Efeitos da temperatura e do tempo nas propriedades físico-químicas e na composição de ácidos graxos da banha na etapa de secagem

Abstract

The quality of lard depends on many factors, from the breed of pig from which the raw materials were obtained and their diet, however, the most significant step is its industrial processing. The lard drying stage consists of applying temperature for a certain time in order to reduce the moisture content in its composition, but this process must be controlled so that there are no changes in the physicochemical properties of the material, composition of fatty acids and mainly, the degradation of the product does not occur. Based on the above, the present study applied a 32 factorial design with triplicates at the central point and the methodology of response surfaces to evaluate the effects of temperature and time on the physicochemical properties (peroxide index, kreis index, color – spectrophotometry and colorimetry, polar compounds) and on the fatty acid composition of lard on the drying stage, with the applied temperatures being 130, 155 and 180 °C and the applied times being 1, 5 and 9 hours. After carrying out the experiments under the proposed conditions and analyzing the samples, statistical tools were applied to evaluate the data obtained, with analysis of variance (ANOVA), where linear and linear-quadratic models were tested, p-value analysis, coefficient of determination R2, Pareto plots of interactions, response surfaces and contour plots. For the answers peroxide index, color analysis, polar compounds and kreis index, the linear-quadratic model was highly significant and with normal distribution of residues. An R2 between 97.19% and 99.99% and a p-value between 9.96.10-12 and 1.5.10-2 were obtained. It was observed that there was an increase in the values obtained for all response variables analyzed with the increase in time and temperature applied in the drying stage. For color analysis by colorimetry, it was observed that the sample became more yellowish and darker with increasing time and temperature. Eleven fatty acids with carbon chains from C14 to C23 were characterized by gas chromatography. Linoleic acid showed the greatest significant reduction (3.87%) between treatments 1 (1 h at 120 °C) and 6 (9 h at 180 °C). There was a reduction of 18.30% in the total concentration of fatty acids in these treatments, showing the direct relationship of degradation with the increase in temperature in relation to time. The analysis of the CPs indicated that the saturated fatty acids of short carbonic chain C14, C16 and C17, tended to increase the concentration in the treatment with the time and higher temperatures. On the other hand, C18:2n6c and C21, C22 and C23, which represent the FA with the highest saturated carbon chain, with the exception of C18:2n6c, tended to increase in concentration in treatments with lower temperature and model time. Based on this, using the response surface methodology (MSR), it was concluded that temperature was the factor that most impacted the variation in the concentrations of the fatty acids studied, in addition to being the most relevant factor that contributed to the increase of the oxidation of the samples, evidenced by the physical-chemical analyzes carried out.