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.     

COMPARISONS OF VOLATILE COMPOUNDS RELEASED DURING CONSUMPTION OF A COMPLEX FOOD BY DIFFERENT ASSESSORS WITH EXPRESSIONS OF PERCEIVED FLAVOR DETERMINED BY FREE CHOICE PROFILING

Comparisons of volatile compounds released during consumption by different assessors with individual differences in the assessors'chewing patterns, saliva production rates and ultimately their expressions of perceived flavor have received little research attention to date, although such comparisons are fundamental to the understanding of flavor. To address this, eight untrained assessors were chosen and each consumed six Cheddar cheeses during Buccal Headspace Analysis of the volatile compounds released, while in parallel measures of each assessor's mastication behavior using Electromyography, their stimulated saliva production during consumption and their sensory perceptions of the cheeses flavor during Free Choice Profiling were determined. Relationships between the volatile compounds released and the sensory and physiological measures were investigated using Principal Components Analysis, Generalised Procrustes Analysis and Partial Least Squares regression. It was found that although there were differences between assessors'mastication behavior and saliva production rates, the assessors'individual volatile profiles obtained by Buccal Headspace Analysis were similar for each cheese examined. Also, Partial Least Squares was successful in predicting the most important flavor differences between cheeses from the volatile compounds released during their consumption by different assessors.     

SENSORY AND INSTRUMENTAL EVALUATIONS OF TEXTURE IN CHEESES MADE FROM OVINE MILKS WITH DIFFERING FAT CONTENTS

The present study considers the influence of reducing the fat content of ovine milk on the sensory and instrumental texture characteristics of the resulting cheeses. Three manufacturing runs were performed. In each run three cheese batches were manufactured using milks with differing percentage fat contents (8%, 4%, and 2% fat). Analysis of cheese samples was performed at 60, 90, and 120 days of ripening.
The instrumental method used to evaluate cheese texture was uniaxial compression at constant speed, taking readings of stress, strain, and modulus of elasticity (E). Statisticalanalysis revealed differences forboth the differentfat contents and the ripening times considered. Instrumental parameter values increased with lower cheese fat contents; with a 20% reduction in the fat to dry matter content from full-fat to reduced-fat cheeses, resulting in a 35% increase in maximum stress and in the slope of the stress-strain curve at the end of ripening. The greatest sensory differences between samples were recorded for firmness.     

Enhancement of cheese flavors with microbial esterases

The characteristic flavor of hard Italian cheeses is associated with the presence of fatty acids, particularly butyric acid, liberated from milk fat during the ripening process. To ensure proper development and control of flavor, animal pregastric esterases or lipases are routinely added to the milk before coagulation of the curd. Such esterases are also used to generate flavor in enzyme modified cheese and other dairy products. Esterases from microbial sources have been investigated as agents to enhance flavor in cheese. We have found that an esterase from Mucor miehei exhibits the type of lipolytic activity needed for this application. Romano and fontina cheeses of excellent quality have been prepared by the use of this esterase. It has also been used successfully in the preparation of enzyme modified cheese, and, in turn, processed American cheese.     

ABILITY OF HAND EVALUATION VERSUS MOUTH EVALUATION TO DIFFERENTIATE TEXTURE OF CHEESE

Hand evaluation and mouth evaluation were compared for texture of cheese. Panelists (n = 11) identified seven mouth terms and five hand terms and developed definitions and standard procedures for evaluation during the course of training. The terms were used to evaluate texture properties of fourteen different types of natural and processed full fat and reduced fat cheeses. Hand and mouth evaluation were able to discriminate cheese texture (P≦0.05). Principal component analysis of data revealed that hand and mouth evaluation differentiated the cheeses in a similar manner. Correlation analysis, factor analysis, and canonical analysis revealed that mouth and hand terms were highly correlated (P≦0.05). Either hand or mouth evaluation can be used to discriminate cheese texture.     

1H HRMAS-NMR based metabolic fingerprints for discrimination of cheeses based on sensory qualities

In this study, the ¹H HRMAS-NMR (High-resolution Magic Angle Spinning-Nuclear Magnetic Resonance) spectra of 52 cheese samples obtained from the South Korean dairy farms were evaluated for their metabolic profiling and intensities associating with the sensory qualities. The NMR profiles displayed a broad range of compounds comprising amino acids, carbohydrates, organic acids, and phospholipids. Afterwards, the cheese samples were categorized into three groups (more likeness - G1, moderate likeness - G2, less likeness - G3), in relating to their sensory scores. The NMR data of the samples were later investigated through multivariate statistical tools to define the variations in metabolic fingerprints of every cheese sample and their intensities hailing in individual sensory groups. The unsupervised PCA employing all cheese samples unveiled the uniqueness in metabolite profiles of the brown and cheddar type cheeses (outliers). Moreover, Gouda and other types of cheeses displayed samples positioning in respective of their metabolite profiles. The pairwise comparison of sensory groups in the supervised models perceived better separation in OPLS-DA than PLS-DA. The corresponding VIP (PLS-DA) and loading (OPLS-DA) plots revealed amino acids and organic acids (lactate, citrate) as significant variables. The discrimination of G 1 Gouda type of cheeses against G 2 and G 3 was highly associated with their citrate levels. Further investigation using heatmaps displayed clear differentiation between each sensory group in terms of the levels of amino acids, lactate, citrate, phospholipids, and glycerol, conveying these variations are likely due to proteolytic and metabolic processes in cheese ripening. This study concluded that ¹H HRMAS-NMR metabolite profile of the Korean cheeses is consistence with their sensory qualities. Further, the candidate metabolites identified in this study confers their potential application as biomarkers in cheese industries for faster and effective validation of sensory characteristics.     

Predictive formulae for goat cheese yield based on milk composition

Prediction of the yield and quality of different types of cheeses that could be produced from a given type and/or amount of goat milk is of great economic benefit to goat milk producers and goat cheese manufacturers. Bulk tank goat milk was used for manufacturing hard, semi-hard and soft cheeses (N = 25, 25 and 24, respectively) to develop predictive formulae of cheese yield based on milk composition. Fat, total solids, total protein and casein contents in milk and moisture-adjusted cheese yield were determined to establish relationships between milk composition and cheese yield. Soft, semi-hard and hard cheeses in this study had moisture contents of 66, 46 and 38%, respectively, which could be used as reference standards. In soft cheese, individual components of goat milk or a combination of two or three components predicted cheese yield with a reasonably high correlation coefficient (R² = 0.73–0.81). However, correlation coefficients of predictions were lower for both semi-hard and hard cheeses. Overall, total solids of goat milk was the strongest indicator of yield in all three types of cheeses, followed by fat and total protein, while casein was not a good predictor for both semi-hard and hard cheeses. When compared with moisture-adjusted cheese yield, there was no difference (P > 0.05) in predicting yield of semi-hard and hard goat milk cheeses between the developed yield formulae in this study and a standard formula (the Van Slyke formula) commonly used for cow cheese. Future research will include further validation of the yield predictive formulae for hard and semi-hard cheeses of goat milk using larger data sets over several lactations, because of variation in relationships between milk components due to breed, stage of lactation, season, feeding regime, somatic cell count and differences in casein variants.     

Winter feeding systems and dairy cow breed have an impact on milk composition and flavour of two Protected Designation of Origin French cheeses

This study investigates the effects of two feeding systems and two dairy cow breeds on milk yield and composition, physical and sensorial properties of Camembert and Pont-l’Evêque cheeses. The experiment consisted of a 2 × 2 factorial arrangement of treatments. A low energy grass diet with only 15% of concentrate (LowGS) was compared with a high-energy maize silage diet with 30% concentrate (HighMS). Thirty-four Holstein (Ho) and 34 Normande (No) cows in early lactation were assigned to one of two feeding systems for a 6-week period. Cows on the LowGS feeding system had lower milk yield, fat and protein content. In both feeding systems, No cows had lower milk yields but higher milk protein contents than Ho cows. The LowGS feeding system altered milk fatty acid (FA) composition by reducing saturated FA. Breed had only a small impact on milk FA. Concerning milk coagulating properties, only the firmness was reduced by the LowGS feeding and the Ho breed. The effects of breed and feeding system on the protein content of cheeses were more marked in Camembert cheese than in Pont-l’Evêque cheese. However, the Camembert cheese from Ho-LowGS was, in fact, characterized especially by lower protein content. LowGS feeding system and No breed produced more yellow cheeses. Feeding systems had limited effects on the firmness of Camembert and Pont-l’Evêque cheeses measured by penetrometry. In sensory analysis, Ho breed and LowGS feeding produced a Camembert cheese with a more melting texture in the mouth due to the increase of spreadability index and of proteolysis. The type of cheese also had an influence: the effects were more important on Camembert cheese than on Pont-l’Evêque cheese. Only the Ho-LowGS treatment produced a very specific Camembert cheese different from the others. The feeding systems and breed of dairy cow have no determinant effect on PDO (protected designation of origin) Camembert and Pont-l’Evêque cheeses, especially regarding taste. In this kind of trial, despite the effects of feeding systems and breed on milk composition, the role of cheese ripening and microbiology appears to be of considerable importance.