The production of acetaldehyde, diacetyl and ethanol was evaluated in whole plain yoghurts manufactured with commercial starter cultures, yoghurt acquired in a local market, and milk fermented by a single culture of either Streptococcus thermophilus or Lactobacillus delbrueckii ssp. bulgaricus. The headspace technique was used for sample preparation, following identification and quantification by gas chromatography. During an 8‐h incubation period, mixed cultures were the most efficient in lowering the pH (from 6.30 to 4.8), followed by S. thermophilus (from 6.30 to 5.18) and L. bulgaricus (from 6.30 to 5.8). During the storage period, however, a single culture of L. bulgaricus decreased the pH more than S. thermophilus, but still less than the mixed commercial cultures. Plain yoghurts acquired in the market, those made with commercial starter cultures, and fermented milks obtained with single cultures showed, after 21 days of storage, concentrations of acetaldehyde from 11 to 35 mg/L, and of diacetyl from 0 to 0.85 mg/L. An increasing concentration of ethanol was observed during the storage period, and its production was observed even in the incubation stage of all products. It was also observed that the acetaldehyde concentration was inversely correlated to ethanol production in some products. The combination of headspace, identification and quantification techniques by gas chromatography in this work was efficient in the identification and quantification of the major aromatic compounds and ethanol content of yoghurt.
A manteiga de garrafa é um produto largamente utilizado no Nordeste do Brasil em geral, e no norte/nordeste do Estado de Minas Gerais em particular, sendo a região de Salinas importante produtora desse tipo de manteiga. Apesar disso, não são encontrados na literatura números significativos de relatos de pesquisas sobre esse produto. Assim, este estudo foi realizado para caracterizar físico-quimicamente manteigas de garrafa produzidas na região de Salinas, norte de Minas Gerais, comparando os dados obtidos com a Legislação vigente para este produto (Brasil, 2002). O nível de umidade variou de 0,6% a 3,0%, a gordura de 95,6% a 98,6%, o pH foi de 2,23 a 6,27, a porcentagem de cloretos variou de 0,74% a 1,79%, as proteínas ficaram em torno de 0,12% a 0,15%, os ácidos graxos livres apresentaram de 7,60 mol/L a 48,08 mol/L e a acidez variou de 0,60% a 9,52% de ácido lático. Todas as manteigas de garrafa analisadas apresentaram-se fora do padrão exigido pela Legislação vigente (BRASIL, 2002).
The economic history of Salinas, Minas Gerais is largely based on cattle-breeding. The discoverers found in the city's region a large potential for the progress of their activities, either in agriculture or in cattle-breeding (OLIVEIRA, 2000). Even today, milk production plays an important role in family farming activities, which besides raw milk, provides curdal cheese, cottage cheese, and "bottled butter fat", which is manufactured with fat extracted from whey. Therefore, this study was conducted to analyze the fatty acid profile of "bottled butter fat" produced in Salinas, in the northern region of Minas Gerais , and also to analyze the ratio of saturated to unsaturated fatty acid of these butters. The fatty acid profile of the "bottled butter fat" was determined by chromatographic analysis, according to methodology advanced by Luddy et al. (1960), and later modified by Abreu (1993). Analysis of variance was applied for comparison of the averages by the Tukey test at 5% probability. The fatty acid profiles of all the "bottled butter fat" were found to be similar. The concentration of saturated fatty acids was higher than that of the unsaturated, with averages of 60,36% and 39,64%, respectively.
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