A NON-PARAMETRIC RANKING METHOD FOR THE STATISTICAL EVALUATION OF SENSORY DATA

Sensory data are rarely normally distributed and should, therefore,be statistically analyzed by non-parametric techniques. A computerprogram was devised for generating tabular data by which upto twenty samples can be compared following evaluation by asmany as seventy-five panelists. When samples are initially ranked,rank sums for each sample may be compared to appropriate entriesin the tables directly. If scalar values are assigned by panelists,the technique is still useful, but the values must first beconverted to ranks. ^*Scientific Article No. A1857, Contribution No. 4767 of theMaryland Agricultural Experiment Station (Food Science Program).     

PERFORMANCE ASSESSMENT OF SENSORY PANELISTS

The replication variance of individual stimulus evaluations and scale utilization across a panelist's stimulus profile are simultaneously employed to develop statistics for assessing performance of panelists. The approach provides opportunities for comparison of panelists to each other, determination of attributes for which panelist confusion is observed, isolation of stimuli presenting unstable properties, and engagement of influence weights (based on relative precision) in subsequent analyses of data. Although the methodology has been developed for applications involving sensory panelists, the statistical concepts may be extended to other data collection scenarios involving replicated determinations from bounded quantitative measurement scales.     

SENSORY ASSESSMENT OF OILINESS IN A LOW MOISTURE FOOD

Relationships between fat content and perceived oiliness were investigated in a dry, cornmeal-based snack food. Paired comparisons suggested that substantial differences in fat content (about 15 g/100 g) are required before consistent differences in perceived oiliness are found. Using magnitude estimation, judgments of oiliness intensity were made when stimuli were (1) ingested under normal conditions, (2) ingested with olfactory, visual, and manual tactile inputs eliminated, and (3) simply rubbed between the fingers. The similarity of the oiliness function under these different conditions suggest that perceptions of oiliness are principally derived from oral textural sensations.     

A SEMI-ASCENDING PAIRED DIFFERENCE METHOD FOR DETERMINING SENSORY THRESHOLDS OF ADDED SUBSTANCES TO BACKGROUND MEDIA

A testing procedure was developed to determine the concentration range including an absolute or difference threshold for a compound added to a background medium. Samples were arranged into three groups, each containing a labeled control and three randomly arranged samples. Random samples in each group included an unlabeled control and two samples containing adjacent concentration levels from a series of six increasing concentrations of the added substance. Groups were presented in ascending order by concentration of the added substance. Within each group, panelists rated each sample on a nine-point intensity scale of difference from the labeled control. Group specific psychological errors in judgement were reduced by subtracting the unlabeled controls from the sample scores. Analysis of variance was applied to these data yielding separate estimates of variance for sample scores within groups. Sets of t-tests from paired comparisons were used to construct a confidence statement regarding a threshold interval.     

SENSORY DIRECTIONALS FOR PIZZA: A DEEPER ANALYSIS

This paper presents a set of analyses on sensory directional attributes used to rate experimentally designed pizza products. Consumers may or may not know the 'optimal' sensory level of attributes for pizza, so that the usefulness of the sensory directional varies by attribute. Furthermore, the sensory magnitude of each sensory directional attribute varies, as shown by the slope (B) relating the two attributes (Sensory Magnitude = A + B (Directional Rating)). The study incorporated sensory directionals into evaluation of products varied according to an experimental design. The optimal product emerging from the design does not necessarily exhibit a sensory directional profile where all attributes are 'on target', nor does a product whose sensory attributes are all on 'target' exhibit the highest level of liking.     

CROSS VALIDATION OF A SENSORY LANGUAGE FOR CHEDDAR CHEESE

Communication and replication of sensory data from different sites are important to track progress on fundamental research issues and to ensure that research efforts are not duplicated. A uniform anchored Cheddar cheese sensory language has previously been identified and refined. The objective of this study was to demonstrate application of the defined sensory language for Cheddar cheese for communication between sensory panels at three different sites. The defined and referenced sensory language for Cheddar cheese was disseminated to panel leaders at the three sites and sensory panels (n ≤ 8) were trained for 40 to 80 h at each site. Ten forty-pound blocks of Cheddar cheese representing different ages were collected and evaluated by the panels. Cheeses were differentiated by the three panels by univariate and multivariate analysis (P<0.05). Cheeses were differentiated by the three panels in a similar manner. Results indicate that it is possible to calibrate panels using a standardized defined sensory language.     

ASSESSMENT OF IMPEDANCE MICROBIOLOGICAL METHOD FOR THE DETECTION OF ESCHERICHIA COLI IN FOODS

This study was conducted to determine the sensitivity and specificity of the impedance-based microbiological method for the detection of Escherichia coli in foods within 24 h of testing. A Malthus Microbiological Analyzer system (Malthus System V, Malthus Instruments Ltd., Bury, United Kingdom), and a modified Malthus Coliform Broth Medium (MCBM), and an incubation temperature of 44C were used. The sensitivity of the impedance method was determined by testing E. coli-negative food samples spiked with different concentrations of E. coli. The specificity of the method was determined by testing E. coli -negative food samples spiked with Klebsiella pneumoniae, Enterobacter cloacae and Pseudomonas aeruginosa. The test results were compared with those obtained by the Most Probable Number (MPN) method. Milk, milk products, raw and ready-to-eat meats, and vegetables were tested for the presence of E. coli by both methods. The sensitivity of the impedance method and the MPN method for the detection of foods containing 10¹ CFU/g was 100% and 84.4%, respectively. Both methods had a specificity of 100% for food samples spiked with 10¹ CFU/g E. coli. The specificity of the impedance and the MPN methods for the detection of E. coli in naturally contaminated milk and meat samples was 100% and 95.7% respectively. E. coli was detected in foods by the impedance method within 4–24 h of testing at a detection limit of 1 CFU/mL. These results demonstrate that the impedance method can be used as a rapid and sensitive method for the detection of E. coli in foods.     

圆形碘泡虫孢子的分离纯化与裂解

近年来 ,粘孢子虫的分子生物学及免疫学逐步发展[1 ,2 ] ,在很多研究中都需以纯净的孢子为材料 ,因此如何从鱼体分离出纯净的孢子就显得格外重要。另一方面 ,粘孢子虫的孢子具坚韧的壳瓣 ,在提取虫体基因组ＤＮＡ时 ,必须先使其裂解 ,方法主要有常规裂解液裂解法、热裂解法、超声破碎法、液氮冷冻研磨法等几种方法 ,本文对这几种方法进行比较后认为 :液氮冷冻研磨法既可使多数虫体裂解 ,对ＤＮＡ的破坏又比较小 ,是较为行之有效的方法。1　材料和方法1 .1　材料　病鱼系武汉市鄂州收集的冻存标本 ,其体表具有大量圆形碘泡虫 (Ｍｙｘｏｂｏｌ…     

NONPARAMETRIC ANALYSIS FOR TRINARY SENSORY DATA

Sensory evaluation data is sometimes collected using trinary category scales. Nonparametric data analysis for such data is discussed and a homogeneity statistic for trinary data is proposed which is simple enough to calculate with a pocket calculator. A statistic for identifying market segmentation in trinary data is also suggested.