Investigating safe storage conditions to mitigate aflatoxin contamination in rice

Abstract

Mold contamination, especially with aflatoxin-producing Aspergillus species, poses a notable issue for rice, particularly in ready-to-eat (RTE) items, turning them inedible for both humans and animals due to the possible presence of aflatoxins (AFs). Understanding accumulation of the molds and their resulting toxic metabolites is critical in designing quality control strategies in the production of RTE rice-based products such as germinated instant rice, extruded rice cakes and crispies, rice-derived malted beer and flour. There is no clear understanding of the growth of A. flavus and AF accumulation on various fractions of hybrid rice cultivars utilized in the manufacture of the RTE rice-derived food products. In the present work, different experiments were conducted to identify the extent to which temperature (20°C, 25°C, and 30°C), relative humidity (RH) (75%, 85%, and 95%), storage period, storage moisture content (MC), and initial spore concentration impacted the growth of AF-producing A. flavus NRRL 3357. The study also examined how these factors affected ergosterol content and aflatoxin B1 (AFB1) production in different hybrid rice fractions including rough, brown, and milled rice, at different MCs (12%, 15%, and 18% w.b.). The samples, both autoclaved and non-autoclaved rice fractions, were inoculated with different A. flavus spore concentrations (1 × 104 and 1 × 106 spores/mL) and incubated at different temperatures and RHs. A. flavus plate count, ergosterol and AFB1 production were measured over time for up to 60 days. The maximum A. flavus growth was observed in brown rice (autoclaved) at 30°C and 95% RH. Brown rice fraction (non-autoclaved) had the highest AFB1 concentration (9.20 μg/g) which was determined after 15 days of incubation at 30°C and 75% RH. Aflatoxin B1 concentration in brown rice (non-autoclaved) fraction inoculated with the highest concentration of A. flavus and stored at 30°C and 95% RH initially increased after 20 days and then decreased towards the end of the storage period. The findings from this research provide important data related to the growth behavior of A. flavus on various rice fractions. The results contribute to understanding of the safety of RTE foods derived from various fractions of rice that is utilized by the food industry.