The microwave mystery
The microwave has been a staple in our kitchens for decades and have given us quick, easy and convenient ways to prepare meals at the press of a button. Microwaves have proven to be helpful yet the rumors swirling around its safety have caused users of microwaves to rethink their choices. You may have heard some of the whispers around saying microwaves spread food with radiation, they destroy essential nutrients in food or that they can even leave behind toxic chemicals in it. Some people go so far as to say that a microwave meal is a health hazard waiting to happen.
The fears seem to come from everywhere. Friends, family and even social media posts. They warn us that our microwave could be silently contaminating every dish it touches. Some claim that the convenience is not worth the supposed risks the microwave poses our health and safety implying that every time you warm a meal, you are trading your health for a few saved minutes.
But are these claims really true? What is the science behind these claims? Are we really putting ourselves at risk or is the microwave more innocent than it seems? Before you decide whether to keep using yours, let us dive into the science and debunk the myths once and for all. Is your microwave really as dangerous as you have been led to believe?
How microwaves really work
What is microwave heating?
Microwave heating is a volumetric heating process, where heat is generated evenly throughout the entire volume of the food material. This is due to the complete interaction between microwave, polar water molecules and charged ions in food. Microwave energy is selectively absorbed by areas of greater moisture, with more uniform temperature and moisture profiles.
The microwave technology has emerged as one of the most promising food processing technologies. It has gained popularity due to its considerable advantages over conventional heating methods. It has been applied in various food processing industries such as cooking, pasteurization, sterilization, thawing, baking, blanching and drying of food materials. Some advantages of microwave heating include high heating rates, lower processing time and more uniform heating. Moreover, microwave heating might change flavor and nutritional qualities of food in a lesser extent as opposed to conventional heating during cooking or reheating process. Microwaves are electromagnetic waves whose frequency varies within 300 MHz to 300 GHz. Domestic microwave appliances operate generally at a frequency of 2.45 GHz, while industrial microwave systems operate at frequencies of 915 MHz and 2.45 GHz.
Principles of microwave heating
Microwave heating is caused by the ability of the materials to absorb microwave energy and convert it into heat. Microwave heating of food materials mainly occurs due to dipolar and ionic mechanisms. Presence of moisture or water causes dielectric heating due to dipolar nature of water. When an oscillating electric field is incident on the water molecules, the permanently polarized dipolar molecules try to realign in the direction of the electric field. Due to high frequency electric field, this realignment occurs at million times per second and causes internal friction of molecules resulting in the volumetric heating of the material. Microwave heating might also occur due to the oscillatory migration of ions in the food which generates heat in presence of high frequency oscillating electric field. There are many factors which affect the microwave heating and its heat distribution and the most important of them are the dielectric properties and penetration depth.
Non ionizing radiation and why food does not absorb radiation
Any type of electromagnetic radiation that does not carry enough energy to ionize atoms or molecules is called Non-ionizing radiation. This means it cannot completely remove an electron from an atom or molecule. This type of radiation is found in the electromagnetic spectrum and includes microwave (MW), ultraviolet (UV), visible light, infrared (IR), radio frequency (RF), and extremely low frequency (ELF) radiation. Microwaves, a type of non-ionizing radiation are used in microwave ovens. Food is heated using a process known as dielectric heating when it is placed in a microwave oven. The food's water molecules vibrate in the microwaves which then produces heat and friction. The meal is heated or cooked by this heat. The radiation is not permanently "absorbed" by the food but rather, the energy is taken from the food and released by the microwaves as heat when the microwave is switched off. The microwaves themselves don't remain in the meal or permanently change its chemical composition so you should not be afraid of using the microwave henceforth. The microwave will always be safe for use as long as we follow the correct and safe guidelines given to us in the microwave manual.
Nutrient factor of microwaving food
Thirty years ago, microwave ovens for home use were first developed. The nutritional preservation of food prepared in a microwave oven was the focus of a lot of early research. As early as 1948, researchers found that using a microwave instead of traditional cooking improves nutrient retention. More recent studies demonstrated that electronic heating improved nutrient retention in fruits and vegetables compared to conventional cooking. They ascribed this to foods cooked with microwave energy having a lower water-to-product ratio and, as a result, less leaching, which in turn increased nutrient retention(Cross and Fung, 1982). Is not rather surprising? Yes cooking food in a microwave helps preserve nutrients better, particularly when a tiny bit of water is added to steam the food from the inside out. A microwave safe lid or wrap can help maintain moisture and nutrients and overcooking should be avoided to prevent nutrient loss. Because it takes less time and requires little to no water, microwave heating is among the least likely to destroy nutrients when compared to other cooking techniques. Microwaving is recognized to effectively protect heat sensitive nutrients, while the extent of nutrient loss varies depending on variables like cooking time, heat intensity and food quality.
Does microwaving food cause cancer?
Microwaves are non-ionizing radiation so they do not have the same risks as x-rays or other types of ionizing radiation. So no, microwave cooking does not cause or pose the risk of cancer. This is supported by the World Health Organization in June 2005. It is important to also know that even though microwave radiation does not pose risk of cancer, it
can heat body tissues the same way it heats food. Exposure to high levels of microwaves can cause skin burns or cataracts. Less is known about what happens to people exposed to low levels of microwaves. To ensure that microwave ovens are safe, manufacturers are required to certify that their microwave oven products meet the strict radiation safety standard created and enforced by the FDA. Microwave energy will not leak from a microwave in good condition. A damaged microwave oven may present a risk of microwave energy leaks.
Contact your microwave's manufacturer for assistance if your microwave oven has damage to its door hinges, latches, or seals, or if the door does not open or close properly
How to use the microwave safely and correctly
Pay attention to the manual as it contains how to use a microwave and microwave safety tips.
Microwave ovens should be periodically tested to detect any damage and removed from use if they are damaged.
It is essential to clean the inside of the microwave before putting food inside.
Use microwave-safe containers, and avoid warming food in plastic containers.
Do not use metal containers as metals are not microwave-proof.
Do not put sealed containers in a microwave as heating food builds pressure within a container and covering will cause it to explode.
Unplug the power plug after every use
References
(Alonso and Banga, 1998), (Guzik et al., 2022), (Chandrasekaran, Ramanathan and Basak, 2013), (Ohlsson and Bengtsson, 2001), (Beddows, 1983), (Definition and Radiation, 1992), (Cross and Fung, 1982), (Abd Rahman and A Rahman, 2021),
Abd Rahman, M.A.A.A. and A Rahman, Z. (2021) ‘Microwave usage and cancer: Do microwaves cause cancer?’, Malaysian Journal of Science Health & Technology, 6(9). Available at: https://doi.org/10.33102/mjosht.v6io.126.
Alonso, A. a and Banga, J.R. (1998) ‘O Ptimal C Ontrol of M Icrowave H Eating U Sing’, (September), pp. 21–23.
Beddows, C.L. (1983) ‘A comparison of temperatures reached after cooking stuffed chickens: Implications for preventing food poisoning’, Journal of the Science of Food and Agriculture, 34(10), pp. 1149–1153. Available at: https://doi.org/10.1002/jsfa.2740341017.
Chandrasekaran, S., Ramanathan, S. and Basak, T. (2013) ‘Microwave food processing-A review’, Food Research International, 52(1), pp. 243–261. Available at: https://doi.org/10.1016/j.foodres.2013.02.033.
Cross, G.A. and Fung, D.Y.C. (1982) ‘The Effect of Microwaves on Nutrient Value of Foods’, C R C Critical Reviews in Food Science and Nutrition, 16(4), pp. 355–381. Available at: https://doi.org/10.1080/10408398209527340.
Definition, T. and Radiation, M. (1992) ‘Chapter 4 Microwave Radiation’.
Guzik, P. et al. (2022) ‘The confrontation of consumer beliefs about the impact of microwave-processing on food and human health with existing research’, Trends in Food Science and Technology, 119(November 2021), pp. 110–121. Available at: https://doi.org/10.1016/j.tifs.2021.11.011.
Ohlsson, T. and Bengtsson, N. (2001) Microwave technology and foods, Advances in Food and Nutrition Research. Available at: https://doi.org/10.1016/S1043-4526(01)43003-8.
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