Nutritional value of South African quality protein maize before and after storage

[摘要] English: Maize is the main source of proteins, minerals, carbohydrates and lipids for many people,and the world-wide demand for these primary nutrients is growing continuously. Thephysical and compositional characteristics of maize are of utmost importance. Qualityprotein maize (QPM) has a high nutritional value, but its nutritional content may beaffected by storage conditions. The objectives of this study were to determine thenutritional composition of South African open-pollinated QPM varieties and a QPMhybrid, compared with normal maize hybrids and finally to evaluate the influence ofdifferent storage conditions on these measured nutritional characteristics. This wasrealised by exposing the seed of these genotypes to 3.6oC, 18.5oC and 30oC for 0, 6 and12 months of storage. The nutritional quality and endosperm characteristics of thesegenotypes were measured first before storage and then after 6 and 12 months of storage,respectively. Before storage, open-pollinated QPM, a QPM hybrid and maize genotypeshad comparable amounts of minerals, amylose and starch, revealing that the two types oftested maize genotypes were not necessarily different from each other. However, proteincontent in QPM was significantly higher than in normal maize genotypes. Some zeinpeaks were also different in QPM than in normal maize genotypes. Zein peaks of bothQPM and normal maize were significantly increased by warm storage conditions (18.5oCand 30oC) for 6 and 12 months of storage. A 5oC temperature did not significantlyinfluence the zein peaks of both QPM and normal maize genotypes for 6 and 12 monthsof storage. During storage, one open-pollinated QPM genotype SYN2QWQPM retainedhigher amylose, starch and protein content than non-QPM and other QPM genotypes.This suggests that optimal conditions for storage are distinctive for different genotypes,and it is possible to suggest some general guidelines for storage to maintain endospermand nutritional characteristics. The protein and endosperm characteristics were negativelyinfluenced by storage at 3.6oC, 18.5oC and 30oC, but SYN15QWQPM was least affected.The 3.6oC for 12 months and 18.5oC for 6 months seemed to be the most favourableconditions to retain kernel stability in terms of the measured characteristics. The resultssuggest that there is a need for adoption of QPM as it had better protein quantity andquality than the normal maize hybrids.

[发布机构] University of the Free State