Coating papers with soy protein isolates as inclusion matrix of carvacrol

Antimicrobial papers were prepared by coating paper with soy protein isolate (SPI) solution as inclusion matrix of carvacrol, an antimicrobial agent. Addition of carvacrol (30% w/w of SPI) to SPI solution (10% w/v) prepared at 25 °C induced soy protein aggregates and viscosity decrease. Heat treatment (50, 70, 90 °C) of SPI solutions and carvacrol addition improved homogeneity reduced particles size and increased viscosity of solutions. The aggregated structure of SPI in the presence of carvacrol at 25 °C may play the role of a trapping structure leading to low carvacrol losses during coating and drying process of paper (9.6% against 37% after heat treatment at 90 °C) and to lower release rates specially the first three days (0.04 g/m2/day and 0.31 g/m2/day when SPI coating solutions were prepared at 25 and 90 °C, respectively). Regardless of the heat treatments received by the SPI solutions, residual carvacrol quantities in the coated papers after 50 days ranged between 0.6 and 0.7 g/m2.