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

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.