Milk stability during thermal processing of pasteurization and UHT (Ultra High Temperature)

Abstract

The present project aims to give continuity to the research field funded by FAPESP (2012/23212-0 and 2012/22165-9), which was the subject of the dissertation of the present candidate for PhD scholarship, whose results have been published recently in one paper accepted (MARTINS et al., 2015a) and one manuscript submitted (MARTINS et al., 2015b). Previous studies indicated that blood acidification and deficiency of pasture or severe feed restriction may reduce the milk stability. However, it is not clear how nutrition and their interactions can alter the milk concentration of ions and the concentration and stability of milk proteins, as milk concentration of ionic calcium and changes in casein subunits were the main milk modifications associated with the incidence of unstable not-acid milk. Moreover, the milk ethanol stability has low reliability to estimate the milk heat stability, which aggravates the problems caused by unstable milk without acquired acidity. Thus, the hypotheses that will be tested in this study are: 1 - the use of buffering/alkalinizing in the diet may reduce ruminal acidification, especially in diets with high non-fiber carbohydrate content, and milk concentration of ionic calcium, which can help to maintain milk stable to reaction with ethanol and during thermal heating; 2 - the adequate ruminal availability of energy and protein maximizes microbial protein synthesis, which provides adequate supply of amino acids to the mammary gland and prevents changes in milk proteins concentrations and stability; 3 - alcohol test has limited capability to estimate the milk heat stability; however, in the present study ethanol concentration in the alcohol solution may be defined more accurately and precisely to discard or destined milk for the most appropriated industrial processing, and also alternative methods to alcohol test can estimate the milk thermal stability in dairy plant processing. In order to test our hypothesis we will divide the project into 3 experiments, where each one will have the following specific objective: 1 - evaluate the accuracy, precision and robustness of the methodologies to estimate the milk heat stability, where the standard result will be the milk stability during thermal processing of pasteurization and UHT (Ultra High Temperature); 2 - evaluate the effect of non-fibrous carbohydrate source, inclusion of buffering/alkalinizing, and their interactions, on the digestive metabolism and the milk composition and stability of lactating dairy cows; 3 - evaluate the effect of PDR/RUP ratio and non-fibrous carbohydrate source (high or moderate ruminal degradability) on the digestive metabolism and the milk composition and stability of the lactating dairy cows.