RESUMO
Rapid analytical methods can contribute to the expansion of milk fatty acid determination for various important practical purposes. The reliability of data resulting from these routine methods plays a crucial role. Bulk and individual milk samples (60 and 345, respectively) were obtained from Czech Fleckvieh and Holstein dairy cows in the Czech Republic. The correlation between milk fatty acid (FA) proportions determined by the routine method (infrared spectroscopy in the mid-region in connection with Fourier transformation; FT-MIR) and the reference method (gas chromatography; GC) was evaluated. To validate the calibration of the FT-MIR method, a linear regression model was used. For bulk milk samples, the correlation coefficients between these methods were higher for the saturated (SFAs) and unsaturated FAs (UFAs) (r = 0.7169 and 0.9232; p < 0.001) than for the trans isomers of UFAs (TFAs) and polyunsaturated FAs (PUFAs) (r = 0.5706 and 0.6278; p < 0.001). Similar results were found for individual milk samples: r = 0.8592 and 0.8666 (p < 0.001) for SFAs and UFAs, 0.1690 (p < 0.01) for TFAs, and 0.3314 (p < 0.001) for PUFAs. The correlation coefficients for TFAs and PUFAs were statistically significant but too low for practical analytical application. The results indicate that the FT-MIR method can be used for routine determination mainly for SFAs and UFAs.
RESUMO
ABSTRACT: Evaluation of fatty acids (FAs) stability in dairy products undergoing technological milk processing is important for subsequent determinations of nutritional value. The aim of the study was to assess FA composition in milk and its dairy product and to explore differences in the FA profile found in yoghurt compared to raw material (goat milk). In the present study, a reduced proportion of volatile FAs (VFA) that cause "goat flavor" was reported in goat yoghurt in comparison to the FA profile of milk. Conversely, an increase of medium-chain as well as beneficial long-chain and unsaturated FAs (UFA) was reported in yoghurt compared with milk. In all cases, the differences in the FA composition between milk and yoghurt were not significant; therefore, it was found that manufacturing of yoghurt had no major influence on FA composition.
RESUMO: A avaliação da estabilidade de ácidos graxos (ags) em produtos lácteos submetidos ao processamento tecnológico de leite é importante para as determinações subsequentes do valor nutricional. O objetivo do estudo foi avaliar a composição de fa no leite e seus produtos lácteos e explorar as diferenças no perfil de fa encontradas no iogurte em comparação com a matéria-prima (leite de cabra). No presente estudo, uma proporção reduzida de ácidos graxos voláteis (agv) que causam "sabor de cabra" foi encontrada no iogurte de cabra em comparação com o perfil de fa do leite. Por outro lado, um aumento de ácidos graxos de cadeia longa e não saturados de cadeia média e benéfica (ufa) foi encontrado no iogurte em comparação com o leite. Em todos os casos, as diferenças na composição de fa entre leite e iogurte não foram significativas. Portanto, verificou-se que a fabricação de iogurte não teve grande influência na composição da fa.