营养山药牛乳的研制

山药是具有高度营养的健康食品。将山药加工成山药乳饮料,可成为具有新型特色和附加值的保健饮料。以山药和还原乳为主要原料,采用正交实验和感官评定,根据原料特点和产品风格,针对护色、稳定剂配方比等工艺难点进行研究。     

奶酒酿造工艺研究

对奶酒发酵原理和工艺改进进行了研究.原料乳经除杂、奶油分离、蛋白提取、脱脂后,再高温瞬时灭菌后进行发酵.通常用65℃杀菌;原料乳热处理后冷却至21～26℃时添加发酵剂.添加量为4%～8%,发酵时间54h;经一次蒸馏和二次蒸馏,奶酒的乙醇含量可达42%vol,蒸发温度控制在40～70℃之间;最后经过兑制、调香及陈酿使奶酒的酒精度达到32%vol,其品质均匀恒定,口感香浓.(孙悟)     

新一代中老年奶粉的研究与开发

新一代中老年奶粉除和维持中老年人的营养需要外，还具有促进人体肠道双歧杆菌的增殖，抑制有害菌的生长，促进钙吸收，增进免疫力等４大功能，它是中老年人理想的功能性食品。     

Ethyl-cellulose rumen-protected methionine enhances performance during the periparturient period and early lactation in Holstein dairy cows

The onset of lactation in dairy cows is characterized by severe negative energy and protein balance. Increasing Met availability during this time may improve milk production, hepatic lipid metabolism, and immune function. The aim of this study was to evaluate the effect of feeding ethyl-cellulose rumen-protected methionine (RPM; Mepron, Evonik Nutrition and Care GmbH, Hanau-Wolfgang, Germany) on the performance of dairy cows during prepartum and early-lactation periods. Sixty multiparous Holstein cows were used in a block design and assigned to either a control or an ethyl-cellulose RPM diet. Ethyl-cellulose RPM was supplied from ?28 to 60 d relative to parturition at a rate of 0.09% and 0.10% of dry matter during the prepartum and postpartum periods, respectively. That rate ensured that the ratio of Lys to Met in metabolizable protein was close to 2.8:1. Cows fed ethyl-cellulose RPM had dry matter intakes (DMI) that were 1.2 kg/d greater during the prepartum period and consequently had overall greater cumulative DMI than cows in the control group. Compared with controls, during the fresh period (1–30 d in milk; DIM) feeding ethyl-cellulose RPM increased DMI by 1.7 kg/d, milk yield by 4.1 kg/d, fat yield by 0.17 kg/d, milk protein yield by 0.20 kg/d, 3.5% fat-corrected milk by 4.3 kg/d, and energy-corrected milk by 4.4 kg/d. Although ethyl-cellulose RPM supplementation increased milk protein content by 0.16 percentage units compared with the control during the fresh period, no differences were observed for milk fat, lactose, and milk urea nitrogen concentration. During the high-producing period (31–60 DIM), cows fed ethyl-cellulose RPM increased DMI and milk yield by 1.45 and 4.4 kg/d, respectively. Ethyl-cellulose RPM also increased fat yield by 0.19 kg/d, milk protein yield by 0.17 kg/d, 3.5% fat-corrected milk by 4.7 kg/d, and energy-corrected milk by 4.8 kg/d compared with controls. Ethyl-cellulose RPM supplementation reduced plasma fatty acids in the fresh period and decreased γ-glutamyl transferase, indicating better liver function. In conclusion, when lysine was adequate, feeding ethyl-cellulose RPM to achieve a ratio close to 2.8:1 in metabolizable protein improved dairy cow performance from parturition through 60 DIM. The greater milk production was, at least in part, driven by the greater voluntary DMI and better liver function.     

Lactation and body composition responses to fat and protein supplies during the dry period in under-conditioned dairy cows

An experiment was designed to study the effect of precalving supplementation with protein (Pr) and rumen-inert fat (F) on body composition and subsequent milk production and composition. Forty Holstein-Friesian dairy cows were allocated to 1 of 4 dietary treatments in the dry period (DP) based on a first-cut ryegrass silage, with 6 mature (in their third or greater pregnancy) and 4 young (in their second pregnancy) cows per treatment. These were low Pr, low F (silage alone); low Pr, high F (silage with 10% rumen-inert fat, mixed on a dry matter basis); high Pr, low F [silage with 5% high-protein corn gluten meal (CGM)]; and high Pr, high F (silage with 5% CGM and 10% rumen-inert fat). All the diets were individually offered ad libitum and dry matter intake (DMI) was recorded daily during the DP. After calving, all cows received ryegrass silage plus 8 kg/d of a commercial dairy concentrate. During the DP, DMI was higher for mature than for young cows. All animals recovered body condition score (0.13 units/wk, 1–5 scale), reaching a maximum score of 2.4 some days before calving. Precalving maximum muscle longissimus dorsi (LD) depth was greater for mature (47.5 mm) than for young cows (45.7 mm), and milk fat concentration was also higher for mature than for young cows (40.2 and 39.0 g/kg, respectively). Supplementation with CGM increased maximum LD depth (from 45.9 to 47.6 mm), calf birth weight (low Pr = 43.2, high Pr = 46.3 kg), and milk crude protein concentration (from 30.8 to 31.6 g/kg). Fat supplementation in the DP of the mature cows increased maximum back fat depth (from 3.6 to 4.5 mm), milk yield (low F = 26.3, high F = 28.7 kg/d), and Pr yields (low F = 837, high F = 899 g/d). Inclusion of F in the DP diets reduced casein concentration in milk at wk 3 of lactation from 26.3 to 24.5 g/kg. Milk CP yield was also increased by CGM supplementation when compared within cows receiving F-supplemented silages (low Pr, high F = 832 g/d; high Pr, high F= 877 g/d). It can be concluded that CGM supplementation in the DP increased subsequent milk Pr concentration, but milk Pr yield increased only in those animals also receiving F supplementation. Dry period diet supplementation with F increased maximum back fat depth and milk and CP yields in the mature cows, and led to more LD muscle mobilization during early lactation. Second-calving cows had a lower DMI and milk fat concentration than mature cows.     

Prediction of coagulation properties, titratable acidity, and pH of bovine milk using mid-infrared spectroscopy

This study investigated the potential application of mid-infrared spectroscopy (MIR 4,000-900 cm⁻¹) for the determination of milk coagulation properties (MCP), titratable acidity (TA), and pH in Brown Swiss milk samples (n = 1,064). Because MCP directly influence the efficiency of the cheese-making process, there is strong industrial interest in developing a rapid method for their assessment. Currently, the determination of MCP involves time-consuming laboratory-based measurements, and it is not feasible to carry out these measurements on the large numbers of milk samples associated with milk recording programs. Mid-infrared spectroscopy is an objective and nondestructive technique providing rapid real-time analysis of food compositional and quality parameters. Analysis of milk rennet coagulation time (RCT, min), curd firmness (a₃₀, mm), TA (SH°/50 mL; SH° = Soxhlet-Henkel degree), and pH was carried out, and MIR data were recorded over the spectral range of 4,000 to 900 cm⁻¹. Models were developed by partial least squares regression using untreated and pretreated spectra. The MCP, TA, and pH prediction models were improved by using the combined spectral ranges of 1,600 to 900 cm⁻¹, 3,040 to 1,700 cm⁻¹, and 4,000 to 3,470 cm⁻¹. The root mean square errors of cross-validation for the developed models were 2.36 min (RCT, range 24.9 min), 6.86 mm (a₃₀, range 58 mm), 0.25 SH°/50 mL (TA, range 3.58 SH°/50 mL), and 0.07 (pH, range 1.15). The most successfully predicted attributes were TA, RCT, and pH. The model for the prediction of TA provided approximate prediction (R² = 0.66), whereas the predictive models developed for RCT and pH could discriminate between high and low values (R² = 0.59 to 0.62). It was concluded that, although the models require further development to improve their accuracy before their application in industry, MIR spectroscopy has potential application for the assessment of RCT, TA, and pH during routine milk analysis in the dairy industry. The implementation of such models could be a means of improving MCP through phenotypic-based selection programs and to amend milk payment systems to incorporate MCP into their payment criteria.     

Fate of lysostaphin in milk from individual cows through pasteurization and cheesemaking

Transgenic cows secreting over 3 μg of lysostaphin/ mL of milk are protected against mastitis caused by Staphylococcus aureus, but it is unknown if active lysostaphin persists through dairy processing procedures or affects the production of fermented dairy foods. The objective of this study was to determine the fate of lysostaphin as milk was pasteurized and then processed into cheese. Raw milk from transgenic cows was heat treated at 63°C for 30 min, 72°C for 15 s (high temperature, short time), or 140°C for 2 s (UHT). Portions of the high temperature, short-time milk were manufactured into semi-hard cheeses. Aliquots taken at each processing step were assayed to determine the quantity (ELISA) and activity (ability to inhibit S. aureus growth) of lysostaphin. Results indicated that most of the lysostaphin was present in the aqueous portion of the milk and was not affected by pasteurization, although UHT treatment reduced enzyme concentration by 60%. The quantity and activity of the lysostaphin decreased during cheesemaking. Based on the amount of lysostaphin present in the starting cheesemilk, 10 to 15% of the lysostaphin was recovered in the whey, 21 to 55% in the cheese curd at d 1, and 21 to 36% in cheese stored at 4°C for 90 d. Enough of the lysostaphin secreted into milk by transgenic cows survived typical dairy processing conditions to impart potential value as a bioprotective agent against staphylococci in dairy foods.     

The influence of temperature and pressure factors in supercritical fluid extraction for optimizing nonpolar lipid extraction from buttermilk powder

The milk fat globule membrane, readily available in buttermilk, contains complex lipids claimed to be beneficial to humans. Phospholipids, including sphingolipids, exhibit antioxidative, anticarcinogenic, and antiatherogenic properties and have essential roles in numerous cell functions. Microfiltration coupled with supercritical fluid extraction (SFE) may provide a method for removing triacylglycerols while concentrating these nutritionally valuable lipids into a novel ingredient. Therefore, SFE as a method for phospholipid concentration needs to be optimized for triacylglycerol removal in buttermilk. The SFE conditions were assessed using a general full factorial design; the experimental factors were pressure (15, 25, and 35 MPa) and temperature (40, 50, and 60°C). Particularly interesting is that only triacylglycerols were removed from buttermilk powder. Little to no protein loss or aggregation was observed compared with the untreated buttermilk powder. Calculated theoretical values showed a linear increase for lipid solubility as pressure, temperature, or both were increased; however, experimental values showed nonlinearity, as an effect of temperature. In addition, the particular SFE parameters of 35 MPa and 50°C displayed enhanced extraction efficiency (70% total lipid reduction).     

Technical note: Flow cytometric identification of bovine milk neutrophils and simultaneous quantification of their viability

The aim of the present study was to develop a flow cytometric procedure for the quantification of the proportion of viable, apoptotic, and necrotic polymorphonuclear neutrophilic leukocytes (PMNL) isolated from both low- and high-somatic-cell-count quarter milk samples. Milk PMNL were differentiated from other cells by indirect fluorescent labeling using a primary anti-bovine granulocyte monoclonal antibody (CH138A) and an Alexa 647-labeled secondary antibody. Polymorphonuclear neutrophilic leukocytes were identified flow cytometrically based on their cytoplasmic granularity and CH138A-positivity. Additional labeling with annexin-V-fluorescein isothiocyanate and propidium iodide was used to determine milk PMNL viability. Thirty milk samples were run in parallel to assess the repeatability of the immunoassay and 6 repeated measurements per sample were performed to assess the instrument stability. Fluorescence microscopic verification of the CH138A staining pattern showed both a high sensitivity (90.9%) and specificity (92.3%). The combination of the side-scatter properties of granulated PMNL and CH138A-Alexa 647 positivity allows the distinction of labeled PMNL from other milk cells and particles that may bind nonspecifically, and from autofluorescent particles present in milk. Quantification of the proportion of PMNL and viable, apoptotic, and necrotic subpopulations in parallel samples gave repeatable results with concordance correlation coefficients varying between 0.93 and 0.99. The average coefficient of variation for repeated measurements in identical samples ranged between 4.2 and 9.7%. In conclusion, this is the first flow cytometric method suited for the simultaneous quantification of viable, apoptotic, and necrotic bovine milk PMNL in a straightforward manner.     

Risk factors for bacteriological quality of bulk tank milk in Prince Edward Island dairy herds. Part 2: Bacteria count-specific risk factors

A case-control study was conducted to identify specific on-farm risk factors that influence bacteriological quality of bulk tank milk in Prince Edward Island dairy herds. Total aerobic (TAC), preliminary incubation (PIC), laboratory pasteurization (LPC), and coliform (CC) counts were used to assess the bacteriological quality of bulk tank milk. Four case-control groups were defined based on the last 6 results of each test before on farm evaluation. A herd was classified as a TAC, PIC, or CC case when the herd had at least 4 high TAC, PIC, or CC counts out of the last 6 analyses for each test, respectively. For the LPC case group, a herd was required to have at least 3 high results out of the last 6 analyses. Control groups had low counts in the last 6 analyses for each test in the corresponding case group (TAC, PIC, CC, and LPC). The results of the study showed that TAC and PIC were mainly associated with cow and stall hygiene: washing the teats with water, not using teat predip, and dirty teats were risk factors. The LPC and CC were related to equipment hygiene, with high counts being associated with low temperature of the cleaning solution, high water-hardness score, and high alkalinity of alkaline detergent wash. Based on the findings of this study it can be concluded that TAC, PIC, LPC, and CC counts are of considerable value in identifying practices that could influence milk quality.