Physical characteristics of germinated wheat starch based aerogels

Aerogels are materials of great interest due to their very low density and high surface area, which provides opportunities for several applications in the pharmaceutical and food fields, as for encapsulation of bioactive compounds and absorbent in food packaging. Natural polymers, such as starch, have been widely used to produce aerogels because of their biocompatibility, biodegradability and low cost. Aiming the production of biodegradable materials from renewable and undervalued precursors, the objective of this study was to produce and characterize physical aerogels of germinated wheat starch. The aerogels were produced by the gelatinization of 10% (w/v) starch in distilled water at 90 ºC followed by freeze/ thaw cycles in order to obtain physical aerogels. Finally, they were lyophilized and evaluated by morphology, crystallinity and water sorption capacity, obtained by weighing the samples before and after immersion in water for 24 hours. The aerogels remained intact, presented homogeneous morphology and pores in its structure. The degree of crystallinity of the aerogels was 25% for the germinated wheat starch and 23% for the non-germinated wheat starch. The crystallinity of a polymeric material is an important parameter to define its application, since crystallinity can determine parameters, such as polymer resistance and its ability to absorb water. Germinated wheat starch aerogels absorbed more water when compared to non-germinated 686.5 ± 4.1 and 625.0 ± 12.0% (p <0.05), respectively. A possible partial depolymerization in germinated wheat starch may promote greater molecular interaction with water and thus contribute to greater absorption from aerogels. This study outcome shows the promising characteristics of the aerogels to be widely applied, as the remaining integrity and being capable of absorbing a large amount of water into their structure. The aerogels are ideal for encapsulating bioactive compounds to be delivered into foods that release a large amount of water.