Stability and safety of maize–legume-fortified flours stored in various packaging materials

Abstract

In an attempt to control mold growth in maize–legume-fortified flours, fermented maize, blanched pigeon pea, and soybean seeds were dried at 65 °C for 8 h. The milled, maize–pigeon pea, and maize–soybean flour, in three concentrations and control samples, were stored in four packaging materials: low density polyethylene, high density polyethylene, plastic (polypropylene) and aluminum containers under simulated tropical conditions of 28 ± 2 °C and 83 ± 2% relative humidity for up to 24 weeks. The stored products were assessed periodically for water activity (a w) and fungal counts. Dominant mold isolates from the flours were further characterized and identified. Results demonstrated that the initial a w (0.15–0.17) increased to 0.17–0.24 after 24 weeks. Fungal counts ranged from 1.69 to 2.31 log10 CFU/g initially to 2.6 to 3.79 log10 CFU/g by the end of storage. The a w of maize–pigeon pea flour and maize–soybean flour, regardless of packaging, was not significantly different (p ≥ 0.05) over time; however, fungal counts were significantly different (p ≤ 0.05). Seven fungal species were identified from the flours: Cladosporium spp., Alternaria alternata, Paecilomyces variotii, Fusarium spp., Rhizopus spp., Scopulariopsis spp., and Epiccocum nigrum. Cladosporium cladosporioides was the dominant mold species in all the flours, with the highest in the maize–pigeon pea flours after 24 weeks of storage. Subsequent aflatoxin analyses indicated low levels (<20 ppb) throughout the storage period, regardless of packaging material. This study demonstrates that a w, fungal counts, and aflatoxin levels of the flours were within tolerable limits. The information from this study may be useful to processors, regulators, or researchers who are interested in identifying suitable packaging materials for these types of flours.