Análise do leite em pó de vaca e cabra por métodos físicos

Abstract

In this paper we present a study of the major organic compounds in cow milk powder and goat milk powder by infrared spectroscopy technique and a study of the average fat of cow milk and goat by thermal lens spectroscopy. We verified based on the obtained data that the absorption peaks are more intense for the compounds of fat and protein, both for cow milk, and for the goat milk. There was similarity between cow and goat regions absorption of compounds in the ranges of fat 3438 cm-1 - 1745 cm-1 which proves the existence of these compounds in the two species. However, it was observed that there were differences in absorption peaks of fat compounds that were only identified in goat milk in the ranges 1455 cm-1 - 1452 cm-1, 1397 cm-1, 1346 cm-1 - 1344 cm-1, 1314 cm-1 - 1323 cm-1. The obtained data were compared to proteins in different species, the region of absorption of protein from cow were marked by peaks with intensities 1660 cm-1 - 1650 cm-1; 1541 cm-1 - 1547 cm-1 ; 1241 cm-1 - 1251 cm-1; 700 cm-1. In the goat sample proteins have been identified in regions 1683 cm-1- 1682 cm-1, 1549 cm-1 - 1547 cm-1 1245 cm-1-1242 cm-1, 1168 cm-1. The compounds of carbohydrate samples of cow and goat milk showed absorption peaks of differentiation. The intervals carbohydrate cow milk have been identified in 1150 cm-1 - 1030 cm-1; 800 cm-1 - 1000 cm-1. In the sample of goat were in regions 1099 cm-1 - 1096 cm-1; 973 cm-1 - 971 cm-1; 890 cm-1. The compounds of polyunsaturated acids have been identified in nearby regions, in cow milk 722 cm-1 and the goat milk in 727 cm-1. By infrared spectroscopy it was possible to identify similarities and differences among the samples of milk powder from cow and goat milk powder, due to high sensitivity of the technique used. It was possible to detect differences between whole goat milk and skimmed goat milk, some compounds with reduced fat, even though the milk is skimmed, it was possible to identify some characteristic fat intervals in this sample. For the analyzes of cow milk fat and goat milk fat, we used the technique of spectroscopy mode mismatched thermal lens in order to study their thermal properties, which were obtained from thermal diffusivity measurements of each sample. The contributions of this work are pioneer for this type of sample and should contribute to a better understanding of the thermal properties of milk fats. The values for the thermal diffusivity of the cow fat of milk were 11,49 x 10-4 cm2/s (GLI) and 8,76 x 10-4 cm2/s (GLII); for goat milk were 11,00 x 10-4 cm2/s (GLC1) and 3,82 x 10-4 cm2/s .This study confirms that the thermal lens technique is sensitive enough to identify differences in the structures of molecules of milk fat between the two species studied here. Finally, the results of this study indicate that both the technique of infrared spectroscopy as the average thermal lens spectroscopy may be useful in establishing new parameters for monitoring quality of milk powder from cow and goat milk powder, as well as fat cow and goat milk.