A THURSTONE-COOMBS MODEL OF CONCURRENT RATINGS WITH SENSORY AND LIKING DIMENSIONS

A popular product testing procedure is to obtain sensory intensity and liking ratings from the same consumers. Consumers are instructed to attend to the sensory attribute, such as sweetness, when generating their liking response. We propose a new model of this concurrent ratings task that conjoins a unidimensional Thurstonian model of the ratings on the sensory dimension with a probabilistic version of Coombs' (1964) unfolding model for the liking dimension. The model assumes that the sensory characteristic of the product has a normal distribution over consumers. An individual consumer selects a sensory rating by comparing the perceived value on the sensory dimension to a set of criteria that partitions the axis into intervals. Each value on the rating scale is associated with a unique interval. To rate liking, the consumer imagines an ideal product, then computes the discrepancy or distance between the product as perceived by the consumer and this imagined ideal. A set of criteria are constructed on this discrepancy dimension that partition the axis into intervals. Each interval is associated with a unique liking rating. The ideal product is assumed to have a univariate normal distribution over consumers on the sensory attribute evaluated. The model is shown to account for 94.2% of the variance in a set of sample data and to fit this data significantly better than a bivariate normal model of the data (concurrent ratings, Thurstonian scaling, Coombs' unfolding model, sensory and liking ratings).     

A COMPARISON OF METHODS FOR EVALUATING THE PERFORMANCE OF A TRAINED SENSORY PANEL1

Cluster analysis, consonance analysis, principal component analysis (PCA) and the GRAPES program (Schlich 1994) were compared for the evaluation of panel performance. Ten judges evaluated 25 Merlot wines for 24 color, aroma and flavor attributes. Cluster analysis grouped similar judges. PCA identified judges according to their attribute use. Consonance analysis determined a numerical index for attribute agreement and the GRAPES program compared judges in their use of the scale, reliability, discrimination and disagreement. Three of the four techniques provided a graphical representation of similarities and differences between judges. Methodologies were best used in conjunction with one another. Ultimately the application of these tools will serve to improve the quality of sensory evaluations.     

An improved protocol for the detection and rapid confirmation within 48 h of Salmonellas in confectionery products

A modified ornithine decarboxylase broth and a selenite cystine trimethlyamine oxide ribose medium were developed to improve selection and detection of Salmonellas. They were used with a third medium, lysine iron cystine neutral red broth (incubated conventionally) in a screen of 80 Salmonellas and 32 non-salmonellas which showed the combination of media to be specific and sensitive. Subsequent evaluation with 90 product samples (spiked and naturally contaminated) resulted in complete agreement by rapid and conventional methods. The detected wells in these experiments were also used to evaluate a latex slide agglutination test for Salmonellas. Carried out directly on the well contents, this was found to be a rapid, specific and sensitive test for confirmation of Salmonella presence. Further tests with 106 routine production samples gave complete agreement by both methods. Presumptive positives were obtained in <1.0–3·8% of the sample wells and subsequent modification to the Bactometer software has greatly reduced these figures in routine use. The method is recommended for Salmonella testing of foodstuffs with low background flora and high fat/low moisture content.     

Enzyme immunoassay for detection of Salmonellae in foods.

An enzyme immunoassay was developed to detect Salmonella in foods. Indirect test protocols were developed for use with microtitration plates or Gilford microcuvettes. Samples from enrichment cultures were mixed with H-specific immunoglobulin G and allowed to react; unbound antibody was removed by three 5-min centrifugation washes; goat anti-rabbit antibody conjugated to alkaline phosphatase was added and allowed to react; and unbound conjugate was removed by centrifugation washing as before. Salmonella-positive samples were indicated by the production of a chromogenic reaction product after the addition of alkaline phosphatase substrate. The color could be read visually or quantified by absorbance. Ninety-eight food samples were examined to compare the enzyme immunoassay with enrichment serology, immunofluorescence, and the Food and Drug Administration pure culture technique. The enzyme immunoassay was sensitive and specific, and it possessed advantages over methods currently in use. Furthermore, when the enzyme immunoassay was used to screen preenrichment media, the results indicated that it might be decidedly more sensitive than the conventional pure culture technique.     

CATEGORY APPRAISAL WITHIN A LIMITED PRODUCT RANGE: A METHODS-ORIENTED CASE HISTORY

This paper presents the author's approach to synthesizing useful direction from product testing when the stimuli are not systematically varied. The approach presented here comprises a research design and data analysis strategy, rather than a conventional product optimization with subsequent validation. The design steps comprise stimulus selection, attribute selection, and product evaluation. The data analysis comprises univariate modeling to show how sensory attributes drive overall liking, reduction of the matrix to factor scores for multivariate modeling, and then the creation of an integrated product model. The outcome is a set of factor scores that can be translated to sensory attributes and in turn to target products.     

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.     

SENSORY EVALUATION BASED ON VERBAL JUDGMENTS

Studies of the repeatability and the homogeneity of expert panel scores in sensory profiling show that lasting and reliable evaluations of food products are difficult to obtain: strong inter- and intra-individual differences are commonly observed. Our hypothesis is that this variability is due to quantification methods that consist of asking panelists to furnish quantitative values (by attributing a numerical point to perceived intensity) and that using natural language in the form of verbal judgements in a hierarchical tree would allow improving the reliability of sensory evaluations. This hypothesis was tested by comparing a numerical value scale and a specific hierarchical semantic scale that subjects devised themselves prior to the experiment. The products (chocolate dessert creams) were evaluated using each of the two methods. The results show that the capacity to discriminate between products is better when verbal judgements are used. We discuss the advantages of hierarchical semantic scales for sensory profiling.     

FUZZY MULTIATTRIBUTE DECISION MAKING APPROACH FOR DEVELOPMENT AND COMPARISON OF SOY FORTIFIED PANEER

Soyfortified paneer (SFP) samples prepared from blends containing different proportions of buffalo milk of varying fat content and soy milk (7.5 °B) were evaluated organoleptically for assessing the quality attributes like body and texture, flavor and taste, color and appearance and the overall acceptability. Sensory data were analyzed using fuzzy logic approach, which addresses the problem of data classification in a unified qualitative and quantitative manner. Results of the study indicated that the fuzzy multiattribute decision making approach provide an adequate and reliable system for product formulation and comparison, based on sensory data. The developed fuzzy mathematical model performed remarkably well in the evaluation and ranking of various SFP samples. The SFP sample made from blend of buffalo milk (4.5% fat) and soy milk (7.5 °B) in the proportion of 90:10 was found to be the most acceptable one for different classes of consumers irrespective of their preferences for a particular sensory quality attribute.     

EFFECTIVENESS OF CATEGORY AND LINE SCALES TO CHARACTERIZE CONSUMER PERCEPTION OF FRUITY FERMENTED FLAVOR IN PEANUTS

Fruity fermented (FF) flavor is a common off‐flavor in peanuts resulting from high‐temperature curing. The 9‐point hedonic scale is the most widely used scale to determine consumer acceptance; however, research has indicated that line scales may provide equal reliability and greater sensitivity. The objectives of this study were to characterize consumer perception of FF flavor in peanuts and to compare the effectiveness of the two scale types. Consumers (n = 208) evaluated control (no FF), low‐intensity (1.0) FF and high‐intensity (3.0) FF peanut pastes for the strength/intensity of roasted peanut flavor (RPF), sweet taste (ST), fresh peanut flavor (FPF) and overall liking (OV) using randomly assigned ballots. Sensitivity in defining consumer perception of off‐flavor in peanuts was greater with use of line scales than with the hedonic scale. The line scale indicated that FF flavor in peanuts, even at low intensity, negatively impacted OV and further identified significantly lower RPF and FPF perception by consumers. The hedonic scale identified only a difference in FPF and was not sensitive enough to show a difference in OV.     

APPLICATIONS OF SENSORY SCIENCE WITHIN THE HOME CARE BUSINESS

Sensory evaluation methods and procedures originally developed for the food and beverage industry are also utilized to conduct evaluations of products for furniture and floor care, laundry care, air care, and insect control. In addition to measuring sensory properties and dealing primarily with “the other senses,” home care product evaluations incorporate assessments of perceived performance as the product interacts with a substrate. Consequently, laboratory evaluations employ a variety of controlled usage conditions — each having specific physical requirements, and evaluations of total performance are conducted under multi-environmental conditions with product users. This presentation examines how traditional sensory methods have been modified and expanded to accommodate the multidimensional aspects of home care products and R&D decisionmaking.     

COMPARISON OF SINGLE PRODUCT SCALING AND RELATIVE-TO-REFERENCE SCALING IN SENSORY EVALUATION OF DAIRY PRODUCTS

Single product scaling and relative-to-reference scaling were compared on the basis of numbers of significant differences among chocolate milks and among vanilla yogurts using both trained and untrained panels. The study involved 920 comparisons among product means with appearance, flavor and mouthfeel attributes. Although there were a greater number of significant t-tests when the relative-to-reference scales were used by both trained and untrained panels, the differences between scale types were minor. Panels showed no advantage with the type of scale they used first. The two methods may be used with equal efficiency for sensory evaluations.     

舟山近海水样环境DNA获取方法的建立

以曼氏无针乌贼(Sepiella japonica)为研究对象, 通过绝对定量技术建立和优化了舟山近海高浊度水样环境DNA(Environmental DNA, eDNA)的获取方法。研究结果如下: (1)同体积水样采用乙醇沉淀法获得的eDNA产量是滤膜抽滤法的1.76—2.53 倍, 但在实际应用中由于受到采样体积、处理方式、配套设备的限制, 乙醇沉淀法难以发挥出优势; (2)滤网对泥沙等杂质无过滤作用, 添加滤网并不能过滤掉泥沙及增加抽滤体积; (3)滤膜孔径的大小对少量水样的eDNA产量有很大影响, 但对大体积水样eDNA的产量无影响; (4)水样静置处理有可能会增大eDNA产量, 但也有可能会增大eDNA结果的波动性, 使生物量评估结果误差较大; (5)阳离子表面活性剂对eDNA降解有明显的抑制作用; (6)去膜法效果优于碎膜法, 建议使用去膜法进行eDNA消化, 使用时增加离心时间; (7)酚抽除沙法虽然不能提高eDNA产量, 但能明显提高产物纯度。研究首次建立了舟山近海水样大生物eDNA最适获取方法, 为相似水域的水样采集及eDNA提取提供了借鉴参考。     

Validation of a handheld display device for an expandable labeled magnitude scale (LMS)

Palmtop computers provide a possible avenue for the convenient collection of subjective ratings from individuals outside of a fixed laboratory setting. One disadvantage of these computers is the small size of their display screens, which may reduce the resolution of responses available as compared with standard display screens. One plausible solution to this problem is to use a scale that expands contingent on an initial response made by the subject, so that the final response is made from a scale with finer resolution. To validate this approach, we compared taste intensity judgments of six sucrose solutions (0.03, 0.06, 0.12, 0.24, 0.48, and 0.96 M), using a labeled magnitude scale either presented in expandable form on a palmtop computer (Palm scale) or in conventional (nonexpandable) form on a standard 17' PC monitor (PC scale). Twenty-four subjects rated all six sucrose solutions thrice, using both scale types, the different scales being used on different days of testing. The scales led to very similar taste intensity ratings at all but the lowest concentration, which was rated less intense on the Palm scale. The Palm scale was used with slightly less precision than the PC scale for the weakest solution concentrations. In summary, the responses of the two scales were similar enough to validate the use of the expandable scale on the palmtop computer outside the laboratory setting.