Korean J. Microbiol. Biotechnol. (2014), 42(3), 267 274 pissn 1598-642X eissn 2234-7305 Korean Journal of Microbiology and Biotechnology 초고압처리가우유의미생물학적및이화학적특성에미치는영향 이지은 1, 최은지 1, 박선영 2, 전가영 3, 장자영 1, 오영준 1, 임슬기 1, 김태운 2, 이종희 2, 박해웅 2, 김현주 1, 전정태 4, 최학종 1 * 1 세계김치연구소대사기능성연구단 2 세계김치연구소미생물발효연구단 3 연세대학교식품영양학과 4 부산대학교식품영양학과 Received: June 2, 2014 / Revised: July 5, 2014 / Accepted: July 7, 2014 Effects of High Pressure Treatment on the Microbiological and Chemical Properties of Milk Jieun Lee 1, Eun-Ji Choi 1, Sun Young Park 2, Ga Young Jeon 3, Ja-Young Jang 1, Young Jun Oh 1, Seul Ki Lim 1, Tae-Woon Kim 2, Jong-Hee Lee 2, Hae Woong Park 2, Hyun Ju Kim 1, Jung Tae Jeon 4, and Hak-Jong Choi 1 * 1 Metabolism and Functionality Research Group, 2 Microbiology and Fermentation Research Group, World Institute of Kimchi, Gwangju 503-360, Republic of Korea 3 Food Science and Nutrition, Yonsei University, Seoul 120-749, Republic of Korea 4 Food Science and Nutrition, Pusan National University, Busan 609-735, Republic of Korea High pressure processing (HPP) is a non-thermal method used to prevent bacterial growth in the food industry. Currently, pasteurization is the most common method in use for most milk processing, but this has the disadvantage that it leads to changes in the milk s nutritional and chemical properties. Therefore, the effects of HPP treatment on the microbiological and chemical properties of milk were investigated in this study. With the treatment of HPP at 600 MPa and 15 o C for 3 min, the quantity of microorganisms and lactic acid bacteria were reduced to the level of 2-3 log CFU/ml, and coliforms were not detected during a storage period of 15 d at 4 o C. An analysis of milk proteins, such as α-casein, β-casein, κ-casein, α-lactalbumin, β-lactoglobulin by on-chip electorophoresis revealed that the electrophoretic pattern of the proteins from HPP-treated milk was different from that of conventionally treated commercial milk. While the quantities of vitamins and minerals in HPP-treated milk were seen to be comparable to amounts found in raw milk, the enzyme activity of lipase, protease and alkaline phosphatase after HPP treatment was reduced. These results suggest that HPP treatment is a viable method for the control of undesirable microorganisms in milk, allowing for minimal nutritional and chemical changes in the milk during the process. Keywords: High pressure treatment, milk, microbial reduction, chemical property 서 론 최근식품원료와제품의신선도를최대한유지하면서유통기한을연장하기위한최소가공기술 (minimal process technology) 에대한관심이높아지고있다. 최소가공기술중초고압처리법 (High Pressure Processing, HPP) 은비열 ( 非熱 ) 가공 (non-thermal process) 기술로서액체또는고체식품을포장하거나포장하지않은상태로 100-1,000 MPa 의정 *Corresponding author Tel: +82-62-610-1729, Fax: +82-62-610-1850 E-mail: hjchoi@wikim.re.kr 2014, The Korean Society for Microbiology and Biotechnology 수압 (hydrostatic pressure) 의압력을처리하는기술이다. HPP는식품의맛, 향, 영양성분에변화를주지않으면서미생물을사멸시키고효소를불활성화시켜효소의작용에의한쓴맛, 냄새의발생을억제하는첨단가공기술로서모든공정이비가열처리되는것이특징이다 [8]. 우유는인류가 10,000여년전부터식품으로사용해온영양적으로균형이맞춰진완전식품으로 2011년현재전세계우유생산량은 7억3천만톤에달하며, 6억명이상의인구가우유를소비하고있다 [26]. 현재가장많이사용되는우유의살균 (pasteurization) 방법은열처리법이며, 63 o C에서 30분간가열하는방식인 Low Temperature Long Time (LTLT), 72-75 o C에서 15초간열처리하는 High Temperature Short Time (HTST), 135 o C에서 2초간살균하는 Ultra-High Tem- September 2014 Vol. 42 No. 3
268 Lee et al. perature (UHT) 방식이가장많이사용되고있다. 이러한가열살균법은우유의단백질및비타민 C와같은성분을변성시키는단점이있으며특히, 고온살균과정중변성된유단백은신생아에게항원으로작용하여심각한알레르기를유발하기도한다 [12]. 알레르기를유발하는주요유단백은 α- lactalbumin (α-la), β-lactoglobulin (β-lg) 및 casein이며, 때때로 bovine serum albumin 및 lactoferrin도문제가되기도한다 [23]. 가열살균처리과정에서변성된알레르기유발유단백질은섭취후소화효소인 trypsin 또는 chymotrypsin에의하여분해된후생체알레르기유발항체인 immunoglobulin (Ig) E와결합을하게되어알레르기를유도한다 [1]. 알레르기저감을위한우유의비가열살균기술로 HPP 처리가적용되고있으며 [11], 최근연구에의하면 HPP 처리우유의 β-lg은 trypsin에의하여가수분해후에도 IgE와결합하는능력을상실한다고보고되었다 [16]. 우유에고압처리시물리적특성이변한다는연구는 1899년처음보고되었으나 [9], HPP 처리가우유의고분자성분에미치는효과에대한세부적인연구는비교적근래에연구가시작되었다 [25]. HPP 처리는 casein micelle에결합된 mineral을용해시켜 casein 입자를작게만들어우유의혼탁도 (turbidity) 를감소시키는효과를보여 cheese 제조에바람직하게우유의성질을변화시킨다 [10, 24]. 또한, HPP 적용조건에따라 whey protein 및 serum protein을변성시켜유단백질매개알레르기를저감시키는효과를나타낸다 [2]. HPP에의한미생물의생육저해효과는 HPP 조건 ( 압력, 시간, 온도, cycle 등 ) 및적용식품의조성, 특성, 미생물의생리학적상태에영향을받는다. 우유의경우, 대부분의효모나곰팡이는압력에민감한것으로나타났으나 [24], 세균은상대적으로높은압력조건이필요하다. 그람양성균은그람음성균보다압력에높은저항성을나타내는데그람음성균의경우, 25 o C 기준, 300-400 MPa에서 10분간처리하였을때생육저해효과가있었으며, 그람양성균의 25 o C 기준, 500-600 MPa에서 10분간처리하였을경우효율적인생육저해효과가나타난다 [25]. 종합적으로 HPP 처리가 LTLT 처리법정도의살균효과를나타내기위해서는원유를 400-500 MPa 수준으로압력을가하였을경우원유에존재하는병원성균및부패균의생육을저해할수있는것으로나타난다 [4]. 따라서최소가공기술인 HPP는우유의살균에적용함으로써우유고유의신선도, 향, 색, 그리고맛을유지하면서도안전한우유살균조건을개발하는연구가필요하다. 본연구에서는비가열살균방법인 HPP를사용하여우유에처리하였을때, 우유내잔존미생물, 우유단백질성분의변화, 기타우유성분의이화학적변화를기존의가열살균처리와비교하여분석하였다. 재료및방법 우유시료본연구에사용된원유와고압살균처리한 HPP 우유는 A사에서공급받았으며, 가열살균우유시료로는 LTLT, HTST 및 UHT 살균법처리우유를시중마트에서구입하여사용하였다. 우유의 HPP 처리우유시료의 HPP 처리는 Baotou Kefa High Pressure Technology (Baotou, China) 사의 5L-HPP-600MPa 장비를이용하여 550-600 MPa 의조건으로수행하였다. 우유의잔존미생물분석 HPP 처리후잔존하는미생물분석은다음과같이수행하였다. 550 MPa (HPP A, 550 MPa에서 3분간 HPP 처리 ) 및 600 MPa (HPP B, 600 MPa에서 3분간 HPP 처리 ) 의조건에서 3분간처리한 HPP 우유를 4 o C에서 15일동안저장하면서일반세균수, 유산균수및대장균군수를측정하였다. 저장기간에따라시료를채취하여멸균식염수에순차적으로희석하여일반세균은 Plate Count Agar (PCA) 배지 (BD Difco, Detroit, MI, USA), 총유산균은 BCP Plate Count (BCP) 배지 (Eiken Chemical Co., Tochigi, Japan), 대장균군은 3M Petrifilm TM E. coli/coliform plates (3M Co., St. Paul, MN, USA) 에도말하였다. 도말된 PCA 배지는 30 o C에서 48시간, BCP 배지는 30 o C에서 72시간, 3M Petrifilm은 30 o C에서 24시간각각배양하였고, BCP 배지의경우 GasPak EZ Container System (BD, Sparks, MD, USA) 을사용하여혐기조건에서배양하였다. 배양후 30-300 개의집락을형성한배지만을계수하였다. 우유의유단백변성도측정우유의 HPP 처리시단백질변성정도를알아보기위하여원유와각각 570, 590 및 600 MPa 의조건에서 3 분또는 5 분간처리한 HPP 우유, 대조군으로 LTLT, HTST, UHT 처리우유의 α-casein, β-casein, κ-casein, α-la, β-lg 의함량을 Nitsche [18] 의방법을변형하여 on-chip 전기영동방법으로측정하여비교하였다. 시료의단백질은 13,000 g 에서 1 시간동안원심분리하여지방층을제거하고남은상등액을이용하여측정하였다. Lab-on-a-chip 측정과시료전처리는 Agilent Protein 80 Kit Quick Start Guide 에따라처리하였으며, 2100 Bioanalyzer (Agilent Technologies, Santa Clara, CA, USA) 을이용하여전기영동한후단백질분리패턴을비교 분석하였다.
Microbiological and Chemical Properties of Milk by High Pressure Treatment 269 효소활성측정초고압처리에따른우유 lipase, protease, alkaline phosphatase 및 lactoperoxidase 활성변화측정은실험항목에따라 vortex mixer를이용한균질및원심분리기를이용한지방층제거등의전처리과정을거친우유를사용하여측정하였다. Lipase 저해활성은 Park 등 [19] 의방법을변형하여측정하였다. 10 nm p-nitrophenyl phosphate 용액 0.1 ml과 50 mm potassium phosphate (ph 7.5) 완충액 0.8 ml를혼합하고여기에 0.1 ml의우유를가한뒤 37 o C에서 15분간반응시킨후유리된 p-nitrophenol의양을 405 nm에서흡광도를측정하였다. Protease 활성은 Gupta 등 [6] 과 Gutelben 등 [7] 의방법을변형하여측정하였다. 0.5% casein 용액 0.1 ml을 37 o C에서 10분간반응시킨후 0.1 ml의우유를가한뒤다시 37 o C에서 10분간반응시켰다. 여기에 0.4 M trichloroacetic acid 용액 0.2 ml을가해 37 o C에서 25분간방치시킨뒤침전물을 0.4 μm syringe filter로여과하였다. 여과액 0.1 ml에 0.4 M Na 2 CO 3 0.5 ml과 Folin-Ciocalteu s phenol reagent액 (Sigma-Aldrich, St. Luis, MO, USA) 0.1 ml을가하여 37 o C에서 20분간발색시킨뒤냉각하여생성된 tyrosine의양을 660 nm에서측정하였다. Alkaline phosphatase의활성은 Alkaline Phosphatase Assay Kit (Abcam, Cambridge, MA, USA) 를제조사의방법에따라측정하였고, lactoperoxidase의활성은 Enzyme-linked Immunosorbent Assay Kit For Lactoperoxidase (Cloud- Clone Co., Houston, TX, USA) 를사용하여제조사의방법에따라측정하였다. 결과및고찰 원유의 HPP 처리에따른미생물분석 HPP 처리에따른우유의살균효과를알아보기위하여원유를 15 o C 에서 550 및 600 MPa 의조건으로각각 3 분동안 우유의비타민및미네랄측정시료의 Vitamin A의잔존함량측정은 Vitakit (Crystal Chem Inc., Chicago, IL, USA), Vitamin B1 함량측정은 VitaFast Vitamin B1 (R-Biopharm, Darmstadt, Germany), ascorbic acid 함량측정은 Ascorbic Acid Assay Kit (Bio- Assay Systems, Hayward, CA, USA) 를사용하여측정하였다. 칼슘의함량은 QuantiChrom Calcium Assay Kit (Bioassay Systems), 마그네슘의함량은 QuantiChrom Magnesium Assay Kit (Bioassay Systems) 을사용하여제조사의방법에따라측정하였다. 통계분석모든실험값은평균과표준편차로표시하였다. 얻은실험값의통계분석은 SPSS 18.0 (SPSS Inc., Chicago, IL, USA) 을이용하여일원분산분석 (one-way analysis of variance) 을실시하였고, 실험군간의유의성은 Duncan s multiple range test (p < 0.05) 수준에서검증하였다. Fig. 1. (A) Total bacteria, (B) Total lactic acid bacteria, (C) Total coliforms from raw milk or high pressure-treated milk during storage at 4 o C. HPP A; high pressure-treated raw milk at 550 MPa for 3 min, HPP B; high pressure-treated raw milk at 600 MPa for 3 min. September 2014 Vol. 42 No. 3
270 Lee et al. Fig. 2. Electrophoreogram and gel-like image of high pressure-treated of heat treated protein in milk. (A) Raw milk, (B) high pressure process (HPP)-treated raw milk at 570 MPa or 3 min, (C) HPP treated raw milk at 570 MPa, 5 min, (D) HPP treated raw milk at 590 MPa, 3 min, (E) HPP treated raw milk at 590 MPa, 5 min, (F) HPP treated raw milk at 600 MPa, 3 min, (G) HPP treated raw milk at 600 MPa, 5 min, (H) LTLT, (I) HTST, (J) UHT. Arrows indicate potentially denatured milk proteins.
Microbiological and Chemical Properties of Milk by High Pressure Treatment 271 초고압처리를하였으며, 그후시료를 4 o C에서 15일간저장하면서일반세균, 유산균및대장균군수의변화를측정하였다. Fig. 1에나타낸바와같이저장 1일차대조구로사용된비살균우유의일반세균수는 4.09 Log CFU/ml로나타났으며, HPP A의경우 1.34 Log CFU/ml로대조구에비하여 2.75 Log CFU/ml 감소하였고, HPP B는 0.85 Log CFU/ml 로 3.25 Log CFU/ml 정도감소하였다. 이는 HPP의처리압력이높을수록효율적으로일반세균이제어되는것을나타낸다. 또한저장기간중 HPP 처리구의일반세균수는대조군과비교하여약 2-3 Log CFU/ml의감소효과를유지하였다. 가열살균우유시료인 HTST와 UHT는 15일동안일반세균이검출되지않았으나, LTLT 처리우유는저장 15일차일반세균이약 3 Log CFU/ml 수준으로검출되었다. 이러한결과는 600 MPa의압력하에 3분간우유를 HPP 처리할경우 LTLT 수준으로살균효과를갖는다는것을나타낸다. 유산균의경우비살균대조군의경우 3.41 Log CFU/ml로 HPP A의 Log CFU/ml 보다 2.56 Log CFU/ml 정도감소하였고, HPP B는 Log CFU/ml로 2.93 Log CFU/ml 만큼감소하였다. 550 MPa 조건보다 600 MPa 처리조건이더큰유산균제어효과를나타냈으며, 이러한경향은일반세균과마찬가지로 15일간저장중꾸준히유지되었다. 대장균군의수는초기비살균우유에서 3.04 Log CFU/ml로검출되던것이 15일차에서 5.85 Log CFU/ml로증가하였으나, HPP 처리군에서는모두불검출되었다. Huppertz 등 [10] 은원유를 600 MPa로처리할경우 4 Log CFU/ml 이상의일반세균감소효과가나타난다고보고하였는데본연구에서는 2-3 Log CFU/ml 정도의일반세균및유산균제어효과가나타났다. 이는각각의연구에사용한초고압살균기의크기및초고압처리시간등이다른것에기인한것으로사료된다. HPP 처리에따른우유의단백질변성도측정최근들어우유를가열살균함에따라 3 차단백질구조가파괴되어변성이일어나게되고이로인해우유의영양소파괴및인체에, 특히신생아에게알레르기를유발하는문제가 Fig. 3. Effect of high pressure treatment of milk at 550 MPa, 570 MPa and 600 MPa for 3 min or 5 min on the enzyme activity of (A) lipase, (B) protease, (C) alkaline phosphatase and (D) lactoperoxidase. The means (±SD) of three independent experiments are shown. September 2014 Vol. 42 No. 3
272 Lee et al. 보고되어왔다 [12]. 본연구에서는초고압처리를통한우유의단백질변성도를기존의가열처리우유와비교해보았으며, 그결과는 Fig. 2에나타내었다. HPP 처리우유와가열살균우유의단백질변성도를비교하기위하여원유를 570, 590 및 600 MPa의조건에서각각 3, 5분동안초고압처리를하였으며, 이를 LTLT, HTST 및 UHT 처리우유와함께 onchip 전기영동법을사용하여우유단백질의변성도를비교 분석하였다. Electropherogram 상에서 α-la, β-lg, α-casein, β-casein 및 κ-casein은각각 8.5 kda, 11.6 kda, 22.8 kda, 27.4 kda 및 34.5 kda의분자량위치에서나타남을확인하였으며, 시판중인가열살균우유는 HPP 처리우유보다단백질의종류가다양하게나타났다. 이는변성된유단백을전기영동으로분석할때전형적으로나타나는현상으로가열살균처리군에비해 HPP 처리군에서단백질변성이약하게일어나는것을의미한다. HPP 처리에따른우유의잔존효소활성측정우유를가열살균할경우대부분의효소는불활성화되거나효소활성이급격하게감소하는데, HPP 처리가우유효소활성에미치는영향을알아보고자 lipase, protease, alkaline phosphatase 및 lactoperoxidase 의활성을측정하였다. Fig. 3A 에나타낸바와같이, lipase 는 HPP 처리시원유에비하여효소활성이급격히감소하였으며, 3 분보다 5 분처리시에활성이더욱감소하였다. 더욱이 HPP 처리에따른 lipase 의활성이가열살균우유보다유의적으로낮게관찰되는것으로보아, HPP 처리는가열살균보다도 lipase 를효율적으로불활성화시키는것을확인하였다. 또한 protease 의경우역시 HPP 처리가가열살균보다 protease 활성을효율적으로불활성화시키는것으로관찰되었다 (Fig. 3B). 하지만 UHT 처리우유에서는 protease 활성이전혀검출되지않는것으로보아우유에존재하는 protease 는 HTST 살균법이상의고온에서활성이소실됨을알수있었다. Alkaline phosphatase 는 570 MPa 조건에서 5 분, 590 및 600 MPa 조건에서 3 또는 5 분처리시에효소활성이유의적으로감소하였으며, LTLT 및 HTST 우유보다효소활성이더욱감소하였다 (Fig. 3C). 또한 alkaline phosphatase 도 protease 와마찬가지로 UTH 처리우유에서는활성이검출되지않았다. Lactoperoxidase 는 HPP 처리시에효소활성이유의적으로감소되었고, 600 MPa 조건에서 5 분간가압하였을때는효소활성감소가가장크게나타나 LTLT 우유와유사한수준이었으며, HTST 및 UHT 처리우유의경우효소활성이가장낮게나타났다 (Fig. 3D). Raynal-Ljutovac 등 [21] 에따르면우유가열살균지표로사용되는 alkaline phosphatase 는열에의해어느정도사멸되지만, 원유의품질에따라가열살균시에도 protease 나 lipase 와마찬가지 로 alkaline phosphatase 의불활성화가완전하게일어나지않을수있다고보고하였다. López-Fandiño 등 [17] 은원유를 380 MPa 에서 60 분처리시 alkaline phosphatase 가완전히불활성화되며, Rademacher 등 [20] 은 alkaline phosphatase 는 600 MPa 에서 10 분간처리시에는 50%, 800 MPa 에서 8 분처리시에는 100% 불활성화된다고보고하였다. 이와유사하게본연구에서는 alkaline phosphatase 활성이원유에비하여유의적으로감소하였다. 우유의 lactoperoxidase 는비교적높은압력조건에도활성이소실되지않는특성을나타내는데 [15, 17], 본연구에서도 HPP 처리시 lactoperoxidase 의활성은원유에비하여약하게감소하나가열살균보다는불활성화정도가낮게검출되었다. HPP 처리에따른우유의잔존비타민및미네랄함량측정일반적으로가열살균처리는우유의비타민 A, B1 및 C 의함량에영향을주는것으로알려져있다 [14]. 본연구에서는 HPP 처리우유의잔존비타민 A 의경우압력이높아질수록함량이유의적으로감소하고, 같은압력조건에서 3 분보다 5 분처리시에함량이유의적으로감소하여압력과시간의영향을많이받음을알수있었으나, 가열살균의경우비타민 A 함량의소실이 HPP 처리보다는높게나타났다 (Table 1). 이는 HPP 처리가가열살균처리에비하여우유의비타민 A 의소실을적게일으키는결과로해석된다. 비타민 B1 과비타민 C 의경우 HPP 처리시에함량이약하게줄어듦을알수있었지만검출된함량이매우낮아 HPP 처리에따른소실정도를파악하기는힘들었다 (Table 1). Table 1. Effect of high pressure treatment of milk at 570 MPa, 590 MPa and 600 MPa for 3 min or 5 min on the concentration of vitamin A, vitamin B1 and ascorbic acid. Concentration of vitamins (mg/dl) Treatment Vitamin A (IU/ml) Vitamin B1 (mg/dl) Ascorbic acid (mg/dl) Raw milk 84.31±0.98 a1) 0.05±0.00 ns2) 0.05±0.02 ns 570 MPa 3 min 52.50±0.70 b 0.04±0.00 0.01±0.01 5 min 39.91±0.48 e 0.03±0.00 0.02±0.02 590 MPa 3 min 48.58±0.20 c 0.03±0.00 0.04±0.01 5 min 28.90±0.40 f 0.03±0.00 0.05±0.02 600 MPa 3 min 42.90±0.73 d 0.03±0.00 0.03±0.00 5 min 27.03±0.36 g 0.03±0.00 0.03±0.00 LTLT 14.29±0.24 i 0.03±0.00 0.12±0.00 HTST 22.23±0.26 h 0.03±0.00 0.06±0.00 UHT 1.39±0.08 j 0.03±0.00 0.03±0.00 1) Means in the same column (a-j) bearing different superscripts are significantly different (p < 0.05). 2) ns; not significantly different.
Microbiological and Chemical Properties of Milk by High Pressure Treatment 273 Table 2. Effect of high pressure treatment of milk at 570 MPa, 590 MPa and 600 MPa for 3 min or 5 min on the concentration of calcium and magnesium. Treatment Concentration of mineral (mg/dl) Calcium Magnesium Raw milk 169.36±2.03 a1) 17.64±0.47 ns2) 570 MPa 3 min 162.19±10.55 a 15.35±2.68 5 min 167.99±9.00 a 16.62±1.55 590 MPa 3 min 168.06±2.85 a 15.22±2.61 5 min 158.99±9.85 a 15.99±2.92 600 MPa 3 min 164.65±11.35 a 15.93±2.04 5 min 166.89±19.92 a 16.30±3.26 LTLT 145.81±5.39 a 13.99±3.44 HTST 153.26±12.00 a 15.07±3.04 UHT 116.80±22.34 b 15.62±2.39 1) Means in the same column (a-b) bearing different superscripts are significantly different (p < 0.05). 2) ns; not significantly different. HPP 처리가우유의미네랄함량에미치는영향을알아보고자우유의대표적미네랄성분인 calcium 및 magnesium 의잔존함량을 HPP 처리후측정하였다. Calcium 은처리한 HPP 의모든압력조건에서도거의감소하지않았으며, magnesium 역시거의유의적인함량의차이를보이지않았다 (Table 2). 본연구결과에서는 HPP 처리시우유의 calcium 함량이거의변하지않고가열살균처리했을시살균온도가가장높은 UHT 처리우유에서의칼슘함량이가장낮게나타나, 우유의 calcium 은저온살균에의하여영향을거의받지않는다고알려져있지만고온에서살균시에는 diffusible calcium 함량이감소하는반면 [3, 22], 600 MPa 이하의압력을처리시에는 ionic calcium 의농도가변하지않거나영향이매우적다고보고된결과와일치하였다 [5, 13]. 요 약 초고압공정 (HPP) 은비가열공정중하나로식품중의세균증식을억제하는방법으로근래들어산업적으로각광받고있다. 현재우유의살균은대부분가열살균법에의존하고있으나, 가열살균은우유의영양소및이화학적특성을변화시키는단점이있다. 따라서본연구에서는초고압처리가우유의미생물학적및이화학적특성에미치는영향을알아보았다. 우유를 15 o C 에서 600 MPa 의압력조건으로 3 분간처리했을시일반세균및유산균의수는 2-3 Log CFU/ml 수준으로감소하였으며, 대장균군은 HPP 처리후 4 o C 에서 15 일저장기간중에검출되지않았다. HPP 처리에따른유단백 의변성을알아보고자유단백의전기영동패턴을분석한결과, HPP 처리우유가가열살균우유에비하여단백질변성도가낮게나타났다. 또한 HPP 처리우유의경우비타민및무기질의함량변화는상대적으로낮았으나, protease, lipase 및 alkaline phsophatase 와같은우유효소는불활성화시키는특징을나타내었다. 이러한결과는 HPP 가우유의영양소파괴및이화학적특성을변화시키지않으면서우유의미생물제어에사용될수있음을제시한다. References 1. Beran M, Klubal R, Molik P, Strohalm J, Urban M, Klaudyova AA, et al. 2009. Influence of high-hydrostatic pressure on tryptic and chymotryptic hydrolysis of milk proteins. High Press. Res. 29: 23-27. 2. Bu G, Luo Y, Chen F, Liu K, Zhu T. 2013. Milk processing as a tool to reduce cow s milk allergenicity: a mini-review. Dairy Sci. Technol. 93: 211-223. 3. Buchheim W, Schrader K, Morr CV, Frede E. 1996. Effects of high pressure on the protein, lipid and mineral phase of milk. In Heat Treatments and Alternative Methods 9602: 202-213. 4. Buffa M, Trujillo AJ, Guamis B. 2001. Changes in textural, microstructure, and colour characteristics during ripening of cheeses made from raw, pasteurised or high-pressure-treated goats milk. Int. Dairy J. 11: 927-934. 5. de la Fuente MA, Olano A, Casal V, Juárez M. 1999. Effects of high pressure and heat treatment on the mineral balance of goats milk. J. Dairy Res. 66: 65-72. 6. Gupta A, Roy I, Khare SK, Gupta MN. 2005. Purification and characterization of a solvent stable protease from Pseudomonas aeruginosa PseA. J. Chromatogr. A. 1069: 155-161. 7. Gutleben W, Tuan ND, Stoiber H, Dierich MP, Sarcletti M, Zemann A. 2001. Capillary electrophoretic separation of protease inhibitors used in human immunodeficiency virus therapy. J. Chromatogr. A. 922: 313-320. 8. He H, Adams RM, Farkas DF, Morrissey MT. 2006. Use of high-pressure processing for oyster shucking and shelf-life extension. J. Food Sci. 67: 640-645. 9. Hite BH. 1899. The effects of pressure in the preservation of milk. West Virginia Agric. Exp. Sta. Bull. 58: 15-35. 10. Huppertz T, Smiddy MA, Upadhyay VK, Kelly AL. 2006. Highpressure-induced changes in bovine milk: a review. Int. J. Dairy Technol. 59: 58-66. 11. Iametti S, Transidico P, Bonomi F, Vecchio G, Pittia P, Rovere P, et al. 1997. Molecular modifications of β-lactoglobulin upon exposure to high pressure. J. Agric. Food Chem. 45: 23-29. 12. Isolauri E, Turjanmaa K. 1996. Combined skin prick and patch testing enhances identification of food allergy in infants with atopic dermatitis. J. Allergy Clin. Immunol. 97: 9-15. 13. Johnston DE, Austin BA, Murphy RJ. 1992. Effects of high hydrostatic pressure on milk. Milchwissenschaft 47: 760-763. September 2014 Vol. 42 No. 3
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