M. Albisu

Indigenous Lactic Acid Bacteria in Idiazábal Ewes’ Milk Cheese

Abstract Three batches of Idiazabal cheese were studied at different production stages. Counts obtained on three solid media (M17, MRS and MSE agar) showed growth during coagulation, pressing and brining operations and a decrease during the two first months of ripening. While the pH and water activity decreased, dry matter and NaCl increased during ripening. Physiological and biochemical characteristics of lactic acid bacteria were studied for their identification. Of the Lactococcus strains, 61% were identified as Lc. lactis subsp. lactis biovar diacetylactis , 30% as Lc. lactis subsp. lactis , 7% as Lc. lactis subsp. cremoris and 2% Lc. raffinolactis . All Lactobacillus isolated from milk and curd and 19% of those isolated from cheese were identified as Lb. plantarum . The predominant Lactobacillus in cheese was Lb. casei subsp. casei (64%). Leuconostoc lactis was identified in cheese.

Seasonal changes in the composition of bulk raw ewe's milk used for Idiazabal cheese manufacture

Seasonal changes in the composition of bulk raw ewes milk used for Idiazabal cheese manufacture and its influence on the cheese yield are reviewed. This review is based on biochemical and microbiological data previously published on the composition of a bulk raw ewes milk collected at three different times of the year. In order to characterize, in a more extensive perspective, the seasonal changes in the composition of this bulk raw ewes milk and its influence on actual cheese yield, multivariate statistical analyses were applied to the compositional data of the milk and the actual cheese yield obtained at the factory. The results show pronounced seasonal changes in the composition of bulk raw ewes milk. Changes in cheese yield, lipolytic activity and microbiological quality of the bulk raw ewes milk are the principal aspects seasonally affected during the cheesemaking period. Also, the seasonal changes observed in the bulk raw ewes milk composition strongly affect the quality of Idiazabal cheeses manufactured over the cheesemaking period.

Consumer preference structures for traditional Spanish cheeses and their relationship with sensory properties

Abstract Eleven different cheeses were sensory profiled by a trained panel using a previously defined methodology. Using the same set of samples a group of 300 consumers resident in the Basque Country (three different regions: Alava, Bizkaia and Gipuzkoa) and Navarra (North of Spain), scored their preferences in a blind-test and taking into account their concepts on the samples. It was observed that there were important differences between consumer concept and sensory preference responses for most of the cheeses, indicating different focusing at the time of assessing preference. Generally, Idiazabal cheese concept was very similar to what consumers defined as the ideal cheese. Sensory descriptive terms nutty, buttery (flavor), sweet, smoky, rennett (odor), firmness and granularity presented a significant correlation coefficient with preference scores, although they were different among the four considered regions and the trained panel. The information obtained in this study could help researchers and marketing professionals elucidate strategies to approach firm products to ideal profiled cheeses.

Lamb rennet paste in ovine cheese (Idiazabal) manufacture. Proteolysis and relationship between analytical and sensory parameters

Abstract Cheeses were manufactured with 2 levels of lamb rennet paste or bovine rennet, at two times of the year, to study the effect of artisanally prepared lamb rennet paste (at high and low levels) on the concentrations of proteolysis products (nitrogen fractions, casein degradation and free amino acids). Cheeses made with the lamb rennet paste presented a significantly different evolution of the αs1-I-casein fraction during ripening, as measured by urea polyacrylamide gel electrophoresis. The time of the year affected the concentrations of 39% of the individual free amino acids, as determined by reversed-phase high-pressure liquid chromatography. The relationship between some biochemical parameters (gross composition, degrees of lipolysis (Lamb rennet paste in ovine cheese manufacture. Lipolysis and flavour. International Dairy Journal (2003) in press) and proteolysis) and the sensory characteristics of the cheese (Virto et al., 2003) were studied by a principal component analysis. The effect of the technological parameters “type of rennet” and “time of the year” on these analytical variables and sensory characteristics of the cheese was described by three principal components which explained 80.8% of the total variance. The factor “rennet paste” included concentrations of short chain free fatty acids, sensory descriptors related to strong odours and flavours, an unidentified peptide A1, and αs1-I-caseins. The effect of the ‘time of the year’ was described by two other factors: the “secondary proteolysis” factor, which included the concentrations of free amino acids and could be related to the different endogenous microflora of the raw milk, and the “seasonal milk composition” factor, which included the fat content and the plasmin activity of the milk.

Sensory profile of Ewe's milk cheeses

Sensory profiles for several ewe’s milk cheeses were developed and main sensory differences evaluated using a specifically designed methodology. It was stated that the existence of several clearly defined groups of sensory terms were negatively correlated. One group consisted of the attributes odor intensity, sharp odor, brine odor, rennet flavor, and butyric acid flavor. The other group consisted of milky odor, toasty odor, buttery odor and flavor, nutty flavor, and sweet flavor. Results pointed out that every descriptor except surface roughness showed a significant difference (p< 0.01) among the samples. Main sensory differences were basically attributable to different manufacturing technologies as well as different ripening periods.

Chemical references in sensory analysis of smoke flavourings

A new descriptive language and the corresponding set of chemical standard references for the evaluation of smoke flavourings is proposed. Analysis of variance (ANOVA) and linear discriminant analysis (LDA) were applied to validate this lexicon as well as to analyse reproducibility, discriminatory ability and homogeneity of the panel. Results confirmed that the developed methology was adequate to describe and discriminate commercial smoke flavourings. The number of low correlations demonstrates the need to maintain the majority of the descriptors for carrying out descriptive quantitative sensory analysis of smoke flavourings.

Comparison of free choice profiling, direct similarity measurements and hedonic data for ewes’ milk cheeses sensory evaluation

Abstract The purpose of this work was to compare the sensory characteristics of ewes’ milk cheeses using several sensory methodologies (free choice profiling (FCP), direct similarity measurements, and hedonic data). For this purpose, visual plot inspection as well as correlation coefficients among sensory dimensions were considered. Multidimensional maps obtained by means of free choice profiling proved difficult to interpret without any other external source of information in contrast to data obtained by direct similarity measurement techniques that gave interpretable solutions. Cheese samples showed specific sensory characteristics mainly based on ripening time and manufacturing procedures. The techniques used in this study revealed great individual variability during sensory assessment of cheese samples mainly attributable to the absence of assessor training. Multidimensional solutions for the different correlation techniques are also discussed.

Brining time effect on physicochemical and microbiological parameters in Idiazábal cheese

Physicochemical and microbiological parameters were compared for three brining times (12, 24 and 36 h) for fresh, young, semihard and hard Idiazabal cheese. Longer brining time produced higher salt, dry matter and salt-moisture ratio and lower water activity values for all types of cheese according to ripening time, while non-significant changes were observed for pH. In fresh cheese (1-15 days ripening), non-significant differences for microbiological counts in relation to brining time were observed, except for moulds. In young and hard cheeses, Lactobacillus and Leuconostoc showed lower counts with longer brining times. In contrast, Micrococaceae, yeast and moulds were stimulated by higher salt content in matured cheeses. In addition. this work has proved that there are lower water activity values and lower microbiological counts in longer-matured Idiazabal cheeses. For the different brining and ripening times, positive correlations were observed among most of the microbial groups studied, but a different behavior was established for Enterococcus, Clostridium tyrobutyricum, yeast and moulds.

Effects of seasonal changes in feeding management under part-time grazing on the evolution of the composition and coagulation properties of raw milk from ewes

Ewe raw milk composition, rennet coagulation parameters, and curd texture were monitored throughout the milk production season in 11 commercial flocks reared under a part-time grazing system. Milking season lasted from February to July. During that period, the diet of the animals shifted from indoor feeding, consisting of concentrate and forage, to an outdoor grazing diet. Lean dry matter, fat, protein, calcium, and magnesium contents increased throughout the milking season, as did rennet coagulation time, curd firmness, and curd resistance to compression. However, lean dry matter, protein content, and curd resistance to compression stabilized when sheep started to graze. Principal component analysis correlated curd resistance to compression and proteins, whereas curd firmness was highly correlated with fat content and minerals. Discriminant analysis distributed milk samples according to the feeding management. Curd firmness, fat, and magnesium turned out to be discriminant variables. Those variables reflected the evolution of the composition and coagulation parameters when fresh pasture prevailed over other feeds in the diet of the flocks. The present study shows that seasonal changes associated with feeding management influence milk technological quality and that milk of good processing quality can be obtained under part-time grazing.

Evaluation of sensory quality of calf chops: A new methodological approach

A new method to evaluate the sensory quality of calf chops was developed by discussion with experts. Resulting method comprised four parameters: quality related to odor, texture, flavor and persistence. For each parameter, the sensory characteristics perceived are marked and, by using decision trees, corresponding quality is directly scored, so making the assessment more objective. Global sensory quality is calculated by weighting these four partial qualities. Due to sensory characteristic collection, the method also provides an exhaustive description of each sample. To check the appropriateness of the method, 127 calf chop samples were evaluated by a panel specifically trained to apply it. Results confirmed the suitability of the method to describe the samples and differentiate among them according to their quality level. This innovative approach can be very useful for quality control and also to study the effects of different factors on meat sensory quality.