Effects of pretreatment and drying temperature on antioxidants and antinutrients of Justicia insularis and Jatropha tanjorensis leaves

Abstract

Antioxidants and antinutrient contents of leafy vegetables may be influenced by post-harvest processing. The present study was carried out to assess the effect of pretreatments (P) and drying temperatures (T) on antioxidants and antinutrients of Justicia insularis and Jatropha tanjorensis leaves. Four groups of samples were prepared, namely: fresh sample (FR), UN-blanched and dried sample (UB), sample blanched in hot water and dried (BHW) and sample blanched in salt water and dried (BSW). Drying was conducted at 40 0C, 50 0C and 60 0C using hot air oven. Antioxidants and antinutrients of the samples were determined. The data collected were subjected to a two-way Analysis of Variance (ANOVA) as well as Dunnett t-test at 5% probability level. Based on the results, BHW between 500 C and 600 C increased the antioxidant activity in both vegetables. BHW 60 0C was able to reduce oxalate and phytate contents to reasonable level while BSW50 0C drastically decreased hydrogen cyanide and tannin contents. However, the overall, individualistic, and interactive effects of P and T had significant ( < 0.05) influence on majority of antioxidant activity and antinutrient contents in both vegetables.