Effects of storage conditions and packaging materials on physico-chemical and microbial properties and shelf-life of extruded and non-extruded nutritious composite flour

The storability of composite nutritious flour is affected by many conditions, such as storage temperature and packaging materials. In this study, white maize, soybeans, millets, biofortified common beans, sesame, and sugar were used to prepare a composite nutritious flour (extruded and non-extruded). The flour was stored at two different temperature conditions (4±1°C and 25±4°C) with relative humidity of 65% and 85 ± 5 % respectively. The composite flour samples of about 250 g were packed in three types of packaging materials: PPnc-based film + paper bag, paper bag and polyethylene bag , each measuring about 20 per 20 cm. Paper bags and polyethylene bags were used as control. Then moisture content (MC), water activity, and color, as well as total coliforms and yeast, moulds were evaluated every 15 days for five months. The moisture content of the flour increases in all packaging types during the storage time, however, no significant differences were observed between the packaging type both in room and refrigerated conditions. For the bio-based + paper bags: The moisture content increases over time from 4.52% at day 0 to 11.77% at 150 days at 25°C. A significant difference (p>0.05) was observed between room and refrigerated temperature. Moreover, the water activity of samples stored in bio-based + paper bags remained relatively stable over time, with only minor variations observed across different temperatures. For samples stored in bio-based bags, a slight reduction in lightness was observed over 150 days at both temperatures. In the case of paper bags, L* values increased significantly at 25°C (from 85.11 to 98.22) after 150 days, which may be attributed to sample degradation. No significant difference was observed for samples stored in bio-based bags over time at both temperatures. For samples stored in paper bags at room temperature (25°C), the b* value increased slightly from 20.04 ± 0.21 at day 0 to 21.23 ± 2.36 at 150 days. A microbial test shows non-extruded samples stored at room temperature in polyethene bags after 90 days of storage contain a higher amount of yeast compared to other samples. Microbial growth increased over time for all samples stored in all bag types, with notable differences between storage at 25°C and 4°C. In general, yeast and mold growth were more pronounced than bacterial growth. For samples stored in bio-based bags, yeast levels slightly increased over time, rising from 2.14 ± 0.04 log CFU/g on day 0 to 3.82 ± 0.07 log CFU/g after 150 days at room temperature. In refrigerated conditions, the yeast population grew from 2.34 ± 0.00 log CFU/g at 90 days to 3.84 ± 0.08 log CFU/g after 150 days. The overall shelf-life study results suggest that the developed bio-based material prototype is an effective packaging solution for preserving the quality of composite flour (both extruded and non-extruded) for up to five months of storage. The shelf study can help in economic production, processing, marketing and distribution of extruded and non-extruded composite flour.