Change in Water Activity and Fungal Counts of Maize-pigeon Pea Flour During Storage Utilizing Various Packaging Materials

Abstract

Maize-pigeon pea fortified flour has been processed with the potential to address protein-malnutrition, especially among children. This combination is preferred since cereals lack amino acids, such as methionine, and legumes lack lysine. When mixed together, the amino acid concentrations can be complemented. However, stored maize is an excellent substrate for Aspergillus spp., especially under warm (20-300C) and humid conditions (70-900C). This study investigated the changes in water activity and fungal counts in maize-pigeon pea flour stored for up to 8 weeks using different packaging materials. Maize pigeon flour was processed at different concentrations of 90:10 to 70:30 from fermented, dried, and milled maize and blanched, dehulled, and milled pigeon pea seeds. The flour samples were packaged into four different packaging materials: low and high density polythene bags, as well as plastic and aluminum containers. These containers were stored under simulated tropical conditions of 28+20C and 83+2% relative humidity in an incubator. Water activity (aw) of the flours was determined and fungi were enumerated using Petrifilm. Initial (day 0) aw of samples ranged from 0.15 to 0.17; after 8 weeks, aw ranged from 0.20 to 0.32 in low density polyethene, while lower aw was recorded for samples stored in the plastic and aluminum containers. Initial fungal counts ranged from 1.69 to 2.31 log10 CFU/g which increased from a range of 2.45 to 2.78 log10 CFU/g after 8 weeks of storage, with higher counts in samples stored in low density polythene bags. These results indicate that aw and fungal counts of the flours increased slightly over time in the different packaging materials, but values appear to be within tolerable limits. Further research will evaluate the stability of amino acids, as well as the level of fungi and resulting aflatoxin production up to 11 months under the storage conditions, formulations, and packaging materials described above.