窖泥中总酸、总酯和总醛测定方法的研究

窖泥是生产白酒的关键材料,窖泥的成分复杂,主要有醇类、酸类、醛类、酯类、酚类及芳香族化合物等。本研究建立了一种窖泥中总酸、总酯和总醛的快速连续测定方法,该方法所得3种物质的标准曲线线性关系良好,精密度试验相对标准偏差（RSD）值分别为1.81%、1.13%、0.887%,稳定性试验RSD值分别为1.35%、1.22%、0.96%,加标回收率平均值分别为98.10%、98.16%和98.69%。结果表明,该方法适合窖泥中总酸、总酯和总醛的测定,对白酒的窖泥发酵生产起到一定的指导意义。     

基于蒙特卡洛法的溶解性总固体测量不确定度评定

目的研究出一种基于蒙特卡洛法的溶解性总固体测量不确定度评定的方法。方法按照溶解性总固体实验过程,建立对应的数学模型。根据蒙特卡洛法分布传播和总结过程,得出蒙特卡洛法的评定结果。同时使用Guide 98-3:2008《测量不确定度表示指南》进行评定,得出对比结果。结果使用蒙特卡洛法所得结果为208.0 mg/L,扩展不确定度为5.2 mg/L。区间为197.82~218.18 mg/L。指南法评定结果为208.6 mg/L,扩展不确定度为5.6 mg/L,计算结果为(208.6±5.6)mg/L。结论蒙特卡洛法评定结果与测量不确定度表示指南法评定的数据相近,可以用于计算溶解性总固体的测量不确定度,为实验室工作人员提供了一种实用的测量不确定度评定方法。     

A cost and returns evaluation of alternative dairy products to determine capital investment and operational feasibility of a small-scale dairy processing facility

This study examines the economic feasibility of 50-and 500-cow dairy processing facilities for fluid milk, yogurt, and cheese. Net present value and internal rate of return calculations for projected costs and returns over a 10-yr period indicate that larger yogurt and cheese processing plants offer the most profitable prospects, whereas a smaller yogurt plant would break even. A smaller cheese plant would have insufficient returns to cover the cost of capital, and fluid milk processing at either scale is economically infeasible. Economic success in processing is greatly contingent upon individual business, financial management, and marketing skills.     

昆明市市售乳制品中总砷含量检测分析

目的通过对2013年昆明市市售乳制品中总砷含量进行分析,进而了解昆明市市售乳制品中总砷污染情况。方法按照GB/T 5009.11-2014《食品安全国家标准食品中总砷及无机砷含量测定》中所述的湿法消解-原子荧光光谱法进行检测分析,根据GB 2762-2012《食品安全国家标准食品中污染物限量》对乳制品中总砷含量标准进行评价。结果 2013年共抽检样品120份,其中巴氏消毒乳20份,灭菌乳36份,发酵乳64份。共有8份样品检出总砷,检出率6.7%;1份样品含量超标,超标率0.8%。其中巴氏消毒乳、灭菌乳、发酵乳的检出率分别为:0%、2.8%、10.9%,超标率分别为0%、0%、1.6%。结论 2013年昆明市市售乳制品中总砷含量检出率较低,砷的污染程度不严重,处于安全水平。     

乳与乳制品中总砷测定的不同前处理方法比较

目的比较不同前处理方法的处理效果,选择适合乳与乳制品中总砷测定的前处理方法。方法分别采用湿法消解、干法灰化、微波消解对乳与乳制品样品进行前处理,利用氢化物原子荧光法测定总砷含量。结果 3种前处理方式的检测结果均满足方法学要求,湿法消解、干法灰化和微波消解的回收率分别为81.7%～86.5%,90.0%～94.4%和90.8%～95.6%,精密度分别为8.84%～9.80%,3.22%～4.37%和3.18%～4.82%;检出限分别为0.0042、0.00068、0.0028mg/kg;微波消解法处理的质控样品结果更接近于标准值。结论微波消解法操作简便、准确性好,适合乳制品企业批量产品检测。     

Direct observation of bacterial exopolysaccharides in dairy products using confocal scanning laser microscopy

The objective of this work was to develop a methodology for direct visualization of bacterial exopolysaccharides (EPS) in fully hydrated dairy products. The new method involved staining EPS with wheat germ agglutinin labeled with Alexa fluor 488 or staining with concanavalin A 488. Samples were observed using confocal scanning laser microscopy. Distribution of EPS produced by Lactococcus lactis (CHCC 3367), a combination of Streptococcus thermophilus (CHCC 3534) and Lactobacillus delbrueckii ssp. bulgaricus (CHCC 769) and Lactobacillus delbrueckii ssp. bulgaricus RR in milk was compared in stirred and unstirred fermented milk. The EPS and proteins were observed as distinct entities, with EPS present in the protein network pores. EPS was observed in greater amounts in milk fermented by the ropy L. lactis culture than in milk fermented by the less ropy strain of S. thermophilus. Stirring the fermented milk caused aggregation of EPS into more extended structures. The more ropy the culture, the longer and larger the strands formed during stirring. The method was also applied to Feta cheese made with an EPS-producing strain of S. thermophilus. EPS was observed in the cheese as thick sheets filling pores in the protein network.     

Admittance measurements to assess the total solids and fat contents in liquid whole egg products

In the present research, a method based on admittance measurements able to assess total solids and fat contents (%) in nine different liquid whole egg products was set up. By means of a tetrapolar platinum cell connected to a signal conditioning circuit, an alternating current generator and a data acquisition system, the effect of 15 different combinations of frequencies of the oscillating field (10, 100, 500, 1000 and 5000 Hz) and input voltage levels (1, 1.5 and 2 V) on the estimation of the total solids and fat contents were analyzed. The influence of the temperature solution on the electrical measurements was also assessed. The best estimations were obtained at 1000 Hz and 1 V (R² = 0.998; SE = 0.14%) for the total solids content and at 5000 Hz and 1 V (R² = 0.995; SE = 0.19%) for the fat content. For both parameters, the measurements conducted at 10 Hz appeared affected by the polarization occurring at the electrodes-solution interface. The admittance of the liquid whole egg products linearly increased with the temperature, and a temperature coefficient θ at 20 °C of about 2.1 was calculated. These excellent results encourage an industrial application of the technique for a rapid and economic assessment of the total solids and fat contents in the liquid egg products.     

水产制品中总糖含量检测方法的研究

目的优化水产制品总糖含量测定的检测方法,为水产制品总糖含量检测标准的制定提供参考。方法通过苯酚-硫酸分光光度法测定水产制品中的总糖含量,设计L9(34)正交试验分析水解条件对总糖含量的影响。优化盐酸浓度、水解时间和水解温度条件,并通过测定鱿鱼丝、干鲍鱼和干贝等样品的总糖含量进行验证。结果水解条件影响水产制品总糖含量,优化后的水解条件是:盐酸浓度20%,温度70℃,水解时间0.5 h。干贝、鱿鱼丝和干鲍鱼3种样品的平均加标回收率为92.3%~117%。结论苯酚-硫酸法准确度和精密度高,可适用于水产制品中总糖含量的测定。     

乳品中肠球菌LAMP快速检测方法的建立及应用

应用环介导等温扩增技术(Loop-mediated isothermal amplification,LAMP),针对肠球菌16sRNA中高度保守的序列分析设计特异性引物,建立乳品中肠球菌特异性快速检测方法。结果表明,所设计的引物具有良好特异性,10株肠球菌均能扩增出特异性片段,而14株非肠球菌均未扩增出相应片段,无假阴性或假阳性情况出现。同时,该方法可在14 h内完成检测,且阳性LAMP反应所需目标菌DNA浓度仅为10 fg/μL。应用本方法对164份婴幼儿配方乳粉的检测结果显示,共在37个批次中检出肠球菌,检出率为22.6%,污染量在0.36~110 g-1(最近似值)间。该方法为肠球菌的快速检测提供了一种重要的技术手段。     

高效液相色谱法检测牛奶及其制品中的溶菌酶

目的建立一种测定牛奶及奶酪制品中低含量溶菌酶的高效液相色谱-荧光检测新方法。方法样品经p H 6.0的氯化钠溶液活化,再在低p H值条件下除蛋白后,采用反相色谱柱(PLRP-S 250 mm×4.6 mm,300?,5μm)用A水(0.1%的三氟乙酸(trifluoroacetic acid,TFA)),B乙腈(0.1%TFA)体系作为流动相进行梯度洗脱,使用荧光检测器在激发波长(λ_(ex))276 nm,发射波长(λ_(em))345 nm处检测。结果最优实验条件下,溶菌酶在2.0~30.0 mg/L浓度范围内线性良好,加标实验结果显示回收率和相对标准偏差(relative standard deviation,RSD)分别在92.3%~104.3%和0.81%~3.26%之间,对牛奶和奶酪制品的检出限分别为20和40 mg/kg。结论该方法操作简便,结果准确、可靠,可用于乳制品中溶菌酶含量测定。     

Effect of dietary dry matter concentration on the sorting behavior of lactating dairy cows fed a total mixed ration

The objective of this study was to determine whether addition of water to a high-moisture total mixed ration reduces feed sorting by dairy cattle. Twelve lactating Holstein cows, individually fed once per day, were tested on 2 diets in a crossover design with 21-d periods. Diets had the same dietary composition and differed only in dry matter content, which was reduced by the addition of water. Treatment diets were 1) dry (57.6% DM) and 2) wet (47.9% DM). Dry matter intake (DMI) and milk production were monitored for each animal for the last 7 d of both treatment periods. For the final 3 d of each period, milk samples were taken for composition analysis and fresh feed and orts were sampled for particle size analysis. The particle size separator had 3 screens (19, 8, and 1.18 mm) and a bottom pan, resulting in 4 fractions (long, medium, short, fine). Sorting was calculated as the actual intake of each particle size fraction expressed as a percentage of the predicted intake of that fraction. Contrary to the hypothesis, cows sorted the wet diet more extensively than the dry diet. Sorting of the dry diet was limited to a tendency to refuse short particles, whereas the wet diet was sorted against long particles and for short and fine particles. Water addition reduced DMI, neutral detergent fiber intake, and starch intake of cows on the wet diet. Increased sorting on the wet diet resulted in a tendency for decreased concentration of dietary neutral detergent fiber consumed and also resulted in increased starch concentration of the diet consumed. Milk production and components were unaffected by treatment. Our results suggest that water addition to high-moisture total mixed rations, containing primarily haylage and silage forage sources, may not be an effective method to reduce sorting. Furthermore, water addition may negatively affect DMI and encourage sorting, resulting in the consumption of a ration with different nutrient composition than intended.     

Invited review: Determination of large-scale individual dry matter intake phenotypes in dairy cattle

Feed efficiency has been widely studied in many areas of dairy science and is currently seeing renewed interest in the field of breeding and genetics. A critical part of determining how efficiently an animal utilizes feed is accurately measuring individual dry matter (DM) intake. Currently, multiple methods are used to measure feed intake or determine the DM content of that feed, resulting in different levels of accuracy of measurement. Furthermore, the scale at which data need to be collected for use in genetic analyses makes some methodologies impractical. This systematic review aims to provide an overview of the current methodologies used to measure both feed intake in ruminants and DM content of feedstuffs, current methods to predict individual DM intake, and applications of large-scale intake measurements. Overall, advances in milk spectral data analysis present a promising method of estimating individual DM intake on a herd scale with further validation of prediction models. Although measurements of individual feed intake rely on the same underlying principle, the methods selected are largely dictated by the costs of capital, labor, and necessary analyses. Finally, DM methodologies were synthesized into a comprehensive protocol for use in a variety of feedstuffs.     

Combining ability and heritability for vitamin C and total soluble solids in pepper (Capsicum annuum L.)

Twenty‐one F₁ hybrids and seven parental genotypes were used to assess combining ability and heritability for vitamin C and total soluble solids in pepper (Capsicum annuum L.). The mean squares for general (GCA) and specific (SCA) combining abilities were highly significant for the two traits, suggesting the importance of both additive and non‐additive gene effects. However, additive gene action was more important, as GCA estimates were much higher than SCA effects. Among the parental genotypes, ‘Mareko Shote’ and ‘PBC 142A’, and ‘PBC 142A’ were good general combiners for vitamin C and total soluble solids, respectively, and could be used to improve these traits in pepper breeding programmes for the accumulation of favourable genes. They also showed the highest per se performance (315.3 mg 100 g^?1 and 18.5 Brix, respectively) for the two quality traits. The narrow sense heritability estimate for vitamin C was relatively high (54.8%) indicating that the environment had a less pronounced effect on this trait. The heritability for total soluble solids was low (15%). Copyright © 2006 Society of Chemical Industry     

几种检测溶解性总固体方法的比较

目的通过比较几种常见的检测溶解性总固体的方法,寻求一种结果准、时间短的检测方法,以便提高检测溶解性总固体的效率。方法对蒸汽法(国标法)、100℃水浴法、烘箱法、电热板、电炉法等几种测定方法的检测结果和检测时间进行比较,并进行统计学计算分析。结果电热板法、电炉法的测定结果与国标方法测定结果相比较,超出国标偏差要求;100℃水浴法测定14份水样的结果与国标法无显著性差异。结论用100℃水浴法测定饮用水中溶解性总固体结果与国标一致,且用时比国标法缩短2 d,显著提高了检测效率,是值得推广的检测方法。     

Melt analysis of process cheese spread or product using a rapid visco analyzer

The objective of this study was to evaluate a rapid visco analyzer (RVA) method for measuring the melting characteristics of process cheese spread or product. The melt properties of 32 commercial process cheese spread and process cheese product samples from 4 manufacturers were analyzed with the RVA, tube melt test, texture profile analysis (TPA) hardness, and dynamic stress rheometry (DSR). For the RVA melt test, a 15-g disc of cheese was packed into the RVA canister and subjected to a heating, holding, and cooling profile during continuous mixing. During the test, the apparent viscosity was continuously measured and several data points (melt time, hot viscosity, time at 5000 cP during cooling, and solidification time) were collected from the viscosity vs. time curve. There was a high correlation (R2= 0.91) between the DSR melt temperature and the tube melt test. There was also a high correlation between the RVA melt time and the DSR melt temperature or the tube melt test (R2= 0.84 and 0.74, respectively). The RVA hot viscosity had a low correlation (R2< 0.44) with the DSR melt temperature and the tube melt test but had a high correlation (R2= 0.74) with DSR G' at 85 degrees C. The results of this study indicate that RVA melt analysis of process cheese spread/product is correlated with the results from other melt tests and is capable of measuring the melt properties quantified by other methods. The RVA melt test may also provide additional information on the melt characteristics of process cheese spread/product not measured in other tests.     

Evaluation of the possible use of potentially probiotic Lactobacillus strains in dairy products

In the study, the ability of two potentially probiotic strains Lactobacillus plantarum 14 and Lactobacillus fermentum 4a to milk fermentation and the possibility to use them in yogurt production were investigated. The strains did not acidify milk during 24 h and 72 h fermentation at 37C, but grew well and remained at the level of 10⁸ colony-forming units (CFU)/mL during 21 days of cold storage. Their application to yogurt production along with commercial starter culture consisted on L. delbrueckii ssp. bulgaricus and S. thermophilus allowed to obtain products with typical sensory properties, pH values and numbers of potentially probiotic bacteria at desired level 10⁷ CFU/mL.     

干红葡萄酒中总糖测定方法的改进

通过对干红葡萄酒中酒精、蛋白质、氨基酸等对总糖测定是否有影响,以及滴定时如何使滴定终点明显易判断进行研究。结果证明,测定干红葡萄酒中总糖时要先除酒精,酒中的蛋白质、氨基酸等对总糖的测定无影响,滴定时将水解液与葡萄糖标准溶液按1：2混合后进行滴定可使终点明显、易判断。     

Thermal conductivity as influenced by the temperature and apparent viscosity of dairy products

This study aimed to evaluate the rheological behavior and thermal conductivity of dairy products, composed of the same chemical components but with different formulations, as a function of temperature. Subsequently, thermal conductivity was related to the apparent viscosity of yogurt, fermented dairy beverage, and fermented milk. Thermal conductivity measures and rheological tests were performed at 5, 10, 15, 20, and 25°C using linear probe heating and an oscillatory rheometer with concentric cylinder geometry, respectively. The results were compared with those calculated using the parallel, series, and Maxwell-Eucken models as a function of temperature, and the discrepancies in the results are discussed. Linear equations were fitted to evaluate the influence of temperature on the thermal conductivity of the dairy products. The rheological behavior, specifically apparent viscosity versus shear rate, was influenced by temperature. Herschel-Bulkley, power law, and Newton's law models were used to fit the experimental data. The Herschel-Bulkley model best described the adjustments for yogurt, the power law model did so for fermented dairy beverages, and Newton's law model did so for fermented milk and was then used to determine the rheological parameters. Fermented milk showed a Newtonian trend, whereas yogurt and fermented dairy beverage were shear thinning. Apparent viscosity was correlated with temperature by the Arrhenius equation. The formulation influenced the effective thermal conductivity. The relationship between the 2 properties was established by fixing the temperature and expressing conductivity as a function of apparent viscosity. Thermal conductivity increased with viscosity and decreased with increasing temperature.