Avaliação dos parâmetros físico-químicos do leite cru refrigerado de propriedades rurais na região noroeste do Rio Grande do Sul

Abstract

The objective was to study the effect of seasons on the evaluation of physical-chemical parameters of refrigerated raw milk from rural properties in Rio Grande do Sul. The present study was developed using monthly data (March 1, 2021 to July 31, 2022) of total solids (TS), lactose, fat and protein from samples from refrigerated raw milk expansion tanks. Milk samples were collected from rural properties in the following municipalities: Ajuricaba, Arroio do Tigre, Boa Vista do Incra, Bozano, Condor, Fortaleza dos Valos, Ibirubá, Ijuí, Palmeira das Missões, Panambi, Passo Fundo, Pejuçara, Quinze de Novembro and Salto do Jacuí. Considering that the composition of milk may vary depending on weather conditions, statistical analyzes took place according to the seasons: spring, summer, autumn and winter. Descriptive statistics, whose average values demonstrate that the samples comply with normative instruction Nº 77 (BRASIL, 2018b) and all have low coefficients of variation within the seasons. Low (r = 0.301) but significant (P = 0.000) correlation for lactose levels indicates that there may have been an effect of somatic cell count and total bacterial count. However the correlations of fat and protein were high and highly significant. Generally, a medium to high correlation between lactose and protein is expected, but in the present study it was low (r = 0.157). The correlation between fat and protein is average. The total solids content demonstrates that in autumn and winter the contents were higher (P = 0.05) than in spring and summer. The lactose content was higher (P = 0.05) in winter compared to the other seasons. Fat content varied (P = 0.05) across all seasons. Protein content did not differ between autumn and winter, and both differed (P = 0.05) from summer and spring, which also differed. The composition of the milk varied according to the seasons.