Effects of High Temperature and Relative Humidity on Mold Content and Quality of Stored Popcorn

Abstract

White and yellow popcorn were stored in different containers at high temperature (35°C) and high relative humidity (85%) conditions for 3 months. Gradual decreases in popping volumes with the lengthening of storage time were observed in both white and yellow popcorn. Internal mold infection was quite low in both white (5.7%) and yellow (3.0%) popcorn at the beginning of storage tests. Few differences were found in total infection levels up to 60 days of storage, except that the Aspergillus glaucus group became established in place of field fungi. A gradual increase in mold infection levels was then observed during the remaining 30 days of storage. Visible mold growth was also observed on the tips of some kernels by the end of storage studies. Internal mold infection in white popcorn stored in an open container was lower (18.3%) than white popcorn stored in a closed plastic bag (75.0%) and closed plastic jar (85.3%), whereas the internal mold infection in yellow popcorn stored in an open container was higher (23.3%) than yellow popcorn stored in a closed plastic bag (6.3%) and closed plastic jar (2.6%). The A. glaucus group were the predominant molds found at the end of storage tests. The ability of toxigenic molds to invade the popcorn was determined using a dry spore inoculum. None of the inoculated molds, which included Aspergillus flavus, Penicillium martensii, and Penicillium viridicatum, were able to invade the popcorn during storage. However, the A. glaucus group predominated at the end of storage tests in the inoculated samples.