Aerated apple leathers: Effect of microstructure on drying and mechanical properties

Abstract

Fruit leathers are restructured products made from drying fruit purees until a leathery consistence is achieved. Aerated apple leathers (AAL) were created in order to incorporate air into the fruit structure and decrease the caloric density. AAL were prepared using gelatin as a foaming agent. Effects of gelatin concentration (0, 0.5, 1.0, and 1.5%) and whipping time (3, 5, 7, and 9 min) on microstructure, drying behavior, and mechanical properties of AAL were studied. Increasing the gelatin content and whipping time increased the gas hold-up up to 42.3% and decreased the mean bubble size of the foam. The time of drying decreased as the aeration level was increased. Samples with 1.5% gelatin and seven minutes’ whipping presented the highest drying rate, taking 2.8 h of drying to reach a moisture content of 0.13 kg H2O/kg dry basis. The drying behavior of samples was satisfactorily modeled with a semi-empirical relationship. Mechanical properties showed differences among aerated products elaborated with different whipping times and gelatin contents. Aeration conferred unique characteristics to apple leathers in terms of appearance and mechanical properties.