Effect of Extrusion Operating Conditions on Aflatoxin Reduction and Product Characteristics of Corn-Peanut Flakes
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Date
2010-04
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Addis Ababa University
Abstract
The study was conducted with the objective of reducing aflatoxin B1 (AFB1), B2 (AFB2), G1 (AFG1), and G2 (AFG2) as a function of extruder operating conditions such as initial moisture content of samples (17% and 21%) barrel temperature (140, 160, and 180 0C), and screw speed (150,200 and 250 rpm) when naturally contaminated composite of corn and fully defatted peanut meal (70/30 ratio) was extrusion-cooked to produce corn flakes. Factorial design was used to conduct the experiment. The amounts of aflatoxin in extruded and unextruded composite samples were measured by using high-performance liquid chromatography (HPLC). Accordingly, the effect of the operating conditions on the physicochemical properties (bulk density, expansion ratio, specific length, fresh product moisture content, water absorption index (WAI), water solubility index (WSI), water holding capacity (WHC), and sensory characteristics (hardness and crispness) on composite of corn and fully defatted peanut meal (70/30 ratio) was investigated. The collected data were subjected to analysis of variance using SPSS statistical soft ware. Extrusion-cooking was observed to reduce aflatoxin (AF) content, which ranged from 60% to 93% depending on the type of AF significantly (P<0.05). Temperature and screw speed had a significant effect on the reduction of AFB1, but moisture content was not found to be a significant factor affecting the levels of AFB1. Major reduction was found at highest temperature (160 0C), as AFB1 and AFB2 were more reduced at it. The water solubility index of extrudates increased with temperature, but decreased with feed moisture content. WAI increased with increased barrel temperature and moisture levels. As barrel temperature increased from 140 0C to 1800C, WAI increased from 4.810 to 5.799 respectively and it was increased from5.317 to 5.417 when moisture grew from 17% to 21 %. WSI increased from 10.641 to 11.798 when the barrel temperature grew from 140 0C to 180 0C. Feed moisture and WSI showed inverse relationship. Screw speed showed direct correlation with WSI, which is as screw speed increased from 150 rpm to 250 rpm, WSI increased by 10.404 to 12.394, respectively. WHC increased from 5.612 to 6.841 when the barrel temperature increase from 1400C to 1800C. As feed moisture content increased from 17% to 21% WHC increased from 6.244 to 6.483. The results indicated that this new product had good flavor and color than pure corn flakes, but it is less crispy. It had also over all acceptances greater than 5. In conclusion 1600C barrel
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temperature, 17% moisture content and 150rpm screw speed has been found to be ideal operating variables for reducing aflatoxin and improving the quality of the corn-peanut flakes.
Key words: Aflatoxin, Extrusion cooking, High Performance liquid Chromatography (HPLC)
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Keywords
Aflatoxin, Extrusion cooking, High Performance liquid Chromatography (HPLC