耐热酶与乳成分对UHT乳稳定性影响的研究
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摘要
UHT乳是指乳经135～150℃高温杀菌而生产的一种长货架期液态乳。而且UHT乳有营养丰富、保存期长、便于携带和饮用，因此倍受消费者青睐。
乳的凝胶现象是UHT乳产品中较常见的质量问题，对其明确原因目前国内外还无定论。通过本研究发现，UHT处理不能完全钝化乳中的酶，因此在产品贮存过程中，乳蛋白酶、脂肪酶能够水解乳中的蛋白质和脂肪，最终使产品发生一定程度的水解，并表现为乳的粘度、酸度增大，使产品具有形成凝胶的倾向，但是在贮存的前150d并未发现凝胶的形成，所以在UHT乳出现凝胶方面有待于进一步深入研究。
脂肪上浮是UHT乳贮存中存在的普遍现象，影响因素也很多，如原料乳脂肪含量的差异、原料乳与产品的长期高温贮存、均质参数的选择等。本试验分析了乳中的酶与乳的理化成分对乳脂肪上浮的影响。乳中存在的蛋白水解酶对产品的脂肪上浮具有重要影响，表现在产品贮存中，随着蛋白水解度的增大发生脂肪上浮越严重。而且原料乳的理化成分，尤其表现为脂肪与蛋白含量的不同比对产品的脂肪上浮影响也很大。当乳中脂肪含量越高时，产品发生脂肪上浮程度越严重。而当乳中含有的脂肪相对于蛋白含量较低(在1.1左右)时，可以通过添加适量的乳化剂来减缓乳脂肪的上浮，但是并不能完全消除脂肪上浮现象。此外加工过程中的均质工艺对乳的质量也产生一定影响，就目前的产品分析来看，采用二级均质效果较好，均质压力为20MP和5MP，可以使脂肪球大小一致并均匀分布。
UHT(Ultra High Temperature) processed milk is a long shelf life liquid milk product, which is sterilized in 135～150℃. Consumers prefer UHT milk by its nourishment enrich, long shelf life, easy to carry and drink.
Coagulation is a common phenomenon in UHT milk. And the real reason is not sure in the world. The research indicated that not all milk enzymes were destroyed by UHT processing. Proteolysis and lipolysis enzymes hydrolyzed milk protein and fat, led to increase of milk viscosity and acidity, tendenced to coagulation, but didnot emerge coagulation during storage for 150 days.
Fat separation is another general phenomenon during UHT milk storage. There are several factors have an effect on it, such as the quantity of milk fat, storage in a high temperature and enzymes. The study showed that the more degree of milk protein hydrolized, the more severity of fat separation. The value of milk fat to protein affected the fat separation. The higher of the compare of milk fat and protein, the more severity of fat separation. When milk fat is relatively lower to milk protein, the fat separation can be weaken by mixing some emulsifier properly, but cannot eliminate this phenomenon. High pressure processing made milk fat globe smaller and well-distributed ,and it is good for milk quality during storage.
乳的凝胶现象是UHT乳产品中较常见的质量问题，对其明确原因目前国内外还无定论。通过本研究发现，UHT处理不能完全钝化乳中的酶，因此在产品贮存过程中，乳蛋白酶、脂肪酶能够水解乳中的蛋白质和脂肪，最终使产品发生一定程度的水解，并表现为乳的粘度、酸度增大，使产品具有形成凝胶的倾向，但是在贮存的前150d并未发现凝胶的形成，所以在UHT乳出现凝胶方面有待于进一步深入研究。
脂肪上浮是UHT乳贮存中存在的普遍现象，影响因素也很多，如原料乳脂肪含量的差异、原料乳与产品的长期高温贮存、均质参数的选择等。本试验分析了乳中的酶与乳的理化成分对乳脂肪上浮的影响。乳中存在的蛋白水解酶对产品的脂肪上浮具有重要影响，表现在产品贮存中，随着蛋白水解度的增大发生脂肪上浮越严重。而且原料乳的理化成分，尤其表现为脂肪与蛋白含量的不同比对产品的脂肪上浮影响也很大。当乳中脂肪含量越高时，产品发生脂肪上浮程度越严重。而当乳中含有的脂肪相对于蛋白含量较低(在1.1左右)时，可以通过添加适量的乳化剂来减缓乳脂肪的上浮，但是并不能完全消除脂肪上浮现象。此外加工过程中的均质工艺对乳的质量也产生一定影响，就目前的产品分析来看，采用二级均质效果较好，均质压力为20MP和5MP，可以使脂肪球大小一致并均匀分布。
UHT(Ultra High Temperature) processed milk is a long shelf life liquid milk product, which is sterilized in 135～150℃. Consumers prefer UHT milk by its nourishment enrich, long shelf life, easy to carry and drink.
Coagulation is a common phenomenon in UHT milk. And the real reason is not sure in the world. The research indicated that not all milk enzymes were destroyed by UHT processing. Proteolysis and lipolysis enzymes hydrolyzed milk protein and fat, led to increase of milk viscosity and acidity, tendenced to coagulation, but didnot emerge coagulation during storage for 150 days.
Fat separation is another general phenomenon during UHT milk storage. There are several factors have an effect on it, such as the quantity of milk fat, storage in a high temperature and enzymes. The study showed that the more degree of milk protein hydrolized, the more severity of fat separation. The value of milk fat to protein affected the fat separation. The higher of the compare of milk fat and protein, the more severity of fat separation. When milk fat is relatively lower to milk protein, the fat separation can be weaken by mixing some emulsifier properly, but cannot eliminate this phenomenon. High pressure processing made milk fat globe smaller and well-distributed ,and it is good for milk quality during storage.
引文
[1] 郭本恒．乳品化学[M]．北京：中国轻工业出版社，2001．
[2] 骆承庠．超高温灭菌乳生产技术[M]，
[3] 武建新．乳制品生产技术[M]．北京：中国轻工业出版社，2000．78-79．
[4] 谢继志．液态乳制品科学与技术[M]．北京：中国轻工业出版社，1999．157-164．
[5] 金世琳．乳品生物化学[M]．北京：轻工业出版社，1988．189．
[6] Korycka-Dahl M, Ribadeau Dumas B, Chene N, et al. Plasmin activity in milk[J].J Dairy Sci, 1983,66:704～711.
[7] 骆承庠．乳与乳制品工艺学[M]．1992．10
[8] Fox P F. Developments in dairy chemistry-1 proteins[M].1982.
[9] 赵平．超高温牛乳常见缺陷及排除方法[J]．中国乳品工业，1999，6：29～31．
[10] 方义仁．原料奶质量对UHT奶制品的影响及控制[J]．中国乳品工业，1990，3：118120．
[11] Eric D, Bastian, Rpdmeu J. Plasmin activity and milk coagulation[J].J Dairy Sci, 1991,74:3677～3685.
[12] Kaminogawa S, Mizobuchi H, Yamauchi K. Comparison of bovine milk protease with plasmin[J].Agr Biol Chem,1972,36:2163～2167.
[13] Maj-Lis Aaltonen. Plasmin activity in milk[J].Milchwissenschaft, 1988,43(9):573～576.
[14] Fajardo-lira C, Oria M. Effect of psychrotrophic bacterea and of an isolated protease from pseudomonas fluorescens M3/6 on the plasmin system of fresh milk[J]. J Dairy Sci, 2000,83:2190～2199.
[15] Mottar J. Heat resistant enzymes in UHT milk and their influence on sensoric changes during uncooled storage[J].Milchwissenschaft, 1981,36(2):87～91.
[16] Richardson B C. The proteinases of bovine milk and the effect of pasterization on their activity[J].N Z J Dairy Sci Technol, 1983,18:223～228.
[17] Eric D, Bastian, Rodney J,. Plasmin in milk and dairy products: an update[J]. Int Dairy J, 1996,6:435-457.
[18] Munro G L. Effects of mastitis on milk yield, milk composition, processing properties and yield and quality of milk products[J]. Aust J Dairy Technol.
1984,39:7～14.
[19] Grieve P A, Kitchen B J. Proteolysis in milk: the significance of proteinases originating from milk leucocytes and a comparison of the action of leucocyte, bacterial and natural proteinases on casein[J].J Dairy Res, 1985,52:101～112.
[20] Electricwala A, Atkinson T. Purification and properties of plasminogen activators from epithelial cell[J].Eur J Biochem. 1985,147:511～518.
[21] Politis I, Lachancce E.. Plasmin and plasminogen in bovine milk: a relationship with involution[J]. J Dairy Sci. 1988,72:900～906.
[22] Richardson B C. Variation of the concentration of plasmin and plasminogen in bovine milk with lactation[J].N Z J Dairy Sci Technol, 1983,18:247～253.
[23] Politis I, Kwai K F, Hang N, et al. Evironmental factors affecting plasmin activity in milk[J].J Dairy Sci, 1989,72:1713～1718.
[24] Kocak H R, Zadow J G. Controlling age gelation of UHT milk with additives[J]. The Australian Journal of Dairy Technology, 1985,6:58～64.
[25] Kohlmann K L, Nielsen S S, Ladisch M.R. Effects of a low concentration of added plasmin on ultra-high temperature processed milk[J].J Dairy Sci, 1991,74:1151～1156.
[26] 徐岩，张继民，汤丹剑等译．现代食品微生物学[M]．北京：中国轻工业出版社，2001．
[27] Driessen F M, Stadhouders J. Thermal activation and inactivation of exocellular lipases of some gram-negative bacteria common in milk[J].Neth milk Dairy J,1974,28:10～16.
[28] Grufferty M B,, Fox P F. Milk alkaline proteinase[J].J Dairy Sci, 1988,55:609～630.
[29] Keogh B P. Influence of enzyme activity of bacteria and leucocytes in raw milk on age gelation after UHT processing[J]. J Food Prot, 1984,47:105～107.
[30] Kocak H R, Zadow J G.Polyphosphate variability in the control of age gelation in UHT milk[J].The Aus J Dairy Technol, 1985,6:65～68.
[31] Politis I, Zavizion B, Barbano D M, et al. Enzymatic assay for the combined determination of plasmin plus plasminogen in milk: revisited[J].J Dairy sci,1993,
76:1260～1267.
[32] Rollema H S, Visser S, Poll J K. Spectrophotometric assay of plasmin and plasminogen in bovin milk[J],1983,38:214～217.
[33] Garcia-Risco M R, Olano A, Ramas M, et al. Micellar changes induced by high pressure, influence in the proteolytic activity and organoleptic properties of milk[J].J Dairy Sci,2000,83:2184～2189.
[34] Mottar J. Heat resistant enzymes in UHT and their influence on sensoric changes during uncooled storage[J].Milchwissenschaft, 1981,36(2):87～91.
[35] 食品分析中国轻工业出版社 1996，6
[36] Choi I W, Jeon I J. Patterns of fatty acids released from milk fat by residual lipase during storage of ultra-high temperature processed milk[J].J Dairy Sci, 1992,76:78～85.
[37] Marvin L speck. Compendium of methods for the microbiological examination of food [M]. American public health association, 1976.
[38] Adams D M, Sarach J T, Speck M L. Heat pesistant proteases produced in milk by psychrotrophic bacteria of dairy origin[J]. J Dairy Sci, 1975,58:828～835.
[39] Verdi R J, Barbano D M. Effect of coagulants, somatic cell enzymes, and extracellular bacterial enzymes on plasminogen activation[J].J Dairy Sci, 1991,74:772～782.
[40] Andersson R E, Danielsson G, Hedlund C B, et al. Effect of heat-resistant microbial lipases on flavor of ultra-high-temperature sterilized milk[J], J Dairy Sci, 1981,64:375～379.
[41] Adams D M, Brawleu T. Heat-resistant bacterial iipases and ultra-high temperature sterilization of dairy products[J]. J Dairy Sci, 1981, 64:1951～1957.
[42] 袁玮，胡海蓉，赵怀跟等．鲜牛乳中乳杆菌的检测及脂肪酶、蛋白酶测定方法的研究[J]．食品与发酵工业，2001，7：35～38．
[43] Bashir Manji,Yukio Kakuda. The role of protein denaturation,extent of proteolysis,and storage temperature on the mechanism of age gelation in a model system[J].J Dairy Sci. 1988, 71:1455～1463.
[44] Kocak H R, Zadow J G Age gelation of UHT whole milk as influenced by storage
temperature[J]. The Australian Journal of Dairy Technology, 1985,3:14～21.
[45] Young Jae Kang, Frank J F. Proteolysis of high quality raw milk during storag at various temperatures[J]. J Dairy Sci, 1988,71:1484～1491.
[46] Mitchell G E, Ewings K N. Quantification of bacterial proteolysis causing gelation in UHT-treated milk [J].New Zealand J Dairy sci and tech, 1985,20,65～76.
[47] Gillis W T, Cartledge M F, Rodriguez I R. Effect of raw milk quality on ultra-high temperature processed milk[J].J Dairy Sci, 1985,68:2875～2879.
[48] 武若飞，李艳，昊平等．UHT奶的质量与原料奶的关系[J]．中国乳品工业，1997，2：34～35．
[49] 于飞，王云．优质的原料优质的产品[J]．中国乳品工业，1999，1：33～34．
[50] 韩海周．超高温奶生产、仓储及运输过程中的卫生、质量控制[J]．中国乳品工业，1998，4：24～26．
[51] Koning P J, Kaper J.Effects of some proteinase inhibitors and of the Maillare reaction on the processes of age-thinning and gelation of UHTST-sterilezed concentrated casein micelle dispersions[J].Neth Milk Dairy J, 1985,39:37～47.
[52] Kang Y J. Proteolysis of high quality raw milk dairy prolonged cold storage[D].Univ Georgia Athens, 1985
[53] Law B A. Reviews of the progress of dairy science:Enzymes of psychrotrophic bacteria and their effects on milk and milk products[J].J Dairy Res, 1979,46:573～588.
[54] Venkatachalam N, Mcmahon D J,Savelio A. Role of protein and lactose interactions in the age gelation of ultra-high temperature processed concentrated skim milk[J]. J Dairy Sci, 1993,76:1882～1894.
[55] 方炜．超高温灭菌乳在贮藏过程中的质量变化[J]．中国乳品工业，1996，3：22～24．
[2] 骆承庠．超高温灭菌乳生产技术[M]，
[3] 武建新．乳制品生产技术[M]．北京：中国轻工业出版社，2000．78-79．
[4] 谢继志．液态乳制品科学与技术[M]．北京：中国轻工业出版社，1999．157-164．
[5] 金世琳．乳品生物化学[M]．北京：轻工业出版社，1988．189．
[6] Korycka-Dahl M, Ribadeau Dumas B, Chene N, et al. Plasmin activity in milk[J].J Dairy Sci, 1983,66:704～711.
[7] 骆承庠．乳与乳制品工艺学[M]．1992．10
[8] Fox P F. Developments in dairy chemistry-1 proteins[M].1982.
[9] 赵平．超高温牛乳常见缺陷及排除方法[J]．中国乳品工业，1999，6：29～31．
[10] 方义仁．原料奶质量对UHT奶制品的影响及控制[J]．中国乳品工业，1990，3：118120．
[11] Eric D, Bastian, Rpdmeu J. Plasmin activity and milk coagulation[J].J Dairy Sci, 1991,74:3677～3685.
[12] Kaminogawa S, Mizobuchi H, Yamauchi K. Comparison of bovine milk protease with plasmin[J].Agr Biol Chem,1972,36:2163～2167.
[13] Maj-Lis Aaltonen. Plasmin activity in milk[J].Milchwissenschaft, 1988,43(9):573～576.
[14] Fajardo-lira C, Oria M. Effect of psychrotrophic bacterea and of an isolated protease from pseudomonas fluorescens M3/6 on the plasmin system of fresh milk[J]. J Dairy Sci, 2000,83:2190～2199.
[15] Mottar J. Heat resistant enzymes in UHT milk and their influence on sensoric changes during uncooled storage[J].Milchwissenschaft, 1981,36(2):87～91.
[16] Richardson B C. The proteinases of bovine milk and the effect of pasterization on their activity[J].N Z J Dairy Sci Technol, 1983,18:223～228.
[17] Eric D, Bastian, Rodney J,. Plasmin in milk and dairy products: an update[J]. Int Dairy J, 1996,6:435-457.
[18] Munro G L. Effects of mastitis on milk yield, milk composition, processing properties and yield and quality of milk products[J]. Aust J Dairy Technol.
1984,39:7～14.
[19] Grieve P A, Kitchen B J. Proteolysis in milk: the significance of proteinases originating from milk leucocytes and a comparison of the action of leucocyte, bacterial and natural proteinases on casein[J].J Dairy Res, 1985,52:101～112.
[20] Electricwala A, Atkinson T. Purification and properties of plasminogen activators from epithelial cell[J].Eur J Biochem. 1985,147:511～518.
[21] Politis I, Lachancce E.. Plasmin and plasminogen in bovine milk: a relationship with involution[J]. J Dairy Sci. 1988,72:900～906.
[22] Richardson B C. Variation of the concentration of plasmin and plasminogen in bovine milk with lactation[J].N Z J Dairy Sci Technol, 1983,18:247～253.
[23] Politis I, Kwai K F, Hang N, et al. Evironmental factors affecting plasmin activity in milk[J].J Dairy Sci, 1989,72:1713～1718.
[24] Kocak H R, Zadow J G. Controlling age gelation of UHT milk with additives[J]. The Australian Journal of Dairy Technology, 1985,6:58～64.
[25] Kohlmann K L, Nielsen S S, Ladisch M.R. Effects of a low concentration of added plasmin on ultra-high temperature processed milk[J].J Dairy Sci, 1991,74:1151～1156.
[26] 徐岩，张继民，汤丹剑等译．现代食品微生物学[M]．北京：中国轻工业出版社，2001．
[27] Driessen F M, Stadhouders J. Thermal activation and inactivation of exocellular lipases of some gram-negative bacteria common in milk[J].Neth milk Dairy J,1974,28:10～16.
[28] Grufferty M B,, Fox P F. Milk alkaline proteinase[J].J Dairy Sci, 1988,55:609～630.
[29] Keogh B P. Influence of enzyme activity of bacteria and leucocytes in raw milk on age gelation after UHT processing[J]. J Food Prot, 1984,47:105～107.
[30] Kocak H R, Zadow J G.Polyphosphate variability in the control of age gelation in UHT milk[J].The Aus J Dairy Technol, 1985,6:65～68.
[31] Politis I, Zavizion B, Barbano D M, et al. Enzymatic assay for the combined determination of plasmin plus plasminogen in milk: revisited[J].J Dairy sci,1993,
76:1260～1267.
[32] Rollema H S, Visser S, Poll J K. Spectrophotometric assay of plasmin and plasminogen in bovin milk[J],1983,38:214～217.
[33] Garcia-Risco M R, Olano A, Ramas M, et al. Micellar changes induced by high pressure, influence in the proteolytic activity and organoleptic properties of milk[J].J Dairy Sci,2000,83:2184～2189.
[34] Mottar J. Heat resistant enzymes in UHT and their influence on sensoric changes during uncooled storage[J].Milchwissenschaft, 1981,36(2):87～91.
[35] 食品分析中国轻工业出版社 1996，6
[36] Choi I W, Jeon I J. Patterns of fatty acids released from milk fat by residual lipase during storage of ultra-high temperature processed milk[J].J Dairy Sci, 1992,76:78～85.
[37] Marvin L speck. Compendium of methods for the microbiological examination of food [M]. American public health association, 1976.
[38] Adams D M, Sarach J T, Speck M L. Heat pesistant proteases produced in milk by psychrotrophic bacteria of dairy origin[J]. J Dairy Sci, 1975,58:828～835.
[39] Verdi R J, Barbano D M. Effect of coagulants, somatic cell enzymes, and extracellular bacterial enzymes on plasminogen activation[J].J Dairy Sci, 1991,74:772～782.
[40] Andersson R E, Danielsson G, Hedlund C B, et al. Effect of heat-resistant microbial lipases on flavor of ultra-high-temperature sterilized milk[J], J Dairy Sci, 1981,64:375～379.
[41] Adams D M, Brawleu T. Heat-resistant bacterial iipases and ultra-high temperature sterilization of dairy products[J]. J Dairy Sci, 1981, 64:1951～1957.
[42] 袁玮，胡海蓉，赵怀跟等．鲜牛乳中乳杆菌的检测及脂肪酶、蛋白酶测定方法的研究[J]．食品与发酵工业，2001，7：35～38．
[43] Bashir Manji,Yukio Kakuda. The role of protein denaturation,extent of proteolysis,and storage temperature on the mechanism of age gelation in a model system[J].J Dairy Sci. 1988, 71:1455～1463.
[44] Kocak H R, Zadow J G Age gelation of UHT whole milk as influenced by storage
temperature[J]. The Australian Journal of Dairy Technology, 1985,3:14～21.
[45] Young Jae Kang, Frank J F. Proteolysis of high quality raw milk during storag at various temperatures[J]. J Dairy Sci, 1988,71:1484～1491.
[46] Mitchell G E, Ewings K N. Quantification of bacterial proteolysis causing gelation in UHT-treated milk [J].New Zealand J Dairy sci and tech, 1985,20,65～76.
[47] Gillis W T, Cartledge M F, Rodriguez I R. Effect of raw milk quality on ultra-high temperature processed milk[J].J Dairy Sci, 1985,68:2875～2879.
[48] 武若飞，李艳，昊平等．UHT奶的质量与原料奶的关系[J]．中国乳品工业，1997，2：34～35．
[49] 于飞，王云．优质的原料优质的产品[J]．中国乳品工业，1999，1：33～34．
[50] 韩海周．超高温奶生产、仓储及运输过程中的卫生、质量控制[J]．中国乳品工业，1998，4：24～26．
[51] Koning P J, Kaper J.Effects of some proteinase inhibitors and of the Maillare reaction on the processes of age-thinning and gelation of UHTST-sterilezed concentrated casein micelle dispersions[J].Neth Milk Dairy J, 1985,39:37～47.
[52] Kang Y J. Proteolysis of high quality raw milk dairy prolonged cold storage[D].Univ Georgia Athens, 1985
[53] Law B A. Reviews of the progress of dairy science:Enzymes of psychrotrophic bacteria and their effects on milk and milk products[J].J Dairy Res, 1979,46:573～588.
[54] Venkatachalam N, Mcmahon D J,Savelio A. Role of protein and lactose interactions in the age gelation of ultra-high temperature processed concentrated skim milk[J]. J Dairy Sci, 1993,76:1882～1894.
[55] 方炜．超高温灭菌乳在贮藏过程中的质量变化[J]．中国乳品工业，1996，3：22～24．