FACTORS IMPACTING U.S. IMPORTED CORN QUALITY IN TROPICAL CLIMATES – A CASE STUDY OF MEXICO

This research investigated factors affecting the quality of U.S. imported corn stored under tropical humid conditions, specifically in southeastern Mexico. Given the region’s high temperatures and humidity, storage environments pose considerable challenges to maintaining grain quality. U.S. corn is characterized by high levels of broken corn and foreign material (BCFM), which is viewed as degraded feedstock of low nutritive value by foreign buyers of U.S. corn.

This study was conducted by sampling imported U.S. corn from grain silos located at four facilities in southeastern, Mexico – Veracruz and Merida. Corn samples were collected at reception and over several storage periods during drawn down for consumption in feed production. Corn was sampled and prepared into four treatments of only BCFM, only whole kernels, corn bulk with BCFM levels as-received and corn bulk with 3% BCFM as in U.S. No.2 grade. Corn treatments were determined for their energy and nutritive values, and the impact of BCFM on susceptibility to spoilage and aflatoxin levels. Additionally, CO₂, temperature and relative humidity (RH) sensors were installed in the bins sampled to monitor the storage condition of the stored corn during the period of sampling at various drawdown levels.

This study confirmed that the nutrient profile of BCFM in imported U.S. corn was similar to that of whole kernels in the bulk, and BCFM retained as much as 96-98% of its energy and nutritive value, except for crude fat which decreased to about 85%. This indicates that BCFM is a valuable feed ingredient with comparative energy and nutritive value as whole corn kernels. However, this study also confirmed that BCFM negatively impacted corn in storage. BCFM alone had higher aflatoxin levels compared to only whole corn kernels and corn bulk blended with BCFM. However, aflatoxin levels of corn sampled at reception were below U.S. FDA actionable level of 20 ppb. Likewise, BCFM alone was more susceptible to spoilage than only whole kernels and a blend of whole kernels and BCFM. Our findings also indicate that some thought must be given on how to handle BCFM if screened off and stored alone than if stored with the bulk. This is because aflatoxin levels of BCFM will most likely increase rapidly if stored alone than in a mixture of whole kernels.

The storage environment in southeastern Mexico was quite challenging for storing corn as is typical of weather in the humid tropics. The development of aeration recommendations for temperature and RH management was investigated, and the window of opportunities for using aeration presented. Despite the challenging humid tropical conditions, imported U.S. corn can be safely stored and utilized under humid tropical conditions by following best stored grain management practices, which can be achieved through personnel training and technology deployment.