Can Microwave Technology Kill Pathogens? What Happens to Food in a Microwave?
For many households, using a microwave for making popcorn in minutes with little mess, heating leftovers, and keeping the coffee steaming are part of everyday life. What is less likely thought about it how food must be heated to a safe internal temperature to kill bacteria and any potential pathogens to achieve food safety with all cooking methods, including microwaved foods.
Because microwave ovens may cook unevenly and leave cold spots, harmful food-borne-illness-causing pathogens may survive. The USDA has recommended temperatures to ensure food safety when microwave cooking. For those of us in the food industry, microwave food has compelling benefits and challenges. Moreover, newer microwave technologies create intriguing opportunities to promote food safety, such as exploring microwave-assisted drying methods (Zielinska et. al., 2019).
What is Happening in a Microwave?
When food is heated in a microwave, the water content in the food is heated, which in turn cooks the food ingredients. Microwaves produce very low-energy electromagnetic radiation, and these waves do not have enough energy to break chemical bonds. Instead, the electromagnetic waves excite electrons in water molecules, causing them to vibrate. According to the Food and Drug Administration (FDA), microwaves cause water molecules in the food to vibrate, producing heat that cooks the food.
The FDA describes radiation of visible light, radiofrequency, and microwaves as being on the spectrum of non-ionizing electromagnetic radiation. Ionizing radiation such as x-ray or ultra-violet light can damage cells and alter atoms and molecules. However, non-ionizing microwaves are low-energy electromagnetic radiation that does not break elemental bonds. They only interact with the positive and negative regions of molecules, like those found in polar substances like water. As food contains water, the microwaves’ electromagnetic radiation generates heat by creating vibration in water molecules which produces heat that cooks the food.
The ability of microwaves to generate heat has far-reaching implications within many industry sectors, particularly agricultural sciences and the food industry. Techniques used in food processing such as sterilization, drying, pasteurization, thawing, and blanching may be assisted by microwave energy. The environmental and efficiency advantages of using microwave technologies are encouraging because of shorter processing times, decreased demand for water in processing, as well as potential reduction of waste (Guzik et. al., 2021).
According to Scientific American, microwaves generate heat in food through the rotation and collision of polar molecules of water. Currently, there is no evidence showing that eating microwaved food has any detrimental effects on humans or animals. However, chemical and physical changes occur in foods at high heat. The high temperatures of conventional cooking and microwaving, causes foods to undergo changes such as hydrolyzed proteins and carbohydrates, vitamin loss, and interactions between food substances such as protein and sugars. A floret of broccoli boiled for too long or overly cooked in the microwave will similarly lose its bright green appearance and firm texture.
What Is the Impact of Microwaving on Food Safety?
One of the significant questions about microwave technology is whether it is capable of killing foodborne pathogens. With proper use—cooking food for the proper length of time at the right temperatures—microwaves can be an effective tool to combat foodborne illnesses.
According to one study observing the effect of short-time microwave exposures on Listeria monocytogenes, microwaving proved to be a cost-effective, practical, and safe method of decontaminating foods. The study showed a significant reduction of microbial pathogens in chicken portions inoculated with L. monocytogenes after microwave heating, increasing the temperature by more than 74°C for at least 60 seconds. (Zeinali et. al., 2015)
Furthermore, microwaves heat food quickly and at a lower temperature than many conventional cooking methods. This helps to maintain nutrient levels in foods. Emerging green technologies are using microwave-assisted extraction methods to recover polyphenols in the nutraceutical industries, as shown by a study recovering polyphenols from Chestnut (Castanea sativa) shells (Pinto et. al., 2021). Nutrition aside, microwave food is at a disadvantage in flavor, color, and texture when compared to other cooking modalities. As consumer acceptability is always a top priority in food production, continued improvements in microwave technology can enhance the sensory qualities of foods (Ibriham et. al., 2012).
As always, we in the food industry are concerned with the prevention of foodborne illnesses. Microwave food can cook unevenly or have cold spots, which enable the growth of harmful bacteria. To ensure the safety of microwaved foods, we encourage food producers to follow the recommendations of the USDA’s Cooking Safely in the Microwave Oven and promote these guidelines to consumers.
Microwave Safety Opportunities
Food companies have a responsibility to understand key facts about ready to heat products and share proper heating instructions for safe consumption.
The Eurofins network of ISO 17025 accredited laboratories, provides industry leading analytical and microbiological testing including process validations to ensure your products meet quality and safety requirements. We have access to over 200,000 analytical methods, enabling us to provide innovation, agility, and individualized service to companies in the food industry.
