Studies on storage stability and nutritional composition of value-added millet flour

Abstract:

A value-added millet flour that tastes wonderful on the day it is milled but turns rancid within weeks of packaging offers little practical benefit to the rural food processing cooperatives investing in its production, which is precisely the gap this six-month storage research set out to measure. Fortified, value-added millet flour was packaged in three materials, vacuum-sealed high-barrier pouches, aluminum foil laminate pouches, and plain plastic pouches, and stored under ambient warehouse conditions at Maputo for six months, with proximate composition, peroxide value, sensory quality, and microbial safety assessed monthly. Vacuum-sealed packaging preserved nutritional and sensory quality most effectively, limiting protein loss to 5.9% and fat loss to 35.4% over six months, against 13.7% protein loss and 68.8% fat loss in plain plastic pouches over the same period. Peroxide value, an indicator of fat rancidity, rose to 4.4 meq O₂/kg under vacuum sealing by month six but reached 8.7 meq O₂/kg under plain plastic packaging, crossing the threshold generally considered to produce noticeably rancid flavor. Sensory acceptability declined across all three packaging materials over the storage period, but the decline under vacuum sealing was gradual while plain plastic packaging showed a sharper drop after month three. Microbial safety remained within acceptable limits across all three materials throughout the six months, indicating that packaging choice in this research affected nutritional and sensory quality considerably more than food safety risk. These findings support vacuum sealing as the packaging investment most likely to protect the value-added quality that fortification and processing were originally intended to deliver, particularly where flour is expected to sit in distribution channels for more than two to three months before reaching consumers.