Effect of lactic starter cultures on the organic acid composition of milk and cheese during ripening—analysis by HPLC

Abstract

The major function of lactic starter cultures in cheese making is to produce lactic and other organic acids from the carbohydrates present in milk. The activity of six starter cultures consisting of two Lactococcus lactis ssp. lactis, two Lactococcus lactis ssp. lactis biovar. diacetylactis and two Leuconostoc strains, was tested by monitoring the evolution of the organic acid composition of milk by a modified HPLC method. In addition, their performance as cheese starters was also tested. The HPLC method developed proved to be a precise tool to monitor the organic acid content. Thus, it can be used to follow the fermentation ability of starter cultures, providing information about the type of fermentation. The use of any of the six starters assayed is suggested for manufacturing Afuega'l Pitu cheese.

Mathematical Expressions for Organic Acids in Early Ripening of a Cheddar Cheese

“…Pyruvic acid (almost undetectable quantities to 200 mg kg À1 ) represented a steady increase up to 12 days of storage after an initial lag-phase. Some workers have reported, however, that pyruvic acid does not follow any particular trend during maturation of Cheddar and other cheeses, mainly as a result of its role as carbon source for, and intermediate in numerous pathways involved in cheese manufacturing (Larson and Hegarty, 1979;Marsili, 1985;Bevilacqua and Califano, 1992;Bouzas et al, 1993;Gonza´lez de Llano et al, 1996).…”

“…Orotic, formic, fumaric, uric and hippuric acids as well as diacetyl were detected infrequently in negligible quantities, although considerably higher quantities have been reported in the literature. Gonza´lez de Llano et al (1996) detected hippuric acid in Cheddar cheese, which disappeared rapidly after coagulation suggesting that it could be utilized as a precursor in benzoic acid synthesis. Studies have reported formic and uric acid to either decrease or increase in minute amounts during maturation (Bevilacqua and Califano, 1992;Gonza´lez de Llano et al, 1996).…”

“…Propionic acid has been reported to increase gradually over the maturation period as it is influenced considerably by non-starter contamination (Marsili, 1985;McGregor and White, 1990;St-Gelais et al, 1991;Bouzas et al, 1993). Propionic acid fermentation, casein amino acids and non-specific esterase activities have been suggested as sources of propionic acid during maturation (Bouzas et al, 1993;Gonza´lez de Llano et al, 1996). Values found for butyric acid during this study could probably be the result of lipase action in milk (Kamaly and Marth, 1989) and corresponded with St-Gelais et al (1991), who observed a gradual increase in butyric acid content over a 6-month maturation period of Cheddar cheese.…”

“…Using a variety of techniques such as high performance liquid chromatography, researchers have identified and quantified a number of organic acids that occur in Cheddar cheeses of varying ages . Although a number of organic acids have been claimed to follow specific patterns during maturation, some organic acids do not follow any particular trend during the maturation of Cheddar and other cheeses, mainly because they act as intermediates in a number of biochemical pathways (Larson and Hegarty, 1979;Marsili, 1985;Bevilacqua and Califano, 1992;Bouzas et al, 1993;Gonza´lez de Llano et al, 1996). In an attempt to quantitate the development of organic acids during cheese maturation, a number of workers have used least-square correlation coefficients, two-way multivariate analysis of variance and post-hoc multiple comparisons to determine the most suitable predictors of the glycolytic age of Cheddar cheese, whereas stepwise regression analysis and stepwise discriminant analysis have also been utilized (Pham and Nakai, 1983;Mohler-Smith and Nakai, 1990;Bouzas et al, 1993).…”

The yctCBA Operon of Yersinia ruckeri , Involved in In Vivo Citrate Uptake, Is Not Required for Virulence

“…Increases of 24.25% Ϯ 5.57% and 48.36% Ϯ 7.79% in yctCBA promoter expression were obtained for RTS and FBS, respectively. High-performance liquid chromatographic (HPLC) analysis of both sera was performed by the method of González de Llano et al (17) using an ionic exclusion column ICSep ION-300 (Transgenomic, San Jose, CA) loaded with 100 l of a serum sample that had previously been diluted 10-fold and filtered (0.45 m). Citric acid elution occurred at 14 min, and quantification was performed by using a linear regression equation (R 2 Ն 0.99) using citric acid at different concentrations as a standard.…”