45D-9 |
Increased moisture barrier properties of coatings obtained from mesquite gum modified matrixes |
E. BOSQUEZ-MOLINA, DBT, Universidad Autonoma Metropolitana, San Rafael Atlixco # 186, Mexico City, 09340, Mexico and E. J. Vernon-Carter, IPH, Universidad Autonoma Metropolitana-Iztapalapa. Composite coatings formulated with a blend of candelilla wax and mineral oil as the lipid phase, and mesquite gum as the structural material have potential as edible coatings for fresh Persian limes, but improvement of their mechanical and water barrier properties is desirable. The ability of hydrophobic substances to retard moisture transfer depends on the homogeneity of their final distribution in the matrix. The objective of this study was to evaluate the effect of different concentrations of glycerol and sorbitol on the structural matrix and water vapor permeability of mesquite gum-candelilla wax and mesquite gum-candelilla-mineral oil coatings. Emulsions were prepared using different ratios of mesquite gum/glycerol or sorbitol (1:0.1, 1:0.2, 1:0.5, 1:0.75, 1:1) as the structural matrix (10%w/w), and candelilla wax or a blend of candelilla wax-mineral oil as the dispersed hydrophobic phase (17.5%w/w). Control formulations were made without the addition of glycerol or sorbitol. Stability of each emulsion to coalescence was determined. Water vapor transmission rate (WVTR) and water vapor permeability (WVP) values calculated using ASTM standard method and WVP correction method, at RH (75 or 92%), for different coatings thickness (0.150, 0.300 mm). Formulations were applied on Persian limes, stored at 20 ± 1°C, 70-85% RH for up to 30 days. The weight loss and color L, a, b values were monitored during storage. A ratio of mesquite gum-glycerol (1:0.2) and a disperse phase of candelilla wax- mineral oil in a 2:1 ratio yielded coatings providing WVP 40% lower than those exhibited by the same formulation without glycerol. Weight loss in Persian limes was also reduced in 40% with this formulation and lime color changes were non-significantly different from control. Glycerol induced changes on the support matrix as evidenced by SEM. Finally, shelf life of Persian limes with this coating was 25 days.
Session 45D, Food Packaging: General
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