不同体细胞数原料乳对UHT乳贮存期间品质的影响
摘要
本实验主要研究了原料乳SCC对UHT乳贮存期间品质的影响。在实验中,采用四组SCC不同的原料乳(SCC<50万个/mL, SCC 50万～100万个/mL, SCC 100万～200万个/mL和SCC>200万个/mL)制成UHT乳,制备好的UHT乳分别于25℃贮存168d,37℃贮存84d。在贮存期间,对各组UHT乳的酶活性、理化指标以及感官指标进行跟踪检测。研究结果显示:
⑴原料乳经过UHT处理后,乳中纤维蛋白溶酶基本完全失活,而脂肪酶活性大约残留20%。原料乳SCC越高,UHT乳中残留的脂肪酶活性越高。
⑵UHT乳贮存期间pH值呈下降趋势,原料乳SCC与UHT乳贮存期间pH值下降率呈显著的正相关,25℃贮存时相关系数为0.8068(P<0.05),37℃贮存时相关系数为0.7700(P<0.05)。
⑶UHT乳贮存期间黏度变化规律不显著(P>0.05)。
⑷UHT乳贮存期间游离钙离子含量变化规律不显著(P>0.05)。
⑸UHT乳贮存期间蛋白水解程度不高,但原料乳SCC较高的两组UHT乳蛋白水解较明显(P<0.05)。UHT乳贮存期间脂肪水解极明显,原料乳SCC较高的两组UHT乳脂肪水解较快(P<0.05)。原料乳SCC与UHT乳贮存期间FFA含量增加率呈极显著的正相关,25℃贮存时相关系数为0.9284(P<0.001),37℃贮存时相关系数为0.9396(P<0.001)。
⑹UHT乳贮存期间并未发生胶凝和蛋白沉淀现象。但是,在贮存7～14d时,各组UHT乳的上层脂肪含量开始增加。贮存期间,原料乳SCC高的UHT乳脂肪上浮较严重,原料乳SCC与UHT乳脂肪上浮速率呈显著的正相关,25℃贮存时相关系数为0.9039(P<0.01),37℃贮存时相关系数为0.8926(P<0.01)。在贮存28d(37℃)和56d(25℃)时,UHT乳的颜色开始变深。贮存期间,原料乳SCC高的UHT乳颜色变化较严重,原料乳SCC与UHT乳颜色变化速率呈显著的正相关,25℃贮存时相关系数为0.8116(P<0.05),37℃贮存时相关系数为0.9250(P<0.001)。感官评价结果表明,在贮存56d(37℃)和112d(25℃)时,原料乳SCC较高的两组UHT乳出现了不良的风味。
⑺UHT乳贮存期间,乳中的脂肪球分布逐渐向粒径大的方向移动。在贮存后期,原料乳SCC较高的UHT乳乳中脂肪球聚集现象较明显。
⑻贮存温度对于UHT乳贮存期间的品质变化也有所影响。37℃贮存的UHT乳贮存期间的pH值下降率、蛋白水解及脂肪水解率、脂肪上浮速度及颜色变化速度都为25℃贮存的UHT乳的2～3倍。
The effect of SCC in raw milk on the quality of UHT milk during storage was investigated. The UHT milks were prepared from raw milk containing four different SCC levels(SCC<50×104cells/mL, SCC 50×104～100×104 cells/mL, SCC 100×104～200×104 cells/mL and SCC>200×104cells/mL). The UHT milks were stored at 25℃for 168d and 37℃for 84d, during storage, their enzyme activities, physical and chemical characters as well as sensory attributes were analyzed. The results showed:
⑴The milks had no residual plasmin activity, but 20% of original lipase activity after UHT processing. The lipase activity in UHT milks increased along with elevated raw milk SCC.
⑵During storage, pH value gradually decreased in UHT milks. There was significant positive correlation between raw milk SCC and pH value descending rate of UHT milks, correlation coefficients were 0.8068(P<0.05) at 25℃and 0.7700(P<0.05) at 37℃.
⑶During storage, no pronounced rule of viscosity change was found(P>0.05).
⑷During storage, no pronounced rule of free calcium content change was found(P> 0.05).
⑸During storage, proteolysis degree in UHT milks was low, but it was more obvious in high SCC milks(P<0.05). During storage, liplysis degree in UHT milks was high, and it was higher in high SCC milks(P<0.05). There was significant positive correlation between raw milk SCC and FFA increasing rate of UHT milks, correlation coefficients were 0.9284(P<0.001) at 25℃and 0.9396(P<0.001) at 37℃.
⑹During storage, age gelation and protein precipitation weren’t observed in UHT milks. The upper layer fat in UHT milks started to increase when UHT milks were stored for 7 ~ 14d. The fat separation was more serious in high SCC milks. There was significant positive correlation between raw milk SCC and fat separating rate of UHT milks, correlation coefficients were 0.9039(P<0.01) at 25℃and 0.8926(P<0.01) at 37℃. The color of UHT milks started to deepen when UHT milks were stored at 25℃for 56d and 37℃for 28d. The color change was more serious in high SCC milks. There was significant positive correlation between raw milk SCC and color changing rate of UHT milks, correlation coefficients were 0.8116(P<0.05) at 25℃and 0.9250(P<0.001) at 37℃. Sensory evaluation results indicated off-flavor was observed when high SCC milks stored at 25℃for 112d and 37℃for 56d.
⑺During storage, fat gluble size of UHT milks gradually increased. Fat gluble aggregation in high SCC milks was more serious during later storage.
⑻Storing temperature also influenced quality of UHT milks. During storage, PH value descending rate, proteolysis and liplysis rate, fat separating and color changing speed of UHT milks stored at 37℃were, repectively, 2～3 times faster than those stored at 25℃.
⑴原料乳经过UHT处理后,乳中纤维蛋白溶酶基本完全失活,而脂肪酶活性大约残留20%。原料乳SCC越高,UHT乳中残留的脂肪酶活性越高。
⑵UHT乳贮存期间pH值呈下降趋势,原料乳SCC与UHT乳贮存期间pH值下降率呈显著的正相关,25℃贮存时相关系数为0.8068(P<0.05),37℃贮存时相关系数为0.7700(P<0.05)。
⑶UHT乳贮存期间黏度变化规律不显著(P>0.05)。
⑷UHT乳贮存期间游离钙离子含量变化规律不显著(P>0.05)。
⑸UHT乳贮存期间蛋白水解程度不高,但原料乳SCC较高的两组UHT乳蛋白水解较明显(P<0.05)。UHT乳贮存期间脂肪水解极明显,原料乳SCC较高的两组UHT乳脂肪水解较快(P<0.05)。原料乳SCC与UHT乳贮存期间FFA含量增加率呈极显著的正相关,25℃贮存时相关系数为0.9284(P<0.001),37℃贮存时相关系数为0.9396(P<0.001)。
⑹UHT乳贮存期间并未发生胶凝和蛋白沉淀现象。但是,在贮存7～14d时,各组UHT乳的上层脂肪含量开始增加。贮存期间,原料乳SCC高的UHT乳脂肪上浮较严重,原料乳SCC与UHT乳脂肪上浮速率呈显著的正相关,25℃贮存时相关系数为0.9039(P<0.01),37℃贮存时相关系数为0.8926(P<0.01)。在贮存28d(37℃)和56d(25℃)时,UHT乳的颜色开始变深。贮存期间,原料乳SCC高的UHT乳颜色变化较严重,原料乳SCC与UHT乳颜色变化速率呈显著的正相关,25℃贮存时相关系数为0.8116(P<0.05),37℃贮存时相关系数为0.9250(P<0.001)。感官评价结果表明,在贮存56d(37℃)和112d(25℃)时,原料乳SCC较高的两组UHT乳出现了不良的风味。
⑺UHT乳贮存期间,乳中的脂肪球分布逐渐向粒径大的方向移动。在贮存后期,原料乳SCC较高的UHT乳乳中脂肪球聚集现象较明显。
⑻贮存温度对于UHT乳贮存期间的品质变化也有所影响。37℃贮存的UHT乳贮存期间的pH值下降率、蛋白水解及脂肪水解率、脂肪上浮速度及颜色变化速度都为25℃贮存的UHT乳的2～3倍。
The effect of SCC in raw milk on the quality of UHT milk during storage was investigated. The UHT milks were prepared from raw milk containing four different SCC levels(SCC<50×104cells/mL, SCC 50×104～100×104 cells/mL, SCC 100×104～200×104 cells/mL and SCC>200×104cells/mL). The UHT milks were stored at 25℃for 168d and 37℃for 84d, during storage, their enzyme activities, physical and chemical characters as well as sensory attributes were analyzed. The results showed:
⑴The milks had no residual plasmin activity, but 20% of original lipase activity after UHT processing. The lipase activity in UHT milks increased along with elevated raw milk SCC.
⑵During storage, pH value gradually decreased in UHT milks. There was significant positive correlation between raw milk SCC and pH value descending rate of UHT milks, correlation coefficients were 0.8068(P<0.05) at 25℃and 0.7700(P<0.05) at 37℃.
⑶During storage, no pronounced rule of viscosity change was found(P>0.05).
⑷During storage, no pronounced rule of free calcium content change was found(P> 0.05).
⑸During storage, proteolysis degree in UHT milks was low, but it was more obvious in high SCC milks(P<0.05). During storage, liplysis degree in UHT milks was high, and it was higher in high SCC milks(P<0.05). There was significant positive correlation between raw milk SCC and FFA increasing rate of UHT milks, correlation coefficients were 0.9284(P<0.001) at 25℃and 0.9396(P<0.001) at 37℃.
⑹During storage, age gelation and protein precipitation weren’t observed in UHT milks. The upper layer fat in UHT milks started to increase when UHT milks were stored for 7 ~ 14d. The fat separation was more serious in high SCC milks. There was significant positive correlation between raw milk SCC and fat separating rate of UHT milks, correlation coefficients were 0.9039(P<0.01) at 25℃and 0.8926(P<0.01) at 37℃. The color of UHT milks started to deepen when UHT milks were stored at 25℃for 56d and 37℃for 28d. The color change was more serious in high SCC milks. There was significant positive correlation between raw milk SCC and color changing rate of UHT milks, correlation coefficients were 0.8116(P<0.05) at 25℃and 0.9250(P<0.001) at 37℃. Sensory evaluation results indicated off-flavor was observed when high SCC milks stored at 25℃for 112d and 37℃for 56d.
⑺During storage, fat gluble size of UHT milks gradually increased. Fat gluble aggregation in high SCC milks was more serious during later storage.
⑻Storing temperature also influenced quality of UHT milks. During storage, PH value descending rate, proteolysis and liplysis rate, fat separating and color changing speed of UHT milks stored at 37℃were, repectively, 2～3 times faster than those stored at 25℃.
引文
1 武建新.乳制品生产技术[M].北京:中国轻工业出版社,2000.78-79
2 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
3 张和平编.金世琳乳品科技文选[M].北京:中国轻工业出版社,2006.143
4 生庆海,张爱霞.UHT 乳贮存中常见问题及其原因分析[J].中国乳品工业,2002,30(5):143-144
5 金世琳.乳品生物化学[M].北京:中国轻工业出版社,1988.189
6 Korycka-Dahl M,Rlbadeau Dumas B,Chene N,et al.Plasmin activity in milk[J].J Dairy Sci,1983,66:704-711
7 郭本恒.乳品化学[M].北京:中国轻工业出版社,1999.82
8 张和平,张列兵.现代乳品工业手册[M].北京:中国轻工业出版社,2005.26
9 何卫加.UHT 灭菌牛乳常见质量问题的原因分析及控制措施[J].中国乳品工业,1999,27(2):33-35
10 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,1996,24(3):22-24
11 赵平.超高温牛乳常见缺陷及排除方法[J].中国乳品工业.1999,27(6):29-31
12 雷晓薇等.应用体细胞计数监测奶牛隐性乳房炎[J].畜牧与兽医,2003,35(12):35-37
13 刘峰,迟玉杰.乳房炎乳的检测方法[J].现代食品科技,2005,21:131-133
14 李建斌等.应用 DHI 提供的体细胞数据控制奶牛乳房炎[J].当代畜牧,2004,2:17-19
15 杨爱君,阮征,曾庆孝.控制体细胞数在优质生鲜奶生产中的应用[J].中国乳品工业,2005,33(1):53-56
16 Green M J,Green L E,Schukken V H,et al.Somatic cell count distributions during lactation predict clinical mastitis [J].J Dairy Sci,2004,87:1256-1264
17 Manji B,Kakuda Y,and Arnott D R.Effect of storage temperature on age gelation of ultra high temperature milk processed by direct and indirect heating systems[J].J Dairy Sci,1986,69:2994-3001
18 Kelly A L,and Foley J.Proteolysis and storage stability of UHT milk as influenced by milk plasmin activity,plasmin/β-lactoglobulin complexation,plasminogen activation and somatic cell count[J].Int.Dairy Journal,1997,7:411-420
19 Kohlmann K L,Nielsen S S,and Ladisch M R.Effects of a low concentration of added plasmin on ultra-high temperature processed milk[J].J Dairy Sci,1991,74:151~156
20 周家春编.食品工艺学[M].北京:化学工业出版社,2003.84
21 Choi I W,and 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,1993,76:78-85
22 张爱霞.耐热酶与乳成分对 UHT 乳稳定性影响的研究[D].河北:河北农业大学,2003
23 于若木主编.乳品工业手册[M].北京:轻工业出版社,2002 .16 ,84
24 王芳,胡松华.体细胞含量与牛奶质量的关系[J].中国奶牛,2005(4):51-52
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26 Azzara C D,and Dimick P S.Liproprotein lipase activity of milk from cows with prolonged subclinical mastitis[J].J Dairy Sci,1985,68:3171-3175
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2 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
3 张和平编.金世琳乳品科技文选[M].北京:中国轻工业出版社,2006.143
4 生庆海,张爱霞.UHT 乳贮存中常见问题及其原因分析[J].中国乳品工业,2002,30(5):143-144
5 金世琳.乳品生物化学[M].北京:中国轻工业出版社,1988.189
6 Korycka-Dahl M,Rlbadeau Dumas B,Chene N,et al.Plasmin activity in milk[J].J Dairy Sci,1983,66:704-711
7 郭本恒.乳品化学[M].北京:中国轻工业出版社,1999.82
8 张和平,张列兵.现代乳品工业手册[M].北京:中国轻工业出版社,2005.26
9 何卫加.UHT 灭菌牛乳常见质量问题的原因分析及控制措施[J].中国乳品工业,1999,27(2):33-35
10 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,1996,24(3):22-24
11 赵平.超高温牛乳常见缺陷及排除方法[J].中国乳品工业.1999,27(6):29-31
12 雷晓薇等.应用体细胞计数监测奶牛隐性乳房炎[J].畜牧与兽医,2003,35(12):35-37
13 刘峰,迟玉杰.乳房炎乳的检测方法[J].现代食品科技,2005,21:131-133
14 李建斌等.应用 DHI 提供的体细胞数据控制奶牛乳房炎[J].当代畜牧,2004,2:17-19
15 杨爱君,阮征,曾庆孝.控制体细胞数在优质生鲜奶生产中的应用[J].中国乳品工业,2005,33(1):53-56
16 Green M J,Green L E,Schukken V H,et al.Somatic cell count distributions during lactation predict clinical mastitis [J].J Dairy Sci,2004,87:1256-1264
17 Manji B,Kakuda Y,and Arnott D R.Effect of storage temperature on age gelation of ultra high temperature milk processed by direct and indirect heating systems[J].J Dairy Sci,1986,69:2994-3001
18 Kelly A L,and Foley J.Proteolysis and storage stability of UHT milk as influenced by milk plasmin activity,plasmin/β-lactoglobulin complexation,plasminogen activation and somatic cell count[J].Int.Dairy Journal,1997,7:411-420
19 Kohlmann K L,Nielsen S S,and Ladisch M R.Effects of a low concentration of added plasmin on ultra-high temperature processed milk[J].J Dairy Sci,1991,74:151~156
20 周家春编.食品工艺学[M].北京:化学工业出版社,2003.84
21 Choi I W,and 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,1993,76:78-85
22 张爱霞.耐热酶与乳成分对 UHT 乳稳定性影响的研究[D].河北:河北农业大学,2003
23 于若木主编.乳品工业手册[M].北京:轻工业出版社,2002 .16 ,84
24 王芳,胡松华.体细胞含量与牛奶质量的关系[J].中国奶牛,2005(4):51-52
25 Polits I,Lacnance E,Block E,and Turner J D.Plasmin and plasminogen in bovine milk:a relationship with involution?[J].J Dairy Sci,1988,12:900-906
26 Azzara C D,and Dimick P S.Liproprotein lipase activity of milk from cows with prolonged subclinical mastitis[J].J Dairy Sci,1985,68:3171-3175
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