Effect of ultra-superheated steam on aflatoxin reduction and roasted peanut properties

Aflatoxins are carcinogenic toxins produced by Aspergillus flavus and Aspergillus parasiticus that are found naturally in peanut. It requires extremely high temperatures to eliminate aflatoxins from the nuts. The aims of this study were to investigate the effect of ultra-superheated steam (USS) on the reduction of aflatoxin B₁ (AFB₁ ) accompanying the roasting process and to determine roasted peanut qualities that affected consumer acceptance.

Whole peanut kernels were intentionally contaminated by AFB₁ standard solution at the level of 50 ± 10 µg kg^-1 before subjecting to USS treatment at 300-400 °C between 10 and 80 s. The high temperature of USS could significantly decrease AFB₁ level to 9.83 ± 3.51, 15.33 ± 2.23 and 8.95 ± 2.32 µg kg^-1 when 300 °C for 80 s, 350 °C for 40 s and 400 °C for 40 s were employed, respectively. AFB₁ was reduced as much as 83.86 ± 2.66% when 400 °C for 40 s was applied. The moisture content of treated peanuts was decreased to less than 3% and browning index was developed from 30.96 ± 1.59 to 95.76 ± 7.23.

Higher roasting degree was obtained according to the increase in browning index. Oil quality showed that peroxide values and acid values were greatly below the allowance level. USS could effectively decrease AFB₁ and render expectable roasting qualities of peanut. © 2017 Society of Chemical Industry.