Drying, one of the traditional food preservation technique, is a complex process defined as a simultaneous heat and mass transfer steps under transient conditions, which leads to significant changes in physicochemical properties of the foodstuffs. The objective of the present study was to assess effects of ovalbumin concentration (as a foaming agent) at three levels of 1, 2 and 3% on green banana drying kinetics and qualitative and quantitative properties of the produced powder using foam-mat drying method.
Ovalbumin, as a foaming agent, and 0.5% (w/w) methyl cellulose, as a stabilizer, were used for the preparation of foams. In this study, effects of ovalbumin concentration (1, 2 and 3% w/w) at 70 °C with foams of 3-mm thickness were assessed on drying kinetics of immature banana pulp and physicochemical properties of the produced powder like bulk density, glass transition temperature and water solubility index. Statistical analysis was carried out using completely randomized design with three replications. Means were compared using Duncan’s multiple range test at 5% levels.
Results showed that increases in ovalbumin concentration caused significant increases in effective moisture diffusion coefficient, decreased the foam density and increased the porosity, expansion and stability of the foam. Bulk density and water absorption index decreased with increasing concentration of the foaming agent. Moreover, Carr index and Hausner ratio respectively increased and decreased by increasing ovalbumin concentration from 1 to 2 and 2 to 3%. The lowest glass transition temperature was achieved at 2% ovalbumin concentrations.
Study of physicochemical properties of the final product showed that the powder produced at 1% ovalbumin concentrations included the highest flowability. Unripe banana pulp powder rich in resistant starch produced by foam-mat drying can be used as a natural product enriched with egg white protein and fiber source, mainly in production of functional products.
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