The objectives of this study were to investigate the relationships among milk composition, renneting time, urea concentration, acidity, density and pH of Anatolian Buffaloes＇ milk. As a total of 115 individual milk s...The objectives of this study were to investigate the relationships among milk composition, renneting time, urea concentration, acidity, density and pH of Anatolian Buffaloes＇ milk. As a total of 115 individual milk samples from 53 Anatolian buffalo cows that calved in 2004 and 2005 on days of their lactations 30 ± 15, 60 ± 15, 90 ±15, 120 ± 15, 150 ± 15, 180± 15, 210 ±15, 240 ± 15 and 270 ± 15 in 8 units of lhkpmar village were collected in morning milkings in June, September, December and March. Samples were analysed for total dry matter （TDM）, fat, protein, ash, density, pH, acidity, renneting time and urea content. Data were classified according to the following environmental factors： lactation stages： （30 ± 15, 60 i 15, 90 ±15 days）： 2 （120±15, 150 ± 15, 180 ± 15 days）： 3 （210 ± 15, 240 ± 15, 270± 15 days）; calving year： 1 （2004）, 2 （2005）; calving season： 1 （January-May）, 2 （September and October）; month of samples collection： 1 （June）, 2 （September）, 3 （December）, 4 （March）; lactation order： 1 and 2：1, 3 and 4：2, 5 and 6：3. Means and correlation coefficients for the characteristics investigated were calculated. There were negative significant correlations between daily milk yield with TDM, fat and protein percentages, and between pH and all of the milk constituents. Density reduces as TDM, fat and protein contents increase. Relationships between density and coagulation time with milk yield and pH were not significant. Relationships between milk urea concentration with none of milk constituents, milk yield, density, pH and titratable acidity were not significant statistically. It was concluded that genetic selection has to be directed towards increasing fat, protein and total not fat dry matter yields. Under selection programs in which milk yield is taken into consideration, fat and protein yields also increase, but fat and protein concentrations decrease.展开更多
Using 2-3 weeks kid abomasums as materials, the ultrasound intensity, extracting time, NaCl concentration and pH valuein extracting solution and ratio of abomasums to extracting solution were studied by ultrasonic met...Using 2-3 weeks kid abomasums as materials, the ultrasound intensity, extracting time, NaCl concentration and pH valuein extracting solution and ratio of abomasums to extracting solution were studied by ultrasonic method. The resultsshowed that the main factor affecting kid rennet activity during extraction was ultrasound intensity, and then NaClconcentration, extracting time and ratio of abomasums to extracting solution in order. Kid rennet activity reached peakwith ultrasound intensity 30 W cm-2, extraction time 40 min, NaCl concentration 8%, pH value 3.0, ratio of abomasums toextracting solution 1:15.展开更多
This study aimed to evaluate the milk clotting capacity (MCA), and caseinolytic activity (CA) of crude coagulant from the stomachs of adult rabbits (RC), and their influence on the composition, proteolysis, and textur...This study aimed to evaluate the milk clotting capacity (MCA), and caseinolytic activity (CA) of crude coagulant from the stomachs of adult rabbits (RC), and their influence on the composition, proteolysis, and texture of type Prato cheese. We tested two ways for salting the abomasum and three levels of pH and times for enzyme activation. The presence of enzymes and caseinolytic activity in RC was assayed by SDS-PAGE. The effects of three pH levels and the milk’s temperature on RC’s water-holding capacity (WHC) were evaluated. Brazilian Prato cheese type was developed and its proximate composition, texture, and change during ripening were assessed. The saturated NaCl solutions (37%, m/v) were more efficient for enzyme extraction from adult rabbit stomachs, and conditions of pH of 4.3 for 24 h showed better performance for enzyme activation into RC. An early and more active proteolytic reaction of RC on bovine caseinate was appreciated at the first 5 min of digestion when compared to commercial chymosin (CC). The water holding capacity of gel coagulated by RC was optimum at pH 6.4 and 37°C and is highly dependent on pH and temperature parameters. Total dry extract and fat were higher for treatment coagulated with RC. Conversely, hardness, gumminess, and chewability were lower in the same treatment. Yield, protein content, and changes that occurred during the ripening stage of cheeses were similar for both treatments, demonstrating that casein proteolysis was developed in a similar way. Coagulants from adult rabbits’ stomachs can be used to make semi-cooked curd cheeses.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
In this study, texture analysis method was used for the determination of rennet flocculation time (tfloc) and rennet clotting time (tclot) of rennet-induced reconstitued milk samples with different CaCl2 concentration...In this study, texture analysis method was used for the determination of rennet flocculation time (tfloc) and rennet clotting time (tclot) of rennet-induced reconstitued milk samples with different CaCl2 concentrations. The rennet flocculation time (RFT) and rennet clotting time (RCT) were also determined by using the Berridge test and sensory evaluation. The hardness value versus renneting time curves derived from texture analysis gave a good modified exponential relationship for each CaCl2 concentration and the curves were used to calculate flocculation time and clotting time parameters. It was found that the parameters (tfloc and tclot) appeared strongly correlated with RFT and RCT, respectively. Texture analysis was proved as a suitable method to control the rennet-induced coagulation and determine the rennet clotting time. It was also determined that enrichment of milk with CaCl2 leaded to a decrease in flocculation and clotting times and an increase in rate of clotting and gel hardness.展开更多
文摘The objectives of this study were to investigate the relationships among milk composition, renneting time, urea concentration, acidity, density and pH of Anatolian Buffaloes＇ milk. As a total of 115 individual milk samples from 53 Anatolian buffalo cows that calved in 2004 and 2005 on days of their lactations 30 ± 15, 60 ± 15, 90 ±15, 120 ± 15, 150 ± 15, 180± 15, 210 ±15, 240 ± 15 and 270 ± 15 in 8 units of lhkpmar village were collected in morning milkings in June, September, December and March. Samples were analysed for total dry matter （TDM）, fat, protein, ash, density, pH, acidity, renneting time and urea content. Data were classified according to the following environmental factors： lactation stages： （30 ± 15, 60 i 15, 90 ±15 days）： 2 （120±15, 150 ± 15, 180 ± 15 days）： 3 （210 ± 15, 240 ± 15, 270± 15 days）; calving year： 1 （2004）, 2 （2005）; calving season： 1 （January-May）, 2 （September and October）; month of samples collection： 1 （June）, 2 （September）, 3 （December）, 4 （March）; lactation order： 1 and 2：1, 3 and 4：2, 5 and 6：3. Means and correlation coefficients for the characteristics investigated were calculated. There were negative significant correlations between daily milk yield with TDM, fat and protein percentages, and between pH and all of the milk constituents. Density reduces as TDM, fat and protein contents increase. Relationships between density and coagulation time with milk yield and pH were not significant. Relationships between milk urea concentration with none of milk constituents, milk yield, density, pH and titratable acidity were not significant statistically. It was concluded that genetic selection has to be directed towards increasing fat, protein and total not fat dry matter yields. Under selection programs in which milk yield is taken into consideration, fat and protein yields also increase, but fat and protein concentrations decrease.
基金The study was supported by Natural Science Founda—tion of Shaanxi Province of China (2003C134)．
文摘Using 2-3 weeks kid abomasums as materials, the ultrasound intensity, extracting time, NaCl concentration and pH valuein extracting solution and ratio of abomasums to extracting solution were studied by ultrasonic method. The resultsshowed that the main factor affecting kid rennet activity during extraction was ultrasound intensity, and then NaClconcentration, extracting time and ratio of abomasums to extracting solution in order. Kid rennet activity reached peakwith ultrasound intensity 30 W cm-2, extraction time 40 min, NaCl concentration 8%, pH value 3.0, ratio of abomasums toextracting solution 1:15.
文摘This study aimed to evaluate the milk clotting capacity (MCA), and caseinolytic activity (CA) of crude coagulant from the stomachs of adult rabbits (RC), and their influence on the composition, proteolysis, and texture of type Prato cheese. We tested two ways for salting the abomasum and three levels of pH and times for enzyme activation. The presence of enzymes and caseinolytic activity in RC was assayed by SDS-PAGE. The effects of three pH levels and the milk’s temperature on RC’s water-holding capacity (WHC) were evaluated. Brazilian Prato cheese type was developed and its proximate composition, texture, and change during ripening were assessed. The saturated NaCl solutions (37%, m/v) were more efficient for enzyme extraction from adult rabbit stomachs, and conditions of pH of 4.3 for 24 h showed better performance for enzyme activation into RC. An early and more active proteolytic reaction of RC on bovine caseinate was appreciated at the first 5 min of digestion when compared to commercial chymosin (CC). The water holding capacity of gel coagulated by RC was optimum at pH 6.4 and 37°C and is highly dependent on pH and temperature parameters. Total dry extract and fat were higher for treatment coagulated with RC. Conversely, hardness, gumminess, and chewability were lower in the same treatment. Yield, protein content, and changes that occurred during the ripening stage of cheeses were similar for both treatments, demonstrating that casein proteolysis was developed in a similar way. Coagulants from adult rabbits’ stomachs can be used to make semi-cooked curd cheeses.
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In this study, texture analysis method was used for the determination of rennet flocculation time (tfloc) and rennet clotting time (tclot) of rennet-induced reconstitued milk samples with different CaCl2 concentrations. The rennet flocculation time (RFT) and rennet clotting time (RCT) were also determined by using the Berridge test and sensory evaluation. The hardness value versus renneting time curves derived from texture analysis gave a good modified exponential relationship for each CaCl2 concentration and the curves were used to calculate flocculation time and clotting time parameters. It was found that the parameters (tfloc and tclot) appeared strongly correlated with RFT and RCT, respectively. Texture analysis was proved as a suitable method to control the rennet-induced coagulation and determine the rennet clotting time. It was also determined that enrichment of milk with CaCl2 leaded to a decrease in flocculation and clotting times and an increase in rate of clotting and gel hardness.
