Amino acids and in vitro protein digestibility changes in green asparagus (Asparagus officinalis, L) during growth and processing

This paper reports on the amino acid, in vitro protein digestibility and dietary fiber changes in green asparagus during development and processing. Green asparagus spears were classified into fine (F, less than or equal to 8 mm), middle (M, 9-11 mm), thick (T, 12-14 mm), very thick (VT, 15-19 mm) and extra thick (ET, greater than or equal to 20 mm). This plant food was found to be a good source of protein (>30% DW), containing most of the essential and nonessential amino acids. However, the arginine, cystine, gamma-amino-butyric acid, glutamine, lysine, ornithine, phenylethanolamine, serine and taurine contents decreased significantly (P less than or equal to 0.05) with blanching and canning. Green asparagus protein showed an adequate amino acid score according to FAO/WHO recommendations, and seemed to contribute most of the essential amino acids, except histidine and lysine, which were limiting amino acids. In-vitro protein digestibility (IVPD) tended to decrease during development (77.30% at F to 71.43% at ET), improving during processing, mainly after blanching. The increase in soluble dietary fiber and decrease in insoluble dietary fiber during processing might relate to the improvement of IVPD noted. (C) 1997 Published by Elsevier Science Ltd on behalf of the Canadian Institute of Food Science and Technology.