Dehydration of phenolic-rich extract from rambutan (Nephelium lappaceum L.) peel by foam mat drying

Foam mat drying was used for the dehydration of a phenolic-rich rambutan peel extract. Foam products were evaluated for their physicochemical stability during storage. Experiments were carried out to determine the effect of foaming (10% of egg albumin/soy protein/pea protein) and stabilizing agents (0.5% of methylcellulose); storage conditions i.e. type of packages (polyethylene, glass), packaging techniques (modified atmosphere packaging, vacuum) under light or dark at 30 degrees C on phenolic compositions, antioxidant activity, water activity (aw), and color of foam products during 5 months storage. Foam products produced from egg albumin showed the highest total phenolic content (TPC) (8.73 +/- 0.17 mg GAE/g) and antioxidant activity (7.47-9.70 mg TE/g). During storage, TPC, antioxidant activity, and the amount of individual phenolic compounds (geraniin, corilagin, rutin, ellagic acid, and quercetin) mostly decreased independent of the presence of light. Aw in all samples increased from 0.25 to 0.38 - 0.45 (except for the samples in glass packaging); whereas the color of the samples was insignificantly changed for 5 months. Rambutan peel phenolic-rich extract encapsulated within egg albumin can be stored at least 5 months with minimal quality changes and might be used as a food preservative ingredient.