Carvacrol losses from soy protein coated papers as a function of drying conditions

The influence of drying conditions (temperature/time) on carvacrol losses was investigated for antimicrobial packaging obtained by coating paper with soy protein solutions containing 30% of carvacrol (w/w of SPI) as antimicrobial agent. The lowest carvacrol losses ranging from 25 to 30% were obtained for three drying conditions: high temperature and short time 250°C for 20 s or mild conditions 50°C for 210 s and 25°C for 3 h. In contrast, intermediate drying conditions (100°C/90 s and 150°C/45 s) led to carvacrol losses higher than 50%. The weaker losses observed for drying at 250°C compared with the intermediate temperatures could be explained by the rapid formation of a thick and protective crust that acted as a selective membrane letting to past water and retaining carvacrol. For drying at 150°C, high losses were related to water vaporization and carvacrol carrying as attested by the presence of holes observed by SEM and due to bubble formation and bursting. If drying conditions affected the carvacrol losses and its retention from coated papers during storage at 30°C and 60% relative humidity, the antimicrobial activity was found only dependent on carvacrol amount of the coated papers.