C.A. Zalazar

Reggianito Argentino cheese: influence of Lactobacillus helveticus strains isolated from natural whey cultures on cheese making and ripening processes

Abstract Reggianito Argentino cheeses were manufactured with three defined single strains Lactobacillus helveticus cultured in sterile whey, and one “natural” whey starter. Gross composition of cheeses did not significantly differ, and viable starter cell counts were similar for all cheeses. Soluble nitrogen at pH 4.6 was also alike for cheeses made with natural or selected starters, but soluble nitrogen in trichloroacetic acid 12% and phosphotungstic acid 2.5% showed significant differences. Electrophoretograms showed that γ casein bands increased during ripening, while β casein band decreased; α s1 casein was also cleaved to α s1 -I. Acid degree values of fat for control and experimental 0-day old cheeses were slightly different, but were similar at 90 and 180 days of ripening. All cheeses were good quality Reggianito, but control and experimental samples differed in aroma and texture. Natural whey starter replacement by selected single starter of Lactobacillus did not alter cheese making and primary proteolysis or lipolysis, but it modified secondary proteolysis and sensory characteristics.

Influence of milk pretreatment on production of free fatty acids and volatile compounds in hard cheeses: Heat treatment and mechanical agitation

This work aimed to identify technological steps that can increase fat hydrolysis and volatile compounds production in hard cheeses; these biochemical events have been related with improved piquant taste and development of genuine flavor during cheese ripening. For that purpose, 2 different pretreatments of cheese milk were tested: heat treatment and mechanical agitation. Both factors were assayed at 2 levels: milk was either batch pasteurized or nonthermally treated, and mechanical agitation was either applied or not applied. For all combinations, hard cheeses (Reggianito type) were produced in a pilot plant and ripened for 90 d. In all cheeses the degree of lipolysis, assessed by gas chromatography, increased similarly during ripening. However, the proportion of short-chain fatty acids was higher in the cheeses made with unpasteurized milk, suggesting a higher activity of lipases with positional specificity toward the sn-3 position of the triglyceride, among which milk lipoprotein lipase is found. Similar results were found for most of the volatile compounds, determined by solid-phase microextraction-gas chromatography flame-ionization detector/mass spectrometry, which constitute the groups of ketones, alcohols, esters, and the group of acids. On the contrary, no effect of mechanical agitation was observed, although some interactions between factors were found. In the conditions of the study, results suggest that heat treatment had a higher effect on cheese lipolysis and volatile compounds production than partial destabilization of the fat emulsion produced by the agitation method applied.

Composition and volatile profiles of commercial Argentinean blue cheeses

BACKGROUND A first approach was made to acquire knowledge of the global composition, proteolysis, lipolysis and volatile profile of Argentinean blue cheeses. A total of 20 samples belonging to six leading commercial brands were analysed. A comparison of the results with bibliographical data on other blue cheeses was performed and the variability among and within dairy plants was also evaluated. RESULTS Values of global composition were intermediate in relation to those reported for mould-ripened cheeses. Levels of proteolysis and lipolysis were lower than those of other blue cheeses. Volatile compound profiles were characterised mainly by short-chain fatty acids, methyl ketones and secondary alcohols, as reported previously for blue cheeses. Wide-ranging values of physicochemical parameters, lipolysis and proteolysis levels as well as volatile compound areas of cheeses produced by each dairy plant were observed. Owing to this high variability in the chemistry and volatile profile of cheeses, principal component analysis of the data did not show groupings by commercial brands. CONCLUSION On the whole, Argentinean blue cheeses were characterised both by gross intermediate composition values and by proteolysis and lipolysis levels lower than those of blue cheeses of different origins. A typical volatile compound profile of blue cheeses was observed. The high variability found within each commercial brand could reflect the lack of standardisation of the technological processes used in blue cheese manufacturing in Argentina.

Multivariate analysis of proteolysis patterns differentiated the impact of six strains of probiotic bacteria on a semi-hard cheese.

The individual contribution of 6 strains of probiotic bacteria (3 of Lactobacillus acidophilus and 3 of the Lactobacillus casei group) to proteolysis patterns in a semi-hard cheese was assessed. Control cheeses (without probiotics) and 2 types of experimental cheeses (with the addition of probiotics either directly to milk or by a 2-step fermentation method) were manufactured. Cheeses containing Lb. acidophilus showed the most extensive peptidolysis, which was evidenced by changes in the peptide profiles and a noticeable increase of free amino acids compared with control cheeses. The strains of the Lb. casei group showed a lower contribution to cheese peptidolysis, which consisted mainly of free amino acid increase. Two-step fermentation improved peptidolytic activity for only one of the cultures of Lb. acidophilus tested. The addition of Lb. acidophilus strains into cheese may be suitable not only for their beneficial health effect but also for their influence on secondary proteolysis, consistent with acceleration of ripening and improved flavor formation.

Production of flavour compounds from fat during cheese ripening by action of lipases and esterases.

The milk fat is an essential component for the development of correct flavour in cheese. The lipolysis and catabolism of fatty acids are two biochemical events very important on flavour development of some cheese varieties. The role and characteristics of various lipolytic agents during cheese ripening is reviewed and discussed. Before starting with the specific study about formation of flavour compounds from milk fat during cheese ripening, a brief review of the technological aspects of cheese production is needed.

Effect of Lactose Hydrolysis during Manufacture and Storage of Drinkable Yogurt

Effect of Lactose Hydrolysis during Manufacture and Storage of Drinkable Yogurt Reduced-lactose yogurts are still not available in the Argentinean market despite the fact in Latin America the incidence of deficient-lactose individual is very high. In this work, variables to hydrolyze the lactose (three levels of β-galactosidase enzyme and the time of its addition) were evaluated during manufacture of natural and sweetened (8% p/v) drinkable yogurts. Experimental yogurts (with enzyme) were compared with controls (without enzyme). The evolution of lactose content, pH, titratable acidity and syneresis were analyzed during 28 days of storage at 5oC.