Impact of opening hermetic storage bags on grain quality, fungal growth and aflatoxin accumulation

Abstract

Purdue Improved Crop Storage (PICS) bags are used by farmers in Sub-Saharan Africa for pest management of stored grains and products, including maize. These bags hermetically seal the products, preventing exchange with external moisture and gases. Biological respiration within the bags create an environment that is unsuitable for insect development and fungal growth. This study was conducted to determine the impact of routine opening of the storage bags for maize consumption on fungal growth and aflatoxin contamination. Maize with moisture contents (MC) high enough to support fungal growth (15%, 16%, 18% and 20%) was stored in PICS bags, which were opened weekly and exposed to humid conditions (85% RH) for 30 min over a period of 8 weeks and 24 weeks. Monitors indicated that oxygen defused into the open bags but did not reach equilibrium with the bottom layers of grain during the 30-min exposure period. Fungal colony forming units obtained from the grain surface increased 3-fold (at 15% MC) to 10,000-fold (at 20% MC) after 8 weeks. At both 8 weeks and 24 weeks, aflatoxin was detected in at least one bag at each grain moisture, suggesting that aflatoxin contamination spread from a planted source of A. flavus-colonized grain to non-inoculated grain. The results indicate that repeatedly breaking the hermetic seal of the PICS bags will increase fungal growth and the risk of aflatoxin contamination, especially in maize stored at high moisture content. This work also further demonstrates that maize should be properly dried prior to storage in PICS bags.

Changes in the Fungal Microbiome of Maize During Hermetic Storage in the United States and Kenya

“…Multiple studies have demonstrated that when grain moisture is high, yeast-like fungi proliferate on the grain surface under hermetic conditions ( Weinberg et al, 2008 ; Williams et al, 2014 ; Tubbs et al, 2016 ). In this study, the initial grain moisture was 14.0% ( Lane and Woloshuk, 2017 ).…”

Effects of Hermetic Storage on Adult Sitophilus oryzae L. (Coleoptera: Curculionidae) Acoustic Activity Patterns and Mortality

“…Previous research has shown that O 2 levels below 3% are most effective in controlling infestations (Navarro 1978, 2012; Moreno-Martinez et al 2000). At farm level with hermetic bags like Purdue Improved Crop Storage (PICS) bags, O 2 levels below 5% are achievable ((Baoua et al 2014; Tubbs et al 2016) and according to literature 5% also causes mortality but requires longer exposure time (Bailey 1955). …”

Cumulative oxygen consumption during development of two postharvest insect pests: Callosobruchus maculatus Fabricius and Plodia interpunctella Hübner

“…The present study is the first to measure cumulative oxygen consumption by individual insects using the OxySense 5250i. Several other studies have used the OxySense to measure oxygen levels related to reproductive behavior of female C. maculatus and maize grain quality and aflatoxin accumulation under hermetic conditions ( Tubbs et al., 2016 ; Yan et al., 2016 ). The OxySense has also been used in conjunction with acoustic studies of feeding behavior of Sitophilus oryzae (L.) ( Njoroge et al., 2017 ).…”