Lei de Newton aplicada ao processo de resfriamento do leite in natura

Abstract

Milk is defined as the product resulting from complete, uninterrupted milking, under hygienic conditions, of healthy, well-fed cows. Dairy farming is practiced throughout almost the entire national territory, generating jobs and income for rural residents and making an important contribution to the country's gross domestic product. With the increase in milk production, obtaining quality milk becomes essential, as it guarantees a safe food with nutritional quality for consumption, as well as increased shelf life and industrial yield for the production of dairy products. The objective of this work was to evaluate the cooling process of raw milk using Newton's Law of Cooling and the linear model. For this purpose, the variation in milk temperature during its cooling process was monitored; the physicochemical parameters of pH, density, stability to alizarol, titratable acidity in Degrees Dornic, cryoscopic index, fat and total dry extract (TDI) and defatted dry extract (DDI) of raw milk were determined; the cooling process of raw milk was modeled using Newton's Law and the linear model; the rate of temperature variation in relation to the time for cooling raw milk was determined. The experiment was conducted on a dairy farm in the municipality of Ramilândia in western Paraná. A mercury thermometer was used to collect temperature data. For the physical-chemical analyses, methodologies described in the literature were used. The experimental data were fitted to the mathematical models of Newton's Law of Cooling and linear model. It can be said that the ambient temperature did not interfere with the collected data. The milk took 140 minutes to reach a temperature of 4°C. Physicochemical analyses showed that the milk after being cooled to 4°C was slightly acidic, but the remaining parameters analyzed were in accordance with current legislation. The time it takes for the milk to reach a temperature of 4°C, obtained using Newton's Law of Cooling, corresponds to the value obtained during the practical experiment, proving the efficiency of the equation used to make predictions about the cooling of raw milk in the direct expansion tank. Both models significantly represented the experimental data. The linear model obtained a coefficient of determination of 0.9931 and an average sum of errors of 16.59, the Newton model obtained 0.9759 and 61.29, respectively. Hygienic and sanitary precautions must be taken to ensure that chilled milk meets the required standards. The Newton model and the linear model can be used to make predictions of the cooling of raw milk under the conditions used in this work.