Effect of Naphtho-y-Pyrones (NGPs) on colour, mechanical and hydration properties of yeast cell wall films

G. REZZANI; F. MATHIEU; E.CHOQUE; DELGADO, J. F.; SALVAY, A. G.; M. PELTZER

Simposio; VI LATIN-AMERICAN POLYMER SYMPOSIUM (SLAP 2018) and XIV IBEROAMERICAN POLYMER CONGRESS (CIP 2018); 2018

INTRODUCTIONActive packaging is gaining more and more interest in order to extend food shelf life. The addition of antioxidants to the food contact material may prevent food oxidation, though increases food shelf life. Naphtho-y-Pyrones (NGPs) are secondary metabolites produced by the filamentous fungi Aspergillus tubingensis that demonstrated high antioxidant capacity (1,2). These natural molecules, the NGPs, are present as monomers or dimers and show different biological properties of interest for food and medical industries (2). The use of natural biopolymers, proteins and polysaccharides to produce materials for food contact applications is also increasing. Yeast cell wall is composed mainly by -glucans (polysaccharide) and mannoproteins which demonstrated promising filmogenic properties (3). The aim of this work is to understand how the incorporation of NGPs to YCW matrices modifies films colour, mechanical and hydration properties.EXPERIMENTAL METHODSNGPs extracts: Mycelial cake from sporulated culture of A. tubingensis was covered with ethanol and sonicated (50 Hz). The mix was then filtered to obtain crude extract (CE) containing both melanin (black) and NGPs (yellow) pigment. CE*3 is CE concentrated to 3V/V. EP was a CE semi-purified via Hypersep methodology (Thermofisher) which only contain NGPs. Enzymatic Yeast cell wall (YCW-E): Yeast cell wall was obtained by enzymatic hydrolysis of yeast cells from bakery yeast biomass. Papain 2.5% was used to perform the hydrolysis at 60 °C during 24 hours and 120 rpm. Active film production: A dispersion of 5% wt of YCW-E was prepared and EP-NGPs and CE*3 NGPs were added at different concentrations. Glycerol was used as plasticizer. Films were obtained by the casting method.Characterization: The colour of the obtained films was measured by using a Minolta chromameter CR-400 by the CIE-Lab system. Tensile test were performed with a load cell of 30 kgf and a speed of 5 mm/min. Water sorption kinetics and water vapour permeability (Pwexp) experiments were done (4). Kinetics experiments provided the solubility of water in the film (Sw) and water diffusion coefficients (Dw), and allowed compare Pw=SwxDw with Pwexp (4).RESULTS AND DISCUSSIONThe colour of the CE*3 darken the film, decreasing L* factor. Indeed, YCW-E-CE*3 samples turned to the red colour (a* increased) and to the blue (b* decreased). The change in the colour was evident and ΔE was near 60. Colour changes in YCW-E-EP samples were not so pronounced but the same trend was observed. Young modulus (YM) was significantly increased by the incorporations of EP-NGPs from 73 ± 17 to 327±53 (MPa) for control and YCW-E-EP 2% respectively. Meanwhile for CE*3 that value decreased but elongation at break was enhanced. As Figure 1 shows, Pwexp was decreased with the addition of 2% of both types of NGPs, barrier to the water vapour was improved mainly due to the decrease in Sw produced by the hydrophobicity of NGPs (5,6). Figure 1. Pwexp of samples with CE*3 and EP.CONCLUSIONPromising results were found by the addition of NGPs on YCW-E matrices. REFERENCES1. Zhang Y et al. J Antibiot 60, 204 ? 210, 20072. Choque E, et al. Appl Microbiol Biotechnol. 99, 1081-1096, 20153. H. Nancollas, In: S. Mann, J. Webb, R.J.P. Williams, editors. Biomineralization. Chemical and biochemical perspectives. New York: VCH, 157-182, 1989. 4. Peltzer et al. Food. Bioproc. Technol. Article sent.5. Delgado J.F. et al., Eur. Polym J. 99, 9-17, 2018.6. Nielsen KF et al. Anal Bioanal Chem 395, 1225?1242, 2009.ACKNOWLEDGMENTSTo the R&D program PUNQ 53/1037 and to the ANPCyT (Argentina) through the PICT-2015-315