The creation of probiotic-containing fermented milk products for use by human is an important research topic and has high potential for development. Also, studies have shown that heat-killed probiotics are more stable and easier to use than live probiotics. However, as of this time, research has not been reported in Korea that has evaluated the product or functionality of fermented milk after the addition of heat-killed probiotics. This study was conducted to verify the physiological activity of heat-killed Enterococcus faecalis EF-2001 after its addition to Lactobacillus-fermented milk. Briefly, NFM normal fermented milk (NFM) was used as the control sample, whereas fermented milk with 100 μg/mL EF-2001 (EFM1) and fermented milk with 500 μg/mL EF-2001 (EFM2) were used as the treated samples. Among the samples, EFM2 had the highest acidity of 1.15, but no other factors significantly differed (p<0.05). Furthermore, EFM2 had the highest Lactobacillus count of 9.22 (p<0.05). ABTS, DPPH and FRAP were measured to determine the antioxidant activity of the samples. With respect to those parameters, EFM2 had the highest antioxidant measurements. Therefore, the study confirmed that the addition of E. faecalis EF-2001 to NFM is suitable with the standard and does not affect the quality of characteristics. In conclusion, the treatment sample had higher antioxidant activity than did NFM; this result may be used as a basic for further research and as a guideline for the manufacturing of heat-killed probiotic-containing NFM.

This study was conducted to investigate the effects of sugars and stabilizers on the qualitative properties of frozen-yogurt. To prepare the yogurt mix, market milk was fermented using a commercial starter culture and sugars, trehalose and sucrose, and to prepare the ice cream mix, stabilizers, carboxy methyl cellulose (CMC) and guar gum, were used. The yogurt and ice cream preparations were mixed in a 1:1 (v/v) ratio to produce frozen-yogurt. Yogurt prepared using trehalose showed a significantly faster increase in pH, titratable acidity, and viable cell count than that prepared using sucrose (p<0.05). Ice cream prepared using guar gum showed a significantly higher viscosity and overrun than the CMC-stabilized preparation (p<0.05). Frozen-yogurt produced using the yogurt-trehalose mix and ice cream-CMC mix showed the highest hardness and lowest overrun. The melt-down rate of frozen-yogurt prepared with the yogurt-trehalose mix was significantly slow (p<0.05). However, there were no significant differences among the yogurt mixes in terms of changes in the viable cell count at 0, 7, 15, 30, and 45 days (p>0.05). In a sensory evaluation, most panels preferred the frozen-yogurt with sucrose over that with trehalose. However, it is expected that using trehalose with other sugar substitutions and guar gums in manufacture of frozen-yogurt have high potentiality than using sucrose and CMC, and it is considered that it could reignite the stagnant domestic milk processing industry.

This study was conducted to evaluate the effect on quality characteristics of grass-fed cow’s milk (GM) and conventional feed-fed cow’s milk (CM) with various conditions of non-thermal high-pressure processing (HPP) sterilization process. The sterilized GM and CM stored at 5℃ and 10℃ for 14 days and their quality characteristics during storage was evaluated. The pH and titratable acidity changes of HPP sterilized milk were maintained acceptable level 6.7-6.8, 0.14-0.16%, respectively. HPP sterilization was efficient in the reduction of total bacterial population to decrease the level of 4-7 Log CFU/ml compare to those of unsterilized control milk, and coliform bacteria was not detected in the HPP sterilized milk. Non-thermal HPP sterilization processing was not affected milk fatty acid composition compare to those of low temperature long time process (LTLT) sterilized milk. GM has lower ratio of n-3:n-6 unsaturated fatty acid level than those of CM. In the sensory evaluation of GM and commercial milk products, overall consumer acceptance of HPP sterilized GM was higher than CM and LTLT commercial product. In conclusion, the effects of HPP was comparable with conventional LTLT sterilization process to control undesirable microorganism in the milk products with minumal nutritional and chemical changes.

본 연구에서는 냉동요구르트 제조 시 trehalose와 sorbitol 첨가가 유산균의 동결변성방지 및 향기성분의 변화에 미치는 영향을 조사하고자 실시하였다. 요구르트를 L. bulgaricus와 S. thermophilus 단독균주 및 혼합균주로 발효시켰을 때 처리구 모두 trehalose와 sorbitol 첨가에 의한 발효과정 중 유산균의 증식효과는 나타나지 않았다. 요구르트를 6주간 냉동저장하는 동안 trehalose와 sorbitol 첨가에 의한 모든 처리구에서 유산균수의 차이가 없었으며, MRS 액상배지에 trehalose와 sorbitol을 각각 2%, 5% 첨가하여 6주간 냉동저장하였을 때는 5% trehalose 처리구의 동결변성방지 효과가 가장 우수한 것으로 나타났다. 냉동저장 기간 동안 고형분 함량이 12%인 처리구와 20%인 처리구의 생균수는 큰 차이가 나타나지 않아 고형분 함량 차이에 의한 trehalose와 sorbitol 효과에는 차이가 없는 결과를 나타내었다. 요구르트의 동결과 해동을 반복하였을 경우 trehalose와 sorbitol 모두 2% 첨가구보다 5% 첨가구가 우수한 동결변성방지 효과를 나타내었다. 전반적으로 Trehalose 첨가구가 sorbitol 첨가구보다 2%, 5% 모두 동결변성방지 효과가 좋은 결과를 나타내었다. Trehalose와 sorbitol을 첨가하여 요구르트를 제조하였을 때 향미성분의 함량은 대조구와 유사하였으며 일반적인 요구르트의 향미를 나타내었다. 냉동저장 중 요구르트 향미성분은 손실되거나, 함량비율의 변화가 발생하지 않았다. 이상의 결과로부터 요구르트의 풍미에는 영향을 미치지 않으면서 냉동저장에 의한 유산균의 동결변성방지제로서의 trehalose첨가가 냉동요구르트의 유산균 안정화에 효과가 있다고 하겠다.

The objective of current study is to determine antioxidant activities of Maillard reaction products (MRPs) obtained from Maillard reaction model systems with different combinations of 15 individual amino acids and 3 different sugars(glucose, fructose and lactose). Antioxidant activities of MRPs were determined using techniques of measuring DPPH and ABTS-radical scavenging activities. The results indicated that radical scavenging activities of MRPs were significantly increased compared to individually thermal treated amino acids and sugars. Among the model systems, the systems containing glycine or lysine + sugars (glucose, fructose and fructose) displayed the stronger DPPH and ABTS radical scavenging activities than other model systems. In addition, when the thermal treatment time was increased, radical scavenging activities of MRPs were increased in a reaction time-dependent manner. Further investigation using bioassay-directed fractionation was performed using two model systems (glycine+glucose, lysine+glucose) which displayed the strongest radical scavenging activities. The reaction solution were subjected to partition with a different polarity of solvent (hexane, ethyl acetate, n-butanol, and water) for evaluation of their radical scavenging activity. Among them, ethyl acetate fraction exhibited the strongest DPPH-radical scavenging activity in both model systems.

This study was carried out to investigate the effects of addition of aged garlic extract (AGE) on the color and lipid oxidation of ground chicken during refrigerated storage. The leg meat from 6 weeks-broiler was chopped and added with 4% of distilled water (control) and AGE, respectively, and then stored at 4±0.2℃ for 8 days. The commercial garlic was aged for the relatively short time (40-90℃/300 hr →natural dryness/40 hr→20-30℃/30-50 hr). The pH value was not significantly different between control and AGE-added chicken. The TBARS level of chicken was remarkably inhibited by addition of AGE during storage. In CIE color values, AGE-added chicken showed lower L* and higher b*, C* and Ho values than those of control during storage. Therefore, the addition of AGE in ground chicken enhanced the lipid oxidative stability and change to dark color.