<0.01) was found in storage periods. Yoghurts fermented through FD starter culture of L. acidophilus RMK567 were determined to contain $155.16{\pm}8.53$ ppm, $243.82{\pm}4.27$ ppm, and $198.64{\pm}23.46$ ppm of GABA, respectively. This study shows that GABA production activity of L. acidophilus RMK567 is not affected during the freeze drying process and would be available for commercial production of yoghurt containing high GABA content.