본 연구는 살균방법이 다른 시유에 항균활성과 항산화활성이 높은 케피어그레인을 첨가하여 코티지치즈를 제조하고 이들 치즈의 품질특성과 저장기간 중 미생물 변화를 분석하여 치즈의 품질차이를 확인하였다. 또한 양파분말을 첨가한 케피어코티지 치즈의 품질특성을 분석하여 기호도를 높인 코티지 치즈 개발을 위하여 자료를 제공하고 상품가능성을 제시하였다.
살균방법이 다른 S milk(UHT), D milk(HTST), P milk(LTLT) 시유로 제조된 S cheese, D cheese, P cheese의 수율과 수분함량은 S cheese가 39.72%, 81.40%로 가장 높았고, D cheese 가 36.89%, 80.67%, P cheese가 36.49%, 79.80%로 가장 낮았다. 회분함량, 조단백질 함량과 조지방 함량은 제조된 S cheese, D cheese, P cheese 시료 간 차이는 없었으나 시유에 함유된 단백질 함량인 3%에 비해 제조된 치즈 내 단백질 함량이 7.11%, 7.20%, 7.19%로 높았다.
제조된 S cheese, D cheese, P cheese에서 가장 많은 함량을 차지하는 균은 세가지 치즈 모두 Lactobacillus kefiranofaciens속이었고 Leuconostoc citreum속과 Enterococcus faceium속, Lactobacillus buchneri속 순으로 나타났다. 유기산은 S cheese, D cheese, P cheese 모두 lactic acid가 가장 많이 함유하였고 malic acid, acetic acid, succinic acid, formic acid 순으로 나타났다.
DPPH radical 소거능과 총페놀화합물 함량은 S cheese(UHT)가 24.77%, 38.98 mgGAE/L로 가장 높았고 D cheese가 17.20%, 31.74 mgGAE/L, P cheese가 16.60%, 30.78 mgGAE/L로 가장 낮았다. 기호도 조사 결과 색(color)을 제외한 향(flavor), 맛(taste), 조직감(texture), 전체적인 기호도(overall acceptability) 모두 S cheese(UHT)가 가장 높았다.
저장 중 pH변화는 S cheese, D cheese, P cheese 모두 유의적 차이가 나타나지 않았으며 적정산도 변화는 20일동안 유의적으로 증가하다가 25일째까지 더 이상 증가하지 않고 일정하게 유지하였다. 유산균 수 변화는 S cheese, D cheese, P cheese 모두 6~7 log CFU/mL 수준에서 5~6 log CFU/mL수준으로 감소하였고 생균 수 또한 이와 유사하게 나타내어 대부분의 생균 수가 유산균이었다. 진균 수는 6 log CFU/mL수준에서 5 log CFU/mL수준으로 감소하였다.
항산화 활성이 높고 기호도가 높게 나타난 S cheese(UHT)에 양파분말을 0%, 0.5%, 1%, 1.5% 첨가하여 제조한 OKC0, OKC1, OKC2, OKC3 치즈의 수분함량은 79.90%, 79.77%, 79.44%, 79.05%로 감소하였고 점도는 1664 cP, 1751 cp, 2090 cp, 2231 cp로 증가하였다. L(lightness)값은 OKC0가 89.53에서 양파분말을 1.5% 첨가한 OKC3이 86.39로 감소하였고 적색도 a(redness)값은 -1.82에서 -1.15로 황색도 b(yellowness)값도 5.49에서 7.28로 증가하였다. 조직감인 경도(hardness), 응집성(cohesiveness), 탄력성(springiness), 검성(gumminess)은 대조군에 비해 양파분말을 첨가할수록 유의적으로 낮아졌다. DPPH radical 소거능과 총페놀화합물 함량은 양파분말을 첨가할수록 유의적으로 증가하였고 양파분말을 첨가한 코티지 치즈의 기호도는 색(color)을 제외한 향(flavor), 맛(taste), 조직감(texture), 전체적인 기호도(overall acceptability)는 모두 양파분말 0.5% 첨가군이 가장 높았다.
S cheese(UHT), D cheese(HTST), P cheese(LTLT) 모두 유산균과 유기산을 함유하고 있으나 S cheese가 수율과 항산화 활성이 높고 맛, 향, 전체적인 기호도가 높아 S milk(UHT)를 이용한 코티지 치즈 제조가 가능할 것으로 판단된다. 또한 S cheese에 양파분말을 0.5% 첨가한 경우 향, 맛, 조직감 등의 기호도가 높고 항산화 활성이 높아 양파분말 첨가한 치즈가 기호도를 높인 코티지 치즈가 될 수 있을 것으로 판단된다.

Cottage cheese was produced by adding kefir grain with potent antimicrobial and antioxidant activities to various types of commercially available milk that were pasteurized differently. Differences in the quality of the cottage cheeses were determined by analyzing the quality characteristics and the change of microbial communities. These data and the determined quality characteristics of kefir cottage cheese with onion powder provide useful data to develop a highly preferable cottage cheese with a potential for commercialization.
The market milk used to prepare cottage cheese included S milk (ultra-high temperature [UHT] pasteurization), D milk (high temperature short time pasteurization), and P milk (low temperature long time pasteurization) (S cheese, D cheese, and P cheese, respectively). S cheese had the highest yield rate (39.72%) and moisture content (81.40%), followed by D cheese (36.89% and 80.67%, respectively) and P cheese (36.49% and 79.80%, respectively).
There were no significant differences in ash content, crude protein content, and crude fat content between S, D, and P cheese. However, the protein contents of the produced cheeses were higher (7.11%, 7.20%, and 7.19%, respectively) than the 3% value of market milk.
In all S, D, and P cheese produced, Lactobacillus kefiranofaciens was the most abundant bacterium, followed by Leuconostoc citreum, Enterococcus faceium, and Lactobacillus buchneri. Lactic acid was the most abundant organic acid in all three cheeses, followed by malic acid, acetic acid, succinic acid, and formic acid.
S cheese produced using UHT pasteurized milk had the highest level of 2,2 diphenyl 1 picrylhydrazyl (DPPH) radical scavenging activity (24.77%) and the highest total phenolic content (38.98 mg gallic acid equivalent [GAE]/L), followed by D cheese (17.20% and 31.74 mg GAE/L), and P cheese (16.60% and 30.78 mg GAE/L). Consumer preference testing revealed that S cheese scored the highest in flavor, taste, and texture, and overall acceptability, but not color.
No statistically significant difference in pH change was evident during storage between the three cheeses. Titratable acidity significantly increased during the first 20 days and plateaued from day 25 onward. Probiotic content decreased in the three cheeses from 6?7 log colony forming units (CFU)/mL to 5?6 log CFU/mL. Changes in the number of microbials also showed a similar trend. The majority of the microbials were probiotics in all three cheeses. The number of fungi decreased from 6 log CFU/mL to 5 log CFU/mL.
S cheese that displayed pronounced antioxidant activity and favorable consumer preference was prepared in the absence of onion powder (OKC0) or with 0.5%, 1%, and 1.5% onion powder (OKC1, OKC2, and OKC3, respectively). The respective water content was 79.90%, 79.77%, 79.44%, and 79.05%. The viscosity of OKC0 cheese was 1664 cP. The viscosity increased with increased content of onion powder (1751 cp, 2090 cp, and 2231 cp, for OKC1, OKC2, and OKC3, respectively).
Lightness (L) value of OKC3 was 86.39, which was lower than that of OKC0 (89.53). Redness (a) and yellowness (b) values of OKC3 (-1.15 and 7.28, respectively) were higher than those of OKC0 (-1.82 and 5.49, respectively). Hardness, cohesiveness, springiness, and gumminess elements of texture were all significantly decreased with increasing addition of onion powder. DPPH radical scavenging activity and total phenolic content progressively increased with greater content of onion powder. Concerning consumer preference of cottage cheese amended with onion powder, 0.5% onion powder was most preferred in terms of flavor, taste, texture, and overall acceptability, but not color.
Although all three cheeses contained probiotics and organic acid, S cheese produced using UHT pasteurized milk had a greater yield rate and water content and higher flavor, taste, and overall acceptability ratings. Furthermore, S cheese prepared using 0.5% onion powder was preferred by consumers concerning flavor, taste, and texture, and had potent antioxidant activity.