饲料中铜含量对猪血清激素动态变化的影响

将 6 0头平均体重为 (19.2 6± 1.2 0 )kg的生长猪 ,随机分成 6组。使用硫酸铜作为铜源 ,对照组铜添加水平为 0mg/kg;试验各组铜添加水平为 10 0 ,15 0 ,2 0 0 ,2 5 0和 30 0mg/kg。试验期为 80d ,测定生长性能及有关血清激素动态变化。试验结果表明 :铜添加量为 15 0～ 30 0mg/kg时 ,对 2 0～6 0kg生长猪具有明显的促生长作用 ,其中以 2 0 0 ,2 5 0mg/kg铜组最佳。同时 ,促生长剂量的铜还会影响机体的代谢激素 ,从而促进猪的生长。饲料中铜水平对血清相关激素动态变化的影响随铜添加水平的不同呈现明显的阶段性差异 ,其差异的显著性与铜的促生长效应是基本一致的。     

流动注射化学发光法测定尿液和血清中培氟沙星残留

建立尿液和血清中培氟沙星药物残留的分析方法。利用Tb3+能增强Ce(Ⅳ)-SO32--PEFX体系的发光强度,建立测定培氟沙星的新方法。体系的发光强度与培氟沙星质量浓度在2×10-9～6×10-7g/mL范围内呈良好的线形关系,方法检出限为8.8×10-10g/mL,对1×10-7g/mL 培氟沙星平行测定11次,相对标准偏差为3.1%。利用该法测定人尿样和鸭血清中培氟沙星,并进行回收率测定,回收率在98.5%～102.5%,结果令人满意。     

大豆黄酮对产蛋后期番鸭生产性能及血清激素水平的影响

基础日粮中分别添加3 mg/kg(试验组Ⅰ)和6 mg/kg(试验组Ⅱ)大豆黄酮饲喂产蛋后期番鸭.结果显示:①与对照组相比,试验组Ⅰ和Ⅱ的产蛋率在试验处理第2周分别提高8.19%(P＜0.05)和17.49%(P＜0.01),第3周分别提高7.46%(P＜0.05)和8.04%(P＜0.05),而第4周和整个试验期内试验组Ⅱ产蛋率分别提高12.98%(P＜0.05)和11.74%(P＜0.01),呈现一定的剂量和时间依赖效应;②与对照组相比,两组的平均蛋重分别提高2.48%(P＜0.01)、1.05%,受精率分别降低3.37%、5.37%(P＜0.05),受精蛋孵化率分别降低0.74%、4.70%(P＜0.05);③试验组Ⅰ、Ⅱ血清T3水平分别提高16.13%(P＜0.05)和25%(P＜0.01),孕酮水平分别提高53.62%(P＞0.05)和69.57%(P＜0.01),而17β-雌二醇、T4均无显著变化.     

Kinetic Parameter Estimation in Conduction Heating Foods Subjected to Dynamic Thermal Treatments

The purpose of this work was to develop a means for determining product and process specific thermal kinetic parameters of constituents in foods that do not heat uniformly. The concept of the method of Paired Equivalent Isothermal Exposures (PEIE) was developed for such products. The ability of the PEIE to define Arrhenius parameters from simulated retort experiments was demonstrated. The PEIE was applied to survival data from retort experiments of canned pea puree inoculated with Bacillus stearothermophilus spores (NCA 1518). Mean activation energy and reaction rate constant (at 121.1°C) of the spores in retort processed canned pea puree were E_a= 250 (± 15) kJ/mol and k_121.1°C= 0.26 (0.23 < k_121.1°C <0.30) min^?1, respectively.     

利用悬浮细胞培养方法提高荞麦中总黄酮含量的研究

利用植物组织培养方法对荞麦不同组织进行愈伤诱导实验,进一步建立荞麦悬浮培养体系,并对其黄酮含量进行比较分析。结果表明,利用荞麦叶柄部分获得的荞麦愈伤组织总黄酮含量较高,达到58.80mg/g,分别是荞麦叶柄总黄酮含量和荞麦茎段总黄酮含量的3.1 倍和3.7 倍,而荞麦细胞悬浮培养物中总黄酮含量可达90.6mg/g,是荞麦叶柄愈伤组织含量的1.54 倍。     

Physicochemical Changes in Prawns (Machrobrachium rosenbergii) Subjected to Multiple Freeze-Thaw Cycles

Fresh prawns were subjected to five freeze-thaw cycles (–29°C ? 22°C) and associated physicochemical changes in muscle were determined. Shear force to break prawn tails was dependent on prawn size, more on weight (r = 0.75–0.81) than on diameter (r = 0.56–0.66). No change (P > 0.05) in shear force was observed in raw prawns after five freeze-thaw cycles. However, shear force of cooked prawns decreased after three freeze-thaw cycles which coincided with accelerated lipid oxidation in raw prawns. Electrophoretic analysis revealed gradual decreases in myosin, actin, and most other myofibrillar proteins with each successive freeze-thaw cycle. Enthalpy of protein denaturation decreased from 16.6 J/g (fresh) to 13.5 J/g after one freeze-thaw cycle with minor changes thereafter.     

Antibacterial Effects and Cell Morphological Changes in Sfaphylococcus aureus Subjected to Low Ethanol Concentrations

Ethanol in low concentrations (5–10% weight) affected aerobic growth (at 37°C) of two strains of Stuphylococcus aureus. Growth inhibition in laboratory media was observed with ethanol about 6–7% weight water activities (a_w) of ～0.97. This suggested that the ethanol antibacterial effect was not only from its a_w lowering ability. Electron microscopy observations showed intense morphological modifications in cells in broth with 5% to 6.5% ethanol, and clearly indicated that cell wall changes of S. aureus was partly responsible for the antibacterial action of ethanol.     

Surface Hydrophobicity and Protein Cross-Linking in Rice Subjected to Varying Drying and Tempering Conditions

ABSTRACT: Rough rice was subjected to 25 °C or 60 °C drying with or without 3 h of tempering at 16.9% relative humidity to obtain rice flours. Proteins extracted from these flours were evaluated for surface hydrophobicity, molecular size, and protein cross-linking via lysine-carbohydrate interaction and formation of S-S bond. Drying at 60 °C significantly increased glutelin surface hydrophobicity ( P < 0.05), but did not affect moisture, protein, glutelin components and their molecular sizes, and cystine and available lysine contents in comparison with drying at 25 °C. Therefore, drying at 60 °C is considered ineffective to cause protein cross-linking and glutelin changes in molecular size.     

Listeria monocytogenes Inactivation in Turkey Rolls and Battered Chicken Nuggets Subjected to Simulated Commercial Cooking

Cured and uncured turkey rolls inoculted with 10⁷Listeria monocytogenes CFU/g were vacuum packaged and cooked to internal temperatures of 68°C and 74°C, respectively, in a steam-injected chamber. Samples were stored up to 15 wk at 4°C. Battered chicken nuggets were also inoculated internally with about 10⁷L. monocytogenes CFU/ g. Nuggets enclosed in bags were cooked under moist heating conditions in a convection oven to an internal temperature of 71°C. Nuggets were flushed with 30% CO₂, 70% N₂ atmosphere and sealed. Chicken nuggets were stored at 4°C up to 30 days. No Listeria monocytogenes were recovered from the cooked products suggesting that similar commercial processes are adequate to reduce populations of L. monocytogenes below detection limits.     

不同处理的精制玉米麸皮单糖组分及阿魏酸含量分析

对去除淀粉和蛋白质的精制玉米麸皮进行酸碱处理,得到酸解产物和碱解产物,用高效液相色谱对精制玉米麸皮、酸解产物及碱解产物的单糖组成及阿魏酸进行分析。结果显示:酸解产物含有44.5%的木糖、20.8%的阿拉伯糖和4.57%的阿魏酸,推测其主要成分是阿魏酸阿拉伯木聚糖;碱解产物含有50.3%的木糖、24.5%的阿拉伯糖,阿魏酸基本未检出,推测其主要成分是阿拉伯木聚糖;玉米麸皮含有3.5%的阿魏酸。     

不同贮藏条件及加工处理后大麦中脱氧雪腐镰刀菌烯醇膳食风险评估

为探究不同贮藏条件及不同加工处理方式的大麦中脱氧雪腐镰刀菌烯醇（deoxynivalenol,DON）膳食摄入风险,在不同温度（5、15、25、35℃）、相对湿度（55%、65%、75%、85%）条件下贮藏大麦180、270、360 d,以蒸制、煮制、发酵工艺进行加工后,通过酶联免疫法检测其DON含量,以点评估与概率评估法探究慢性与急性膳食DON摄入风险。结果表明,初始大麦中DON的每日估计摄入量为0.000 30～0.001 30 mg/kg、慢性风险评价指数为0.30～1.31,经过360 d贮藏后慢性风险评价指数最高增加0.63,对于食用人群存在32.7%的暴露风险,而国家估计短期摄入量为0.002 6～0.005 5 mg/kg,急性风险评价指数为0.33～0.69,不存在急性暴露风险。经过加工处理后,慢性风险评价指数由0.60～2.60降为0.17～2.34,急性风险评价指数最高可降低0.64。长期贮藏后的大麦中DON暴露量较高,存在一定的健康风险,而经加工处理后可有效降低风险,且儿童暴露风险大于成人,需重点关注。     

关于牛乳中激素等微量生理活性物质的来源及安全控制讨论

2010年8月,国内各大媒体相继报道了乳品激素事件,卫生部最终的解释为:个别婴儿性发育异常现象,与食用奶粉没有直接的关联.然而,有关食品中雌激素的存在形式、含量、对人体发育的影响等已引起大众的广泛关注.     

不同清洗方式下克氏原螯虾肉细菌群落及理化性质的变化

该研究探讨了克氏原螯虾的三种清洗预处理方式（清洗剂清洗,CA;超声波清洗,UL;清洗剂结合超声清洗,CA+UL;对照组,CK）对克氏原螯虾虾肉的细菌群落以及理化性质的影响。测定了清洗前后小龙虾虾肉菌落总数、假单胞菌、霉菌酵母、嗜温菌、嗜冷菌、pH、质构特性和风味物质的变化。结果表明,CA+UL处理组减菌效果最好,清洗后菌落总数减少1.12 lg CFU/g,对霉菌酵母,产硫化菌,嗜冷菌也有较好的抑制效果,分别减少了0.66、0.9、0.82 lg CFU/g。而CA组与UL组对于霉菌、嗜温菌等细菌减少的效果不太明显,且清洗后虾肉pH有所上升;而CA+UL组pH变化不大;经过清洗后的虾肉品质整体有略微下降。不同清洗方式对挥发性物质也有较大的影响,产生了N-甲基异丙基胺等不良气味风味物质。因此,结合虾肉细菌群落结果与理化性质来看,超声波与清洗剂结合清洗的效果更优。     

超声辅助浸渍冷冻对冻藏期间猪肉水饺肉馅水分分布和品质特性的影响

本实验采用不同超声功率研究超声辅助浸渍冷冻(ultrasonic-assisted immersion freezing,UIF)对猪肉水饺肉馅在冻藏期间肉馅水分分布和品质特性的影响.结果表明,与其他组相比,功率为90 W的UIF(UIF-90)样品持水性最高,蒸煮损失最少,破损强度在贮藏后期最大(P<0.05),说明...     

牛乳中反式脂肪酸在不同热处理条件下的含量变化及热杀菌工艺评价

目的：探讨牛乳中反式脂肪酸(TFA)在不同热处理条件下的变化规律,为工艺参数确立提供依据。方法：采用罗兹-哥特里法提取乳中脂肪,经甲酯化反应后进行气相色谱分析,对牛乳中的TFA含量进行分析比较。结果：在85℃条件下,随着加热时间的延长,牛乳中TFA含量呈显著上升趋势(P＜0.05);相同时间内在超高温(T＞133℃)条件下,提高灭菌温度,牛乳中TFA含量变化不大(P＞0.05);延长灭菌时间,TFA含量明显增加(P＜0.05)。结论：以减少TFA生成量为主要依据确立的巴氏杀菌工艺参数是：85℃、15s;UHT工艺参数为(137±2)℃、4s。     

High‐Throughput Sequencing of Viable Microbial Communities in Raw Pork Subjected to a Fast Cooling Process

This study aimed to investigate the effect of the fast cooling process on the microbiological community in chilled fresh pork during storage. We established a culture‐independent method to study viable microbes in raw pork. Tray‐packaged fresh pork and chilled fresh pork were completely spoiled after 18 and 49 d in aseptic bags at 4 °C, respectively. 16S/18S ribosomal RNAs were reverse transcribed to cDNA to characterize the activity of viable bacteria/fungi in the 2 types of pork. Both cDNA and total DNA were analyzed by high‐throughput sequencing, which revealed that viable Bacteroides sp. were the most active genus in rotten pork, although viable Myroides sp. and Pseudomonas sp. were also active. Moreover, viable fungi were only detected in chilled fresh pork. The sequencing results revealed that the fast cooling process could suppress the growth of microbes present initially in the raw meat to extend its shelf life. Our results also suggested that fungi associated with pork spoilage could not grow well in aseptic tray‐packaged conditions.     

高压均质处理次数对肌原纤维蛋白水溶液结构及理化特性的影响

以鸡肉中的肌原纤维蛋白（myofibrillar proteins,MP）为对象,研究在103 MPa压力条件下不同高压均质（high pressure homogenization,HPH）处理次数（1～6 次）对MP水溶液结构以及理化特性的影响。结果表明：HPH可以显著提高MP在水中的溶解性（P＜0.05）。随着HPH处理次数的增加,MP在水溶液中的粒径先减小后变大;表观黏度减小,流动能力增强;表面疏水性和活性巯基含量先增加后减少;圆二色光谱结果显示不同HPH处理次数对MP水溶液的二级结构构象的影响不同;过多的HPH处理次数会导致MP水溶液中蛋白质聚集,从而影响其溶解性和稳定性;经过4 次HPH处理的MP水溶液具有较好的溶解性和稳定性。说明通过选择适当次数的HPH处理可以实现对MP在水中溶解性的调控,为其在食品加工中的应用提供新思路。