Chemical composition and nutritive value of mung, pigeon peas, urd, lentils and peas : A thesis submitted in fulfilment of partial requirements for the degree of Master of Science in the University of Canterbury [Lincoln College]

Abstract

In this work the proximate composition and nutritive value of five legumes: mung, pigeon pea, urd, lentils and peas were studied. The proximate composition of mung, pigeon pea, urd, lentils and peas were similar. They are good sources of dietary protein containing on average 20 to 30% protein. All seeds contained low levels of fat, ash and acid detergent. The amino acid composition of mung, pigeon pea and urd revealed that all were deficient in essential amino acids methionine and threonine. Pigeon pea was also deficient in isoleucine.

Rat trials were carried out to determine the protein quality of the five legumes. Cooking increased the true digestibility and net protein utilisation of the proteins in almost all cases. Although cooking led to small increases in biological value of lentil proteins, it led to small decreases in biological value of proteins of mung, pigeon pea and urd. The biological value of pea proteins were significantly decreased on cooking.

Diets made from mung, pigeon pea and urd protein were supplemented with between 0.025 and 0.30% methionine to investigate the effects of addition of the first limiting amino acid. Significant increases in biological value of both raw and cooked seeds confirmed methionine to be the first limiting amino acid in all cases.

Diets made from cooked mung, pigeon pea and urd were supplemented with optimum level of methionine and with between 0.10 to 0.30% tryptophan to investigate if tryptophan was the second limiting amino acid. The fall in biological value of mung, urd and pigeon pea proteins confirmed that tryptophan was not the second limiting amino acid in these legumes.

Trypsin inhibitor contents of the legumes showed that pigeon pea contained higher levels of inhibitor than the others. Cooking destroyed the trypsin inhibitor content almost completely in all cases.

Bomb calorimetry was used to determine the gross energy and cockerel trials were carried out to determine the digestible energy and true metabolizable energy of the seeds. The gross energy of the five legumes were similar. Cooking had different effects on true metabolizable energy of the legumes. The true metabolizable energy of mung and pigeon pea increased and the true metabolizable energy of peas fell on cooking. Cooking had no effect on true metabolizable energy content of urd and lentils