Microbiological evaluation and shelf life of seed flour mixes used for infant feeding in rural northern Nigeria

Abstract

This study investigates microbial load and shelf life of locally processed cereal-legume-oil seed flour mixes used for infant feeding in rural northern Nigeria. Free fatty acid (FFA), water activity (a_w), pH, total viable count (TVC) and presence of yeast, coliform bacteria and mold were the parameters determined. Hungry rice or Digitaria exilis, benne seed or Sesamum indicum and soybean or Glycine max seeds flours were produced using traditional processing methods, including washing, boiling, fermenting and roasting. The test samples were milled into flour that could pass through a 70 mm mesh sieve and blended on protein basis at 70:30 cereal-legume/oilseed ratios to produce D₇₀S₃₀, D₇₀G₃₀, D₇₀S₁₅G₁₅, D₇₀S₂₀G₁₀ and D₇₀S₁₀G₂₀ and stored at 30 to 32°C for 60 days. The parameters were determined at day 0 and intervals of 14, 28, 42 and 60 days. At the end of the storage period, all the parameters increased. FFA increased from 0.15 - 0.16% to 0.47 - 0.58%; aw from 0.46 - 0.48 to 0.72 - 0.80; pH from 3.9 to 4.7 - 4.9 and TVC from <1.0x10² to 2.2x10³ to 3.6×10⁴cfu/g for 0 and 60 days, respectively. The differences between the values of the parameters of the formulations were significant (p<0.05) especially from day 14. Yeast and coliform were not detected in all the samples but mold was detected from days 14 to 60. The formulation D₇₀S₃₀ had best shelf life; however, the samples should be consumed within 14 days of production.

Key words: Seed flour, multi-mixes, children, microbial load, shelf life.