Storage And Packaging Studies On Degermed Maize Flour

ABSTRACT

Preservation and storage of whole maize flour poses a lot of problems owing to its fat content among other factors. This study therefore sought to develop processing and preservation procedures for maize flour and also to determine the effect of storage time on some quality indices o f the product. Degermed maize flour was prepared using a maize sheller and grits obtained milled into flour using a disc attrition mill and non-degermed maize flour prepared by direct milling of the maize into the flour. Flour drying was by oven and solar drying at 40°C for 4 hours and 30-45°C for 6 hours respectively. Chemical (proximate) analyses were determined using AOAC (1990) methods. Physical and functional properties o f the maize flours were determined. Water absorption characteristics were also determined and related to storage. The proximate composition of degermed maize flour showed lower fat, ash, and fiber content as compared to non-degermed maize flour (control). The percentage fat, ash, and fiber content were 1.42 ± 0.34, 0.2 ± 0.03, and 0.51 ± 0.01 respectively for degenned maize flour and 6.02 ± 0.63, 1.51 ± 0.16,and 1.84 ± 0.05 for non-degenned flour. Carbohydrate content was relatively higher (79.96%) in degenned maize flour than in the non-degermed maize flour which was 74.14% as a result of germ and hull. The moisture sorption isotherm of degermed maize flour (DF) and nondegermed maize flour (nDF) followed a type (II) isotherm pattern (Labuza,1984). The water absorption pattern of DF and nDF in relation to the various W ater Activities (Aw) was higher for DF as compared to nDF at Aw between 0.11 to 0.71 indicating that the DF is more hygroscopic. DF showed a higher monolayer value of 3 .9g/l 00 solid matter as compared to nDF which was 2.98 g/100 solid matter. The heat of absorption of DF and nDF decreased with increasing moisture concentration. But at low Aw ranging from 0.11 to 0.44 the total heat of absorption of nDF is higher than that o f DF. Water vapor permeability test conducted on packaging materials used, showed that low Density Polyethylene has a higher water vapor transmission rate than Polypropylene (PP) and High Density (HD) which had sim ilar rates. The initial moisture content of the flour samples ranged between 10.39 ± 0.49% (solar dried sample) and 10.74 ± 0.87% (Oven dried sample) for nDF, and 11.0 ± 0.6 % (solar dried sample) and 10.57 ± 0.78 % (Oven XVdried sample) for DF when packaged in HD and PP packaging materials and stored at 29 ± 1°C. A fter.six months storage period, the final moisture content attained by both flour samples were between 10.63 ± 0.63 % (Solar dried sample) and 12.61± 0.77% (Oven dried sample) for nDF and 12.37 ± 0.31% (Oven dried sample) and 11.27 ± 0.48% (solar dried sample) for DF. These values are less than 13% moisture standard set for the storage of cereal flour (Kent, et al., 1970). After 6 months storage the non-degermed maize flour samples showed high percentage free fatty acid content (0.54 ± 00 %) as compared to degermed maize flour samples (0.44 ± 00 %) owing to the initial differences of fat content of the flour samples. Based on the results obtained it can be concluded that degermed maize flour can be stored for at least 6 months or longer with minimal changes in quality; and that the degermed maize flour has a higher potential for storage than the non-degermed maize flour.