Effect of drying methods on the nutritional and anti-nutritional quality of African nightshade (Solanum sp.)

Abstract

African nightshade (ANS) is a luminary food plant, considered a cheap and potential dietary source for micronutrients and bioactive compounds. This study evaluated the effects of drying techniques on nutritional (minerals & vitamin C) and anti-nutritional (oxalates & phytate) contents of Solanum scabrum (SS) and S. villosum (SV). The study employed three methods of drying; indirect solar drying (ISD), mixed solar drying (MSD), and open sun drying (OSD). Furthermore, blanching (85 °C, 2 min) with and without 3% NaCl were used as pre-treatments. Results showed that the ISD method retained more vitamin C in a range of 14.76% - 19.2% in both SS and SV leaves. The ISD was the most effective method in Ca (92.90%, 96.57%), Fe (77.88%, 71.54%), and Zn (86.94%, 90.09%) retention for both SS and SV leaves, respectively. On the other hand, all drying methods significantly reduced the oxalate and phytate content. The effect of pre-treatment methods on nutrient retention and anti-nutrients remaoval was also recorded. Results showed that ISD to be the best method for vitamin C and minerals retention and anti-nutrient reduction. Therefore, ISD can be a suitable method for preserving ANS while retaining nutrients and reducing anti-nutrients.