Effect of edible wheat gluten-based films and coatings on refrigerated strawberry (Fragaria ananassa) quality

Edible coatings and films can provide an alternative for extending the postharvest life of fresh fruits and vegetables. The effect of different wheat gluten-based coatings and films on refrigerated strawberry quality and shelf life was studied. Coatings were formed directly on the surface of the fruit and films were previously formed (on Teflon surfaces) and then used to pack fruit. Fruit quality was evaluated by weight loss, firmness retention, visible decay, surface color development, titratable acidity, total soluble solids, reducing sugar content and a sensory evaluation. The bilayer coating of wheat gluten and lipids (beeswax, stearic and palmitic acids) had a significant effect on the retention of firmness, reduced the weight loss and showed better results from the physico-chemical analysis compared to the control fruit. All the treatments with gluten film (except with the film pouch) also showed a beneficial effect on firmness retention compared to the control fruit. The gluten film (except the film wrap) seemed to be more promising for controlling decay than the coatings. Sensory evaluation of the strawberries showed that the gluten and the composite coatings maintained the visual quality of the fruit during the storage time, and the taste of the strawberries with the gluten coating was acceptable to consumers. However, the appearance and taste of the bilayer-coated fruit were unacceptable. © 2004 Elsevier B. V. All rights reserved.36219920

Effect of fatty acids and 'Brazilian elemi' on composite films based on gelatin

Composite edible/degradable films produced with hydrocolloids and lipids can result in better functionality than films produced with the components, especially with respect to their barrier properties. Of the lipids, waxes produce the best water vapor barrier properties, but produce fragile/brittle films. The problem of incorporating lipids into a hydrocolloid in a homogenous way has still to be solved. The objective of this research was the incorporation of 'Brazilian elemi', a highly hydrophobic resinous exudate of the botanical family Burseraceae, into gelatin films, using a blend of stearic and palmitic acids to dissolve the elemi, and subsequent emulsification of the filmogenic solution using triacetin as plasticizer. Films with the addition of acids, the blend and the blend and the elemi presented better water vapor barrier properties as compared to the gelatin/triacetin film. The mechanical resistance decreased with the addition of the lipids and the opacity and soluble matter increased. The confocal laser scanning microscopy showed the size distribution of the lipid drops and their localization in the matrix. They were not homogeneously incorporated despite the improvement in the water barrier property and the fact that the films appeared to be homogenous and malleable. The analyses by differential scanning calorimetry showed additional melting points besides that characteristic of the protein rich fraction, representing melting of the part of the lipid not incorporated into the filmogenic matrix. Dynamic mechanical calorimetry also showed the presence of more than one glass transition temperature (T g), indicating the occurrence of phase separation. (C) 2004 Elsevier Ltd. All rights reserved.191738