PREPARATION AND CHARACTERIZATION OF NOVEL BIODEGRADABLE ACTIVE FILMS BASED ON YEAST CELL WALL AND THYMOL

M. PELTZER; J.F. DELGADO; A. SALVAY; R, CANEL; A. MOAVRO; V. LUDEMANN; J.R.WAGNER

Punta del Este

Congreso; 2º Congreso Iberoamericano de Ingeniería de los Alimentos; 2016

Yeast cell wall (YCW) is composed principally β-glucans and mananoproteins.Among the exceptional properties of β-glucans it was reported its capacity to form films with promising characteristics. The use of YCW for such applications, agrees with the interest of revalorization of industrial residues since it is a byproduct of the yeast extract industry. The development of active materials to increased food shelflife by the addition of antioxidants and antimicrobials agents is an important trend of innovations in food industry. The aim of this work is to develop a novel active and biodegradable material based on YCW and thymol as antimicrobial agent.Films were obtained by preparing YCW dispersion at 5wt% (pH 11) and thenthermally treated (90 ºC, 20 min). Glycerol was added as plasticizer (25%wt/wt dry matter) and different concentrations of thymol were tested: 6, 8 y 10 wt% (g thymol/g dry matter). Formulations were poured in plastic Petri dishes and films were obtained by the casting method (35ºC y 50% relative humidity).Characterization of the active films was performed to study the influence of the thymol on the film properties. Thermogravimetric analysis was carried out to determine the thermal stability of the material and no detrimental changes were observed by the addition of thymol. Possible changes and interactions between the polymer matrix and thymol were studied by FTIR. Mechanical properties were assayed by uniaxial tests and no significant changes in tensile strength, Young modulus and elongation at break were appreciated. Finally, the antimicrobial activity of films was tested against typical fungus present in food: Geotrichum candidum, Aspergillus niger, Mucor racemosus, by using the agar diffusion method. Growth inhibition was detected for the three studied fungus and the relative sensibility to the thymol was G. candidum > A. niger > Mucor and as expected the antimicrobial effect was increased with the increasing amount of thymol in the formulation.