• Food Science and Biotechnology
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• 제17권1호
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• pp.58-65
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• 2008

To see the possibility of irradiation as an alternative to ultra high temperature (UHT) sterilization, the quality characteristics of milk were analyzed. Milk treated by UHT ($135^{\circ}C$ for 4 sec) and irradiation at higher than 3 kGy showed no viable counts after 7 days of storage at $4^{\circ}C$. The contents of certain amino acids of milk, such as Arg, Asp, Glu, Ile, Leu, Lys, Pro, Ser, Thr, and Tyr, were lower in irradiated groups at 10 kGy than in UHT-treated one, but no difference was observed between irradiated milks at less than 5 kGy and UHT. The capillary electrophoresis (CE) patterns of the milk irradiated at 10 kGy showed a similar trend to the raw milk, low temperature long time (LTLT, $63^{\circ}C$ for 30 min), and high temperature short time (HTST, $72^{\circ}C$ for 15 sec) treated. However, the CE pattern of UHT-treated milk was different. Rennet coagulation test agreed with the CE results, showing that all milk samples were coagulated by rennet addition except for UHT-treated milk after 1 hr. These results suggest that irradiation of milk reduce the content of individual amino acids but it may not induce severe conformational change at a protein level when compared with UHT treatment.

• Journal of Dairy Science and Biotechnology
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• 제35권4호
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• pp.270-285
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• 2017

Among milk proteins, caseins are not subjected to chemical changes during heat treatment of milk; however, whey proteins are partially denatured following heat treatment. The degree of whey protein denaturation by heat treatment is decreased in the order of high temperature short time (HTST) > low temperature long time (LTLT) > direct-ultra-high temperature (UHT) > indirect-UHT. As a result of heat treatment, several changes, including variations in milk nitrogen, interactions between beta-lactoglobulin and k-casein, variations in calcium sulfate and casein micelle size, and delay of milk coagulation by chymosin action, were observed. Lysine, an important essential amino acid found in milk, was partially inactivated during heat treatment. Therefore, the available amount of lysine decreased slightly (1~4% decrease) after heat treatment, However, the influence of heat treatment on the nutritional value of milk was negligible. Nutritional value and nitrogen balance did not differ significantly between UHT and LTLT in milk. In conclusion, our results showed that heat treatment of milk did not alter protein quality. Whey proteins denatured to a limited extent during the heat treatment process, and the nutritional value and protein quality were unaffected by heat treatment.

• 한국축산식품학회지
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• 제18권2호
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• pp.157-163
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• 1998

This study was carried out to examine that pepsin-hydrolyzed bovine lactoferrin has applicabilities which are market milk and dairy products. The stability of pepsin-hydrolyzed bovine apo-lactoferrin and the change of its antibacterial character has been studied under various method for pasteurization (LTLT; 65$^{\circ}C$ / 30min., HTST ; 75$^{\circ}C$ / 15sec., UHT ; 135$^{\circ}C$ / 3sec.) and pH Values (pH 2.0, pH 4.0, pH 6.8). The ehated samples were assayed for minimal bacteriocidal concentrations (MBCs) and bacteriocidal effect against E. coli. The results obtained were summarized as follows: After fractionation of pepsin-hydrolyzed bovine lactofeerin by gel filtration. several peptide fractions were found that had strong antibacterial activity. SDS-PAGE showed that the one of these fractions with strong antibacterial activity, which had a molecular mass a range of 30∼33KDa. The MBCs for pepsin-hydrolyzed bovine lactoferrin fraction No. 2 against E. coli required to cause complete inhibition of growth varied within the range of 200∼400 $\mu\textrm{g}$/ml, depending on heat treatments and pH conditions. The peptide fraction No. 2 showed strong bacteriocidal activity against E. coli at LTLT and HTST treatments under acidic pH conditions. and was reduced activity at UHT treatment under pH 6.8 condition.

• 한국식품영양과학회지
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• 제22권2호
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• pp.161-164
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• 1993

본 연구에서는 Kjeldahl 방법으로 시유의 질소분획물의 함량과 유청단백질 변성정도를 측정함으로써 이들이 시유의 열처리 정도를 비교할 수 있는 검색의 지표로서 타당하는지 알아보았다. 각 열처리법에 따른 질소분획물들의 함량을 보면, 원유에서는 시료 100g당 총질소가 431.3mg, 케이신질소가 341.0mg, 비케이신질소가 90.3mg, 이 중에서 비단백태질소가 31.6mg그리고 유청단백질소는 58.8mg을 보인 반면, 시유인 저온살균유, 고온순간살균유, 초고온처 리유의 질소분획물들의 함량이 다르게 나타났다. 유청단백질 변성정도는 저온살균유가 26.7%, 고온순간살균유가 32.9%, 초고온살균유가 60.7%, 그리고 초고온멸균유가 38.4%를 보여 열처리 정도가 높아질수록 변성정도도 높게 나타남으로써 열처리법에 따라 유청단백질의 변성정도의 구분이 뚜렷하였다.

• Journal of Dairy Science and Biotechnology
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• 제23권2호
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• pp.93-98
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• 2005

본 연구는 항원성을 저감한 우유 및 유제품 개발을 위한 기초자료 도출을 위해 열처리와 감마선 조사 처리 시 우유의 화학적, 미생물학적 및 면역적 변화를 비교하였다. 열처리와 감마선 조사 처리 시 열처리 온도와 조사량이 높을수록 유리지방산 함량이 증가하는 경향을 나타내었으며 UHT 처리시와 5 kGy 조사시 유리지방산 함량은 유사하였다. $10^3$ CFU/mL 수준의 원유를 저온, 고온, 초고온으로 열처리시와 1${sim}$10 kGy로 감마선 조사처리 시 모두 일반세균과 대장균 군이 검출되지 않았으나, 일주일 지난 후에도 UHT 처리유와 5kGy 이상 조사 처리유에서 일반세균과 대장균 군이 검출되지 않았다. 원유를 열처리시 arginine, asparate, iso-leucine, leucine, lysine, methionine이 감소된 반면 조사처리에 의해 aspartate, histidine, iso-leucine, leucine, lysine이 감소되어 열처리와 조사처리가 단백질의 일차구조에도 영향을 미칠 수 있는 것(p<0.05)으로 나타났다. 또한, 우유의 항원성은 감마선 조사처리시 5kGy 이상에서 유의적(p<0.05)으로 감소하였다. 이상의 결과로 볼 때 5 kGy 정도의 감마선 조사처리로 UHT 처리시와 유사한 화학적, 미생물학적 효과와 우유의 항원성 감소효과를 기대할 수 있다.

• 한국식품영양과학회지
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• 제20권6호
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• pp.546-550
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• 1991

우유의 열처리 정도를 검색할 수 있는 지표 설정을 위한 유효성분을 채택하기 위하여 시판우유의 pH, 적정산도, 불변성 유청단백질 함량과 유효성 lysine의 함량 변화를 비교한 결과, pH 및 정적산도는 열처리에 따른 변화가 없었고, serun 100ml당 불변성 유청 단백질 함량은 저온살균유가 413.7mg, 고온순간살균유가 341.3mg, 초고온살균유는 6.9mg, 초고온멸균유는 96.6mg으로 열처리에 따라 뚜렷한 차이가 있었다. 원유에 대한 각 열처리 우유들의 유효성 lysine 감소율은 저온살균유에서 1.4%, 고온순간살균유에서 0.2%, 초고온살균유에서 6.3%, 초고온멸균유에서 4.9%로 초고온처리에서 명확히 구분되지 않았다.