Cis-trans retinol isomerisation: Influence of microorganisms during the production of pasta filata cheeses

The isomerisation index, or degree of retinol isomerisation (DRI), i.e. the percentage ratio between 13 -cis and all-trans retinol, could be used as process and product index in dairy products. To better investigate microbial influence on retinol isomerisation, retinol isomerisation and microbial levels have been monitored during the technological process and the storage of different "pasta filata" cheeses. In the investigated cheeses, after a saponification procedure and HPLC analysis, 13 -cis retinol, all-trans retinol and other cis retinols were detected. During production, an increase of 13-cis retinol and of the DRI was found. As to their initial values, an increment in almost all microorganisms, most remarkable for lactic acid bacteria, was detected. The isomerisation index was found to be significantly correlated to the growth of thermophilic lactic acid bacteria during the production process.(c) 2022 Elsevier Ltd. All rights reserved.