A FAST (fluorescence of advanced Maillard products and Soluble Tryptophan) method for identification of recon- stituted milk made from skim milk powder in the fresh milk was developed. Considering milk and skim milk p...A FAST (fluorescence of advanced Maillard products and Soluble Tryptophan) method for identification of recon- stituted milk made from skim milk powder in the fresh milk was developed. Considering milk and skim milk powders variations from different seasons and countries, milk was collected from different dairy farms in different seasons and skim milk powders were collected from different countries to measure the Tryptophan (Trp), advanced Maillard products (AMP) fluorescence values. The results showed that there were differences (P<0.01) between raw and reconstituted milk. The plot of values in each mixed level of raw and reconstituted milk had a correlation coefficient >0.97. The FAST method is a simple, rapid, low-cost and sensitive method enabling the detection of 5% reconstituted milk in fresh milk. The measurement of the Trp, AMP fluorescence values and calculation of the FAST index is a suitable method for large-scale monitoring of fresh milk samples.展开更多
Limited enzymatic hydrolysis of skim milk by trypsin was investigated in this paper, and it was found that the degree of hydrolysis (DH) of milk proteins had a relationship of DH -1 =a+bt -1 with the time(t) o...Limited enzymatic hydrolysis of skim milk by trypsin was investigated in this paper, and it was found that the degree of hydrolysis (DH) of milk proteins had a relationship of DH -1 =a+bt -1 with the time(t) of hydrolysis at low enzyme concentrations, some properties of the protein such as NSI in PI or TCA were changed obviously. It was suggested that most milk proteins would be degraded into peptides by trypsin .展开更多
For a long time, fermented dairy products have been consumed for human’s nutrition and health. Recently, consumption of whole dairy products, such as full fat yoghurt, has declined due to the awareness of probable ha...For a long time, fermented dairy products have been consumed for human’s nutrition and health. Recently, consumption of whole dairy products, such as full fat yoghurt, has declined due to the awareness of probable harmful effects of fat on consumers’ health, resulting change of market interest in favor of low or non fat dairy products. It is a challenge for food scientists to produce a suitable fat substitute providing the functionality of the missing fat. The present investigation was carried out to examine the effect of 0 to 50% renneted skim milk (RSM) as a fat mimetic upon the physico-chemical, physical, rheological and sensory characteristics of nonfat yoghurt in comparison to control samples (full fat and skim yoghurt). By increasing RSM content, the chemical characteristics (titratable acidity, pH as well as the content of fat and total protein) of yoghurts did not alter except decrease of total solid in sample with 50% RSM. The yoghurts with more content of RSM exhibited higher b*and a* values, while the highest L* value, viscosity, water holding capacity (WHC), firmness and lowest syneresis were found in sample containing 30% RSM. It seems that new interaction in gel network of yoghurts containing RSM, exhibited greater ability to bind water than control skim yoghurt. In addition, probably new bridges between milk proteins (interacting partially hydrolyzed casein with casein) can increase the number of bounds between protein particles leading to lower syneresis. However, excessive RSM content (higher than 30%) did not increase the L* value, viscosity and WHC of samples probably because of too much aggregation of casein. Sensory results revealed that sample containing 30% RSM was exactly alike to full fat yoghurt in terms of overall sensory attributes. New formulation of palatable skim yoghurt was developed using 3% RSM successfully.展开更多
The biofilm formation on equipment surfaces in dairy manufacturing is a major concern for industry and consumers alike, which may affect the safety and quality of dairy products. In order to identify the bio-contamina...The biofilm formation on equipment surfaces in dairy manufacturing is a major concern for industry and consumers alike, which may affect the safety and quality of dairy products. In order to identify the bio-contamination risk of materials commonly used in dairy manufacturing,</span><span style="font-family:""> </span><span style="font-family:Verdana;">adhesion of </span><span style="font-family:Verdana;"><i></span><i><span style="font-family:Verdana;">Staphylococcus aureus</span></i><i><span style="font-family:Verdana;"></i></span></i><span style="font-family:Verdana;"> on glass coated by two kinds of UHT milk (whole milk and skimmed milk) was investigated. It is known that adhesion is mainly governed by surface physicochemical properties, for that,</span><span style="font-family:""> </span><span style="font-family:Verdana;">the effect of milk components on physicochemical properties of glass and bacterial surfaces were exanimated through contact angle measurements. MATLAB software was used to evaluate the ability of </span><span style="font-family:Verdana;"><i></span><i><span style="font-family:Verdana;">S.</span></i><i><span style="font-family:""> </span></i><i><span style="font-family:Verdana;">aureus</span></i><i><span style="font-family:Verdana;"></i></span></i><i><span style="font-family:""> </span></i><span style="font-family:Verdana;">adhesion on glass.</span><span style="font-family:""> </span><span style="font-family:Verdana;">The hydrophobic quantitative and electron acceptor characteristics of the glass appear to increase with the presence of fat in milk, while its electron donor property</span><span style="font-family:""> </span><span style="font-family:Verdana;">decreases with this component. The percentage of occupied surface of untreated glass was more important than in treated surfaces for 50% of the strains studied.</span><span style="font-family:""> </span><span style="font-family:Verdana;">As well, the percentage of occupied surface by bacterial strains in untreated glass by skimmed milk is generally more important compared to the whole milk. Therefore, the risk of bio-contamination of untreated glass is more favorable for bacteria cultured in skimmed milk compared to these in whole milk but the bio-contamination risk on covered glass by milk is not milk dependent and is strain dependent.展开更多
蛋白质是牛乳中重要的营养成分,然而关于脱脂处理对牛乳蛋白含量的影响尚不清楚。本文采用串联质谱标签(Tandem Mass Tags,TMT)标记定量蛋白组学方法,对全脂牛乳和脱脂牛乳中全蛋白组进行分析,探究脱脂对牛乳蛋白的影响。全脂和脱脂牛...蛋白质是牛乳中重要的营养成分,然而关于脱脂处理对牛乳蛋白含量的影响尚不清楚。本文采用串联质谱标签(Tandem Mass Tags,TMT)标记定量蛋白组学方法,对全脂牛乳和脱脂牛乳中全蛋白组进行分析,探究脱脂对牛乳蛋白的影响。全脂和脱脂牛乳中共鉴定出1352个蛋白,筛选出199个差异表达蛋白。与全脂牛乳相比,脱脂后有67个蛋白上调,132个蛋白下调。牛乳主要活性蛋白中,κ-酪蛋白在脱脂后相对含量降低,而β-乳球蛋白和乳铁蛋白在脱脂后相对含量升高,α-乳白蛋白、αs1-酪蛋白、αs2-酪蛋白、β-酪蛋白、牛血清蛋白及乳过氧化物酶相对含量则无显著性差异。乳脂肪球膜蛋白中嗜乳脂蛋白和乳凝集素在脱脂后相对含量降低。脱脂对牛乳中骨架蛋白、代谢相关蛋白等也有影响,改变了牛乳品质及营养价值。通过对全脂和脱脂牛乳中蛋白质分析,明确了脱脂对牛乳蛋白的影响,可以为婴幼儿乳品开发及消费者购买不同脂肪含量的牛奶提供参考。展开更多
Pseudoperonospora cubensis(Berk.& M.A.Curtis)Rostovzev,the causal agent of cucumber downy mildew,is an obligate parasitic fungus.Up to now it can not be preserved on culture medium.In this study,the sporangia of P...Pseudoperonospora cubensis(Berk.& M.A.Curtis)Rostovzev,the causal agent of cucumber downy mildew,is an obligate parasitic fungus.Up to now it can not be preserved on culture medium.In this study,the sporangia of P.cubensis were preserved in protective substances of 10% dimethyl sulfoxide plus 5% skim milk,10% dimethyl sulfoxide plus 10% skim milk,sterilized water and leaves in vitro,and stored at-20℃,-70℃,and preliminary freezing at-20℃ for 24 h prior to-70℃ respectively.The results showed that the sporangia preserved in 10% dimethyl sulfoxide plus 5% skim milk,preliminary freezing at-20℃ for 24 h prior to-70℃ were still highly pathogenic after 12 months preservation.The percentage of germination of sporangia,incidence and disease index were 46%,50.0% and 40.0 respectively 9 d after inoculation.This method solved the problem of P.cubensis preservation.展开更多
基金Project (No. 2002BA518A06) supported by the Hi-Tech Researchand Development Program (863) of China
文摘A FAST (fluorescence of advanced Maillard products and Soluble Tryptophan) method for identification of recon- stituted milk made from skim milk powder in the fresh milk was developed. Considering milk and skim milk powders variations from different seasons and countries, milk was collected from different dairy farms in different seasons and skim milk powders were collected from different countries to measure the Tryptophan (Trp), advanced Maillard products (AMP) fluorescence values. The results showed that there were differences (P<0.01) between raw and reconstituted milk. The plot of values in each mixed level of raw and reconstituted milk had a correlation coefficient >0.97. The FAST method is a simple, rapid, low-cost and sensitive method enabling the detection of 5% reconstituted milk in fresh milk. The measurement of the Trp, AMP fluorescence values and calculation of the FAST index is a suitable method for large-scale monitoring of fresh milk samples.
文摘Limited enzymatic hydrolysis of skim milk by trypsin was investigated in this paper, and it was found that the degree of hydrolysis (DH) of milk proteins had a relationship of DH -1 =a+bt -1 with the time(t) of hydrolysis at low enzyme concentrations, some properties of the protein such as NSI in PI or TCA were changed obviously. It was suggested that most milk proteins would be degraded into peptides by trypsin .
文摘For a long time, fermented dairy products have been consumed for human’s nutrition and health. Recently, consumption of whole dairy products, such as full fat yoghurt, has declined due to the awareness of probable harmful effects of fat on consumers’ health, resulting change of market interest in favor of low or non fat dairy products. It is a challenge for food scientists to produce a suitable fat substitute providing the functionality of the missing fat. The present investigation was carried out to examine the effect of 0 to 50% renneted skim milk (RSM) as a fat mimetic upon the physico-chemical, physical, rheological and sensory characteristics of nonfat yoghurt in comparison to control samples (full fat and skim yoghurt). By increasing RSM content, the chemical characteristics (titratable acidity, pH as well as the content of fat and total protein) of yoghurts did not alter except decrease of total solid in sample with 50% RSM. The yoghurts with more content of RSM exhibited higher b*and a* values, while the highest L* value, viscosity, water holding capacity (WHC), firmness and lowest syneresis were found in sample containing 30% RSM. It seems that new interaction in gel network of yoghurts containing RSM, exhibited greater ability to bind water than control skim yoghurt. In addition, probably new bridges between milk proteins (interacting partially hydrolyzed casein with casein) can increase the number of bounds between protein particles leading to lower syneresis. However, excessive RSM content (higher than 30%) did not increase the L* value, viscosity and WHC of samples probably because of too much aggregation of casein. Sensory results revealed that sample containing 30% RSM was exactly alike to full fat yoghurt in terms of overall sensory attributes. New formulation of palatable skim yoghurt was developed using 3% RSM successfully.
文摘The biofilm formation on equipment surfaces in dairy manufacturing is a major concern for industry and consumers alike, which may affect the safety and quality of dairy products. In order to identify the bio-contamination risk of materials commonly used in dairy manufacturing,</span><span style="font-family:""> </span><span style="font-family:Verdana;">adhesion of </span><span style="font-family:Verdana;"><i></span><i><span style="font-family:Verdana;">Staphylococcus aureus</span></i><i><span style="font-family:Verdana;"></i></span></i><span style="font-family:Verdana;"> on glass coated by two kinds of UHT milk (whole milk and skimmed milk) was investigated. It is known that adhesion is mainly governed by surface physicochemical properties, for that,</span><span style="font-family:""> </span><span style="font-family:Verdana;">the effect of milk components on physicochemical properties of glass and bacterial surfaces were exanimated through contact angle measurements. MATLAB software was used to evaluate the ability of </span><span style="font-family:Verdana;"><i></span><i><span style="font-family:Verdana;">S.</span></i><i><span style="font-family:""> </span></i><i><span style="font-family:Verdana;">aureus</span></i><i><span style="font-family:Verdana;"></i></span></i><i><span style="font-family:""> </span></i><span style="font-family:Verdana;">adhesion on glass.</span><span style="font-family:""> </span><span style="font-family:Verdana;">The hydrophobic quantitative and electron acceptor characteristics of the glass appear to increase with the presence of fat in milk, while its electron donor property</span><span style="font-family:""> </span><span style="font-family:Verdana;">decreases with this component. The percentage of occupied surface of untreated glass was more important than in treated surfaces for 50% of the strains studied.</span><span style="font-family:""> </span><span style="font-family:Verdana;">As well, the percentage of occupied surface by bacterial strains in untreated glass by skimmed milk is generally more important compared to the whole milk. Therefore, the risk of bio-contamination of untreated glass is more favorable for bacteria cultured in skimmed milk compared to these in whole milk but the bio-contamination risk on covered glass by milk is not milk dependent and is strain dependent.
文摘蛋白质是牛乳中重要的营养成分,然而关于脱脂处理对牛乳蛋白含量的影响尚不清楚。本文采用串联质谱标签(Tandem Mass Tags,TMT)标记定量蛋白组学方法,对全脂牛乳和脱脂牛乳中全蛋白组进行分析,探究脱脂对牛乳蛋白的影响。全脂和脱脂牛乳中共鉴定出1352个蛋白,筛选出199个差异表达蛋白。与全脂牛乳相比,脱脂后有67个蛋白上调,132个蛋白下调。牛乳主要活性蛋白中,κ-酪蛋白在脱脂后相对含量降低,而β-乳球蛋白和乳铁蛋白在脱脂后相对含量升高,α-乳白蛋白、αs1-酪蛋白、αs2-酪蛋白、β-酪蛋白、牛血清蛋白及乳过氧化物酶相对含量则无显著性差异。乳脂肪球膜蛋白中嗜乳脂蛋白和乳凝集素在脱脂后相对含量降低。脱脂对牛乳中骨架蛋白、代谢相关蛋白等也有影响,改变了牛乳品质及营养价值。通过对全脂和脱脂牛乳中蛋白质分析,明确了脱脂对牛乳蛋白的影响,可以为婴幼儿乳品开发及消费者购买不同脂肪含量的牛奶提供参考。
文摘Pseudoperonospora cubensis(Berk.& M.A.Curtis)Rostovzev,the causal agent of cucumber downy mildew,is an obligate parasitic fungus.Up to now it can not be preserved on culture medium.In this study,the sporangia of P.cubensis were preserved in protective substances of 10% dimethyl sulfoxide plus 5% skim milk,10% dimethyl sulfoxide plus 10% skim milk,sterilized water and leaves in vitro,and stored at-20℃,-70℃,and preliminary freezing at-20℃ for 24 h prior to-70℃ respectively.The results showed that the sporangia preserved in 10% dimethyl sulfoxide plus 5% skim milk,preliminary freezing at-20℃ for 24 h prior to-70℃ were still highly pathogenic after 12 months preservation.The percentage of germination of sporangia,incidence and disease index were 46%,50.0% and 40.0 respectively 9 d after inoculation.This method solved the problem of P.cubensis preservation.
