Influência da temperatura na agregação e desnaturação da β-Lactoglobulina

Abstract

In its composition, the milk presents water, carbohydrates, fat, protein, minerals and vitamins. The two main proteins, β-lactoglobulin and α-lactalbumin have been the subject of numerous studies to elucidate and explore possible structure / function relationships that cause aggregations and incrustations harmful to the milk industry. In this sense, in order to understand the influence of temperature on the denaturation and aggregation of the β-lactoglobulin protein (β-LG) in the presence or not of calcium ions, this work was developed. The sample used consists of a protein isolate of β-lactoglobulin at 97% purity, and 5 hydrated solutions of β lactoglobulin are prepared, both for the analysis of laser granulometry and for Nuclear Magnetic Resonance (NMR). At the temperature at 75ºC the particle size analysis showed that the "White" sample presented larger clusters in relation to the "Ice" sample due to the heating time from 1 hour to "White" and 30 minutes to "Ice". In the NMR reading of samples A and B, it was observed that there are some differences of overlap in the spectrum considering the absence and presence of calcium. For the temperature at 80 ° C and 90 ° C, in the granulometric analysis, it was observed that the "Heating" (C) samples denatureed and gelled very fast, even making the reading impossible, since they were no longer in the liquid state. In the NMR reading of samples C and D, it can be observed that there are some differences in the spectrum due to the time and the heating method in the presence of calcium that differ from one sample to another. Thus, it is concluded that the higher the temperature the shorter the time required for denaturation of the protein. However, the temperature is directly proportional to the action of calcium, that is, the higher the temperature, the larger the protein agglomerates will form in the presence of calcium.