Improving the Quality of Roasted Hazelnuts during their Shelf-life using Film Coating Starch-Based

The "film coating" is a process of depositing a thin layer edible transparent film of material onto a food, in order to provide a functional protective barrier covering its outer surface. The protective function of edible films and coating is to prevent the transfer of moisture, oxygen, flavour, and/or lipid content, between food and the surrounding medium and/or between different compartments in a heterogeneous food. Water-based coating suspensions are desirable to avoid the drawbacks of organic solvent-based coating suspensions. Starch can be used in coating technology; to overcome brittleness inherent of starch films, the incorporation of a plasticiser (reducing intermolecular forces and increasing the mobility of polymer chains, decreasing the glass transition temperature of these materials and improving their flexibility), is required. They must be compatible with the film-forming polymers; hydrophilic compounds, such as polyols are commonly used in starch films (GARCIA et al. 2000; JAGANNATH et al. 2005). Hazelnut seeds (Corylus avellana L.) are largely used in confectionary, chocolate and creams production. The whole roasted hazelnuts are susceptible of oxidation during their shelf-life, because the high content in mono- and polyunsaturated fatty acids. Aim of our work was (1) the elaboration of a coating film (High Amylose Whey Edible Films, HAWEF, under Patenting) able to protect from oxidation roasted hazelnuts in a model system, and (2). the study of peroxidation evolution in coated roasted hazelnuts in plain chocolate tablets. Two plasticisers (sorbitol and glycerol) at two different concentrations were used in film type A (with high % of plasticiser), and type B (with low % of plasticiser), respectively. The protective effect vs. the oxidation was evaluated during the storage after 0, 30, 60, 90, and 180 days from coating (peroxide and acidity values). The best compromise in terms of appearance, transparency, detachment of the film after handling and protection to oxidation was identified in the high-amylose edible film with glycerol (type B). We highlight a significant reduction of peroxidation (10-25%) in coated hazelnuts. No changes in aroma were identified in coated samples. Finally, we confirmed the protection of this film vs the oxidation and the souring of the hazelnuts used to prepare plain chocolate with whole hazelnuts. In conclusion, we suggest the use of this edible film for the coating of roasted hazelnut in order to improve their quality during their shelf life.