Nutritive Value and Inherent Anti-Nutritive Factors in Processed Peanut ( Arachis hypogaea)

Abstract

Processing conditions and even the form of the food being processed as they affect nutrient availability is critical to develop structured foods to meet the nutritional needs of end users. The effect of heat treatments (roasting, boiling and autoclaving) on the physical, nutritional and functional properties of in-shell and shelled peanut ( Arachis hypogaea ) was determined. Unprocessed shelled peanut served as the control. Nutrient and anti-nutrient compositions of peanut samples were determined by standard methods, while physical (colour) and functional properties were also carried out. Analysis of variance was used to analyze the treatment groups and Duncan's multiple range tests to determine significant difference at p≤0.05. The result of proximate composition revealed that raw peanut had protein (32.7%), ash (1.37%), fibre (5.15%), fat (42.9%) and carbohydrate (12.1%). However, processing methods significantly increased the fat and ash contents. Peanut is high in calcium, magnesium and potassium but low in iron and zinc; processing significantly increased the elemental concentration of peanut. Phytate, tannin, oxalate, alkaloid, trypsin inhibitor and flavonoid were determined in the peanut samples and all were significantly affected by the processing method employed. However, boiling of shelled peanut was more effective in reducing the anti-nutrients than roasting and autoclaving. The aflatoxin concentration was in a range of 2.06-8.05 ppb. Shelled peanuts subjected to the processing methods had lower aflatoxin levels compared with in-shell processed peanuts. There exist variation in bulk densities (packed and loosed), water and oil absorption capacities as a result of processing method employed. The colour of peanut was significantly affected by the processing method. In general, processing of shelled peanut resulted in flour with better nutritional quality and functionality than in-shell peanut. The findings showed that boiling has proved to be an efficient method in processing of peanut.