冷鲜水牛肉保鲜技术

采用真空包装、热收缩膜包装、保鲜剂配合热收缩膜包装冷鲜水牛肉,在0～4℃条件贮藏.通过分析贮藏期间的嫩度、pH值、挥发性盐基氮、菌落总数、大肠菌群和感官评定等,研究包装方式对水牛肉保鲜效果的影响.结果表明:对照组、实验组1、2、3的货架期分别为9、15、18、27d.采用热收缩膜配合复合保鲜剂包装能有效延长保质期(27d),保鲜效果最好.     

Characterisation of cow and buffalo ghee using fluorescence spectroscopy

Fluorescence spectroscopy has been utilised to characterise ghee extracted from buffalo and cow milk. Using an excitation wavelength of 320 nm, emission spectra of buffalo and cow ghee; vitamins A, B₁₂, D, E, K; and conjugated linoleic acid (CLA) were acquired by using spectrofluorometer. The bands at 390, 440, 480 and 525 nm were assigned to fat‐soluble vitamins, CLA, vitamin A and beta‐carotene. Moreover, spectra of vitamins and CLA confirmed their presence in both ghee types. The spectral differences were highlighted through principle component analysis that has been applied for the detection of adulteration of cow  milk  in buffalo ghee.     

Mode of action of yeast culture (YEA-SACC 1026) for stimulation of rumen fermentation in buffalo calves

The effect of daily supplementation of 5 g Saccharomyces cerevisiae yeast culture (YC, YEA-SACC 1026), 30 g NaHCO₃, supernatant from 5 g YC (YCS), 5 g autoclaved YC (YCH) or 5 g γ-irradiated YC (YCR) to the diet of buffalo calves on rumen microbial populations and fermentation pattern was examined. Addition of 30 g NaHCO₃ increased the rumen pH to the level observed with YC group. The pH and the concentrations of total, total viable and cellulolytic bacteria and total volatile fatty acids (VFA) were significantly higher while that of lactic acid, hexose-unit oligosaccharides and NH₃-N were significantly lower in the rumen fluid of YC compared with the control group. The effect of NaHCO₃ was 39·5 and 59·5% in decreasing the concentrations of lactic acid and hexose-unit oligosaccharides, 48·1, 47·2 and 45·5% in increasing the numbers of total, total viable and cellulolytic bacteria, 50·0 and 58·1% in increasing the concentrations of total VFA and protein and 51·3% in decreasing the concentration of NH₃-N of YC. The corresponding values for YCR addition in the diet were 38·6, 45·7, 48·5, 44·4, 51·5, 39·1, 48·1 and 46·5%. The effect of YCS and YCH was only marginal, but conspicuous up to 2 h after feeding, in changing the above rumen variables when compared with the YC group. The results indicated that contribution of increase in pH in changing the rumen variables was approximately 50% of YC and almost all the stimulatory activity was associated with live yeast cells. Autoclaving of YC destroyed almost all and γ-irradiation of YC retained about 50% of stimulatory activity of YC. The effect of YC on rumen fermentation, which was maximum up to 2 to 4 h after feeding, decreased with time. © 1998 SCI.     

Detection of buffalo milk adulteration with cow milk by capillary electrophoresis analysis

The addition of cow milk during the production of buffalo mozzarella is a common fraud in dairy industries because of the lower price and greater availability of cow milk throughout the year. The aim of this study was to develop a new, rapid, and robust capillary electrophoresis method for detecting and quantifying cow milk in buffalo milk by exploiting cow α-lactalbumin as a marker of adulteration. In particular, a linear calibration curve was generated, using a training set of calibrators consisting of 7 series of 17 buffalo/bovine whey mixtures, obtained after casein precipitation, with increasing percentages of cow whey. The capillary electrophoresis method showed high linearity (R² = 0.968), repeatability [relative standard deviation (RSD) = 2.11, 3.02, 4.38, and 1.18%, respectively for 5, 10, 20, and 50% of buffalo/bovine whey mixtures], and intermediate precision (RSD = 2.18, 2.49, 5.09, and 3.19%, respectively, for 5, 10, 20, and 50% buffalo/bovine whey mixtures). Moreover, the minimum amount of detectable fraudulent cow milk was 1%, and the limit of quantification was 3.1%.     

Antimicrobial Effect of Malpighia Punicifolia and Extension of Water Buffalo Steak Shelf‐Life

In the present study, a multiple approach was used to characterize Malpighia punicifolia extract and to evaluate its inhibitory activity against several meat spoilage bacteria. First, volatile fraction, vitamins and phenolic compounds of the extract obtained by supercritical fluid extraction were determined by GC‐MS and HPLC. Then, the antimicrobial action of the extract was in vitro evaluated against Pseudomonas putida DSMZ 291^T, Pseudomonas fluorescens DSMZ 50009^T, Pseudomonas fragi DSMZ 3456^T, and Brochothrix thermosphacta DSMZ 20171^T by the agar well diffusion assay and by the agar dilution test. Based on the results of the minimum inhibitory concentration (MIC) against the assayed bacteria, 4 different concentrations of the extract were used in a challenge test on water buffalo steaks stored for 21 d at 4 °C. Results of chemical analyses showed that M. punicifolia extract is characterized by the presence of several compounds, already described for their antimicrobial (phenolic acids, flavonones, and furanes) and antioxidant (ascorbic acid) properties. The in vitro detection of antimicrobial activities highlighted that the extract, used at 8% concentration, was able to inhibit all the target bacteria. Moreover, very low MIC values (up to 0.025%) were detected. In situ tests, performed on water buffalo steaks treated with the extract in the concentration range 0.025% to 0.05%, showed a strong inhibition of both intentionally inoculated bacteria and naturally occurring microorganisms. Positive results, in terms of color and odor, were also observed during the entire storage of steaks preserved with the extract.     

几种关键工艺条件对芒果水牛酸乳稳定性及其结构特性影响的研究

为了探索工艺条件对芒果水牛酸乳稳定性及其结构的影响作用,从其持水力（WHC）、黏度、zeta电位3个方面对样品的作用特性进行了研究。结果表明:当3种稳定剂总量浓度达到0.15%时,水牛酸乳样品的WHC值达到最大,稳定性最好。酪蛋白胶粒表面稳定剂吸附量随着稳定剂添加量的增加而增多,zeta电位减小,电负性进一步增加,所形成复合大分子间斥力加大,从而抑制了酪蛋白的聚集沉淀,增强了体系的稳定性。添加3种不同稳定剂的酸乳样品的WHC、黏度随着pH的下降而下降,表明酸度增加导致体系的稳定性降低。均质压力增加,酸乳WHC值呈增大趋势,体系黏度并未随之增大,体系ζ-电位呈增加的趋势。      

中国水牛乳中α-乳白蛋白活性分离方法比较

以水牛乳为原料,离心分离脂肪,再采用等电点缓慢酸沉去除酪蛋白,结合铁盐沉淀法和钙盐沉淀法两种方法分别对乳清蛋白中α-乳白蛋白进行活性分离,在保证α-乳白蛋白分离纯度的同时,对其活性和得率分析检测。结果显示,铁盐沉淀法分离α-乳白蛋白时,在pH4.5⁴.7的酸性条件下采用质量分数0.04%的铁盐分离α-乳白蛋白保证α-乳白蛋白纯度达到电泳纯的同时,其活性比例和得率分别达到44.68%和21.06%;而在pH7.0的中性条件下采用质量分数0.005%的铁盐分离α-乳白蛋白也可保证α-乳白蛋白的纯度达到电泳纯,此时,其活性比例和得率分别达到64.00%和13.23%。钙盐沉淀法可很好地保持α-乳白蛋白的活性,但分离纯度过低。      

Vitamin B12 and its binding proteins in milk from cow and buffalo in relation to bioavailability of B12

Milk is an important source of highly bioavailable vitamin B₁₂ (cobalamin) in human nutrition. In most animal products, vitamin B₁₂ is strongly bound to various specific protein carriers. The 2 vitamin B₁₂-specific proteins, predominantly transcobalamin (TC) and haptocorrin (HC), were earlier found in milk from Holstein Friesian cows and in human or sow milk, respectively. As the type of vitamin B₁₂ binders may influence bioavailability of the vitamin, we examined vitamin B₁₂ carriers in pooled milk specimens derived from European and Indian cow and buffalo herds. The total endogenous vitamin B₁₂ concentration was comparable in all milk pools (≈3 nM), but the vitamin carriers varied considerably: TC + caseins in Danish cows, TC + HC in Indian cows and buffaloes, and mainly HC in Italian buffaloes. Danish cow milk contained half as much TC as vitamin B₁₂, and the surplus vitamin was all attached via a single coordination bond to abundantly available histidine residues of casein. The specific binding proteins in Indian cow milk (TC + HC) approximately matched the molar content of vitamin B₁₂. Milk from the 2 buffalo breeds contained more specific binders than vitamin B₁₂, and the surplus proteins included the unsaturated TC ≈ 3 nM (Indian stock), or both TC ≈ 4 nM and HC ≈ 23 nM (Italian stock). The abundant HC of the latter sample bound nearly all endogenous vitamin B₁₂. We tested (in vitro) the transfer of vitamin B₁₂ from milk proteins to human carriers, involved in the intestinal uptake. The bovine TC-vitamin B₁₂ complex rapidly dissociated at pH 2 (time of half reaction, τ_1/2 < 1 min, 37°C) and was susceptible to digestion with trypsin + chymotrypsin (pH 7.5). Transfer of vitamin B₁₂ from the precipitated bovine casein (pH 2) to human carriers proceeded with τ_1/2 ≈ 7 min (37°C) and τ_1/2 ≈ 35 min (20°C). Liberation of vitamin B₁₂ from buffalo HC was hampered because of its pH stability and slow proteolysis. Nutritional availability of vitamin B₁₂ is expected to be high in cow milk (with TC-vitamin B₁₂ and casein-vitamin B₁₂ complexes) but potentially constrained in buffalo milk (with HC-vitamin B₁₂). This especially concerns the Italian buffalo milk, where a high excess of HC was found. We speculate whether the isolated stock of Italian buffalo maintained the ancestral secretion of carriers (HC ≫ vitamin B₁₂, TC ≈ 0), whereas intensive crossbreeding of cows and buffaloes from other regions caused a change to TC ≤ vitamin B₁₂, with low or absent HC. The substitution of HC by less sturdy carriers is apparently more beneficial to human consumers as far as vitamin B₁₂ bioavailability is concerned.     

基于高通量测序分析不同品种水牛生乳中细菌多样性

目的 利用16S rRNA高通量测序研究广西水牛研究所种畜厂内摩拉、尼里-拉菲及三品杂3品种水牛生鲜乳中的细菌多样。方法 提取当天采集的生水牛乳样本细菌总DNA,PCR扩增细菌的16S rDNA,纯化PCR扩增目的片断,将PCR产物与pMD18-T载体连接,构建其菌群的16S rDNA文库。用Miseq对其16S rRNA基因的V3-V4可变区进行测序以及BLAST比对。结果 3品种27个样本共获得1223个OUTs, M、N、S独有的OTU分别为295、41和42,共有OTU为511。物种组成与丰度差异显示：3品种优势菌门为：变形菌门(Proteobacteria)、厚壁菌门(Firmicutes)、拟杆菌门(Bacteroidetes)。优势菌属为：金黄杆菌属(Chryseobacterium)、不动杆菌属(Acinetobacter)、乳球菌属(Lactococcus)、假单胞菌属(Pseusomonas)。样本层级聚类显示：3品种样本间菌落组成相似度较高。PCA与PLS-DA分析表明：3品种样本组内菌群多样性差异不显著,但组间菌群丰度差异明显。结论 摩拉、尼里-拉菲及三品杂水牛生鲜乳中细菌菌群均呈现较丰富的多样性,其共有的优势菌群为金黄杆菌(Chryseobacterium)、不动杆菌(Acinetobacter)、乳球菌(Lactococcus)、假单胞菌(Pseusomonas)。各品种间菌群组成种类整体相似,但其主要菌落丰富度差异明显。     

不同品代水牛奶理化性质的研究

研究了摩拉水牛、尼里-拉菲水牛、一代杂交水牛、二代杂交水牛、高代杂交水牛等5个品代水牛奶的理化性质。结果表明,杂交水牛奶的全乳固体、乳脂肪、蛋白质、乳糖的平均值均高于纯种摩拉水牛和尼里-拉菲水牛,杂交水牛奶的灰分总体高于纯种河流型水牛,在杂交水牛中,由高到低的顺序为:一代杂、二代杂、高代杂。纯种摩拉水牛和尼里-拉菲水牛之间的全乳固体、乳脂肪、蛋白质和乳糖差异不显著(P>0.5),而杂交水牛的全乳固体、乳脂肪、蛋白质和乳糖与纯种河流型水牛相比,差异显著(P<0.05)。各品代水牛之间钙、磷含量的差异不显著(P>0.5),但从总体上看,杂交水牛的含量要高于纯种河流型水牛,杂交水牛中又以杂交一代水牛为最高。各品代水牛奶的各种氨基酸含量随蛋白质总量的变化而变化,除杂交水牛之外,各品代水牛之间的各种氨基酸比例比较接近。各品代水牛奶的密度平均值变化范围为1.028～1.032;酸度平均值变化范围是15.36～19.82°T;pH值的平均值变化范围从6.46～6.88;黏度平均值的变化范围由2.44～3.11 Pa.s。