Gas and solute barrier properties of wheat gluten films: Application to the design of "Active Biopackagings"

Active packaging provide a supplementary means to control physiological, mi crobiological and physicochemical changes in food products. In this paper, we will expand on the use of wheat gluten films as active layers, i.e. when the film contribute by itself to the food preservation. Some potential use s of these biomaterials (e.g. modified atmosphere packaging of fruits and v egetables, slow release of food preservatives) are described with examples. The development of biopackaging or edible films with selective gas permeab ility is very promising for controlling respiratory exchange and improving the conservation of fresh or minimally processed fruits and vegetables. Whe at gluten films appear to have suitable O-2 barrier properties while remain ing relatively permeable to CO2. The gas permeability's of gluten based fil ms were measured at various temperatures and relative humidites. O-2/CO2 se lectivity increased from 3 (at 4 degrees C and low RH) to more than 45 (at 40 degrees c and 95%RH). Some selective gluten-based films have been shown to lead to the creation of very original atmospheres when used to wrap fres h mushrooms. The modified atmosphere rise to an equilibrium composition of 2-3% CO2 and 2-3% O-2 which is favourable to the mushroom overall quality. The diffusion of sorbic acid in various wheat gluten film was studied and t he release from the film to a model food was measured and modelled, The ant i-microbial effect of various edible gluten I sorbic acid based films was e valuated against Penicillium notatum. Simple gluten-based films had no own fungicidal effect but the gluten I lipid based films showed a strong sorbic acid retention and a marked own fungicidal effect, either at 30 degrees C or 4 degrees C, delaying the Penicillium notatum growth for more then 21 da ys.