• 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.

• Food Science of Animal Resources
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• v.25 no.1
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• pp.84-91
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• 2005

We investigated fermentation characteristics and the amount of exopolysaccharide (EPS) produced, and the correlation between EPS and rheological properties in stirred yogurt fermented with Streptococcus thermophilus St-Body 1. The changes of pH and lactic acid concentrations of yogurt showed different patterns according to fermentation temperatures. About 20 to 40% of lactose was utilized during 6 hrs incubation. The higher number of lactic acid bacteria was obtained at 31℃ incubation temperature rather than other incubation temperatures. The higher amount of EPS was produced at 12 hr or 24 hr rather than other incubation period at the same fermentation temperatures. The viscosity continuously increased during the fermentation period, however the syneresis of yogurt was shown the lowest value at 37℃ for 30 hrs incubation. In physical properties, the hardness and adhesiveness increased continuously with decreasing cohesiveness and elasticity as incubation process was extended. The stirred yogurt fermented with S. thermophilus St-Body 1 at 37℃ for 24 hr resulted in the highest score at each sensory evaluation category.

• Food Science of Animal Resources
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• v.38 no.3
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• pp.451-467
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• 2018

Hot pepper has anti-obesity effects by controlling appetite and reducing blood fat level. To reduce the pungency of capsaicin, red or green hot pepper juice was fermented with Bacillus licheniformis SK1230. Fermented hot pepper juice was then added into yogurt at different ratios. The pH of yogurt added with hot pepper juice was decreased from 4.61 to 4.48. Titratable acidity and counts of lactic acid bacteria were increased with increasing amount of pepper juice added. However, the viscosity was decreased significantly compared to the control. On chromaticity test, when more pepper juice was added, $L^*-value$ was decreased whereas $a^*$- and $b^*$- values were increased significantly (p<0.05). The spectrum of antimicrobial activity of yogurt was slightly changed compared to using pepper juice. Total polyphenol contents and antioxidant activity were increased with increasing amount of pepper juice added. Stirred yogurt added with fermented red pepper juice at 3% or green pepper juice at 1% showed high scores in flavor, appearance, texture, and overall acceptance in sensory test. Yogurt added with fermented pepper juice with reduced pungency showed also good palatability during storage at $4^{\circ}C$. Yogurt with added hot pepper juice can be play an important role in functional food relative to anti-obesity.

• Food Engineering Progress
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• v.13 no.1
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• pp.70-73
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• 2009

The yield stress of stirred yogurt was measured by the vane viscometer at different pre-shearing conditions, such as pre-shear speed, pre-shear time, and wait time, and temperature (12-38${^{\circ}C}$). The yield stress ranged from ~17.6 to 10 Pa and from 34.2 to 11.9 Pa, depending on the pre-shearing conditions and temperature, respectively. The preshear speed and the wait time significantly affected the yield stress. The temperature dependence of the yield stress was described by the Eyring's kinetic model. The linear function of the temperature on the yield stress was limited at the 22${^{\circ}C}$, and at the above 22${^{\circ}C}$, the yield stress was maintained to be a constant (~12.5 Pa).

• Food Science of Animal Resources
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• v.40 no.4
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• pp.613-627
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• 2020

Paprika is known to contain polyphenolic compounds that have good antioxidant properties. This study was conducted to investigate the benefits of adding paprika juice of different colors to yogurt and to determine how paprika affects the quality characteristics of yogurt. Stirred yogurt samples supplemented with different levels of red, orange, or yellow paprika juice were inoculated with mixes of Streptococcus thermophilus and Lactobacillus delbrueckii ssp. bulgaricus. Paprika addition decreased the pH but increased titratable acidity, lactic acid bacteria (LAB) counts, total polyphenol content (TPC), levels of vitamin A and C, and antioxidant activity. Proteolysis and viscosity of paprika-containing yogurts were significantly higher than those of the control yogurt without paprika juice (p<0.05). In particular, the viscosity of red paprika yogurt was significantly higher than that of yogurts containing 5% orange and yellow paprika juices (each p<0.05). The antioxidant activity of the methanol extract of the yogurt containing 2.5% orange paprika juice was the highest. Storage at 4℃ for 15 days only slightly altered LAB counts, antioxidant activity, and TPC of paprika yogurt. These results indicate that paprika could be used as a natural food additive for the development of functional yogurts.

• Korean Journal of Food Science and Technology
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• v.24 no.4
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• pp.353-360
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• 1992

This study was carried out to investigate the changes of quality in yogurt during delivery and storage. To do this, microbiological, physico-chemical and sensory properties in stirred yogurt were studied at different temperatures $(10^{\circ}C$ & $20^{\circ}C)$ and shakings (100 rpm & 200 rpm for 30 min). Titratable acidity and TCA soluble nitrogen in yogurt were increased in accordance with increase of temperature and time, while pH, lactose and lactic acid bacteria tended to be decreased. Interestingly enough, shaking conditions almost did not influence these studies. In sensory evaluation it showed that acidity was strong and sweetness was weak as increasing the storage temperature and time, but there were no significant differences until 10 days at $10^{\circ}C$ and 3 days at $20^{\circ}C$. Off-flavor was developed after 12 days at $10^{\circ}C$ with only 200 rpm shaking and after 6 days at $20^{\circ}C$ in both shaking conditions. These yogurts were not suitable for consumer. Viscosity in the yogurt became high as the temperature and time were increased. Viscosity was lower in yogurt shaked at 200 rpm than in non-shaked yogurt. Finally, this study indicates that temperature and shaking during delivery of yogurt may be critical in keeping quality of yogurt.

• Proceedings of the Korean Society for Food Science of Animal Resources Conference
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• 2004.05a
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• pp.291-294
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• 2004

본 연구는 EPS 생성 유산균을 이용한 stirred 요구르트 제조의 기초 자료로 활용하고자 실시하였다. EPS 분리 실험결과에서 발효 온도가 낮을수록 더 많은 EPS가 생성하고, 발효 12시간과 24시간에 많은 EPS를 생성하는 것으로 관찰되었다. 점도는 EPS 함량과 무관하게 발효 시간이 증가할수록 증가하였으며, $40^{\circ}C$, 발효 30시간에 가장 높은 점도가 측정되었고, syneresis는 $37^{\circ}C$에서 30시간 발효한 요구르트가 가장 적은 것으로 관찰되었다. 경도와 접착성은 발효가 진행될수록 증가한 반면에 점착성과 탄력성은 발효가 진행될수록 감소하였으며, 관능검사 결과에서는 $37^{\circ}C$, 24시간 발효한 요구르트가 가장 높은 수치를 나타내었다.

• Journal of Dairy Science and Biotechnology
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• v.23 no.2
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• pp.149-153
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• 2005

Lactic acid bacteria had been widely utilized in fermented foods such as fermented dairy products, traditional sauces, kimchi, fermented sausages, medicines or probiotic feed additives for a long time. LAB are also widely distributed in the mammalian gastrointestinal tracts, oral cavity, vagina, and various foods or soils. The most familiar examples of using LAB would be the fermented milk products, and those had become one of the favorite foods in Korea f3r more than 34 years of history. The main benefits of the fermented milk products were originally the improvement of the balance of intestinal flora to control diarrhea and congestion disorders, and gradually, they were chosen by the consumer preference of the taste. The very beginning of the fermented milk products in Korea was the Yakult type products in 1971, and it was the commencement of the solid foundation of the dairy industry and the understanding beneficial effect of probiotic yogurt. After middle of 80's, stirred type fermented milk products had been firstly produced, and it was the time that the domestic dairy industry took root in Korea. From 90's, functional fermented milk products were produced, and drink type yogurt sales a mount increased drastically, and these products began to be chosen not only with the values of nutrition but also with physiological functions. The health claims are classified into intestinal health, gastric health and hepatic health. The prospects for the Korean market are as follows; The majority of leading products would be the premium functional yogurt products as it was last year. It is because the sales of lower cost products shows slow-down, and industries tend to increase the commercial advertisements of premium functional yogurt products through mass media. These tendencies would make the market situation become more competitive.

• Korean Journal of Food Science and Technology
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• v.25 no.6
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• pp.620-625
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• 1993

This experiment was carried out to predict the sensory properties of yogurt by instrumental methodology. Sensory attributes such as viscosity, mouth-feel, taste and quality were investigated. Instrumental parameters were measured with refractometer, viscometer, consistometer and rheometer. Sensory data showed that viscosity of peach yogurt was higher than that of strawberry and tropical-fruit-mixed (TFM) yogurts (p<.05). All instrumental parameters of peach yogurt were higher than those of strawberry and TFM yogurts, except cohesiveness and elasticity (p<.05). Viscosity measured by panelists was significantly correlated with instrumental viscosity, consistency, hardness, adhesiveness and gumminess in the fruit yogurts (p<.05). But mouth-feel and quality of yogurts showed poor relationships with instrumental parameters. The effective instrumental parameters for predicting sensory viscosity ($Y_{1}$) of yogurts were consistency ($X_{1}$), viscosity ($X_{2}$) and cohesiveness ($X_{3}$). And those for predicting mouth-feel ($Y_{2}$) were consistency. The estimated regression equations were as follows; $Y_{1}=4.968-0.0486X_{1}+0.00012X_{2}+0.0348X_{3},\;Y_{2}=5.701+0.0154X_{1}$.

• Korean Journal of Food Science and Technology
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• v.40 no.3
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• pp.337-342
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• 2008

In this study, HPLC was used to determine the total sugar contents of processed foods as well as main and side dishes that were acquired from noncommercial foodservices. The total sugar content was identified as the total amount of both mono- and di-saccharides according to the nutritional information standard defined by the Korea Food and Drug Administration. The results for the processed foods were as follows: $25.3{\pm}9.5%$ for biscuits, $11.7{\pm}10.6%$ for snacks, $29.9{\pm}17.7%$ for chocolate, $35.5{\pm}9.3%$ for processed chocolate products, $11.0{\pm}2.7%$ for fruit juice, $10.0{\pm}3.6%$ for carbonated beverages, $23.0{\pm}3.2%$ for ice cream, $24.5{\pm}3.2%$ for ice milk, and $11.4{\pm}2.6%$ for stirred yogurt. Overall, candy items had relatively higher total sugar contents ($71.1{\pm}19.3%$ ) than any other items. Foods in the school zone had $52.3{\pm}24.4%$ total sugars. The noncommercial foodservice foods were classified into 5 main dish categories and 12 side dish categories. The total sugar contents of the main dishes were $2.6{\pm}1.9%$ for cooked rice with seasoning, and $4.7{\pm}0.1%$ for spaghetti. Among the side dishes, hard boiled foods and stir-fried foods contained the highest amounts of sugar, which were dependent on the main ingredients in the foods. Other side dishes with high sugar contents included seasoned vegetables/dried fish/seaweed ($5.5{\pm}5.3%$), salads ($5.6{\pm}3.1%$), and kimchies ($5.7{\pm}4.1%$). The total sugar contents of the side dishes ranged widely, and were significantly different according to main ingredients, cooking method, and amount of spice.