Influence of heat processing methods on the nutrient composition and lipid characterization of groundnut (Arachis hypogaea) seed pastes.

Abstract

The effects of heat processing methods on the proximate composition, caloric value, mineral concentrations, vitamins A and C levels and lipid characterization of seed pastes of Arachis hypogaea were investigated. Moisture content was highest (25.2 ± 0.36%) in boiled seeds (BS) followed by raw seeds (RS) (4.58± 0.24%) and was lowest (1.21 ±0.20%) in fried seeds (FS) while ash ranged from 1.31 ± 0.01% in BS to 2.15 ± 0.07% in FS. Protein was highest in FS (28.45+0.21%) followed by RS (26.40 ± 0.18%) and lowest in BS (18.64±0.22%). RS had the highest crude fat of 51.1 ± 0.16% while BS had the lowest value of 25.23 ± 0.38%. Total carbohydrate was lowest in RS followed by FS and the highest value of 29.62 + 0.30% in BS. The energy content in kcal/100g sample was in the order RS > FS > BS. The seeds were found to be good sources of copper, iron, zinc, sulphate and chloride. Boiling and frying had no significant effect (P>0.05) on copper but significantly (P< 0.05) decreased iron and zinc. Boiling significantly (P<0.05) decreased sulphate and chloride which were significantly increased by frying. Boiling decreased the concentrations of vitamins A and C which were further decreased by frying. The % free fatty acid, peroxide value, acid value and iodine value were highest in RS and the lowest values were obtained in FS, BS, FS and FS respectively. No significant difference (P > 0.05) was obtained in the saponification number of the three samples analyzed and values ranged from 161.3 ±2.92 in RS to 163.0 ± 2.60 in FS. Heat processing (boiling and frying) generally decreased significantly (p<0.05) the crude protein, crude fat, caloric value, Fe, Zn, vitamins A and C as well as % free fatty acid and peroxide value but had no significant effect on Cu, acid value, iodine value and saponification number. However, frying increased significantly (P<0.05) the dry matter, ash, S04 2-, Cl- and unsaponifiable matter. These findings may offer scientific basis for the use of the processed seeds as food for humans and oil extracts for the manufacture of industrial products.

Key words: Heat processing methods, Arachis hypogaea seeds, nutrient composition, lipid characterization.