• Food Engineering Progress
• /
• v.14 no.1
• /
• pp.14-20
• /
• 2010

The objective of the current study was to determine the cryoprotective effects of trehaolse on lactic acid bacteria in the frozen yoghurt during long-term frozen storage conditions. The frozen yoghurts were prepared using starter culture containing Lactobacillus bulgaricus and Streptococcus thermophilus, as well as trehalose and sorbitol as a cryoprotectant. The viable cell numbers of lactic acid bacteria in frozen yoghurt did not significantly decreased during six weeks frozen storage conditions. The MRS broth, which contains either trehalose or sorbitol, cultured with L. bulgaricus and/or S. thermophilus, and then the cultured medium was kept in the frozen condition for six weeks. The results indicated that lactic acid bacteria viability significantly increased with trehalose addition (2 and 5%) in the media compared to those of control and sorbitol supplement groups. The lactic acid bacteria viability in the yoghurts was examined on the effects of repeated freeze and thaw events. The freeze-thaw resistance of lactic acid bacteria significantly increased with trehalose supplement in the yoghurt. The major volatile aroma compounds (acetaldehyde, acetone, ethanol, diacetyl, and acetoin) in yoghurt were separated and indentified by headspace GC-FID analysis. Distinct flavor components and their ratios are known as important quality factors for yoghurt notes. Trehalose addition to the yoghurt was not influenced these factors during lactic acid fermentation. The results in this study demonstrated that trehalose potentially can be applicable as an effective cryoprotectant for lactic acid bacteria in the frozen yoghurt products.

• Journal of Dairy Science and Biotechnology
• /
• v.14 no.1
• /
• pp.71-84
• /
• 1996

This study was conducted to examine the usability of sorbitol for the manufacture as low-calory ingredient and cryoprotectant against frost damage. When frozen yoghrt was made of replacing sucrose by sorbitol at yoghurt mix, the change of physicochemical and lactic acid bacteria, such as Str. thermophilus, L. bulgaricus, and mixed culture of Str. thermophilus, and L. bulgaricus(1:1), was studied during the frozen storage(-20$^{\circ}$C). During the incubation of yoghurt mix, the rapid growth of lactic acid bacteria in all sample was observed as the increase of sorbitol addition, but sample A and D were almost similar. This results suggested that sucrose could play role of effecting the growth stimulator, otherwise, sorbitol could inhibit the death of microorganism, following the genus. At the survival rate between lactic acid bacteria during freezing of -5$^{\circ}$C by ice cream freezer Str. thermophilus showed 26.19 to 34.76%, L. bulgaricus 3.97 to 5.20%, and mixed culture 17.16 to 40.87% respectively. L. bulgaricus showed the greater lethal rate than other genus. Sample C which mixed sucrose with sorbitol (1:2 ratio) was showed the lowest lethal rate. Therefore, it suggested that the use of this ration could be used for better anti-frost damage. During the storage of -20$^{\circ}$C, the number of lactic acid bacteria generally decreased in the stand point of genus and frozen storage period. The survival of lactic acid bacteria might be the addition of sorbitol which could have the effect of anti-forst damage. In all treatment, lactase activity showed the rapid decrease after freezing. During the period of frozen storage, it was shown the slow decreasing trend. In spite· of decreasing, the result during yoghurt mix incubation -5$^{\circ}$C freezing, and -20$^{\circ}$C frozen storage was different at the level. After 80 days of storage, the lactase activity was similar among all genus and sample. Despite differenting viscosity followed by genus, combination of mix, and pH, the ratio of 1 to 2(sucrose : sorbitol) showed the greatest viscosity. The water holding capacity of frozen yoghurt mix was closely related to viscosity. As increasing sorbitol amounts, hardness and cohesiveness were increased, but elastisity was decreased. The significant differences between sample was inoculated with Str. thermophilus. However, there were not significant difference from the sample inoculated with L. bulgaricus and mixed culture.

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

• Journal of the Korean Society of Food Culture
• /
• v.20 no.5
• /
• pp.594-602
• /
• 2005

The purpose of this study was to investigate eating behaviors related to snack and self-purchasing snack (SPS) among elementary school children. Self-administered questionnairs were completed by 352, 5th and 6th grade elementary school students living in 3 different regions which included apartment region in Bundangn, Sungnam (apartment group, n=116), residences in Seodaemun-Gu and Mapo-Gu, Seoul (kang-buk group, n=103) and residence in industrial region in Sungnam (industry group, n=133). The results were as follows: A significantly higher proportion (64.7%) of the apartment group had breakfast every morning than those of kang-buk (48.6%) or industry (52.1%) group (p<0.01). As for the frequency rate of snack and self-purchasing snack (SPS), 53.9% of the subjects answered taking snack more than once per day, 22.8%, once for few days and 23.3%, almost not. However, 15.5% of the subject had SPS once or more per day, 30.7%, 1-2 times per week and 22.4%, almost not. Those of apartment group showed significantly lower SPS frequencies (p<0.01), since higher proportions answered having SPS 1-2times per week (40.9%) and almost not (31.3%) compared to other groups. The reasons for having SPS turned out to be 'hunger' 54.7%, 'being habitual', 15.9%, 'bing bored', 15.7% and 'with peers' 13.7%. When subjects selected SPS foods, they considered taste (31.5%), price (23.0%), mood at the time (14.1%), sanitorial aspect (10.2%) and quantity (10.1%) rather than nutritional aspect (7.2%). Subjects' pocket money was estimated as 3736 won per week and SPS expense per time as 706 won. But subjects who spent more than 2000 won for SPS expense were significantly higher (33.0%) in apartment group than those of other groups (p<0.01). The favorite snack items that subjects having at home were fruit, ice cream, milk and yoghurt, cookies, ramen and bread in order. And favorite SPS items turned out to be ice cream, cookies, duckbokki, frozen bars, gum, chocholate and candy in order. The frequency rate of SPS were evaluated to be significantly related by several variables: those living in apartment area (p<0.01), those taking breakfast regularly (p<0.01), those of normal weight status by Rohrer index (p<0.05) and those receiving less pocket money (p<0.01) showed lower SPS frequency rate.