SENSORY EVALUATION OF VANILLA-DAIRY DESSERTS BY REPERTORY GRID METHOD AND FREE CHOICE PROFILE

“Natillas” are semisolid dairy desserts widely consumed in Spain, with notable differences existing between commercial brands in their composition and sensory and physical properties. The repertory grid method, in conjunction with the free choice profile (FCP), was used to provide data on how consumers perceived eight commercial “natillas” samples. The most frequent terms used were: vanilla flavor, sweetness, consistency and liquid texture as described by 77, 67, 57 and 53% of the consumers, respectively. A three‐dimensional solution was chosen. Dimension 1 accounted for 27.23% of variance and separated the samples largely by yellow‐color intensity and consistency. Dimension 2 (15.88%) was mainly related to the visual attributes of texture, creaminess and different notes of flavor. The third dimension (11.34%) was related to structural‐texture attributes, orange‐yellow color and acid and artificial flavors. The assessors plot showed two clusters. Analysis of each group data revealed differences in their perception of sample variation, mainly regarding texture and color.     

SELECTION AND SCREENING OF A DESCRIPTIVE PANEL FOR EWES MILK CHEESE SENSORY PROFILING

The aim of this work was to select a competent sensory panel considering its ability to describe ewes milk cheese sensory properties. The panelists evaluated the sensory characteristics of several ewes milk cheeses in terms of odor, flavor and texture. The performance of judges was assessed taking into account the following aspects: (1) individual discriminatory ability and reproducibility for each sensory attribute; (2) group discriminatory ability and reproducibility and agreement between judges for each attribute; (3) panel homogeneity; (4) panel consonance; and (5) overall panel discriminatory ability. The panel performance was checked with a set of statistical procedures. The results obtained by the selected group were better than the initial panel from the point of view of discriminant power, reproducibility and agreement. The suggested method can be easily applied in routine control of assessors performance and to discover deviant behavior or differences in individual perception of the samples.     

Detection of abnormal fermentations in wine process by multivariate statistics and pattern recognition techniques

Three multivariate statistical techniques (Multiway Principal Component Analysis, Multiway Partial Least Squares, and Stepwise Linear Discriminant Analysis) and one artificial intelligence method (Artificial Neural Networks) were evaluated to detect and predict early abnormal behaviors of wine fermentations. The techniques were tested with data of thirty-two variables at different stages of fermentation from industrial wine fermentations of Cabernet Sauvignon. All the techniques studied considered a pre-treatment to obtain a homogeneous space and reduce the overfitting. The results were encouraging; it was possible to classify at 72h 100% of the fermentation correctly with three variables using Multiway Partial Least Squares and Artificial Neural Networks. Additional and complementary results were obtained with Stepwise Linear Discriminant Analysis, which found that ethanol, sugars and density measurements are able to discriminate abnormal behavior.     

A COMPARISON OF TWO MULTIVARIATE METHODS FOR THE ANALYSIS OF SENSORY PROFILE DATA

Tables of means, over assessors, are often used to summarize the results of sensory profile experiments. These tables are sometimes further summarized by Principal Components Analysis (PCA) to give plots of the samples in the principal sensory dimensions. An alternative procedure is to use Generalized Procrutes Analysis (GPA) on the assessor data to allow for differences in usage of the vocabulary and in the proportion of the scale used. It is shown that these methods give different configurations in the principal sensory dimensions when applied to the data from a study of cheeses (Muir et al. 1995). Using a Jackknife method to calculate the variability of the samples in the principal sensory dimensions, the results from the GPA method are shown to have a higher dimensionality than from the PCA method. Jackknife estimates of variability are used to calculate confidence ellipses to attach to the sensory space maps.     

SENSORY EVALUATION OF INDIAN-STYLE MARINATED CHICKEN BY MALAYSIAN AND EUROPEAN NAÏVE ASSESSORS

This study was carried out to determine the sensory acceptability of chicken breast fillets marinated with 13 different commercially available Indian-style marinades. Thirty-four naïve assessors (untrained panelists), 20 Malaysian and 14 European, were selected to assess the following sensory attributes: color, color uniformity, Tikka-Masala aroma, Tikka-Masala flavor, herblike flavor, hotness, authenticity, juiciness and overall acceptability. The color of the cooked samples and the pH, moisture and fat content of the marinades were analyzed instrumentally. Marinades were applied to the chicken fillets, which were then dry cooked at 170C for 15 min to an internal temperature of 73C. Sensory evaluation showed significant differences ( P <  0.05) in color uniformity, hotness and juiciness of the cooked marinated chicken perceived between groups. Samples marinated with marinades L and I received the highest score from the Malaysian panelists in terms of overall acceptability, whereas marinades A and F were chosen by the European group.

PRACTICAL APPLICATIONS

The findings from this research will benefit manufacturers of marinade and marinated chicken products in developing or optimizing their products for the local and international markets. The optimal characteristics of an ideal marinade were identified for each assessor group. These results are also of interest to individuals undertaking cross-cultural consumer studies, even though the results presented here used naïve assessors.     

A STUDY OF TEXTURE-FLAVOR INTERACTIONS USING FREE-CHOICE PROFILING

Interactions between perceptions of texture and volatile flavors were assessed by free-choice profiling using gelatin desserts as a model product. Gels were prepared with all combinations of 2 levels of gelatin, and 2 concentrations of 2 different flavors. A trained sensory panel profiled each sample for aroma, flavor, and oral and manual texture. Generalized Procrustes Analysis was carried out separately for each sensory modality. The results indicate that while gelatin concentration and flavor type both modified perception of flavor, flavor concentration did not. Gelatin content influenced instrumental, oral, and manual evaluations of texture; however, the type and level of flavoring had little influence on oral perception of texture.     

CONSUMER PREFERENCE OF DULCE DE LECHE AMONG STUDENTS IN THE UNITED KINGDOM

Dulce de Leche is a dairy-based confectionary product virtually unknown outside Latin America. A 2⁴ factorial design was implemented to study the influence of sugar composition, type of neutralizer, cooking time and presence of vanilla essence on the preference of Dulce de Leche by UK university students. A fractional factorial pattern was used in sen'ing samples to assessors. Analysis of variance showed that the preferred levels were: 40% replacement of sucrose by glucose syrup, 100% sodium bicarbonate as neutralizer, and no vanilla essence. Cooking time did not significantly affect preference. Partial least squares regression was used to relate preference to sensory profile scores. The correlation was good for appearance and texture, not so for flavor and aftertaste. A mapping technique showed consumers to be uniformly grouped for appearance and texture, not so for flavor. Results from preference and general acceptability were encouraging in promoting this new dairy product in Great Britain.     

SENSORY PROFILE DESCRIPTION OF MOZZARELLA CHEESE AND ITS RELATIONSHIP WITH CONSUMER PREFERENCE

The aim of this work was to set up the sensory profile and consumer preference test of three different Mozzarella cheeses (from full-fat cow milk, from low-fat cow milk and from full-fat water buffalo milk). The most remarkable difference in composition was the fat content. Nine commercial Mozzarella cheeses (three for each type) were evaluated in triplicate by a trained panel consisting of 10 assessors. Six Mozzarella cheeses (two for each type) out of the nine samples were selected and used for the preference test by 105 consumers. The three different Mozzarella cheeses were sensorially well differentiated. A good discrimination between the Mozzarella cheeses was obtained using the internal preference map method. The combination of cluster analysis and internal preference mapping has lead to a deeper understanding of consumer liking for Mozzarella cheeses.     

Rapid Quantification of Methamphetamine: Using Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR) and Chemometrics

In Australia and increasingly worldwide, methamphetamine is one of the most commonly seized drugs analysed by forensic chemists. The current well-established GC/MS methods used to identify and quantify methamphetamine are lengthy, expensive processes, but often rapid analysis is requested by undercover police leading to an interest in developing this new analytical technique. Ninety six illicit drug seizures containing methamphetamine (0.1%–78.6%) were analysed using Fourier Transform Infrared Spectroscopy with an Attenuated Total Reflectance attachment and Chemometrics. Two Partial Least Squares models were developed, one using the principal Infrared Spectroscopy peaks of methamphetamine and the other a Hierarchical Partial Least Squares model. Both of these models were refined to choose the variables that were most closely associated with the methamphetamine % vector. Both of the models were excellent, with the principal peaks in the Partial Least Squares model having Root Mean Square Error of Prediction 3.8, R² 0.9779 and lower limit of quantification 7% methamphetamine. The Hierarchical Partial Least Squares model had lower limit of quantification 0.3% methamphetamine, Root Mean Square Error of Prediction 5.2 and R² 0.9637. Such models offer rapid and effective methods for screening illicit drug samples to determine the percentage of methamphetamine they contain.     

Production of sulfur flavors by ten strains of Geotrichum candidum

Ten strains of Geotrichum candidum were studied on a liquid cheese model medium for the production of sulfur compounds which contribute to the aroma of cheeses. The volatile components produced by each cultured strain were extracted by dynamic headspace extractions, separated and quantified by gas chromatography (GC), and identified by GC-mass spectrometry. It was shown that four strains of this microorganism produced significant quantities of S-methyl thioacetate, S-methyl thiopropionate, S-methyl thiobutanoate, S-methyl thioisobutanoate, S-methyl thioisovalerate, and S-methyl thiohexanoate. This is the first example of the production of these compounds by a fungus. In addition, dimethyldisulfide, dimethyltrisulfide, dimethylsulfide, and methanethiol, which are more commonly associated with the development of cheese flavor in bacterial cultures, were also produced by G. candidum in various yields, depending on the strain selected. The potential application of these strains in cultured microbial associations to produce modified cheeses with more desirable organoleptic properties is discussed.     

Identifying Breeding Priorities for Blueberry Flavor Using Biochemical,Sensory, and Genotype by Environment Analyses

Breeding for a subjective goal such as flavor is challenging, as many blueberry cultivars are grown worldwide, and identifying breeding targets relating to blueberry flavor biochemistry that have a high degree of genetic control and low environmental variability are priorities. A variety of biochemical compounds and physical characters induce the sensory responses of taste, olfaction, and somatosensation, all of which interact to create what is perceived flavor. The goal of this study was to identify the flavor compounds with a larger genetic versus environmental component regulating their expression over an array of cultivars, locations, and years. Over the course of three years, consumer panelists rated overall liking, texture, sweetness, sourness, and flavor intensity of 19 southern highbush blueberry (Vaccinium corymbosum hybrids) genotypes in 30 sensory panels. Significant positive correlations to overall liking of blueberry fruit (P<0.001) were found with sweetness (R² = 0.70), texture (R² = 0.68), and flavor (R² = 0.63). Sourness had a significantly negative relationship with overall liking (R² = 0.55). The relationship between flavor and texture liking was also linear (R² = 0.73, P<0.0001) demonstrating interaction between olfaction and somatosensation. Partial least squares analysis was used to identify sugars, acids, and volatile compounds contributing to liking and sensory intensities, and revealed strong effects of fructose, pH, and several volatile compounds upon all sensory parameters measured. To assess the feasibility of breeding for flavor components, a three year study was conducted to compare genetic and environmental influences on flavor biochemistry. Panelists could discern genotypic variation in blueberry sensory components, and many of the compounds affecting consumer favor of blueberries, such as fructose, pH, β-caryophyllene oxide and 2-heptanone, were sufficiently genetically controlled that allocating resources for their breeding is worthwhile.     

ASSOCIATION OF STRAWBERRY YOGURT SENSORY PROPERTIES WITH PRODUCT COMPOSITION BY PROCRUSTES ANALYSIS

The flavor of eight samples of commercial strawberry yogurt was studied by Free-Choice Profile analysis (FCP). Generalized Procrustes Analysis (GPA) applied to FCP allowed differentiation between samples and highlighted flavor attributes responsible for the observed differences. The relation between sensory and physicochemical datasets was studied by means of GPA. Those samples with higher carbohydrate content were perceived as sweeter, having stronger strawberry flavor, and with more dairy and yogurt flavors. Samples with higher titratable acidity, ash and protein content were perceived as more acidic and higher in intensity of "faulty" or "defective" flavors. Higher moisture content was associated with lower intensity of "dairy" flavors (creamy, dairy, and yogurt) and greater intensity of rancid flavor. It is concluded that, though not often used to this end, GPA is a suitable method to study the relationship of sensory and instrumental measurements.