近红外光谱技术在牛奶及其制品质量检测中的应用

近红外光谱技术作为一种新型的分析检测技术,正在获得越来越广泛的应用。本文阐述了近红外光谱技术的基本原理、具体检测步骤和国内近红外光谱技术在牛奶及乳制品质量分析方面应用的最新研究进展。对目前研究存在的问题进行了分析,对以后进一步的研究进行了展望,并提出了一些建议。     

The occurrence of Staphylococcus aureus in fermented milk products (Fura and Manshanu) in Nigeria

Ninety-three samples of fermented milk cereal (Fura) and 79 of local butter (Manshanu) were collected from four different markets around Zaria. For Fura the mean content of Staphylococci for each of the four markets ranged from 4.5 × 10³ to 4.3 × 10⁴ cfu/ml and the mean aerobic mesophilic plate count from 5.6 × 10⁵ to 2.7 × 10⁶ cfu/ml. For Manshanu the mean staphylococcal count and aerobic mesophilic plate count ranged from 3.4 × 10² to 2.2 × 10³ cfu/ml and 6.7 × 10⁴ to 1.1 × 10⁶ cfu/ml respectively. Significant differences were seen between the different markets.     

Properties of Edible Films from Total Milk Protein

The mechanical properties and water vapor permeability of edible films made from various total milk proteins (TMPs) were investigated. Two TMPs obtained from nonfat dry milk (NDM) by removing lactose and three TMPs obtained from a commercial source were studied. Lactose was extracted from NDM by ultrafiltration or suspension in ethanol followed by filtration. TMP concentrate obtained by ultrafiltration (UF) produced films with the lowest water vapor permeability (WVP) and the highest tensile strength at break. Commercial TMP concentrates produced films more ductile than those from the UF-TMP or retentate from ethanol extraction. Further research is needed to improve mechanical properties of UF-TMP films without increasing the WVP.     

Copper bioavailability from breakfasts containing tea. Influence of the addition of milk

The influence of drinking tea on copper bioavailability is unclear, particularly when tea is consumed with food. A breakfast meal containing white bread, margarine, strawberry jam, cheese and tea, with or without milk, was digested in; vitro and the dialysis of copper investigated. Reference breakfasts were prepared with water and water with milk. Copper dialysability (percentage of copper dialysed) was markedly increased by tea. The influence of adding milk to tea was not significant. A second study was carried out in rats using the breakfasts containing tea and water. They were spiked with ⁶⁴Cu and given orally to the animals in a single dose. Whole-body ⁶⁴Cu retention was measured over a 4-day period after administration. In order to determine the true absorption of ⁶⁴Cu a control group of rats received the dose intraperitioneally. The results in vivo indicate a tendency to higher absorption and retention of ⁶⁴Cu with tea. Liver ⁶⁴Cu retention was significantly elevated by tea. Therefore, the presence of tea in a breakfast meal favours the formation of soluble low-molecular-weight ligands which can be absorbed and retained by rats. The concomitant increase in liver copper retetition may be associated with higher bioavailability and/or lower copper mobilisation.     

婴幼儿配方乳粉中叶黄素的测定及其储存过程中损失率的研究

目的建立一种婴幼儿配方乳粉中叶黄素含量的测定方法。并确定叶黄素标准储备液的有效期和考察婴幼儿配方乳粉储存和食用过程中叶黄素含量的损失率。方法样品经超纯水溶解后以0.1%BHT-丙酮溶液超声提取。以甲醇-甲基叔丁基醚为流动相等度洗脱,流速为1.0 m L/min,进样量50μL,柱温25℃,二极管阵列检测器检测,检测波长445 nm。结果在15 min内完成目标物的分离分析,叶黄素在0.1、1.0、10.0μg/100g 3个浓度水平的回收率为90.0%~98.9%,相对标准偏差小于1.47%(n=6),方法定量限为0.5μg/100 g。叶黄素储备液在-70℃冰箱中保存12个月内含量稳定。结论该方法快速、准确、灵敏,适合测定婴幼儿配方乳粉中叶黄素含量的检测,婴幼儿配方乳粉在储存过程中叶黄素含量有下降趋势,保质期内符合国家标准要求。     

牛奶蛋白纤维的结构与性能

利用扫描电子显微镜观察了牛奶蛋白纤维的形态结构。结果表明,牛奶蛋白纤维是异形纤维,截面上有微孔,表面有凹槽;对牛奶蛋白纤维的X-射线衍射分析显示聚乙烯醇分子规则排列构成结晶部分,牛奶蛋白形成无定形区;测试和分析了牛奶蛋白纤维的吸湿、拉伸、摩擦等性能,结果表明牛奶蛋白纤维是集蚕丝和合成纤维优良性能于一身的纺织新材料。     

牦牛酸乳分离发酵乳杆菌发酵豆浆的胃溃疡预防效果研究

以采自川西青藏高原的自然发酵牦牛酸乳样品中分离纯化得到的1 株发酵乳杆菌（Lactobacillusfermentum Zhao,LFZ）作为研究对象,探索比较其与商业用嗜热链球菌（Streptococcus thermophilus,ST）发酵豆浆的胃溃疡预防效果。通过利血平诱导胃溃疡小鼠模型,LFZ组小鼠的IL-6、IL-12、TNF-α和IFN-γ细胞因子低于ST组小鼠;血清生长抑素和血管活性肠肽水平高于ST组,胃动素和P物质水平低于ST组,且LFZ组小鼠胃溃疡面积也低于ST组小鼠。由此可知,Lactobacillus fermentum Zhao发酵豆浆的品质优于标准嗜热链球菌发酵豆浆,且其对胃溃疡有很好的预防效果。     

Short communication: Investigation of Coxiella burnetii occurrence in dairy sheep flocks by bulk-tank milk analysis and antibody level determination

To estimate the prevalence of Coxiella burnetii in the dairy sheep population from the Basque Country (northern Spain), a study was carried out combining molecular and serological techniques. First, bulk-tank milk samples from 154 flocks belonging to the Latxa Breed Farmers Association were analyzed by PCR, with 22% of flocks testing positive for C. burnetii. Then, a selection of 34 flocks (7 PCR positive and 17 negative) was investigated for the presence of serum antibodies by ELISA test on 1,011 ewes (approximately 30 ewes per flock). A total of 8.9% of the animals were seropositive, 67.6% of the flocks had at least one seropositive animal, but only in 14.7% of them was seroprevalence greater than 25%. Older ewes showed a significantly greater prevalence (17.5%) compared with yearlings (7.5%) or replacement lambs (1.5%). A marginally significant association was found between seroprevalence and PCR detection of C. burnetii in bulk-tank milk. The widespread distribution of C. burnetii in the region advocates for the implementation of Q fever control strategies and highlights the potential risk of sheep as a reservoir and infection source for other domestic and wildlife species and the human population.     

Effects of level and form of dietary zinc on dairy cow performance and health

A basal mixed ration supplying 36 mg of Zn/kg of dry matter (DM) was supplemented with 1 of 4 concentrates differing in level and form of dietary Zn. The concentrates were fed at 2 kg/cow per day and contained 300 mg of Zn/kg (to supply the total recommended level, according to NRC (2001); R) or 60 mg of Zn/kg (to supply 0.66 of the total recommended level; L), either supplemented as ZnO (I) or organically chelated Zn (O). Forty-four Holstein-Friesian dairy cows (12 primiparous and 32 multiparous), on average 31 d (SD ± 11.4) into lactation, were allocated to 1 of the 4 treatments. All cows remained on the treatment for 14 wk. The data was analyzed by ANOVA as a 2 × 2 factorial design. Dry matter intake averaged 23.5 kg/d and did not differ between treatments. Cows supplemented with organically chelated Zn at the recommended level of inclusion (RO) had a higher milk yield (37.6 kg/d) than those fed inorganic Zn at the recommended level (RI; 35.2 kg/d) or organically chelated Zn at the low level (LO; 35.2 kg/d), but was not different from those fed inorganic Zn at the low level (LI; 36.0 kg/d). Milk composition was unaffected by dietary treatment. Animals that received the low level of Zn (LI and LO) had higher somatic cell counts [3.97 and 3.93 versus 4.35 and 4.55 (log_e) for RI, RO, LI, and LO, respectively] and milk amyloid A levels than those receiving the recommended levels (RO and RI). There was no effect of treatment on body condition score, body weight, or locomotion score. Hoof hardness improved over the duration of the study but there were no differences between treatments. Similarly, blood plasma mineral levels for Zn, Cu, Mo, and Fe were not affected by treatment, whereas there was a trend for increased ceruloplasmin levels in cows receiving the recommended compared with the low level of Zn, but there was no effect of mineral form. There was also no effect of treatment on superoxide dismutase activity or blood hematology. It is concluded that supplementing Zn at the recommended level reduced somatic cell counts and milk amyloid A levels, whereas supplementation in an organic form at the recommended level also increased milk yield.     

Udder measurements and milk production in two Awassi sheep genotypes and their crosses

To improve the effectiveness of community-based breeding programs for increased milk production, the values of different udder measurements for predicting milk production traits during the milking period were assessed over 3 yr on 273 Awassi ewes. Machine milking of ewes began after weaning, 56 d after parturition, and continued until the milk yield of the ewes was <200 mL/d. Milk yield obtained by hand milking and milk composition were measured weekly, and days in milk, total milk yield, and total yields of protein, fat, and nonfat solids in milk were calculated for each ewe. On d 70 of milking, morphological traits of the whole udder (circumference, width, height, and length), udder cistern (height), and teats (length, width, and position score) were measured. On the same day, the milk yield of ewes was recorded by hand milking. Positive and moderate to strong correlations (r = 0.36 to 0.76) between udder circumference and width, teat width, and milk production traits of total milk yield, and total yields of protein, fat, and nonfat solids were found. However, a more accurate predictor of milk production traits was milk yield on d 70, as higher positive correlations between this variable and the milk production traits were found (r = 0.63 to 0.89). Nine farmers were invited to independently estimate the hand-milked milk yield performance of a sample of 169 ewes (d 15 to 45 of milking) by visually observing each ewe and making a subjective linear score (1 to 5). Their assessments were significantly correlated with milk yield on the day of the observation (r = 0.52), total milk yield (r = 0.50), and days in milk (r = 0.45). Considering the perception details provided by farmers concerning each of the subjective linear scores, it was found that most predictive linear udder measurements of udder circumference and width and teat width identified in this study were implicit in these scores. The predictive ability of the measurements studied have practical implications for community-based breeding programs involving improvement of milk production—not just in Syria, but in other countries in dry areas as well—because it is possible for experienced farmers to visually assess milk production of dairy ewes or take simple udder measurements with predictive value.