EFFECT OF VACUUM DRYING CONDITIONS ON THE QUALITY OF YACON (SMALLANTHUS SONCHIFOLIUS) SLICES: PROCESS OPTIMIZATION TOWARD COLOR QUALITY

Abstract

This study was aimed at studying the effect of the drying temperature, slice thickness and citric acid concentration in the enzymatic browning inhibition solution on yacon slices' color and texture during vacuum drying and at optimizing the operation conditions toward final product quality. Color was expressed as CIE L*a*b* and CIE L*C*h* parameters, and texture was expressed as hardness. Vacuum drying caused decrease in L* and reflectance and increase in a* and b* values. Product hardness varied little on initial stages of drying, followed by softening and hardening. The effects of the factors on final product L* value and average value of b* and C* were very well fitted by polynomial models. The desirable product quality is represented by high L* values (low browning), high b* values (golden yellow color) and high C* values (high colorfulness), which can be achieved by combining high-drying temperature, low slice thickness and high acid concentration. PRACTICAL APPLICATIONS This work provides optimized drying conditions in order to obtain shelf-stable dried yacon with ideal appearance. Yacon is a functional tuber that is rich in phenolic compounds and dietary fiber. Appearance is the first quality attribute evaluated by consumers when choosing a food product. Vacuum drying showed to be appropriate for drying yacon, as lower temperatures can be used in this process. In this way, the functional and sensory features of yacon are preserved. This work can be used as a reference for drying yacon, increasing the shelf life of this food system while preserving its desirable original features.