Abstract
Maize (Zea mays) is an important staple food crop produced by the majority of smallholder farmers that provides household food security through direct consumption and income generation. However, postharvest grain losses caused by insect pests during storage pose a major constraint to household food security. Hermetic storage technology is an alternative method that minimises postharvest losses by depleting oxygen and increasing carbon dioxide levels within the storage container through metabolic respiration of the grains, insects, and microorganism. Maize grain was stored for 180 days in hermetic bags or open-weave polypropylene bags to compare quality preservation when subject to initial grain moisture contents of 12, 14, 16, and 18 percent and infestation by Sitophilus zeamais. The moisture content of grain in hermetic bags remained unchanged while in polypropylene bags decreased. Dry grains (12% moisture content) stored well in hermetic bags and suffered 1.2% weight loss while for equivalent grains in polypropylene bags the weight loss was 35.8%. Moist grains (18% moisture content) recorded the lowest insect density (7 adults/kg grain) in hermetic bags while polypropylene bags had the highest (1273 adults/kg grain). Hermetic and polypropylene bags recorded the lowest (0–4 adults/kg grain) and highest (16–41 adults/kg grain) Prostephanus truncatus population, respectively. Discoloured grains were 4, 6, and 12 times more in grains at 14, 16, and 18 than 12 percent moisture content in hermetic bags. Grains at 18% moisture content recorded significantly lower oxygen (10.2%) and higher carbon dioxide (18.9%) levels. Holes made by P. truncatus in the hermetic bags were observed. In conclusion, storage of moist grains (14–18% moisture content) in hermetic bags may pose health risk due to grain discolouration caused by fungal growth that produces mycotoxins if the grains enter the food chain. The study was on only one site which was hot and dry and further investigation under cool, hot, and humid conditions is required.
Highlights
Maize (Zea mays L.) is an important staple food in subSaharan Africa but is used for industrial purposes and animal feed worldwide [1]
Samples of grain at three further moisture contents 14, 16, and 18% were prepared by adding predetermined amount of distilled water mixing thoroughly in plastic bags [3, 27]. e amount of water added was calculated as follows: Q A ((b−a)/(100−a)), where A weight of grain, b desired moisture content, and a initial grain moisture content. e bags were kept in a cold room for two weeks
Moisture content and temperature are among the most critical factors that affect the quality of grains during storage. e normal harvesting moisture content for most maize farmers in the tropics, in Africa, is 18–20%. e ears are usually put into drying cribs to reduce the moisture content to around 14%, shelled and bagged
Summary
Maize (Zea mays L.) is an important staple food in subSaharan Africa but is used for industrial purposes and animal feed worldwide [1]. Due to the demand for high quality and safe food by the consumers, there is a need to maintain and protect maize grain from insect damage and fungal infection [4]. Important physical factors that may a ect the quality of stored grain are moisture content; temperature; the type of storage structure used; and the gaseous environment, levels of carbon dioxide and oxygen [5]. All these factors may have interactive e ects on mould growth and insect pests [6, 7], evolution of carbon dioxide [8], and grain
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