Drying of ‘yacon’ pretreated by pulsed vacuum osmotic dehydration

Letícia F Oliveira,Paula G Silveira,João R De J Junqueira,Jefferson L G Corrêa,Marina B Vilela

doi:10.1590/1807-1929/agriambi.v25n8p560-565

Abstract

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.

Highlights

The ‘yacon’ (Smallanthus sonchifolius) is a seasonal plant originating from the Andean region (South America), with high concentrations of fructooligosaccharides (FOS) as the main storage carbohydrate
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
The moisture content of the fresh, osmodehydrated, and dried ‘yacon’ slices was determined according to AOAC (2010), and the aw performed using an Aqualab hygrometer (Decagon Devices, Inc., CX-2T model, Pullman, WA, USA)

Summary

Introduction

The ‘yacon’ (Smallanthus sonchifolius) is a seasonal plant originating from the Andean region (South America), with high concentrations of fructooligosaccharides (FOS) as the main storage carbohydrate. These saccharides are related to prebiotic characteristics, and their maintenance is imperative. The ‘yacon’ presents high water activity and moisture content; the FOS hydrolyses quickly after harvesting, which reduces its shelf life (Mendonça et al, 2017). Osmotic dehydration (OD) could minimize nutrient losses and decrease moisture content, preserving food materials (Kaushal & Sharma, 2016; Bakhara et al, 2018). The OD transfers could be intensified with the application of reduced pressure during the process beginning, namely pulsed vacuum osmotic dehydration (PVOD) (Utkucan & Kemal, 2016; Junqueira et al, 2017). Oliveira et al (2016) optimized PVOD for obtaining a semi-dehydrated product with high FOS concentration but did not obtain a final product by further drying

Objectives

Methods

Results