羊奶干酪加工过程中酸度及乳成分变化规律的研究

以西农莎能奶山羊的新鲜奶为原料,添加ＥＺＡＬ ＭＡ０１１乳酸发了剂,研究羊奶干酪加工过程中酸度和乳成分变化规律,以及不同凝乳酶对它们的影响。结果表明,羊奶干酷加工过程中,酸度缓慢上升,而不同凝乳酸对酸度无显著影响;从鲜奶至消毒奶,乳成分基本不变;加发酵剂后,乳脂和乳蛋白基本不变,乳糖明显下降;加凝乳酶后各种乳成分显著下降。     

Major elements in milk of the West African dwarf goats as affected by stage of lactation.

Tweove adult West African dwarf (Fouta djallon) does, about 2 years old and weighing from 25 to 28 kg were kept for lactation studies lasting two 19-week periods. During these periods the does were hand-milked twice daily and the daily samples were bulked for each animal for subsequent analysis. The results showed that the colostrum was much richer in its content (g/kg) of Na 1.44 +/- 0.17, K 3.38 +/- 0.22 and Cl 4.83 +/- 0.29 than the mature milk which contained (g/kg) Na 0.65 +/- 0.09, K 1.57 +/- 0.19 and Cl 2.46 +/- 0.58. The corresponding values obtained for Ca (0.65 +/- 0.02) and P (0.36 +/- 0.10) in the colostrum were, however, lower than 2.01 +/- 0.98 and 1.18 +/- 0.28 g/kg obtained for Ca and P respectively in the mature milk. The composition of these elements in the colostrum approached that of the normal goat's milk on the sixth d after parturition. The results showed a rise in Ca, P, Na and Cl levels with stage of lactation and a fall in K content of the milk with advancing lactation with the trends being highly significant (P less than 0.01).     

Effect of kappa-casein polymorphism on milk composition in the Orobica goat

The aim of this work was to study the effects of isoelectrofocusing (IEF) milk protein variants on milk composition in the Italian Orobica goat breed, which is characterized by a rather high frequency of the κ-casein (CSN3) B^IEF allele. Significant associations were found between the IEF phenotype and protein and casein percentages. A favorable effect of the CSN3 B^IEF variant was found for both protein and casein percentages, with a codominance trend for the 3 phenotypes: BB > AB > AA. Depending on the selection purpose, emphasis could be given to different κ-casein variants in breeding. The high frequency of B^IEF could be exploited in breeding strategies to improve the protein and casein percentages when cheese making is a selection objective.     

Studies on the milk composition of West African dwarf, Red Sokoto and Saanen goats at different stages of lactation. I. Total solids, butterfat, solids-not-fat, protein, lactose and energy contents of milk.

Nine West African dwarf (Fouta djallon), Red Sokoto (Maradi) and Saanen lactating goats, hand-milked, were used for these studies, which lasted 12 weeks. The Saanen goat's milk was obtained weekly from the Western State Ministry of Agriculture and Natural Resources Urban Dairy Farm at Iwo Road, while similar samples were collected from the herd at the University of Ibadan Teaching and Research Farm. The goats were balanced for stage of lactation, namely early, mid- and late-lactation. They were each maintained on giant star grass (Cynodon nlemfuensis) ad lib. and 1 kg dairy concentrate mixture daily. The mean contents, with standard deviations, of the milks of Saanen, West African dwarf and Red Sokoto goats at mid-lactation respectively were: (in percentages), total solids 12-25 plus or minus 0-078, 18-18 plus or minus 0-392, 15-85 plus or minus 0-077; solids-not-fat (SNF) 8-91 plus or minus 0-42, 10-48 plus or minus 0-471, 10-53 plus or minus 0-140; butterfat 3-34 plus or minus 0-141, 7-78 plus or minus 0-621, 5-32 plus or minus 0-098; protein 3-04 plus or minus 0-139, 5-30 plus or minus 0-292, 4-74 plus or minus 0-021; lactose 4-56 plus or minus 0-167, 5-19 plus or minus 0-176, 4-77 plus or minus 0-053; energy (kj/g dried milk), 21-08 plus or minus 1-11, 25-51 plus or minus 1-74, 22-17 plus or minus 0-51. Breed differences were significant (P less than 0-01). The milk of West African dwarf goats contained more of these milk components than the milk of the Red Sokoto or Saanen goats. The Red Sokoto goats gave milk of higher content than did Saanen goats, even at an early stage of lactation. Butterfat, protein, lactose and energy values were significantly affected by stages of lactation (P less than 0-05) and tended to rise with advancing lactation; this was particularly so with West African dwarf goats.     

Effects of goat milk or milk replacer diet on meat quality and fat composition of suckling goat kids

The effects of a diet with goat milk "GM" or milk replacer "MR" on the meat quality and fat composition of suckling Murciano-Granadina kids were studied. MR consisted of powdered skimmed milk, coconut oil and fat, and cereal products and by-products. Raw meat quality (moisture, protein, lipids, ash, collagen, cholesterol, haem pigments, CIELab colour, pH and water retention capacity), fatty acid "FA" composition and eating quality of cooked meat (odour, flavour and texture) were determined. Diet had only a slight effect on raw meat quality but had a pronounced effect on fatty acid composition and eating quality of cooked meat. MR diet increased the water/protein proportion in the muscle. The saturated/unsaturated FA ratio in GM and MR fat was 0.94 and 2.27, respectively. The major FA in GM and MR fat were C16:0 and C18:1, respectively. Short-chain C4-C12 hardly accumulated in the adipose tissue of suckling kid, increasing the relative percentages of C14-C20. This effect was more pronounced in MR fat, due to the fact that MR contained more short-chain fatty acids than GM. MR diet gave cooked meat a more intense characteristic goat meat odour and flavour, more tenderness and more juiciness than the natural suckling diet. This fact could be related to differences in meat and fat composition.     

Effect of temporary food or water deprivation on milk secretion and milk composition in the goat

When four goats were subjected to total water deprivation for 48 h once in early lactation and once in mid lactation and their voluntary food intake and effects on milk secretion were observed, milk volume decreased and lactose and fat concentration increased during both periods. However, when the goats were then fed the mean of their own food intake at the two previous water deprivation experiments, and were left free access to water, it was found that decreased food consumption had only a minor influence on milk secretion. When six goats were subjected to 48 h of food deprivation and six to 48 h of water deprivation, milk secretion decreased, but the reduction was delayed and of smaller magnitude during water deprivation. During food deprivation lactose concentration decreased and the milk protein and fat increased; the fatty acid composition changed from a greater proportion of short-chain to more long-chain fatty acids. During water deprivation milk fat and lactose concentrations increased, and only after 44 h did a change from short-chain to a larger proportion of long-chain fatty acids become evident. These experiments indicate that not only food intake, but also water intake are concerned with milk production.     

Predictive formulas for different measures of cheese yield using milk composition from individual goat samples

The objective of this study was to develop formulas based on milk composition of individual goat samples for predicting cheese yield (%CY) traits (fresh curd, milk solids, and water retained in the curd). The specific aims were to assess and quantify (1) the contribution of major milk components (fat, protein, and casein) and udder health indicators (lactose, somatic cell count, pH, and bacterial count) on %CY traits (fresh curd, milk solids, and water retained in the curd); (2) the cheese-making method; and (3) goat breed effects on prediction accuracy of the %CY formulas. The %CY traits were analyzed in duplicate from 600 goats, using an individual laboratory cheese-making procedure (9-MilCA method; 9 mL of milk per observation) for a total of 1,200 observations. Goats were reared in 36 herds and belonged to 6 breeds (Saanen, Murciano-Granadina, Camosciata delle Alpi, Maltese, Sarda, and Sarda Primitiva). Fresh %CY (%CY_CURD), total solids (%CY_SOLIDS), and water retained (%CY_WATER) in the curd were used as response variables. Single and multiple linear regression models were tested via different combinations of standard milk components (fat, protein, casein) and indirect udder health indicators (UHI; lactose, somatic cell count, pH, and bacterial count). The 2 %CY observations within animal were averaged, and a cross-validation (CrV) scheme was adopted, in which 80% of observations were randomly assigned to the calibration (CAL) set and 20% to the validation (VAL) set. The procedure was repeated 10 times to account for sampling variability. Further, the model presenting the best prediction accuracy in CrV (i.e., comprehensive formula) was used in a secondary analysis to assess the accuracy of the %CY predictive formulas as part of the laboratory cheese-making procedure (within-animal validation, WAV), in which the first %CY observation within animal was assigned to CAL, and the second to the VAL set. Finally, a stratified CrV (SCrV) was adopted to assess the %CY traits prediction accuracy across goat breeds, again using the best model, in which 5 breeds were included in CAL and the remaining one in the VAL set. Fitting statistics of the formulas were assessed by coefficient of determination of validation (R²_VAL) and the root mean square error of validation (RMSE_VAL). In CrV, the formula with the best prediction accuracy for all %CY traits included fat, casein, and UHI (R²_VAL = 0.65, 0.96, and 0.23 for %CY_CURD, %CY_SOLIDS, and %CY_WATER, respectively). The WAV procedure showed R²_VAL higher than those obtained in CrV, evidencing a low effect of the 9-MilCA method and, indirectly, its high repeatability. In the SCrV, large differences for %CY_CURD and %CY_WATER among breeds evidenced that the breed is a fundamental factor to consider in %CY predictive formulas. These results may be useful to monitor milk composition and quantify the influence of milk traits in the composite selection indices of specific breeds, and for the direct genetic improvement of cheese production.     

Effects of milk protein genetic variants on milk yield and composition

Effects of genetic variants of the milk proteins, alpha S1-casein, beta-casein, kappa-casein and beta-lactoglobulin (beta-lg), on milk yield and composition, particularly the protein composition, were investigated in milk samples from 289 Jersey and 249 Friesian cows in eight commercial herds. Milk protein genotypes had no significant effect on yields over a complete lactation of milk and fat, but significant differences in fat content were detected for beta-casein (B, A1B, A2 greater than A1A2) and beta-lg (B, AB greater than A) variants. Significant differences between beta-lg variants were also found with total solids (B, AB greater than A), casein (B, AB greater than A), whey protein (A greater than AB greater than B) and beta-lg (A greater than AB, AC greater than B greater than BC) concentrations. Casein genotypes were not significantly different in total protein and casein concentrations but many differences were found in casein composition. alpha S1-Casein variants significantly affected alpha S1-casein (BC greater than B) and kappa-casein (B greater than BC) concentrations. beta-Casein variants affected concentration and proportion of beta-casein (A1B, A2B greater than A1, A1A2, A2, B), alpha S1-casein (A1, A2 greater than B) and kappa-casein (B greater than A2) and concentration of whey protein (A1 greater than most other beta-casein variants). kappa-Casein variants affected concentration and proportion of kappa-casein (B greater than AB greater than A), proportion of alpha S1-casein (A greater than AB greater than B) and concentrations of beta-lg (A greater than AB, B) and alpha-lactalbumin (A, AB greater than B). Differences in milk composition were found between breeds, herds and ages, and with stage of lactation. The potential use of milk protein genotypes as an aid in dairy cattle breeding is discussed.     

Day-to-day variation in milk yield and milk composition at the udder-quarter level

Automatic in-line measurement of milk composition and milk yield could be a useful tool in management of the dairy herd. Data on milk components and milk yield provide information on milk quality alterations and cow health status but are also useful in planning feeding and breeding. In automatic milking systems, udder quarters are milked individually, enabling analysis and recording at the udder-quarter level. Frequent records of components require knowledge about day-to-day variations. A component with greater day-to-day variation needs more frequent sampling when used as a diagnostic tool and for management decisions. Earlier studies have described the day-to-day variations in milk components for cow composite milk, but with the quarter milking technique and the possible sampling at the udder-quarter level, knowledge about day-to-day variations at the udder-quarter level is needed. In this study, udder-quarter and cow composite milk samples were collected from 42 consecutive milkings of 10 cows during 21 d. Milk yield was recorded and the milk was analyzed for total protein, whey protein, casein, fat, lactose, and somatic cell count. The results showed that the day-to-day variations and mean values for 4 healthy udder quarters within a cow were similar. In addition, different milk components had different levels of day-to-day variation, the least variation being found in lactose (0.9%) and the greatest in fat (7.7%). This suggests that repeated milk sampling and analysis at the udder-quarter level can be used to detect alterations in composition and cow health and would, thus, be helpful in the management of the dairy herd.     

Effect of partial substitution of cow's milk with soymilk on yield and quality attributes of West African soft cheese

Warankasi , a soft unripened cheese, was made from milk containing up to 20% soymilk. The best cheeses were obtained from soymilk prepared by grinding in boiling water soybeans that had been preheated by dipping in hot water, 95–100°C, for 15–20 sec. Cheeses containing soymilk were comparable with controls made from whole cow's milk in yield, nitrogen and fat content, and flavour. Cheeses with up to 10% soymilk had a slight brownish colour, but overall acceptability was not impaired, relative to controls. Cheeses with 20% soymilk were acceptable although inferior to controls.     

Aetiology of intramammary infection and its effect on milk composition in goat flocks

Although there has been little study of the origin of intramammary infection (IMI) in goats, a common view is that most bacterial infection in goats occurs during milking. In the present study, the dynamics of occurrence of udder infection during and between lactations in three Anglo-Nubian goat farms in Israel was monitored. Coagulase-negative staphylococci were the predominant bacteria in the IMIs. We found that about 15% of the yearling does were already infected with bacteria when they joined the flock, whereas about 8% of the goats that dried-off returned with new IMIs. Moreover, virtually none of the goats acquired infection during lactation. Thus, our study showed that the aetiology of IMI in goats is very similar to that in dairy cows. A preventive treatment during the dry period should, therefore, be considered as an effective means of reducing the current rate of bacterial infections in goats.     

Effect of goat milk composition on cheesemaking traits and daily cheese production

Cheese yield is strongly influenced by the composition of milk, especially fat and protein contents, and by the efficiency of the recovery of each milk component in the curd. The real effect of milk composition on cheesemaking ability of goat milk is still unknown. The aims of this study were to quantify the effects of milk composition; namely, fat, protein, and casein contents, on milk nutrient recovery in the curd, cheese yield, and average daily yield. Individual milk samples were collected from 560 goats of 6 different breeds. Each sample was analyzed in duplicate using the 9-laboratory milk cheesemaking assessment, a laboratory method that mimicked cheesemaking procedures, with milk heating, rennet addition, coagulation, curd cutting, and draining. Data were submitted to statistical analysis; results showed that the increase of milk fat content was associated with a large improvement of cheese yield because of the higher recovery of all milk nutrients in the curd, and thus a higher individual daily cheese yield. The increase of milk protein content affected the recovery of fat, total solids, and energy in the curd. Casein number, calculated as casein-to-protein ratio, did not affect protein recovery but strongly influenced the recovery of fat, showing a curvilinear pattern and the most favorable data for the intermediate values of casein number. In conclusion, increased fat and protein contents in the milk had an effect on cheese yield not only for the greater quantity of nutrients available but also for the improved efficiency of the recovery in the curd of all nutrients. These results are useful to improve knowledge on cheesemaking processes in the caprine dairy industry.     

发酵黄芪粉对奶牛产奶量及乳成分的影响研究

研究发酵黄芪粉对奶牛产奶量及乳品质的影响.对照组奶牛饲喂基础日粮,试验Ⅰ、Ⅱ和Ⅲ组奶牛分别饲喂10、20和30 g/(头·d)的发酵黄芪粉基础日粮.结果表明:与对照组相比,试验组奶牛产奶量增加了0.95、1.45和1.58 kg/(头·d),但试验Ⅱ、Ⅲ组组间差异不显著;可显著提高奶牛乳蛋白率,但对奶牛乳脂率、乳糖及非脂固型物均无显著影响;可降低奶牛乳体细胞数,其中试验Ⅱ、Ⅲ组奶牛乳体细胞数显著低于对照组和试验Ⅰ组,但试验Ⅱ、Ⅲ组组间差异不显著;可提高奶牛经济效益,各试验组奶牛经济效益分别高于对照组2.6、3.4和2.72元/(头·d).该试验条件下,发酵黄芪粉以20 g/(头·d)的添加量较好.     

Milk composition and yield of the black Bedouin goat during dehydration and rehydration

Milk composition and yield were measured in the black Bedouin goat during 4 d of dehydration followed by 2 d of rehydration. During this time the goats were exposed to strong solar radiation with no access to shade; all of these conditions occur commonly in the desert. Milk yield, initially similar to that found in the desert, was maintained during the first 2 d of dehydration, fell to 35% of the initial value over the third and fourth days and recovered fully during 2 d of rehydration. As yield fell, milk osmolality, and milk fat and protein concentrations rose. During rehydration all 3 fell once more, but whereas osmolality finished below initial values the concentrations of fat and protein remained higher than before dehydration. The milk remained isosmolar with plasma throughout. Total yields of milk solids and milk water during the whole experimental period were 70 and 67% of normal respectively and normal growth of the young was not disturbed.     

Effects of trace element supplementation on milk yield and composition in camels

Objective of the study was to determine milk yield and quality (fat, protein, mineral content) of camels reared in north-east Africa, supplemented with trace elements for the first nine months of lactation. Twelve multiparous lactating camels were divided into two groups: control and treated (trace element supplemented). Addition of trace elements did not affect milk production and milk fat and protein content (respectively 3.09 vs. 3.51 kg d⁻¹; 2.86 vs. 2.56%; 3.31 vs. 3.19%, treatment vs. control). Calcium and zinc contents of milk were significantly higher in treated animals (1.20 vs. 0.94 g L⁻¹ and 3.16 vs. 2.52 mg L⁻¹; P<0.01). Mineral status of lactating camels and of their calves was assessed by analysis of plasma. Camel control diet was deficient in copper and supplementation did not allow reaching, neither in milk nor in plasma, the threshold values. Results suggest that oral trace element supplementation could increase zinc excretion in camels’ milk, despite the low levels of zinc in plasma.     

The influence of pasteurization temperature on the physicochemical composition and colour of Murciano-Granadina goat milk

An evaluation of the physicochemical characteristics and colour in Murciano-Granadina goat milk was carried out on several samples subjected to different pasteurization treatments (72°C/15 s, 76°C/15 s and 80°C/10 s). An apparent increase in the level of caseins was observed along with a decrease in the serum protein contents at pasteurization temperatures of 76 and 80°C. This change can be partly justified by the interactions between β-lactoglobulin and K-casein in pasteurized milk. The fat content, viscosity and density of the milk showed minimal sensitivity to the thermal treatments, but the heat treatment did affect the parameters which defined the colour of the milk, as shown by a decrease in the Yellow Index and an increase in the difference in colour.     

Predicting energy × protein interaction on milk yield and milk composition in dairy cows

Feed management is one of the principal levers by which the production and composition of milk by dairy cows can be modulated in the short term. The response of milk yield and milk composition to variations in either energy or protein supplies is well known. However, in practice, dietary supplies of energy and protein vary simultaneously, and their interaction is still not well understood. The objective of this trial was to determine whether energy and protein interacted in their effects on milk production and milk composition and whether the response to changes in the diets depended on the parity and potential production of cows. From the results, a model was built to predict the response of milk yield and milk composition to simultaneous variations in energy and protein supplies relative to requirements of cows. Nine treatments, defined by their energy and protein supplies, were applied to 48 cows divided into 4 homogeneous groups (primiparous or multiparous × high or low milk potential) over three 4-wk periods. The control treatment was calculated to cover the predicted requirements of the group of cows in the middle of the trial and was applied to each cow. The other 8 treatments corresponded to fixed supplies of energy and protein, higher or lower than those of the control treatment. The results highlighted a significant energy × protein interaction not only on milk yield but also on protein content and yield. The response of milk yield to energy supply was zero with a negative protein balance and increased with protein supply equal to or higher than requirements. The response of milk yield to changes in the diet was greater for cows with high production potential than for those with low production potential, and the response of milk protein content was higher for primiparous cows than for multiparous cows. The model for the response of milk yield, protein yield, and protein content obtained in this trial made it possible to predict more accurately the variations in production and composition of milk relative to the potential of the cow because of changes in diet composition. In addition, the interaction obtained was in line with a response corresponding to the more limiting of 2 factors: energy or protein.     

Influence of storage and preservation on fossomatic cell count and composition of goat milk

This study was designed to evaluate the effects of different test conditions on the somatic cell count (SCC) and composition of goat milk. To this end, 3600 tests were performed on 1800 aliquots taken from 40 goat milk samples using a combined instrument set-up based on flow cytometry for SCC and Fourier transform infrared analysis for fat, total protein, lactose, total solids, and freezing point determinations. The conditions tested were storage temperature (refrigeration and freezing), use of a preservative [no preservative (NP), azidiol (AZ), and bronopol (BR)], and age of the milk samples at each storage temperature (24 h to 42 d at refrigeration temperature and 21 to 105 d at freezing temperature). Significant effects on logSCC variation were shown by the storage temperature, the preservation treatment, the interaction of storage temperature × preservation treatment, and milk age within the interaction of storage temperature × preservative. Highest counts were recorded in the BR-preserved milk samples (logSCC = 5.877), and lowest counts were recorded in milk samples preserved using AZ (logSCC = 5.803). The use of frozen/thawed samples led to a significantly decreased logSCC for the treatments AZ and NP; the logSCC was not modified when BR-preserved frozen/thawed samples were analyzed. During storage, variations in the SCC observed for BR-preserved samples stored at refrigeration temperature for up to 25 d and at freezing temperature for all times tested were always <10%. The preservation treatment was the main factor affecting the milk composition variables examined. Highest values of most variables were obtained in the BR-preserved samples, and the lowest values were obtained in the AZ-preserved samples. The freezing point was lower in the preserved samples than in the NP samples. The levels of milk constituents recorded in the BR-preserved samples were independent of both the storage temperature and age of milk sample. Our findings indicate that the freezing point of goat milk must be interpreted according to the preservative used.     

Effects of administration of bovine somatotropin on milk yield and composition

Thirty-two Holstein cows were assigned to four treatment groups in a continuous lactation trial to evaluate effects of daily subcutaneous injections of 0 (A), 5.15 (B), 10.3 (C), and 20.6 mg (D) of recombinantly derived bovine somatotropin monomer. Responses were milk yield and composition, component yields, net energy intake, body weight, and somatic cell counts. Treatments began in fall, 28 to 35 d postpartum, and continued for 266 d. Base ration was corn silage and concentrate. Least squares means of milk and constituent yields and gross efficiency of milk production differed among treatments, but percentage fat and protein, energy intake, body weights, and somatic cell counts did not. Least squares means of 3.5% FCM were 21.3 (A), 25.0 (B), 26.2 (C), and 28.5 kg/d (D); fat and protein yields showed similar response to treatment. Milk yields adjusted for pretreatment yields were 21.1 (A), 25.5 (B), 26.5 (C), and 29.3 kg/d (D). Orthogonal contrasts showed lower milk and constituent yields and net energy intake for control (A) than for hormone-injected cows (B, C, D), but no differences were detected between treatments B, C, and D. Gross efficiency of production (3.5% FCM/feed net energy intake) was greater for hormone-injected cows.     

The composition of milk of the friesian cattle imported into Nigeria

Here the results of analyses of milk of Friesian cows imported into the University Teaching and Research Farm from Western Germany are reported. Twenty-five of the cows were milked from the first day after parturition for a lactation of 305 days (average yield 3000 ± 88kg). The colostrum contained higher percentages of total solids (TS), crude protein (CP), fats and ash but lower lactose than the mature milk. Concentration of major minerals in the colostrum were higher than the corresponding values in the mature milk. The composition of the colostrum approached normal values on the seventh day after parturition. Contents of TS, CP, lactose and fats in milk were highest in the first month of lactation and then decreased with advance in lactation. The trends were highly significant (P<0.01). On the other hand, the concentration of the minerals increased except for potassium which decreased with advance in lactation with the trends being highly significant (P < 0.01). The values obtained for the gross composition of milk (except total ash) were higher than those reported for the Friesian cow's milk in temperate countries.