Preliminary study on kinetics of pyroglutamic acid formation in fermented milk

Pyroglutamic acid (pGlu) influences the aromatic and sensory properties of foods and has several benefits for human health. The presence and kinetics of pGlu formation in fermented milk samples were investigated from a chemical point of view. Plain yoghurt, kefir and other probiotic fermented milk products available on the market were analysed to quantify lactic acid and pGlu. The pGlu concentrations in fermented milks ranged from 51.65 to 277.37 mg 100 g-1 dry matter. Laboratory- scale fermented milk was produced, and samples were taken at different times of fermentation and storage to construct the kinetics curve. At the beginning of the fermentation process, pGlu was already present in UHT milk (188.69 mg 100 g-1 dry matter) used to elaborate fermented milk, and its content increased not only during fermentation but during storage as well, reaching up to 403.56 mg 100 g-1 dry matter after 30 days.