| Summary: | 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. The
physical and compositional characteristics of maize are of utmost importance. Quality
protein maize (QPM) has a high nutritional value, but its nutritional content may be
affected by storage conditions. The objectives of this study were to determine the
nutritional composition of South African open-pollinated QPM varieties and a QPM
hybrid, compared with normal maize hybrids and finally to evaluate the influence of
different storage conditions on these measured nutritional characteristics. This was
realised by exposing the seed of these genotypes to 3.6oC, 18.5oC and 30oC for 0, 6 and
12 months of storage. The nutritional quality and endosperm characteristics of these
genotypes 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 genotypes
had comparable amounts of minerals, amylose and starch, revealing that the two types of
tested maize genotypes were not necessarily different from each other. However, protein
content in QPM was significantly higher than in normal maize genotypes. Some zein
peaks were also different in QPM than in normal maize genotypes. Zein peaks of both
QPM and normal maize were significantly increased by warm storage conditions (18.5oC
and 30oC) for 6 and 12 months of storage. A 5oC temperature did not significantly
influence the zein peaks of both QPM and normal maize genotypes for 6 and 12 months
of storage. During storage, one open-pollinated QPM genotype SYN2QWQPM retained
higher 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 endosperm
and nutritional characteristics. The protein and endosperm characteristics were negatively
influenced 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 favourable
conditions to retain kernel stability in terms of the measured characteristics. The results
suggest that there is a need for adoption of QPM as it had better protein quantity and
quality than the normal maize hybrids.
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