Drying of ‘yacon’ pretreated by pulsed vacuum osmotic dehydration¹

Secagem de yacon pré-tratado por desidratação osmótica com pulso de vácuo

HIGHLIGHTS

Mathematical models could adjust the drying behavior.

Osmotic pretreatment, higher drying temperature, and vacuum preserve the characteristics of the ‘yacon’.

ABSTRACT

In this study, the ‘yacon’ was dried using pulsed vacuum osmotic dehydration as pretreatment followed by vacuum drying (at different temperatures) or convective drying. The use of osmotic dehydration and vacuum drying had their influence evaluated concerning drying kinetics and quality of the final product, considering fructan retention, color, and water activity. Fick’s second law and Page’s equation were suitable for the fitting of drying evolution. It was observed that higher temperatures (60 °C) resulted in shorter drying time, higher diffusivity, and higher fructan retention when compared to 40 and 50 °C. The osmotic pretreatment and the vacuum drying differed in fructan retention (p ≤ 0.05). Moreover, the dried product, osmotically pretreated, presented a shorter drying time. The best condition was vacuum drying at 60 ºC, preceded by pulsed vacuum osmotic dehydration that resulted in fructan retention of approximately 38% in a quicker, higher diffusivity and lighter color product concerning the other tested conditions.

Key words:
fructooligosaccharides (FOS); fructan concentration; sorbitol; Smallanthus sonchifolius