The evolution of some biochemical indexes during the processing of some acid dairy products, under the influence of some external stimuli

Abstract

The acid dairy products are obtained by milk fermentation using lactic cultures and, in some cases, dairy bacteria associated with some yeast varieties for a mixed fermentation. The acid dairy products possess a high nutritive value. The fulfilled tests indicated that not all pursued parameters were modified during the processes for obtaining acid dairy products. The most significant changes were observed at the acidity samples parameters (pH, titrable acidity), changes produced due to the activity of lactic bacteria from the starter cultures which have consumed lactose from the milk and changed it in lactic acid; also the pH decreases and the acidity increases between some limits. It was also observed a difference between the values of the percentage of free amino acids at the raw material and at the finite product, namely it is greater for the finite product, especially for the butter milk than for the yoghurt. This difference indicates the progress of a proteolysis process, smaller at the yoghurt and more intense at the butter milk. The various added supplements influenced the fermentation but also the proteolysis, lipolysis, and protein coagulation and have also changed the physical, chemical and organoleptic properties of the finite product.