Effect of hygiene status in maize storage facilities on pests, molds and aflatoxin contamination in Nakuru Country, Kenya

Infestation of harvested agricultural produce with pests, pathogens or contamination with mycotoxins during storage negates efforts to eradicate food and nutrition insecurity. Preventive measures, primarily suitable storage structures and cautious adherence to hygiene constitute key actions for effective control of pests and pathogens. However, contribution of recommended postharvest handling and hygiene practices as avenues for timely mitigation have never been examined. The aim of this study was to assess the effect of hygiene in maize storage facilities on pest infestation, mold and aflatoxin contamination. A cross-sectional survey was conducted in 2017 to assess postharvest handling practices, levels of hygiene and their effect on the magnitude of losses in maize farmers’ storehouses. A total of 342 rural farmers spread across the high potential moist transitional agro-ecological zone in Nakuru County were interviewed and data recorded in a semi-structured questionnaire and a checklist. In addition, the hygiene status of 40 storehouses where shelled maize grain was stored in bags was assessed and the grains sampled. The stores were ranked into ‘poor’, ‘average’ or ‘good’ hygiene categories depending on the level of adherence to recommended storage hygiene practices. Maize grains that had been harvested and stored in farmer’s stores were sampled at intervals of two months beginning April to October 2017. The samples were analyzed for moisture content, quality compliance, insect population, grain damage, weight loss, mold incidence and aflatoxin levels. The main storage bags were polypropylene used by 98.2% of the farmers. Bagged maize was stored either in granaries or designated rooms within dwelling houses. Overall, 90% of the farmers cleaned their storehouses before the most recent harvest was loaded, while only 50% cleaned the storehouses after the harvest had been loaded. Farmers reported 8.3 ± 0.5% weight losses resulting from insects, rodents, molds and theft. Laboratory analysis of maize sampled from farmers’ storehouses revealed a significant (P = 0.002) increase (from 12.2 to 14.2%) in moisture content of maize stored under poor hygiene conditions beginning from the second month of storage. Interaction between hygiene status, population of Sitophilus zeamais and storage time was highly significant (P <0.001). Good hygiene practices slowed the rate of grain damage and corresponding weight loss. The total population of molds across all the stores increased significantly after four (P < 0.001) and six (P < 0.001) months of storage. Additionally, stores adhering to good hygiene practices recorded significantly lower incidence of Aspergillus spp. at the fourth (P = 0.002) and sixth (P < 0.001) months of storage, respectively. This was followed by corresponding significantly (P = 0.041) lower levels of total aflatoxin (range 7 – 64 ppb) after four months of storage. Total aflatoxin levels increased approximately four fold for maize stored under hygienic conditions, six fold for storehouses characterized by average hygiene practices, and seven fold for grain stored under conditions of poor hygiene throughout the storage period. At the commencement of the trial, 15% and 22% of samples from hygienic and unhygienic stores respectively had total aflatoxin levels beyond the 10 ppb threshold set by the Kenya Bureau of Standards (KEBS). This proportion increased to 100% and 71% in unhygienic and hygienic stores respectively four months after commencement of the trial. From the Fractional Response Model, high hygiene scores correlated significantly with lower grain losses. Storing maize grains in the bedroom or living room correlated with lower losses by 2.8 and 4.6 percentage points, respectively; compared to storage in granaries, while storage in the kitchen correlated with higher losses by a margin of 19 percentage points. Storage of maize together with other grains or farm equipment was associated with higher losses by 2.8 percentage points. Storage of maize in hermetic containers did not result in significantly lower losses. In addition, repairing or disinfecting the store before introducing a new harvest did not significantly reduce grain losses. Training in grain storage did not have a significant effect either, while maize farming experience and younger age were associated with lower losses by 2.8 and 5.9 percentage points, respectively. Stores where majority of the postharvest handling decisions were made by women had lower losses by 2.8 percent points. This study demonstrates that storing grain under hygienic conditions can help smallholder farmers retard proliferation of molds, aflatoxin contamination and storage pests and consequently prolong safe storage duration of maize grains.