Introducing GSP in Cereal Spoilage Prevention and Control (Part 1)
Founded as a nutritional ingredient manufacturer in 1961 by R. WW and Mary Nelson, Kemin Industries, Inc., is a private company headquartered in Des Moines, Iowa, USA. It produces ingredients and invents processes that provide nutritional and health solutions for humans and animals.
Grain Storage Practices (GSPs) is the primary mechanism developed by Kemin Industries to control and reduce hazards in cereals. All GSPs recommend the use of suitable and approved preservatives (e.g. Myco Curb range of nutricines) to prevent heating and mold growth.
Grains are seeds from cereal plantsmembers of the grass family, Gramineae. They constitute the bulk of the high-energy (carbonaceous) feeds. Some contain as much as 85% carbohydrate (starch) and 6% fat. Most harvested feed grains have relatively little moisture, about 10%, and are not as variable in composition as forages. Representing more than 60% of the total tonnage of concentrate feed, corn is, by far, the most widely used high-energy feed in the United States and elsewhere.
It is widely recognized that grains are always contaminated with molds and always susceptible to mite infestation. This is because grains are ideal substrates (media) for mold growth, and they can be initially contaminated by so-called field molds such as Fusarium, while developing on the plants in the field. During storage, storage molds such as Aspergillus and Penicillium become the predominant spoilage organisms. Storage molds can grow at relatively low moisture content. These various mold species can produce several toxic metabolites as mycotoxins, which can be food contaminants.
Safe grain is a prerequisite for safe food, and good animal performance can only be achieved with hygienically safe grain.
THE SPOILAGE SYSTEM
Biodeterioration is the result of numerous interacting spoilage agents. These factors which contribute primarily to biodeterioration (including mold growth) are moisture, temperature and pests.
Molds can grow over a wide range of temperatures. In grains, molds utilize inter-granular water vapor (free water). For a given moisture content, different grains can have different water activities and, consequently, different rates and types of mold growth. Typical water activities which are necessary for mold growth range from 0.65 to 0.97. The water activity and the propensity for mold growth increases with temperature. Corn, for example, can be stored relatively safe for one year at a moisture level of 14% and a temperature of 10°C. However, the same corn stored at 30°C will be substantially affected by molds within two months.
Insects and mites (arthropods) can also contribute significantly in the biodeterioration of grain because of the physical damage and nutrient losses caused by their activity, and also because of their complex interaction with molds and mycotoxins. The metabolic activity of insects and mites causes an increase in both the moisture content and temperature of the infested grain. Arthropods also act as carriers of mold spores, and their fecal material can be utilized as a nutrient source by molds. Furthermore, molds can be a nutrient source for insects and mites and, in some cases, may also act as pathogens.
Another important factor that can influence mold growth is the proportion of broken kernels in a consignment of grain. Broken kernels, caused by general handling and/or insect damage, are predisposed to mold invasion of the , exposed endosperm, the carbohydrate portion of seed. Mold growth is also affected by the proportions of oxygen, nitrogen, and carbon dioxide in the inter-granular atmosphere. Many molds will grow at very low oxygen concentrations. Interactions between the gases and the prevailing water activity also influence mold growth.
Molds consume nutrients and oxygen, and produce carbon dioxide, water, and heat. Water and heat cause the humidity of the air surrounding nearby kernels to increase above 65% to 70% and results in further mold growth.
The grain surface absorbs atmospheric moisture, mainly in cold weather, increasing significantly the moisture content and mycotoxins production. Moisture fluctuation can create important wet spots. It is due to the natural convection currents originating from the head space. Condensation of the grain surface and underside of the roof also occurs when weather conditions fluctuate.
THE CONSEQUENCES OF BAD STORAGE
Mold growth will reduce the nutritional value of the grains. The balance of essential nutrients such as vitamins and amino acids will be disturbed, and the energy content reduced. Feeding animals on molded grains will lower the animal performance.
Molds produce mycotoxins, which will also have a significant impact on animal performance. Mycotoxins are also considered to be one of the most important food contaminants due to their negative impact on food safety and public health.
Mite infestation during grain storage is also a common phenomenon. Storage mites are extremely small but widely distributed. These insects are of increasing concern with reported allergenic effects to humans and well-documented detrimental effects that cause loss of nutritional quality and reduction of palatability. Mites can cause dermatitis, and digestive and respiratory disorders in farm animals and humans. These also act as carriers of mycotoxins, mold spores, and bacteria such as Salmonella, and their fecal material can be utilized as a nutrient source by molds.
STORAGE PESTS
Grains are highly vulnerable to pest infestation. Insect and mite storage pests belong to the most widespread animal groups on earth.
Majority of grain storage pests are-small beetles, moths, and mites, and in many cases it is very difficult to see them. It is important to know the local insect and mite species and the temperature and moisture requirements for each species.
Pest beetles in stored grain and grain stores: Grain beetles (Oryzaephilus, Cryptolestes, Sitophilus and Ahasverus sp.), lesser grain borer (Rhyzopertha dominica), clover weevil (Sitona sp.), ground beetle (Carabidae), and mold and fungus bettle (Mycetophagidae, Typhaea, Lathridiidae and Cryptophagus sp.)
Pest moths in stored grain and grain stores: White-shouldered house moth (Endrosis sarcitrella), grain moth (Sitotroga cerealella), brown house moth (Hofmannophila pseudospretella), and mill/flour moth (Ephestia kuehniella).
Pest mites in stored grain and grain stores: Grain mite (Glycyphagus destructor), predatory mite (Cheyletus eruditus and Gamasina), flour mite (Acarus siro), and cosmopolitan food mite (Lepidoglyphus destructor).
DETECTING AND MONITORING PESTS
Detecting insects in grain, according to Kemin, requires corrective actions to be taken. Monitoring pests assesses effectiveness of control measures.
Sample sacks help determine the infestation status of the grain, and visual inspection is an extremely useful tool. Insect monitoring traps have been used for many years. Results from trapping can be reliable because traps operate continuously. If the trap incorporates a lure, there is a considerable positive attraction factor. Bait bags are attractive to most storage beetles. Traps, however, are not very effective for quantifying insect infestations but can indicate population trends. Detecting insects visually in bulks of grain is, in some cases, almost impossible. Sampling is a poor method for detecting insects and mites. Even a single insect in a 1-kilogram sample may represent potentially serious infestation.
Mites can be monitored by using mite traps or by sieving. Mites are most likely to infest a grain surface again when it absorbs moisture from the atmosphere in cold weather.
GOOD STORAGE PRACTICES
The following are the storage practices from Kemin that must be kept in mind to ensure safe storage and management of cereals, oilseeds and pulses used in animal feeds:
Prevent losses from insects, mites and molds by storing grain, oilseed and pulse crops properly; preventing infestation is easier, safer and less expensive than curative
interventions.
Prepare the bin before storing the new crop. Stores must be clean, dry and well ventilated. Handling equipment must work properly to reduce grain damage.
Install an aeration system to reduce grain temperatures and to reduce moisture migration.
Dry crops, for tough or damp crops are more likely to become moldy or infested with insects and mites than dry crops. There are two basic methods of drying grain: heated air and bulk drying.
Cool after drying to stop insects breeding, prevent pest increase, and reduce relative humidity.
The use of a suitable preservative (e.g. Myco Curb) is beneficial for cereals to avoid heating and molding as storage conditions change in the course of the storage period.
The preservative should be applied promptly with appropriate application equipment to provide even coverage of the whole batch of grain being treated.
Monitor and control moisture and temperature as these two factors interact to provide favorable conditions for growth of molds and mites. As a result of monitoring, apply possible required corrective actions.
Monitor pest and rodents, and apply possible required corrective actions.