Efeito da lipólise na mensuração dos teores de gordura e proteína do leite pelos métodos de espectroscopia no infravermelho por filtro e transformada de fourier (ftir)

Abstract

The objective was to quantify the effect of lipolysis in the measurement of fat and milk protein by IR spectroscopy, comparing the methods of analysis of filter and FTIR (Fourier Transfor Infrared). Ten liters of raw milk were collected from the Experimental Farm Prof. Hélio Barbosa,UFMG. The milk has undergone pasteurization (65°C/30 seconds) and the total volume was homogenized and aliquoted into 40 ml samples containing bronopol. To promote lipolysis enzyme used was Pseudomonas fluorescens (Sigma Aldrich®, 20.000U/g). Aliquots of the enzyme were added in three concentrations (100U, 300U, 600U) and incubated at 7 ° C, 20 ° C, 30 ° C and 40 ° C. Samples without addition of enzyme were considered as control samples. The analyzes occurred after incubation periods of 0, 3, 6, 24, 48 and 96 hours. Samples incubated at 7° C were analyzed by the period of 168 hours. All samples were analyzed by means of IR spectroscopy by filter (Bentley® 2000) and FTIR (Combiscope®). It has been shown significant effect of milk lipolysis in the measurement of fat and protein by IR spectroscopy, with a drop in the reading of the fat content and increased reading of protein content. The different spectroscopy methods in IV showed significant statistical differences (p <0.05) in reading the fat, but no significant statistical differences (p> 0.05) in reading the protein. The IR spectroscopic equipment for filter showed the greatest variation reading the fat content when compared to the equipment of IR spectroscopy by FTIR. The samples incubated at 20 ° C, 30 ° C and 40 ° C were similar statistically, as well as periods of 24, 48, 96 and 168 hours. It follows that the effect of lipolysis can have a significant effect on fat content and protein determined by IR spectroscopy. The storage temperature and the period between the collection and analysis are essential to preserve the quality of milk samples for analysis.