The potential of agricultural wastes [Pawpaw (Carica papaya) seeds and watermelon (Citrillus lanatus) Rinds] as a protein source for supplementary food production

Abstract

Extracts of pawpaw seeds (PSE) and watermelon rinds (WRE) were produced and analysed for proximate composition, amino acid profile, protein quality and some biochemical analysis of the extracts were fed to Wistar rats. The pawpaw seeds were scrubbed off, washed, drained and wet milled. The watermelon rinds were sliced and diced into small cubes. They were then washed in water, drained and wet milled. Twenty-five millilitres of each sample was added to 250ml (1:10) of a 5g/L NaCl solution, homogenized and the sediments filtered off with a muslin cloth. The supernatant was acidified with 1% acetic acid, centrifuged at 2000rpm and then filtered. The extract was dried at 60⁰C. The results of proximate composition showed crude protein (35.69 and 24.26%); fat content (7.68 and 5.62%); crude fibre (3.88 and 4.12%); ash content (7.95 and 9.96%); moisture content (1.99 and 1.85%), essential amino acids were leucine (6.89 and 7.24mg/100g), lysine (4.03 and 5.63mg/100g), isoleucine (2.62 and 3.01mg/100g), phenylalanine (4.26 and 3.64mg/100g), valine (3.01 and 3.19mg/100g), methionine (0.91 and 1.23mg/100g), arginine (4.82 and 5.16mg/100g), tyrosine (3.19 and 2.24mg /100g), histidine (2.18 and 2.20mg/100g), threonine (3.19 and 2.89mg/100g). Chemical score showed 1st and 2nd limiting amino acids were methionine and isoleucine. Results of animal experiment showed PER (6.8 and 6.3) were not significantly different to control (6.5). Values of biochemical analysis showed results for haematological indices were PCV (36.5 and 34%), WBC (4.0 and 3.3g/l), albumin (7.8 and 7.4g/dl) and creatine (143 and 124mmol/L). The extracts provided higher quality and quantity protein in relative comparison to most known legumes and oil seeds plants.

Keywords: Agricultural waste, chemical score, essential amino acids, pawpaw seeds, watermelon rinds