Cereal Grains Testing: Here Are Some of the New Methods Emerging for Rapid Detection

A successful business relies on developing and maintaining consumer trust and confidence in the products they buy. For food manufacturers, building this trusting relationship is even more essential, given the primary importance of food to health and well-being. A product contaminated with microorganisms or toxins that may cause foodborne illness can taint consumer confidence far beyond the product recall.

As a staple ingredient in many food products, cereal grains play a prominent role in the food supply chain. Corn, wheat, barley, rice, oats, rye, millet, and sorghum are the main cereal grains used worldwide as the raw materials for many food products, such as flours, cornmeal, breads, pasta, breakfast cereal, cakes, and tortillas, and for beverages such as beer. Over the past 50 years, worldwide production and yield of these grains has increased to meet the needs of a growing population.

Given the critical and growing reliance on these grains worldwide, ensuring their quality and safety is vital for a strong and reliable food supply chain. The safety of these grains has come under particular scrutiny over the past years due to outbreaks of foodborne illness and recalls attributed to contaminated wheat flour. A 2019 study, published in the Journal of Food Protection, was conducted to assess a baseline level of contamination of pathogens in more than 5,000 raw wheat samples prior to milling and found the prevalence of Salmonella (1.23% of the samples), Escherichia coli (0.44%), and Listeria spp (0.08%) was sufficiently high to indicate a risk for foodborne illness. Along with the health risk, the investigators underscored the potential subsequent loss of revenue for food manufacturers, and a subsequent dent in consumer confidence (J Food Protection. 2019;82:1022–1027).

Understanding the ways in which cereal grains can be contaminated, the types of tests used to mitigate that risk, and gaps and vulnerabilities that persist in ensuring the safety and quality of cereal grains is important for food manufacturers, who must know their food supply chain. “Knowing the origin of the bulk commodity and understanding the processing interventions used by the supply chain to ensure food safety is important, as you can predict some of the quality and safety defects that might occur,” says Douglas L. Marshall, PhD, CFS, the chief scientific officer for Eurofins Microbiology Laboratories in Fort Collins, Colo. “Testing for both desirable quality attributes and for detrimental food safety hazards improves trust in the supply chain and keeps everyone honest.”

Newer Tests for Safety and Quality

Infectious microorganisms such as Salmonella and E. coli are considered major types of biological hazards to food safety associated with grains. Mycotoxins are another type of biological hazard. Along with these, cereals can also be contaminated by chemical and physical hazards (See “Table 1. Potential Contaminants of Cereal Grains”).

Much of the testing for safety of cereal grain is focused on biological contaminants, as these can occur throughout the grain supply chain—from crop growth through harvesting and post-harvesting drying and storage—and may directly affect the quality and safety of the grains used for milling and food production.

“[Cereal grains] are biological materials, living and breathing materials that continue to respire after harvest,” says Gerardo Morantes, PhD, director of food safety at Plymouth, Minn.-based Bühler, a food processing and manufacturing technology group. “Best agricultural practices, weather events, and supply–demand cycles will have an effect on every single crop produced.” Food processors, he adds, should keep this in mind when sourcing these grains, as the quality and food safety challenges faced throughout the food supply chain are directly related to these factors.

Dr. Morantes describes mycotoxins as a universal hazard addressed by all supply chains worldwide. More recent attention and allocation of resources, he says, are focused on infectious microorganisms, such as Salmonella, to better understand alternatives in risk mitigation to prevent foodborne outbreaks such as those recently caused by contaminated raw flour.

Andreia Bianchini, PhD, an associate professor in the department of food science and technology at the University of Nebraska in Lincoln, highlights how important it is for food processors to recognize the emerging hazard posed by pathogenic bacteria. “Until 10 or 15 years ago, microbiological concerns related to grains perhaps were more directed to molds and their potential to produce mycotoxins,” she says. Today, she adds, food scientists understand that pathogenic bacteria can also be associated with these products.

According to Dr. Bianchini, traditional methods continue to be the gold standard for reference testing for both mycotoxins and bacterial contaminants, but newer methods for rapid detection have emerged.

Dr. Morantes says that, unlike traditional culture-based methods that can take up to five days for preliminary results, rapid testing can significantly reduce the time needed to make an informed decision about the release of a product. This in turn, he says, can have significant implications for preventing foodborne outbreaks and reducing food losses.

Table 2 (below) lists a number of these newer rapid detection tests. Of these, Dr. Bianchini says that ELISA and PCR-based methods are the most commonly used. “No matter what testing platform is used, it is important that it be validated for the matrix (e.g., flour) in which it is to be used so [that] results obtained with the rapid methods are equivalent to those obtained using standard methods,” she says.

To ensure quality in cereal grains, Dr. Marshall underscores that the quality determines whether the grain is fit for use in a certain application. “The proximate composition of the grain determines its functional properties, such as amount of starch, protein, lipid, fiber, and moisture,” he says. “For example, the protein content of wheat dictates its performance as flour for pastas, breads, or cakes.”

Devin Rose, PhD, an associate professor of food science and technology and agronomy/horticulture at the University of Nebraska in Lincoln, says that the definition of quality in cereal grains means different things, depending on the industry. “Among others, wheat growers are concerned with disease resistance, drought tolerance, protein concentration, and yield; millers are concerned with wheat kernel size, shape, weight, hardness, and protein concentration; and bakers are concerned with such things as protein quality and sprout damage,” he adds.

Although many tests for cereal grains analysis are not new, Dr. Rose says that new applications are being discovered daily. He and Dr. Marshall highlight a number of new tests currently in use (see “Table 3: Newer Ways to Test Quality of Cereal Grains”).

Dr. Morantes highlights the new possibilities with near infra-red spectroscopy for measuring gluten, water absorption, and starch damage in wheat flour milling. “By using this type of analysis, it’s possible to assure constant product quality, which makes a consistent contribution to the profitability of mills,” he says.

Gaps and Vulnerabilities in Grains Testing

Dr. Bianchini notes that, although the potential for contamination of cereal grains from mycotoxins and bacterial pathogens always exists, ensuring food safety will require more than relying on sample testing alone because of the low incidence and low levels of toxins and bacterial pathogens that will be found.

Instead, testing needs to be a part of a preventive approach to food safety that may include screening methods, she says. For example, testing for indicator organisms can help reduce the amount of inferior or low-quality products from reaching the market. “We still have knowledge gaps that must be addressed, like a better understanding of routes and sources of these contaminations, natural frequency of occurrence and incidence levels, and the effect of emerging or innovative processing technologies on these contaminants,” she adds.

Dr. Morantes highlights the prohibitive cost of cereal grains testing that restricts testing protocols based on a reliable, statistically sound sampling of the grains and reduces such testing to “finding a needle in a haystack,” as he puts it. “As rapid-testing technology further develops, the potential to decrease cost without sacrificing accuracy opens up opportunities for improvement,” he says.

The need for rapid testing is also a priority for quality testing, according to Dr. Rose, who underscores the challenge of how long it takes to evaluate the end-use quality of cereals. “Baking bread, for instance, takes several days to prepare and analyze flour and then several hours to make the bread,” he says. “Efforts are always underway to establish rapid methods to assess the quality of cereal without having to go through the long processes of making food products.”