Effectiveness of Triple-Layer Hermetic Bags against Aflatoxins in Stored Maize

Abstract

Aflatoxin contamination of agricultural commodities is gaining public prominence in Africa where it is pervasive due to favourable environmental conditions and high consumption of maize. Aflatoxins are toxic secondary fungal metabolites that contaminate dietary staples such as maize and groundnut resulting in adverse effect on food security, health and trade. This study evaluated the effectiveness of triple-layer hermetic bag to control aflatoxin in stored maize. A factorial experiment was conducted involving 2.5 kg of Obatanpa maize variety at moisture content between 12%-13%. Two storage bags (triple-layer hermetic bag and polypropylene interwoven bag) and two insect pests (Sitophillus zeamais and Prostephanus truncatus) were used in the study. Oxygen depletion and carbon dioxide elevation, temperature, relative humidity and dew point in the different storage bags and the storage environment were measured during the six months storage period. Different levels of temperature (16 oC, 30 oC and 38 oC) were also monitored to ascertain their effect on the performance of the triple-layer bag against aflatoxins in stored maize. The study showed that most farmers introduced to the hermetic technology by NGOs adopted and used it to preserve various agricultural commodities from insect pests. The vulnerability of the high-density polyethylene (HDP) bags to leakages and tearing and the cost of replacing a torn HDP bag were predominant concerns expressed by farmers during the survey in the Techiman Municipality. Field studies revealed that extreme fluctuation in temperature in the field negated the effectiveness of the air-tight condition created in the triple-layer hermetic bag to control aflatoxigenic fungi. There was significant difference (p<0.05) in moisture content of maize grains in the different storage bags with respect to insect infestation and changes in season from dry to rainy season in the storage crib. The mean aflatoxin level of maize infested with insect pests in the conventional bag was significantly higher (p<0.05) than insect-infested grains in the triple-layer hermetic bag. The triple-layer hermetic bag preserved the germination capacity of the seed maize much longer than polypropylene interwoven bag. There were significant differences (p<0.05) in the concentration of aflatoxin at the different temperature levels in the different storage bag technologies. The polypropylene bag had aflatoxin level (38.8 μg/kg) near the initial aflatoxin content of 38.2 μg/kg after three months of storing at a constant warm temperature (38 oC). The result of the research showed that, irrespective of the type of storage bag used for storing maize, the most critical factor to control aflatoxin is storing grains at save moisture content (<11%) and keeping them in storage structures that ensure environmental conditions that are relatively stable.