Grain storage specialists utilize this information to relate equilibrium moisture content of grain and R.H. of the surrounding air for a range of stored cereals. Relationships calculated for a range of cereals stored at a temperature of 25 C are shown in Table 1. Grain moisture content in equilibrium with an R.H. of 70% (shown in bold type) is the figure beyond which the stored cereal grain becomes at risk of microbial damage and therefore mycotoxin contamination. In practical terms this means grain scheduled for storage at 25 C should be dried to and maintained at that maximum moisture level. Equilibrium grain moisture contents and corresponding R.H. levels are recalculated for higher or lower storage temperatures.
Getting the measure of mycotoxins
Exactly when and where to test along the supply chain is now formalized into Hazard Analysis Critical Control Point (HACCP) testing. Experienced operators will already be aware of inherently high risk points where testing has always been advised. This may be grain loads coming in from different parts of the farm and experiencing different growing conditions including soil moisture and irrigation levels. Mycotoxin testing will alert the farmer to any real-time mycotoxin problems and provide important farm and crop data for later use.
Routine testing of grain loads from different sources for mixing in silos or during feed manufacture is clearly a priority for managers of central grain depots and feed mills. Any point along the supply chain where grain and other debris can accumulate, whether in conveyors at the grain store or feed mixers and bins in the feed mill, are high risk points for fungal growth and mycotoxin accumulation.
Mycotoxins are not randomly or uniformly distributed throughout static grain or feed loads but tend to occur in so-called “hot spots” corresponding to damp spots and pockets of mechanically damaged or insect-infested grain that encourage mold growth. Sampling a moving stream of grain, feed ingredient or finished product reduces any selection bias associated with sampling and testing a static load. Static grain loads should be probed many times and all over, with sub samples bulked to produce a more representative gross sample for testing.
Speed and sensitivity of testing are the twin main thrusts of mycotoxin testing over the last two decades, including actual time taken to obtain an accurate and actionable reading and result. If a test result is achieved on-site within minutes, then “rogue loads” can be dealt with promptly and isolated without contaminating the main bulk of grain, feed ingredient or finished feed. When samples were taken back to laboratories for testing, no prompt action was possible for suspicious loads with visible mold or a musty smell, without holding up operations. Traditional methods to analyze mycotoxins include fluorometer and LC methods using immunoaffinity (IA) columns. Chosen for their ability to isolate mycotoxins in simple or complex sample types, IA columns ensure precise measurements whether in the field or laboratory setting and provide the most comprehensive range for detection of single or multiple mycotoxins.
Maximum protection against the threat of mycotoxin contamination is achieved when inbound raw materials such as rice, corn, wheat, cottonseed meal or barley are screened prior to storage or use in feed production. This need to know on-site and on-time led to the development of portable on-site testing equipment like the VICAM Vertu® Lateral Flow reader — used to identify and quantify key mycotoxin hazards at critical control points right along the feed and grain supply chain. VICAM has gone one stage further with the introduction of five-minute on-site quantitative strip tests to detect DON (DON-V™) and aflatoxins (Afla-V™).
VICAM’s quantitative strip tests are designed for use with the Vertu® Lateral Flow Reader and can be performed with a minimum of on-site training and technical expertise. These tests employ the highly sensitive and selective monoclonal antibodies required to accurately measure DON and aflatoxins in grain or feed material.
Current passion is to drive down testing times to several minutes. More important is the overall on-site ability for prompt testing by nonscientists anywhere along the supply chain to secure prompt, accurate and repeatable results over the sensitivity range required. Whether the testing time is three or five minutes is secondary.