STUDY OF ROASTING EFFECT ON NUTRITIVE AND ANTIOXIDANT PROPERTIES OF LEAFY VEGETABLES CONSUMED IN NORTHERN CÔTE D’IVOIRE

Abstract

African leafy vegetables (ALVs), also known as African spinach, contribute significantly to household  food  security  and  add  variety  to  cereal-based  staple  diets.  Five  leafy  vegetable  species (Amaranthus   hybridus,   Andasonia   digitata,   Ceiba   patendra,   Hibiscus   sabdariffa   and   Vigna unguiculata) that are used for sauce preparation in Northern Côte d’Ivoire were subjected to roasting in order to evaluate the impact of this non conventional processing method on their nutritive value and antioxidant  properties.  This  study  showed  that  longer  time (higher  than  2  min)  of  roasting  at  180-200°C  caused negative  impact  with  nutrients  losses  but  positive  impact by  reducing  anti-nutrients such  as  oxalates  and  phytates.  The  registered  losses at  2  min  were  as  follow:  ash  (0.09  –  6.58 %), proteins (1.22 – 29.31 %), vitamin C (77.56 – 89.01%), carotenoids (11.24 – 45.16 %) oxalates (2.30 –  20.51 %)  and  phytates  (5.20  –  63.82  %).  Roasting  processing of  the  studied  leafy  vegetables highlighted a significant increase (4.77 – 32.71 %) of polyphenols contents coupled with increasing of antioxidant activity. Moreover, after 2 min of roasting time, the residual contents of minerals were: calcium  (294.78  -  879.74  mg/100g),  magnesium  (175.87  -  480.54  mg/100g),  potassium  (159.72  - 371.33  mg/100g), iron  (15.54  -  84.97  mg/100g)  and  zinc  (13.27  -  38.85  mg/100g).  All  these  results suggest  that  roasting  of  leafy  vegetables  (less  than 2  min)  may  be  used  as  alternative  method  of cooking  in  order  to  minimize  nutrients  losses  and  to  contribute efficiently  to  the  food  security  of Ivorian population.