Characterization of typical Tunisian fermented milk, rayeb
Traditional Tunisian fermented milk, rayeb, was produced according to the traditional method. Physicochemical, microstructural, microbiological characteristics and major aromatic compounds evaluation were studied. The results show a decrease in lactose content and pH value and an increase in lactic acid during spontaneous fermentation. The microstructure of rayeb consisted of individualized particles that were coalesced in chains leading to relatively homogeneous sieve. Lactic acid bacteria (LAB) and yeasts present in rayeb were responsible for lactic acid fermentation and aroma development. Dynamic headspace (DHS) extraction procedure shows the existence of four major volatile compounds: acetaldehyde, ethanol, diacetyl and acetoin in the rayeb.
Key words: Rayeb, spontaneous fermentation, physicochemical composition, microstructure, microbiological, volatile compounds.