Effect of extrusion conditions on aflatoxin content of corn–peanut flakes

Abstract

The study was conducted to evaluate the influence of extrusion operating conditions on the reduction of total and individual aflatoxins (B₁ and B₂) in corn-peanut flakes. Aflatoxin - contaminated corn and peanut were converted into flour separately and mixed in a proportion of 70 % corn and 30 % fully defattened peanut flour (FDPF).

Corn-peanut extrudates and flakes were then produced at various combinations of feed moisture contents (17% and 21%,) barrel temperatures (140°C, 160°C and 180°C) and screw speeds (150 rpm,200 rpm and 250 rpm)in a double screw extruder under factorial design. The process parameters were recorded during the experiment.

The total and individual aflatoxins were measured using a high-performance liquid chromatography (HPLC) before and after extrusion. The collected data were then subjected to analysis of variance by SPSS statistical software. The results showed that the total aflatoxin was cut by more than 95% (from 583 ppb to 30 ppb) at constant (150) rpm while other parameters varying. Similarly, aflatoxins B₁ and B₂ decreased by nearly 93.8% (240 to 15 ppm) and 83.5% (23 to 3.8 ppb), respectively (P<0.05) at different combinations. Of all the conditions, 17 %, 160 ⁰C and 200 rpm reduced both B₁ (240 to 15ppb) and B₂ (23 to 7.5 ppb) at the same time.

Corn and peanut are crops partly used for making Injera and edible oil in Ethiopia, respectively. Corn ranks next to Teff in area coverage and first in total production in Ethiopia. The inclusion of peanut in the production of corn flakes improves the protein content. Corn and peanut are excellent substrates for the growth of mycotoxins (example aflatoxin). Aflatoxins are toxic metabolites which can be observed on food stuffs or animal feeds. It is estimated that at least 25 % of the world’s cereal production is contaminated with mycotoxins [1]. They are the causes of human illness and death [2, 3].

Among all the mycotoxins, aflatoxin generates the greatest loss and the highest management cost due to its extremely high toxicity. Aflatoxins have been found to contaminate a wide variety of important agricultural products worldwide such as peanuts, corn, rice, cotton seed and wheat [4]. Although aflatoxins are not automatically produced whenever grain becomes moldy, the risk of contamination is greater in damaged corn than in those with little mold. Aflatoxins are harmful to humans and livestock, and are considered carcinogenic (cancer causing). The prime condition for the fungi to produce toxin is warm season in a period of drought [5]. Frequently encountered individual aflatoxins include B₁, B₂, G₁, G₂, M₁ and M₂.

Keywords: Aflatoxin, Corn-peanut flakes, Extrusion cooking, HPLC