Maize needs to be stored using effective and safe postharvest management measures to
prevent physical insect damage as well as ensure stability of nutritional quality during
storage. In this study, conducted in February–December 2016, insect pest management
methods for bagged maize preservation in storehouses located in markets in Nigeria
were evaluated for their ability to preserve nutritional quality. Study locations were in
three grain markets, namely Eleekara market in Oyo town and Arisekola market in
Ibadan, Oyo State, South West Nigeria, and Ago market in Ilorin, Kwara State, North
Central Nigeria. Treatments comprised
Piper guineense
(Botanical), Bularafa
diatomaceous earth (DE), permethrin powder (Rambo™) (Permethrin), PICS bags
(hermetic) and ZeroFly® bags (non-hermetic). The study also had negative control
(Control) comprising untreated maize in polypropylene bags. In general, as a result of
insect infestation, protein content increased in all treatments except PICS which had the
least infestation. After 11 months of storage, Permethrin and PICS treatments had the
lowest insect infestation levels and the highest energy levels. Energy level in the
Botanical treatment was also high and similar to levels in Permethrin and PICS
treatments most likely due to fats and essential oils in
P. guineense being adsorbed
and/or absorbed by kernels. Fat content was lower in the Control and DE treatments
likely due to the Control having the highest insect infestation and the DE adsorbing
and/or absorbing fat from kernels. During storage carbohydrate content decreased in all
treatments except the Control. However, even in the Control, there was a clear trend of
decrease in carbohydrate content. Because the Control had the highest insect
(
Sitophilus zeamais) infestation and insect damaged kernels (IDK), this trend in
decrease in carbohydrate content may be insect related. Ash content increased in the
ZeroFly treatment, was unchanged in Botanical, Control, and PICS treatments, and
decreased in DE and Permethrin treatments. Nutritional quality variables in this study
were within or close to the known value ranges for maize. Therefore, use of maize that
had been fumigated well and had a relatively low initial grain MC (9.1%), in addition
to the effects of the treatments most likely slowed down population growth of the
several insect species that were found and contributed to preserving nutritional quality.
The relatively low insect populations in all treatments, including the Control, during the
February–September period probably reduced the clarity of effects of infestation on
nutritional composition reported in this study.