• Journal of Dairy Science and Biotechnology
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• v.24 no.1
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• pp.65-73
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• 2006

This study was to review recent reports in effects of various starter cultures on the viscosity in stirred yogurt. The rheological properties of yogurt have received considerable attention in the literature. Most yogurts are typically made by mixed cultures of Lactobacillus bulgaricus and Streptococcus thermophilus. The viscosity of yogurt made by mixed cultures was much higher than that of yogurt by single cultures. Since texture of stirred yogurt is the result of both acid aggregation of casein micelles and production of exopoly-saccharides, it is suggested that yogurt be made by the exopolysaccharide-producing cultures in order to increase viscosity, Both types of exopolysaccharides are capsule and loose slime(ropy). But it is desirable to use encapsulated nonropy strains. And Bifidobacteria affects adversely to the viscosity of yogurt. Therefore, starter cultures which have an effect on yogurt viscosity have been widely demonstrated. This review is the search for the development of viscosity in stirred yogurt.

• Journal of Dairy Science and Biotechnology
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• v.18 no.1
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• pp.61-72
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• 2000

Consumers primarily consider flavor when they take yogurt. Recent researches on yogurt flavor productron its analytical technique have been extensively developed. These studies have provided a better understanding on the role of starter culture microorganisms on flavor formation and degradation. Yogurt volatile flavor compounds produced by the lactic cultures include acetaldehyde, diacetyl, ethanol and organic acid. Among them, acetaldehyde is recognized as a principal flavor component. since yogurt contains a delicate and low intense flavor, mild sample isolation techniques and sensitive identification means might be used. This paper attempts to discuss recent findings in yogurt flavor and to describe the application of yogurt flavor separation techniques. The section on practical aspects of culture selection based on flavor compound production and flavor analysis is also included.

• Korean Journal of Food Science and Technology
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• v.20 no.2
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• pp.140-147
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• 1988

The pysicochemical and bacteriological properties of yogurts made by single or mixed cultures of L. bulgaricus FRI025 and S. thermophilus CHI were investigated. L. bulgaricus FRI025 which was isolated from raw milk was selected as starter culture among 22 strains of lactic culture by measuring viscosity, flavor, growth and acid production ability. The acid production and number of viable cell were increased by using L. bulgaricus FRI025 and S. thermophilus CHI together in ratio of apporximately 1:1. The pH, titratable acidity, viable cell number and viscosity of yogurt were 4.08, 1.14%, $2.5{\times}10^{10}/ml$ and 2100 cp after 9 hours incubation at $40^{\circ}C$, respectively. The pH and viable cell number were decreased on the other hand titratable acidity and viscosity were increased after 7 days of storage at $4^{\circ}C$. The changes of quality did not show significantly after storage. The selected starter was much higher than commercial yogurt starter in the acid production and growth of starter. The yogurt nanufactured with selected starter was better than with commercial yogurt in sensory evalution such as taste, texture, flavor and overall acceptability.

• Korean journal of food and cookery science
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• v.21 no.2 s.86
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• pp.217-224
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• 2005

The storage characteristics of frozen soy yogurt prepared with hydrolyzed soy protein isolates were evaluated. In order to facilitate lactic fermentation bacteria grow and produce lactic acid as fast rate as possible, soy protein isolate(SPI) was hydrolyzed using two kinds of proteases; bromelain and a-chymotrypsin. The cultural systems employed thereafter for lactic fermentations were Bifidobacterium bifidum or B. bifidum and Lactobacillus bulgaricus. The viable cell counts, normal- and bile acid tolerances from the mixed cultures of B. bifidum and L. bulgaricus decreased sharply during the initial first 3 days of frozen storage and then showed a gradual decrease thereafter. Melt-down percent of the all frozen products have been favorably affected as was shown by less melting at raised testing temperature during 28 days of frozen storage except for the initial 3 days during which a minor change has been observed. Among the various volatile flavor components, the contents of acetaldehyde, acetone, diacetyl and methanol generally increased during the frozen storage. In sensory test, the frozen soy yogurt prepared with a-chymotrypsin and mixed culture of B. bifidum and L. bulgaricus was the most desirable, the highest scores in sourness, bitterness and mouthfeel.

• Microbiology and Biotechnology Letters
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• v.47 no.2
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• pp.211-219
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• 2019

The effect of microencapsulation on previously isolated Lactobacillus delbrueckii 94/L4 as starter culture for yogurt, and Lactobacillus casei 97/L3 as a probiotic candidate was investigated. Preliminary results showed that L. delbrueckii 94/L4 exhibited tolerance to bile, unlike L. casei 97/L3. Freeze drying significantly (p < 0.05) reduced the viability of both isolates by log 0.71-2.70. Although microencapsulation preserved the viability of L. casei 97/L3 cells exposed to simulated gastrointestinal tract conditions for 120 min, it did not impart significant (p < 0.05) protection against loss of viability during the first 30 min of exposure. Conversely, microencapsulated L. delbrueckii 94/L4 with the addition of Streptococcus thermophilus 24/S1 as starter culture was successfully incorporated into milk to form yogurt, yielding a significantly (p < 0.05) improved product quality.

• Korean Journal of Food Science and Technology
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• v.33 no.6
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• pp.676-681
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• 2001

This study was carried out to evaluate the quality characteristics of frozen soy yogurts prepared with different proteolytic enzymes and starter culture. The viable cell counts of lactic acid bacteria in frozen soy yogurts were measured $10^8$ CFU/g by the single culture method, while $10^9$ CFU/g by the mixed culture method except ${\alpha}-chymotrypsin$ treatment. The viable cell counts of lactic acid bacteria did not decrease after freezing for 30 min in ice cream maker. The lactic acid bacteria from the mixed culture showed better bile acid tolerance than those from the single culture. The lactic acid bacteria from the frozen soy yogurt prepared with ${\alpha}-chymotrypsin$ and mixed culture of Bifidobacterium bifidum and Lactobacillus bulgaricus showed better acid tolerance and bile acid tolerance. The highest(73.45%) overrun was observed in the frozen soy yogurt treated with ${\alpha}-chymotrypsin$ and mixed culture of B. bifidum and L. bulgaricus. The melt-down percent was higher in the single culture than the mixed culture. In sensory test, the frozen soy yogurt prepared with ${\alpha}-chymotrypsin$ and mixed culture of B. bifidum and L. bulgaricus was the most desirable, the highest scores in sourness, bitterness and mouthfeel.

• Microbiology and Biotechnology Letters
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• v.46 no.3
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• pp.201-209
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• 2018

Streptococcus thermophilus, Lactobacillus delbrueckii, Lactobacillus fermentum and Lactobacillus casei were successfully isolated from indigenous Indonesian fresh milk based on the general morphological and biochemical classification as described in Bergey's manual. Verification was conducted by sequencing of 16S rRNA after selection using the classification method mentioned in the manual. All isolates exhibited antimicrobial activity against Escherichia coli and Staphylococcus aureus in the well diffusion test. The susceptibilities of the isolated S. thermophilus 24/S1 and L. delbrueckii 94/L4 against 22 different antibiotics were determined by the disc diffusion method and variable susceptibility patterns were observed. Both isolates were susceptible to amoxicillin, the most commonly prescribed antibiotic, and resistant to sulfonamide. The presence of a plasmid was not detected after extraction. S. thermophilus 24/S1 and L. delbrueckii 94/L4 starter cultures were prepared for yogurt production after 9.5 h of incubation and the yogurt was evaluated for its flavor and quality by 30 volunteers. A score of $4.93{\pm}0.45$ out of 7 was obtained as compared to the yogurt prepared using commercial starter cultures which yielded a score of $4.76{\pm}0.30$ out of 7.

• Food Science of Animal Resources
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• v.36 no.3
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• pp.427-434
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• 2016

Benzoic acid is occasionally used as a raw material supplement in food products and is sometimes generated during the fermentation process. In this study, the production of naturally occurring yogurt preservatives was investigated for various starter cultures and incubation temperatures, and considered food regulations. Streptococcus thermophilus, Lactobacillus acidophilus, Lactobacillus delbrueckii subsp. bulgaricus, Lactobacillus rhamnosus, Lactobacillus casei, Lactobacillus paracasei, Lactobacillus reuteri, Lactobacillus plantarum, Bifidobacterium longum, Bifidobacterium lactis, Bifidobacterium bifidum, Bifidobacterium infantis, and Bifidobacterium breve were used as yogurt starter cultures in commercial starters. Among these strains, L. rhamnosus and L. paracasei showed the highest production of benzoic acid. Therefore, the use of L. rhamnosus, L. paracasei, S. thermophilus, and different incubation temperatures were examined to optimize benzoic acid production. Response surface methodology (RSM) based on a central composite design was performed for various incubation temperatures (35-44℃) and starter culture inoculum ratios (0-0.04%) in a commercial range of dairy fermentation processes. The optimum conditions were 0.04% L. rhamnosus, 0.01% L. paracasei, 0.02% S. thermophilus, and 38.12℃, and the predicted and estimated concentrations of benzoic acid were 13.31 and 13.94 mg/kg, respectively. These conditions maximized naturally occurring benzoic acid production during the yogurt fermentation process, and the observed production levels satisfied regulatory guidelines for benzoic acid in dairy products.

• Korean Journal of Food Science and Technology
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• v.33 no.5
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• pp.603-610
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• 2001

The quality characteristics of soy yogurt prepared with different proteolytic enzymes and starter culture were evaluated. In order to facilitate the growth of lactic acid bacteria and subsequent production of lactic acid, soy protein isolate(SPI) was hydrolyzed using three kinds of proteases; one extracted from Aspergillus oryzae, bromelain and ${\alpha}-chymotrypsin$. The cultural systems employed thereafter for lactic fermentations were: 1) Bifidobacterium bifidum, 2) B. bifidum and Lactobacillus acidophilus, 3) B. bifidum and Lactobacillus bulgaricus. In soy yogurt, pH was more decreased by mixed culture method than single culture method with the accumulation of lactic acid. Viable cells of lactic acid bacteria in soy yogurts were measured $10^8$ CFU/g by the single culture method while $10^9$ CFU/g by the mixed culture method except ${\alpha}-chymotrypsin$ treatment. The amount of free amino acids in soy yogurts were substaintially increased by enzyme treatment. Viscosity was decreased by enzyme treatment, resulting in higher viscosity by ${\alpha}-chymotrypsin$ treatment. Water holding capacity was found to be higher in the single culture method in case of enzyme treatment. Among the various volatile flavor components isolated and identified after enzyme hydrolysis, acetaldehyde, ethanol, diacetyl, butyl alcohol contents tended to increase by lactic fermentation.

• Food Science of Animal Resources
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• v.35 no.3
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• pp.339-349
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• 2015

The objective of this study was to identify lactic acid bacteria (LAB) isolated from kimchi and to evaluate its characteristics and functional properties for application in fermented dairy products as a probiotic or commercial starter culture. Eight stains isolated from kimchi were selected through an investigation of phenotypic characteristics. Two strains (DK211 and DK303) were identified as Lactobacillus plantarum, another two (DK207 and DK215) as Lactobacillus paracasei, and one (DK301) as Lactobacillus sakei. The remaining three strains were identified as species of Weissella. All selected Lactobacillus strains had acid and bile tolerance, even though there was wide variation in the ability of each strain. DK303 showed a remarkably higher proteolytic activity. There were no significant differences in β-galactosidase activity among the tested strains, except that DK301 showed no activity. Auto-aggregation varied between 82.1 and 90.0%, and hydrophobicity values ranged from 0.5 to 51.6%.The strongest auto-aggregation and hydrophobicity were observed in DK211. All selected strains showed better 1,1-diphenyl-2-picrylhydrzyl (DPPH) scavenging activity than commercial strains. DK211, DK215, DK301, and DK303 had effective inhibitory activity against all pathogens tested except E. coli. When selected strains were used for yogurt preparation as a single starter culture, the time required to reach target titratable acidity (0.9) was 11-12 h. The yogurt fermented with DK211 had favorable panelists ratings for most sensory attributes, which were comparable with yogurt fermented with a commercial strain. The results suggest that strains isolated from kimchi could be potential probiotic and starter cultures for use in yogurt manufacturing.