健康奶牛和乳腺炎奶牛乳汁中微生物组成的特征及差异研究

奶牛乳腺炎的发生与多种病原微生物密切相关,乳汁中菌群特征的分析对建立乳房炎防控体系和提高乳制品质量和安全具有重要意义。本研究通过16S r RNA基因的V3-V4区测序,分析河南省某奶牛场17头健康奶牛和10头乳房炎奶牛乳汁中微生物菌群结构的多样性和丰富度。结果发现,微生物菌群在11个门、24个纲、37个目、82个科和184个属水平上的相对丰度存在显著差异。乳腺炎奶牛乳汁中微生物菌群结构的多样性和丰富度显著低于健康奶牛乳汁,在乳腺炎奶牛乳汁中厚壁菌门、变形菌门、放线菌门的相对丰度较高。乳腺感染后,变形菌门、软壁菌门的丰度显著降低;互养菌门的丰度显著升高。乳腺炎奶牛乳汁中的链球菌科、链球菌属的相对丰度增加,棒状杆菌科、罗尔斯通氏菌属、假单胞菌属的相对丰度下降。优势菌属中有4个嗜冷菌,健康奶牛和乳腺炎奶牛乳汁中的嗜冷菌总丰度分别为19.5%和42.0%。提示乳汁中微生物组成变化可能与奶牛乳腺炎的发生发展有密切联系,该研究为奶牛场乳房炎的防控及原料奶的质量控制提供了理论依据。     

基于高通量测序技术比较不同来源原料乳中的细菌特征

本文采用二代高通量测序技术研究北京、河北、内蒙古、天津四地区不同季节原料乳样品中的细菌多样性并对其进行功能预测。收集四地区不同季节原料乳样品23份,提取基因组DNA后使用Illumina Mi Seq测序平台对细菌16S rRNA的V3-V4"可变区"进行测序,结合数据库对原料乳中微生物群落分布、相对丰度和细菌功能基因代谢途径进行分析。原料乳中的细菌可分为33门732属,其中变形菌门(Proteobacteria),厚壁菌门(Firmicutes),拟杆菌门(Bacteroidetes)和放线菌门(Actinobacteria)为主要菌门,平均相对丰度占微生物总数的99.37%。优势菌属为假单胞菌属(Pseudomonas)和不动杆菌属(Acinetobacter),平均相对丰度之和为60.55%。不同地区、不同季节原料乳微生物群落的结构组成和相对丰度存在差异,且假单胞菌属和气单胞菌属的相对丰度在不同季节原料乳中存在显著性差异(p0.05)。氨基酸代谢、碳水化合物代谢和膜运输为原料乳细菌主要的代谢途径。     

杭州地区原料奶中嗜冷菌的分离鉴定

以杭州地区牧场的原料奶为实验对象,对原料奶受嗜冷菌污染情况进行调研,并对其中的嗜冷菌进行分离鉴定,确定革兰氏阴性嗜冷菌占绝大部分,其中荧光假单胞菌、鲁氏不动杆菌、阪崎肠杆菌为优势嗜冷菌种,为进一步研究出一种快速检测原料奶嗜冷菌的方法奠定理论基础。     

原料乳中嗜冷菌的危害分析及控制研究

采用分离培养基从牧场的原料乳样品中分离得到嗜冷菌,经鉴定为荧光假单胞菌.进一步研究了不同杀菌方式下嗜冷菌对贮存过程中乳品品质的影响,结果表明,原料乳经115℃高温灭菌,然后进行55℃保温1h灭酶处理,有助于控制嗜冷菌的生长,与25℃贮存相比,在4℃贮存8d后,其蛋白质和脂肪含量相对较高.     

低温储存条件对原料乳嗜冷菌及细菌多样性的影响

分析了储存条件对原料乳中嗜冷菌细菌多样性及牛乳品质的影响,为原料乳低温储存条件的筛选提供科学依据。通过16SrRNA高通量测序分析了原料乳在4℃储存一天后的细菌多样性,依据现行国标方法监测了4,10℃和15℃储存期间原料乳中嗜冷菌数和菌落总数的变化。原料乳在4℃储存过程中,微生物繁殖比较缓慢,但其微生物群落组成变化明显,储存24小时后,假单胞菌、黄杆菌等嗜冷菌的相对丰度占原料乳中细菌总量的90%以上;根据微生物计数结果和国标限量,低温储存4℃≤24 h,10℃≤16 h,15℃≤8 h,原料乳中菌落总数能满足生乳的食品安全国家标准,但嗜冷菌大量增殖可能会引起牛乳品质的下降。     

基于16S rDNA高通量测序方法比较新疆西北部地区乳品中微生物的多样性

为更加全面地了解新疆特色乳品中微生物多样性,比较不同动物来源的原奶和酸奶的细菌群落结构,运用高通量测序技术,对乳品中细菌16S r DNA V4-V5区测序,进而对新疆克州和塔城地区牛奶、驼奶、马奶、羊奶、酸牛奶、酸驼奶和酸马奶7种乳品中细菌群落组成和多样性进行分析。研究共获得539 557条有效序列,379个OTU。多样性分析表明,原奶样品中细菌Shannon-Wiener指数明显高于酸奶样品。微生物群落组成分析发现,不同乳品之间菌群组成差异较大。7种乳品中的菌群均以厚壁菌门和变形菌门为主,但原奶样品主要以变形菌门为主,而酸奶样品主要以厚壁菌门为主。在属水平上,牛奶主要以假单胞菌属(Pseudomonas)为主,驼奶主要以埃希菌属-志贺菌属(Escherichia-Shigella),马奶主要以明串珠菌属(Leuconostoc)为主,羊奶中的优势菌属为乳球菌属(Lactococcus),而酸牛奶、酸驼奶和酸马奶都是以乳杆菌属(Lactobacillus)为优势菌属。不同动物来源的原奶和酸奶样品中的微生物多样性存在显著差异,并且原奶中检测到的环境污染菌和致病菌(或条件致病菌)的丰度也相对较高。本研究结果将为准确评估乳品中的微生物群落对新疆地区少数民族健康的影响提供一定的数据基础。     

牛乳中嗜冷菌数与胞外蛋白酶活性相关性的研究

主要研究了牛乳中嗜冷菌数与其产生的耐热性胞外蛋白酶活性的相关性.从原料乳中分离出一株优势嗜冷菌,实验室初步鉴定后用API20NE系统进行鉴定,鉴定该菌为荧光假单胞菌(Pseudomonas Fluorescens),产酶实验结果表明,该菌产耐热性胞外蛋白酶.利用该菌株研究牛乳中单一嗜冷菌菌数与蛋白酶活性的关系,结果表明菌数与蛋白酶活性呈一定正相关,回归方程为Y=0.4548ln(X) 0.4178,决定系数R2=0.8172,相关系数R=0.9039,差异极显著(P<0.01);自然状态下,原料乳中嗜冷菌数与蛋白酶活性关系实验结果表明,原料乳在不同条件下贮存,嗜冷菌数有明显的增加趋势,但原料奶中嗜冷菌数和蛋白酶活性之间没有多少相关性.     

超高压处理对冷藏鲈鱼片细菌群落结构的影响

为研究超高压处理对冷藏鲈鱼片贮藏期间细菌菌群结构的影响,以压力250 MPa,时间9 min的超高压条件处理鲈鱼片,并以0.1 MPa处理样品为对照组。将处理后的样品置于4℃冰箱中贮藏,分别在0,3,6,9,11,13,15 d进行总挥发性盐基氮(TVB-N)与微生物指标(细菌总数、希瓦氏菌数、假单胞菌数和嗜冷菌数)测定,并作相关性分析,评价超高压处理对冷藏鲈鱼片品质的影响。随后分别提取两组样品在贮藏前期、中期、中后期与末期4个阶段的宏基因组,通过高通量测序技术分析冷藏鲈鱼肉不同阶段的细菌菌群。结果表明,样品经超高压处理,其TVB-N值、细菌总数、假单胞菌数、希瓦氏菌数和嗜冷菌数等指标的上升速度明显缓于对照组。相关性分析表明,TVB-N值与微生物指标可作为鲜度评价指标,用于分析鲈鱼片超高压处理后贮藏期间的品质变化。高通量测序结果表明,对照组与处理组样品在贮藏前期的主要细菌有芽孢杆菌属、大洋芽孢杆菌属与乳球菌属;在贮藏中后期与末期两个阶段,超高压处理组与对照组的菌相组成呈显著差异,优势腐败菌种类不同,对照组在中后期的主要细菌为假单胞菌属,超高压处理组在中后期的主要细菌为嗜冷菌属,对照组末期主要腐败菌为嗜冷菌属、假单胞菌属、希瓦氏菌属和气单胞菌属,超高压处理组末期主要腐败菌为嗜冷菌数、假单胞菌属与耶尔森氏菌属。可见,超高压处理在抑制TVB-N值与微生物指标升高的同时,也对其贮藏期间的菌相组成产生明显的影响,使嗜冷菌与希瓦氏菌的生长受到抑制。     

原料乳中嗜冷假单胞菌危害及控制研究进展

假单胞菌是对原料乳危害最大的嗜冷菌之一,极易在冷藏条件下成为优势菌群。大多数嗜冷假单胞菌有分泌蛋白酶和脂肪酶的能力,并导致原料乳及产品变质。本文对原料乳假单胞菌的危害特点,快速检测和新型控制工艺研究进展进行综述。最后探讨了嗜冷假单胞菌的研究方向。     

Illumina MiSeq高通量测序技术研究原料乳及环境中细菌多样性和致病菌的分布情况

利用Illumina MiSeq高通量测序方法测定原料乳及其环境中的细菌微生物的多样性及致病菌的分布情况。提取DNA和PCR扩增后测序,主要测定稀释性曲线、OTU相对丰度曲线以及菌群分布图。结果表明:菌群具有多样性,在输乳管路外侧和盛装原料奶的空贮罐中均检测出金黄色葡萄球菌。应严格监控奶牛生活环境及储奶设施的卫生情况,从而保障原料乳质量安全。     

Ovarian structures and circulating steroids in heifers and lactating cows in summer and lactating and dry cows in winter

Two experiments compared follicular and luteal development and circulating steroid concentrations from induced luteolysis to ovulation in lactating Holstein cows (n = 27; 40.0 +/- 1.5 kg milk/day) vs. nulliparous heifers (n = 28; 11 to 17 mo-old) during summer (Experiment 1), and in lactating (n = 27; 45.9 +/- 1.4 kg milk/d) vs. dry cows (n = 26) during winter (experiment 2). All females received PGF2,, 6 d after ovulation and were monitored until next ovulation by daily ultrasound and assay of serum progesterone (P4) and estradiol (E2). Every female was used two or three times. In Experiment 1, lactating cows had high incidence of multiple ovulation (63.5%) compared with heifers (1.3%). Among single ovulators, there was no difference in maximal size of ovulatory follicles between lactating cows and heifers (15.8 vs. 16.5 mm, respectively). However, lactating cows had lower peak serum E2 (8.6 vs. 12.1 pg/ml), took longer to ovulate after luteolysis (4.6 vs. 3.8 d), developed more luteal tissue volume (7,293.6 vs. 5,515.2 mm3), and had lower serum P4 on d 6 after ovulation (2.0 vs. 3.0 ng/ml) than heifers (data included multiple ovulators). In experiment 2, multiple ovulations were similar between lactating and dry cows (17.9 vs. 17.2%, respectively). Peak serum E2 was also similar between lactating and dry cows (7.6 vs. 8.5 pg/ml) although lactating cows had larger ovulatory follicles (18.6 vs. 16.2 +/- 0.4 mm). Lactating cows took longer to ovulate (4.8 vs. 4.2 d), developed more luteal tissue (7,599 vs. 5,139 +/- 468 mm3), but had similar serum P4 (2.2 vs. 1.9 ng/ ml) compared with dry cows. Therefore, lactating cows had similar or lower circulating steroid concentrations than dry cows or heifers, respectively, despite having larger ovarian structures.     

Fertilization and early embryonic development in heifers and lactating cows in summer and lactating and dry cows in winter

Two experiments in two seasons evaluated fertilization rate and embryonic development in dairy cattle. Experiment 1 (summer) compared lactating Holstein cows (n = 27; 97.3 +/- 4.1 d postpartum [dppl; 40.0 +/- 1.5 kg milk/d) to nulliparous heifers (n = 28; 11 to 17 mo old). Experiment 2 (winter) compared lactating cows (n = 27; 46.4 +/- 1.6 dpp; 45.9 +/- 1.4 kg milk/d) to dry cows (n = 26). Inseminations based on estrus included combined semen from four high-fertility bulls. Embryos and oocytes recovered 5 d after ovulation were evaluated for fertilization, embryo quality (1 = excellent to 5 = degenerate), nuclei/embryo, and accessory sperm. In experiment 1, 21 embryos and 17 unfertilized oocytes (UFO) were recovered from lactating cows versus 32 embryos and no UFO from heifers (55% vs. 100% fertilization). Embryos from lactating cows had inferior quality scores (3.8 +/- 0.4 vs. 2.2 +/- 0.3), fewer nuclei/embryo (19.3 +/- 3.7 vs. 36.8 +/- 3.0) but more accessory sperm (37.3 +/- 5.8 vs. 22.4 +/- 5.5/embryo) than embryos from heifers. Sperm were attached to 80% of UFO (17.8 +/- 12.1 sperm/UFO). In experiment 2, lactating cows yielded 36 embryos and 5 UFO versus 34 embryos and 4 UFO from dry cows (87.8 vs. 89.5% fertilization). Embryo quality from lactating cows was inferior to dry cows (3.1 +/- 0.3 vs. 2.2 +/- 0.3), but embryos had similar numbers of nuclei (27.2 +/- 2.7 vs. 30.6 +/- 2.1) and accessory sperm (42.0 +/- 9.4 vs. 36.5 +/- 6.3). From 53% of the flushings from lactating cows and 28% from dry cows, only nonviable embryos were collected. Thus, embryos of lactating dairy cows were detectably inferior to embryos from nonlactating females as early as 5 d after ovulation, with a surprisingly high percentage of nonviable embryos. In addition, fertilization rate was reduced only in summer, apparently due to an effect of heat stress on the oocyte.     

Sweetness and aroma perceptions in dairy desserts varying in sucrose and aroma levels and in textural agent

Sweetness–aroma interactions were investigated in model dairy desserts varying in sucrose concentration, aroma concentration and in textural characteristics using different textural agents (κ-, ι-, λ-carrageenans and an equal-mix of the three). Overall intensities of sweetness and aroma perceptions were evaluated by sensory analysis and apparent partition coefficients of aroma compounds were measured by static headspace—GC.Sweetness–aroma interaction was characterised by a non-reciprocal relationship. Concentration of aroma had no impact on sweetness intensity, whatever be the sucrose concentration or textural characteristics of desserts, whereas varying texture or sucrose concentration modified aroma intensity. However, effects on aroma assessment were effective only when aroma concentration was the highest. In this condition, use of λ-carrageenan or increasing sucrose concentration from 25 to 50 g kg⁻¹ enhanced aroma intensity, but no extra enhancement was observed when sucrose concentration was 100 g kg⁻¹. As the air–dessert partition coefficient remained constant, impact of textural characteristics and sweetness variation on aroma perception did not result from physico-chemical interaction.     

Aluminium and fluoride in hospital daily diets and in teas

The levels of aluminium and fluoride have been determined in hospital daily diets including breakfast, dinner and supper, as well as in black teas and herbal teas purchased from the local market. In tea, aluminium was determined directly in a sample solution by atomic absorption spectroscopy using nitrous oxide and an acetylene flame. For analysis of the hospital diet, samples containing lower levels of aluminium were analysed using a spectrophotometric method which measured aluminium in the form of a 8-hydroxyquinoline complex. Decomposition of the samples was achieved using a mixture of concentrated acids [nitric (HNO₃), perchloric (HClO₄) and sulphuric (H₂SO₄)] in platinum dishes. Fluoride was assayed by spectrophotometry using a microdiffusion procedure with a mixture of concentrated HClO₄ and silver sulphate, trace amounts of the released fluoride [as hydrogen fluoride (HF)] were trapped on the alkaline surface of a Petri dish and then determined in the form of an alizarin-fluoride complex. The mean level of aluminium found in hospital daily diets amounted to 21.3±12.3 mg and the mean level of fluoride was 1.38±1.12 mg per adult person. In the 16 samples of commercially available brands of black teas, the levels of aluminium and fluroide ranged from 445 to 1552 ppm (mean=897±264 ppm) and from 30 to 340 ppm (mean 141±85 ppm), respectively. In six herbal teas, the mean levels of aluminium and fluoride were lower, and amounted to 218.9±150.7 ppm and 6.0±6.9 ppm, respectively. This study has shown that concern about a high intake of aluminium and fluoride from these foods is unfounded.     

2018年深圳市售蔬菜和鸡蛋中氟虫腈及其代谢物的检测分析

目的 建立超高效液相色谱-串联质谱法同时测定蔬菜和鸡蛋中氟虫腈及其代谢物(氟甲腈、氟虫腈砜和氟虫腈亚砜), 并对深圳市售的蔬菜和鸡蛋中氟虫腈及其代谢物残留状况进行抽样检测。方法 采用QuEChERS前处理方法, 以C18色谱柱为分离柱, 以乙腈和10 mmol甲酸+6 mmol甲酸铵水溶液为流动相进行梯度洗脱, 用超高效液相色谱-串联质谱(ultra performance liquid chromatography-mass spectrometry/mass spectrometry, UPLC-MS/MS), 电喷雾电离(electrospray ionization, ESI), 多反应监测(multiple reaction monitoring, MRM)模式检测, 外标法同时定量测定氟虫腈及其代谢物。结果 方法的线性范围为0.1~2.0 μg/L, 线性相关系数均大于0.9994, 检出限0.0005 mg/kg, 定量限0.001 mg/kg; 蔬菜中3个水平的平均加标回收率88.0%~101.2%, 相对标准偏差(relative standard deviation, RSD)均小于8.5%; 鸡蛋中3个水平的平均加标回收率86.1%~104.8%, 相对标准偏差(RSD)均小于9.2%。结论 该方法具有操作简单、干扰少、快速、准确可靠等特点, 可适用于蔬菜鸡蛋中氟虫腈及其代谢物的检测。     

芝麻饼粕及其在烟草上应用研究现状

概述了芝麻饼粕的有效营养成分及其作为有机肥的加工方法,介绍了芝麻饼粕在烟草生产上的应用效果。并就进一步促进芝麻饼粕在烟草上的应用提出了建议,以期为烟叶生产过程中科学使用芝麻饼粕提供参考资料。     

Characterization of limestones and their effects in vitro and in vivo in dairy cattle

Capacities of limestones of differing particle size to neutralize acid in vitro and to modify pH and utilization of feedstuffs in vivo were compared. Acid neutralization during pH-stat titrations was faster for fine than for coarse limestone, and mixed microbial cultures were more resistant to pH change when they contained fine calcium carbonate. Diets containing 25:75 corn silage to concentrates and .95% calcium from either coarse or fine limestone were fed to rumen-fistulated heifers. Total ruminal volatile fatty acid concentrations were higher for the fine limestone treatment. Ruminal volumes, dry matter disappearance, and ruminal fluid pH and dilution rate did not differ between fine and coarse limestone treatments. Ruminal fluid volume, osmolality, ratios of acetate to propionate, and concentrations of total volatile fatty acids were unaffected in rumen-fistulated Holstein cows fed 60:40 corn silage to concentrates and either .5% calcium (control) or 1.0% calcium from either coarse or fine limestone. Ruminal pH increased .07 to .10 units with limestone supplementation. Ruminal fluid dilution and particulate turnover rates were slower for the coarse limestone than the control treatment. Differences between coarse and fine limestones in vitro were observed under some conditions in vivo, but they were not consistent.     

Flavour and vitamin stability in pasteurized milk in polyethylene-coated cartons and in polyethylene bottles

Commercially pasteurized, non-homogenized full cream milk in 2-pt white polyethylene (PE)-coated cartons overprinted with blue, and in 4-pt PE bottles was stored for 4 d in the dark or under white fluorescent light of 4000 1x, at a temperature of 7°C. The flavour of milks kept in the dark remained good, but exposure to light resulted in early off-flavour development: cartoned milk was disliked by a flavour panel after about 17.5 h exposure and milk in the PE bottles after 9 h. Vitamins A and B₂ were stable in the milk during 4 d storage in the dark in both bottles and cartons, and in cartons exposed to light. In the bottled milks, light-induced losses of these vitamins after 4 d were, respectively, 15% and 35%. but there was little or no loss before the development of light-induced flavour. Loss of total vitamin C by day 4 was about 50% in the dark, irrespective of container. In the cartons exposed to light, 66% of the vitamin C was lost, while virtually none remained in the exposed, bottled milk. There was also a markedly greater loss of vitamin C in the bottled milk than in the cartoned milk at the time the flavour became unacceptable. The dissolved O₂ concentration dropped considerably in the bottled milk exposed to light, but only marginally in the cartons. There were small increases in dissolved O₂ in the dark in both types of container.     

开封市畜禽沙门菌污染状况及血清学鉴定分析

了解开封市畜禽肉中沙门菌的污染状况及血清学分布,为沙门菌引起的食源性疾病的防控提供依据。方法 依据GB 4789.4—2010《中华人民共和国国家标准食品卫生微生物学检验方法》和2011年国家食源性疾病监测网监测方案,定期对开封市畜禽养殖场和屠宰场进行随机采样监测。结果 在691份样品中,沙门菌检出率为35.9%(248/691);分离出沙门菌253株,有17个血清型。结论 开封市生鸡肉和生猪肉不同程度受到沙门菌的污染,以生鸡肉污染最严重。应加强禽畜类养殖、屠宰加工等过程的卫生监管,减少食源性疾病的发生。     

Heavy metals in vegetables grown in The Netherlands and in domestic and imported fruits

The contents of cadmium, lead mercury, copper, manganese and zinc in 242 samples of 37 different species of domestic and imported fruits have been determined. Also contents of the same heavy metals, except mercury, have been determined in 205 samples of 7 species of domestic vegetables (lettuce, spinach, endive, beetroots, onions, celeriac and Swedish turnips). The median contents (in mg/kg fresh mass of the edible part) found for fruits are: Cd 0.002; Pb 0.017; Hg 0.002; Cu 0.61; Mn 0.52 and Zn 0.99. In the vegetables median levels have been found (mg/kg) of 0.009-0.073 for Cd, 0.01-0.03 for Pb, less than 0.2-0.3 for Cu, 0.69-1.41 for Mn and 0.95-5.5 for Zn. The contribution of fruits to the tolerable daily intakes of Cd, Pb and Hg is, for an average consumption pattern, less than 1%. On the other hand, the contribution to the recommended amounts of the essential elements Cu, Mn, and Zn is no more than 1%-3%. From the vegetables an average portion of spinach contains 19% and 2.6% of the tolerable daily amounts of Cd and Pb, respectively. For the other species of vegetables these figures are less than 5% for Cd (except for endive, 6.8%) and for lead less than 1%. Spinach contributes considerably to the need for Cu, Mn and Zn, in general more than 10% of the recommended daily amounts. The other species of vegetables contribute only from less than 1% to less than few percents.