Comparison of different methods to quantify fat classes in bakery products

The definition of fat differs in different countries; thus whether fat is listed on food labels depends on the country. Some countries list crude fat content in the ‘Fat’ section on the food label, whereas other countries list total fat. In this study, three methods were used for determining fat classes and content in bakery products: the Folch method, the automated Soxhlet method, and the AOAC 996.06 method. The results using these methods were compared. Fat (crude) extracted by the Folch and Soxhlet methods was gravimetrically determined and assessed by fat class using capillary gas chromatography (GC). In most samples, fat (total) content determined by the AOAC 996.06 method was lower than the fat (crude) content determined by the Folch or automated Soxhlet methods. Furthermore, monounsaturated fat or saturated fat content determined by the AOAC 996.06 method was lowest. Almost no difference was observed between fat (crude) content determined by the Folch method and that determined by the automated Soxhlet method for nearly all samples. In three samples (wheat biscuits, butter cookies-1, and chocolate chip cookies), monounsaturated fat, saturated fat, and trans fat content obtained by the automated Soxhlet method was higher than that obtained by the Folch method. The polyunsaturated fat content obtained by the automated Soxhlet method was not higher than that obtained by the Folch method in any sample.     

Assessing the performance of methods to detect and quantify African dust in airborne particulates

African dust (AD) contributions to particulate matter (PM) levels may be reported by Member States to the European Commission during justification of exceedances of the daily limit value (DLV). However, the detection and subsequent quantification of the AD contribution to PM levels is complex, and only two measurement-based methods are available in the literature: the Spanish-Portuguese reference method (SPR), and the Tel Aviv University method (TAU). In the present study, both methods were assessed. The SPR method was more conservative in the detection of episodes (71 days identified as AD by SPR, vs 81 by TAU), as it is less affected by interferences with local dust sources. The mean annual contribution of AD was lower with the TAU method than with SPR (2.7 vs 3.5 ± 1.5 μg/m(3)). The SPR and TAU AD time series were correlated with daily aluminum levels (a known tracer of AD), as well as with an AD source identified by the Positive Matrix Factorization (PMF) receptor model. Higher r(2) values were obtained with the SPR method than with TAU in both cases (r(2) = 0.72 vs 0.56, y = 0.05x vs y = 0.06x with aluminum levels; r(2)=0.79 vs 0.43, y = 0.8x vs y = 0.4x with the PMF source). We conclude that the SPR method is more adequate from an EU policy perspective (justification of DLV exceedances) due to the fact that it is more conservative than the TAU method. Based on our results, the TAU method requires adaptation of the thresholds in the algorithm to refine detection of low-impact episodes and avoid misclassification of local events as AD.     

Development of real-time PCR methods to quantify patulin-producing molds in food products

Patulin is a mycotoxin produced by different Penicillium and Aspergillus strains isolated from food products. To improve food safety, the presence of patulin-producing molds in foods should be quantified. In the present work, two real-time (RTi) PCR protocols based on SYBR Green and TaqMan were developed. Thirty four patulin producers and 28 non-producers strains belonging to different species usually reported in food products were used. The patulin production was tested by mycellar electrokinetic capillary electrophoresis (MECE) and high-pressure liquid chromatography-mass spectrometry (HPLC-MS). A primer pair F-idhtrb/R-idhtrb and the probe IDHprobe were designed from the isoepoxydon dehydrogenase (idh) gene, involved in patulin biosynthesis. The functionality of the developed method was demonstrated by the high linear relationship of the standard curves constructed with the idh gene copy number and Ct values for the different patulin producers tested. The ability to quantify patulin producers of the developed SYBR Green and TaqMan assays in artificially inoculated food samples was successful, with a minimum threshold of 10 conidia g⁻¹ per reaction. The developed methods quantified with high efficiency fungal load in foods. These RTi-PCR protocols, are proposed to be used to quantify patulin-producing molds in food products and to prevent patulin from entering the food chain.     

HPLC和UV对比测定栀子和西红花中西红花苷的含量

目的：对比考察HPLC和UV法测定西红花苷-1的线性关系及方法的精密度、稳定性、重现性和回收率。方法：采用HPLC和UV测定栀子和西红花药材西红花苷含量。结果：栀子药材紫外测定结果与高效液相色谱测定结果接近,而西红花药材高效液相色谱测定结果显著高于紫外结果。结论：两种方法都具有较好的线性关系,精密度、稳定性、重现性和回收率都符合要求（RSD〈3％）。     

Improved field methods to quantify methane oxidation in landfill cover materials using stable carbon isotopes

Stable carbon isotopes provide a robust approach toward quantification of methanotrophic activity in landfill covers. The field method often applied to date has compared the delta13C of emitted to anaerobic zone CH4. Recent laboratory mass balance studies have indicated thatthis approach tends to underestimate CH4 oxidation. Therefore, we examined the CH4-delta13C at various soil depths in field settings and compared these values to emitted CH4. At 5-10 cm depth, we observed the most enrichment in CH4-delta13C (-46.0 to -32.1 per thousand). Emitted CH4-delta13C was more negative, ranging from -56.5 to -43.0 per thousand. The decrease in CH4-delta13C values from the shallow subsurface to the surface is the result of processes that result in selective emission of 12CH4 and selective retention of 13CH4 within the soil. Seasonal percent oxidation was calculated at seven sites representing four cover materials. Probe samples averaged greater (21 +/- 2%, p < 0.001, n = 7) oxidation than emitted CH4 data. We argue that calculations of fraction oxidized based on soil derived CH4 should yield upper limit values. When considered with emitted CH4 values, this combined approach will more realistically bracket the actual oxidation value. Following this guideline, we found the percent oxidation to be 23 +/- 3% and 38 +/- 16% for four soil and three compost covers, respectively.     

动物肌肉组织基因组DNA两种提取方法的比较

以猪、牛、羊、鸡等动物新鲜冷冻样品为实验材料,采用SDS法和异硫氰酸胍法提取动物肌肉组织基因组DNA,对提取的DNA进行光密度、琼脂糖凝胶电泳和PCR检测,比较了这两种方法的提取效果。结果表明:采用SDS法和异硫氰酸胍法均能从动物肌肉组织提取到完整的基因组DNA,均可满足PCR等后继分子生物学实验的要求。但是异硫氰酸胍法提取的基因组在纯度和浓度及稳定性方面优于SDS法,且操作简单,耗时短,更利于快速检测。      

Comparison of two methods to assess the intake of flavouring substances

It is important to assess the intake of flavouring substances in order to be confident that exposure to the substance from its intended use presents no significant risk. A number of methods exist to estimate intake of food ingredients. Two such methods, one using a detailed dietary analysis based on food consumption and composition and one using 10 times the annual volume of use on a per capita basis (per capita x 10), were compared for their precision and practicality in assessing the intake of 10 flavouring substances. The detailed dietary analysis method of determining exposure resulted in good estimates of the distribution of intakes across the population, as well as patterns of intake of individuals. This method is both expensive and labour intensive. The per capita x 10 method yields results that, compared with those obtained by detailed dietary analysis, tend consistently to overstate exposure. Thus, this method is a conservative and practical approach to assessing exposure to flavouring substances and other food ingredients.     

Comparison of treatment records and inventory of empty drug containers to quantify antimicrobial usage in dairy herds

Assessment of antimicrobial use (AMU) is vital for interpreting the origin of changes in antimicrobial resistance (AMR). The objectives of the present study were to estimate the association between AMU determined using on-farm treatment records (TR) and inventory of empty drug containers (INV). Herds were selected to represent Canadian dairy farms. Producers were asked to record animal health events and treatments on a standard General Health Event form. For inventory data, 40-L receptacles were placed at various locations considered convenient to deposit all empty drug containers. Antimicrobial defined-daily dosages (ADD) were calculated for 51 Canadian herds using the 2 methods. Estimation of AMU was 31,840 ADD using the INV and 14,487 ADD using the TR, indicating that for every TR entry, 2.20 times more treatments were observed using the INV. Mastitis, reproductive conditions, and dry cow therapy were the most frequent reasons for antimicrobial therapy when assessing TR. For all antimicrobials evaluated, mean ADD was higher using the INV versus TR. Regardless, a strong positive correlation (0.80) was observed between the 2 methods, indicating that herds with increased number of ADD recorded using the INV also had increased number of ADD recorded using TR. Furthermore, a positive association was observed for the 6 most commonly used antimicrobials. In comparison to methods used in surveillance programs on AMU in livestock that assume a constant use in all herds (i.e., sales data), INV provided a herd-level specific quantity of AMU positively correlated with AMU recorded at the animal level in general. The INV was easy to implement and provided a measure of total AMU in the herd. Availability of such information would be valuable for interpreting changes in AMR at the herd level and enabling evaluation of interventions for decreasing AMR.     

Comparison of gas chromotography, spectrophotometry and near infrared spectroscopy to quantify prussic acid potential in forages

BACKGROUND: Sorghum [Sorghum bicolor (L.) Moench] has been shown to contain the cyanogenic glycoside dhurrin, which is responsible for the disorder known as prussic acid poisoning in livestock. The current standard method for estimating hydrogen cyanide (HCN) uses spectrophotometry to measure the aglycone, p‐hydroxybenzaldehyde (p‐HB), after hydrolysis. Errors may occur due to the inability of this method to solely estimate the absorbance of p‐HB at a given wavelength. The objective of this study was to compare the use of gas chromatography (GC) and near infrared spectroscopy (NIRS) methods, along with a spectrophotometry method to estimate the potential for prussic acid (HCNp) of sorghum and sudangrasses over three stages maturities. RESULTS: It was shown that the GC produced higher HCNp estimates than the spectrophotometer for the grain sorghums, but lower concentrations for the sudangrass. Based on what is known about the analytical process of each method, the GC data is likely closer to the true HCNp concentrations of the forages. Both the GC and spectrophotometry methods yielded robust equations with the NIRS method; however, using GC as the calibration method resulted in more accurate and repeatable estimates. CONCLUSION: The HCNp values obtained from using the GC quantification method are believed to be closer to the actual values of the forage, and that use of this method will provide a more accurate and easily automated means of quantifying prussic acid. Copyright © 2011 Society of Chemical Industry     

纺织品耐摩擦牢度测试方法比较

分析GB/T 3920—2008与AATCC 8-2005耐摩擦色牢度两种测试方法标准的异同,发现影响耐湿摩擦色牢度测定结果的主要因素是被测湿摩擦布的含水量和摩擦布的规格,用这两种测试方法所测得的耐摩擦色牢度值之间存在一定的差异,其中AATCC 8-2005标准测定的耐湿摩擦色牢度比GB/T 3920—2008低。     

Comparison of analytical methods

A technique for comparing two analytical methods is presented in this paper. Frequently a new method, generally simpler, faster or less expensive, is compared with a reference method. The deterministic relationships between two methods, subject only to random errors, is first discussed. However, the relationship between two methods may be stochastic (non-deterministic); this problem is also discussed here. The concept of the sensitivity ratio of Mandel furnishes an appropriate basis of comparison. The use of the correlation coefficient may be completely erroneous for this purpose. Tests are presented for the significance of constants in the regression equation. Dangers in the use of stochastic relationships are strongly emphasized because of the unstable estimation of constants in the regression formula. Some systematizing principles not generally known by food scientists are presented here.     

Comparison of alternative neutral detergent fiber methods to the AOAC definitive method

Neutral detergent fiber (NDF) is the most commonly reported metric for fiber in dairy cattle nutrition. An empirical method, NDF is defined by the procedure used to measure it. The current definitive method for NDF treated with amylase (aNDF) is AOAC Official Method 2002.04 performed on dried samples ground through the 1-mm screen of a cutting mill with refluxing and then filtration through Gooch crucibles without (AOAC−; reference method) or with (AOAC+) a glass fiber filter filtration aid. Other methods in use include grinding materials through the 1-mm screen of an abrasion mill, using filtration through a Buchner funnel with a glass fiber filter (Buch), and use of the ANKOM system (ANKOM Technology, Macedon, NY) that simultaneously extracts and filters samples through filter bags with larger (F57) or smaller (F58) particle size retentions. Our objective was to compare the AOAC and alternative methods using samples ground through the 1-mm screens of cutting or abrasion mills. Materials analyzed were 2 alfalfa silages, 2 corn silages, dry ground and high-moisture corn grains, mixed grass hay, ryegrass silage, soybean hulls, calf starter, and sugar beet pulp. Samples were run in duplicate in replicate analytical runs performed on different days by experienced technicians. Compared with cutting mill–ground samples, the aNDF% of dry matter results from abrasion mill–ground samples were or tended to be lower for 8 of 11 samples. Method affected aNDF% results for all materials, with method × grind interactions for 6 of 11 samples. For ash-free aNDF% assessed with cutting mill–ground materials, a priori selected contrasts showed that the number of materials for which methods differed or tended to differ from the AOAC methods were 4 (Buch), 8 (F57), and 3 (F58); and 3 for AOAC– versus AOAC+. However, statistically different does not necessarily mean substantially different. For a given feed and grind, a positive value for the absolute difference between the AOAC– mean and an alternative method mean minus 2 times the standard deviation of AOAC− suggests that values for the alternative method fall outside of the range of results likely to be observed for the reference method. The number of observed positive values for materials processed with cutting and abrasion mills, respectively, were 0 and 2 (AOAC+); 2 and 2 (Buch); 8 and 10 (F57); 4 and 7 (F58); and 0 and 4 (AOAC−). With the materials tested, methods in order of agreement with the reference method were Buch, F58, and F57, which often gave lower values. The AOAC+ gave results similar to AOAC−, substantiating it as an allowed modification of AOAC−. Best agreement between the reference method and variant NDF methods was achieved with the 1-mm screen cutting mill grind. The 1-mm abrasion mill grind produced more aNDF% results that were lower than the reference method but with fewer differences when filter particle retention size was smaller. The use of filters that retain finer particles could be explored to improve comparability of variant NDF methods and grinds. Further evaluation with an expanded set of materials is warranted.     

鱼体新鲜度近红外光谱检测方法的比较研究

目的 建立针对淡水鱼整鱼鱼体新鲜度的快速无损检测方法. 方法 通过比较不同的光谱与相应挥发性盐基氮(TVB-N)值的建模结果, 以及对比分析竞争性自适应重加权算法(CARS)、遗传算法(GA)及连续投影算法(SPA)三种特征波长选择方法对模型的优化结果, 对鱼鳞及光谱采集部位等影响因素进行研究。结果 鱼体有鳞时的尾部为最佳新鲜度检测部位。CARS法较优且鱼体新鲜度检测的最优波段为800~1100 nm, 采用CARS特征波长选择方法选择出23个波长变量重新建立PLS模型, 模型预测集相关系数RP=0.957, 预测均方根误差RMSEP=0.589 mg/100 g。利用CARS方法选择的23个波长变量对淡水鱼进行新鲜度评价, 准确率达96.67%。结论 该方法为淡水鱼整鱼新鲜度快速无损检测提供了一种有效的方法。     

Comparison of methods to monitor liking of food during consumption

The measure of the liking of a product remains mainly accomplished through a single integrated response. Whether liking exhibits dynamic changes during the consumption of a food remains largely unexplored. Besides, studying the temporal aspects of perceptions during eating is a growing research topic in sensory science. Different tools are available to measure the time course of one or more perceptions during food consumption, such as time intensity or temporal dominance of sensations. The studies using these tools have shown that panellists can provide information on the temporality of their perceptions and monitor their perceptions from onset through extinction. The aim of our study was to adapt the latter approach to investigate the temporal aspects of hedonic assessment. As such, we proposed, tested and compared two methods to measure the liking throughout the consumption of a food. Forty-nine consumers participated in the tasting of three different cereals. One method consisted of eliciting any liking change during consumption, whereas the other method consisted of scoring liking at four predefined time-points during consumption. We also proposed a new method to analyse the data and graphically represent the dynamics of liking. At a panel level, the two methods showed similar dynamics of liking for two of the three products. However, the changes of liking during consumption were quite low partly due to a poor consensus among subjects. Yet, the individual responses showed many different patterns of dynamic liking. K-means analyses resulted in a two-cluster partition for each method. Although not similar, the two partitions showed large overlap. Finally, correlation coefficients calculated per subject between overall liking scores and dynamic liking data suggested the importance of the beginning of the consumption event in the overall liking (i.e., the time averaged response).     

Using chromium stable isotope ratios to quantify Cr(VI) reduction: lack of sorption effects

Chromium stable isotope values can be effectively used to monitor reduction of Cr(VI) in natural waters. We investigate effects of sorption during transport of Cr(VI) which may also shift Cr isotopes values, complicating efforts to quantify reduction. This study shows that Cr stable isotope fractionation caused by sorption is negligible. Equilibrium fractionation of Cr stable isotopes between dissolved Cr(VI) and Cr(VI) adsorbed onto gamma-Al2O3 and goethite is less than 0.04 per thousand (53Cr/52Cr) under environmentally relevant pH conditions. Batch experiments at pH 4.0 and pH 6.0 were conducted in series to sequentially magnify small isotope fractionations. A simple transport model suggests that adsorption may cause amplification of a small isotope fractionation along extreme fringes of a plume, leading to shifts in 53Cr/52Cr values. We therefore suggest that isotope values at extreme fringes of Cr plumes be critically evaluated for sorption effects. A kinetic effect was observed in experiments with goethite at pH 4 where apparently lighter isotopes diffuse into goethite clumps at a faster rate before eventually reaching equilibrium. This observed kinetic effect may be important in a natural system that has not attained equilibrium and is in need of further study. Cr isotope fractionation caused by speciation of Cr(VI) between HCrO4- and CrO4(2-) was also examined, and we conclude that it is not measurable. In the absence of isotope fractionation caused by equilibrium speciation and sorption, most of the variation in delta53Cr values may be attributed to reduction, and reliable estimates of Cr reduction can be made.     

比较3种不同前处理方法结合高分辨质谱测定姜中农药残留的效果

利用超高效液相色谱-四极杆/静电场轨道阱高分辨质谱对比研究了三种不同前处理方法：未净化法、QuEChERS前处理法、氨基柱固相萃取法（SPE）在姜中农药残留检测的效果。分别从基质效应、净化效果、回收率和定量限等方面进行考察。通过分析发现：方法不同其优缺点不同。未净化法、QuEChERS法和氨基柱固相萃取法在姜中表现为无基质效应的农药占比分别为0%,4%,21.6%。氨基柱固相萃取法（SPE）具有较好的净化效果,基质效应小,但较繁琐费时,且一部分农药回收率低于70%。未净化法和QuEChERS方法简单高效,适用于大批量样品进行检测,同时能保证大多数农药回收率在70%~120%之间。未净化法的净化效果差,QuEChERS方法的基质效应较氨基柱固相萃取法强,但定量限均能满足测定要求。在检测分析中,可根据不同需要选择前处理方法。     

Comparison of different methods to determine the spreadability and firmness of processed cheese

Summary Current texture-measuring instruments and a recently developed measuring method (two-dimensional measuring of the force necessary to spread a sample) were compared in measuring the spreadability of processed cheese. How far subjective assessment by a qualified panel correlates with the instrumental results in determining spreadability and firmness was also investigated. Samples of processed cheese with various consistencies were measured by an Universal testing machine, a buttermeasuring instrument (DIN 10331), a rotational-type rheometer (oscillation mode) and a two-dimensional force measuring instrument. The evaluation of the results shows that an oscillating rheometer is most suitable to measure the spreadability of processed cheese; the correlation coefficient (r) between the dynamic Weissenberg number, calculated from parameters of the rheometer, and the subjective judgement by the panel wasr=0.91. For the determination of firmness the two-dimensional force measuring instrument is most suitable. The correlation coefficient between the parameter tangential energy (S _t) and the sensorially evaluated firmness wasr=0.95.

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Vergleich verschiedener Bestimmungsmethoden für die Streichfähigkeit und Festigkeit von Schmelzkäse

Zusammenfassung Verschiedene gebräuchliche Meßinstrumente und ein neu entwickeltes Gerät zur zweidimensionalen Messung der Kräfte, die zum Ausstreichen einer Probe erforderlich sind, wurden vergleichend zur Charakterisierung der Streichfähigkeit von Schmelzkäse erprobt. Dabei wurde auch geprüft, inwieweit die subjektiven Beurteilungen eines qualifizierten Prüferpanels mit den Meßwerten für Streichfähigkeit und Festigkeit korrelierten. Gemessen wurde mit einer Universalprüfmaschine, dem Butterprüfgerät (DIN 10331), einem Rotationsrheometer und mit dem zweidimensional registrierenden Kraftmeßgerät. Dabei zeigte sich, daß das Rheometer im oscillierenden Modus die Streichfähigkeit am besten zu charakterisieren vermag. Die Korrelation zwischen den Rheometerwerten, berechnet als dynamische Weissenbergzahl, und den sensorisch ermittelten Werten für die Streichfähigkeit betrugr=0,91. Zur Bestimmung der Festigkeit ist das zweidimensional registrierende Kraftmeßgerät am besten geeignet, was sich in einem Korrelationskoeffizienten vonr=0,95 zwischen dem ParameterS _t und den im Sensoriktest ermittelten Werten für dieFestigkeit ausdrückt.

     

服装构成方法比较及新方法的生成

对比了比例法、原型法、立体法裁剪这三种服装结构构成方法的原理、特点及应用结果，探讨了不同服装结构构成方法的科学性，指出在实践中应将这几种服装结构构成方法优势互补、灵活运用．进而提出以建立服装结构设计经验数据库为桥梁将不同服装结构构成方法有机连接起来的新方法。