Food is the fundamental nutrient source to man, and this undoubtedly determines our health. The undeniable contribution food has in our wellbeing is so important that an absence of one or more nutrients could lead to a series of malnutrition cases.
In most cases, the preparation process employed in cooking our foods, especially the whole plant foods has been the reason for alterations in food nutrients and their availability in us.
Plant foods are naturally loaded with nutrients which are responsible for enhancing the body's health and ensuring that the body is well supplied with nutrients that facilitate healing, repair, prevention and defence which are the reason for the concern of how the different preparation processes affect the availability of these nutrients and our health.
Quickly, let us highlight the different cooking processes we have.
Cooking has been an age-long practice in the history of man's existence. The early cooking method was predominantly open-fire roasting. One that entailed that the food was directly placed into the fire. Yes, like right into the ashes.
Over the years, several other cooking methods have surfaced, and little consideration has been placed on the nutritional content of the foods.
The very major cooking methods include:
Boiling
Poaching
Stewing
Braising
Steaming
Baking
Roasting/ grilling
Frying
1. Boiling
This is when food is prepared in a liquid; water, milk, stock, etc. The food could either be put in the water at room temperature and then brought to a boil by increasing the temperature. Or placed in the boiling liquid, reboiled, and the heat is later reduced allowing the liquid to simmer more gently. Boiling saves time and energy as believed by many. The boiling procedure is a popular cooking practice.
2. Poaching
Poaching entails simmering food in a small or large amount of liquid at boiling or near boiling point. Poaching could be either of shallow or deep style. In both forms, the food is placed upon the boiling liquid and made to poach right in or on the liquid at a controlled temperature.
3. Stewing
Stewing is a cooking process where the food is cut in small pieces and cooked in a minimum amount of liquid (water, stock, sauce) for a long time using low heat. The food and the cooking liquid are served together. Stews are most often thick and have a uniform consistency. Cooked in an oven, or cooktop.
4. Braising
The food is cooked in a casserole or a pan placed in the oven. Most times, a little liquid is put in it.
The food is cooked in liquid in a covered pan or casserole. It is a combination of stewing and pot roasting.
5. Steaming
A cooking procedure that engages the use of steam at various degrees and pressure.
It is a slow cooking process that ensures the total or thorough cooking of the food items by the use of steam.
6. Baking
Baking would entail cooking food by dry heat in an oven, It could be a brick oven or a modern household oven. Both dry and light steam (moisture from the food) work to soften the food and cause cooking.
7. Roasting
Roasting entails cooking with dry heat and with the use of fats or oil. Food is dressed and placed at a distance over an open fire or heat source.
8. Frying
The use of pre-heated fats and oils are what characterises the frying process. Frying is when oil is used to cook. It could either be deep-frying (immersing the entire food in the oil) or shallow frying where only a little portion of fat is used in cooking.
Cooking processes and its duration are responsible for how the food will turn out to be. The nutritional value and its availability are also a factor of the cooking process used. The Process used also says a lot about how much of the nutrient our body can absorb and what impact it will have on the health.
Cooking Processes, Nutrient loss and your health
Vegetables and fruits which are very rich in vitamins and minerals are very fragile, and can easily have their nutrients lost when the right preparation method is not employed, or when the preparation time is unnecessarily lengthened.
Studies have revealed that food preparation processes and how they are preserved have a great impact on the availability and the number of nutrients especially minerals and vitamins in the food. Micronutrients deficiency which we also call hidden hunger sometimes, are most often caused by the nutrient loss due to the food preparation processes. Micronutrient deficiency has been very much linked to poor health, reduced productivity, increased lifestyle diseases, and even death in some cases. We will be examining some of them here.
In a study of some African indigenous vegetables and how much free amino acids in them are affected after cooking, they used several cooking procedures and came up with a recommendation. The vegetables used were sweet potatoes, cabbage, snap pea, spinach, komatsuna, western carrot, kintoki carrot. First, they found that low to high differences is seen in the amino acid contents of the vegetables after each procedure depending on the vegetable.
Of all the procedures employed, boiling recorded the highest nutrient losses in the food samples, although almost half of the nutrient lost in the vegetable was found in the broth (water). A good reason why you should not preheat vegetables before cooking it so as not to lose key nutrients. Also, some free amino acids were completely denatured. Vegetables that cannot be eaten raw are best steamed and for a short time to preserve most of its nutrients. Grilling produces carcinogens (Advanced Glycation End-products) in high protein and carbohydrate foods when exposed to dry heat.
In some other studies where frying is observed, along with the excessive oil content in the food which is also a public health concern and a high risk for heart diseases, some nutrient loss was also observed.
The study considered so many factors including the type of fat used in frying and the fat content of the food item being cooked as well. It was found that some oils are more prone to oxidation or have the ability to be saturated and form transfat on heating it up or on its repeated usage. Olive oil, corn oil were recommended as they are more resistant to oxidation when compared to other oil sources.
Now, when food is fried either deep or shallow frying, the energy content of the food item is raised based on the fact that the food will et to soak up a portion of the oil, even while denaturing or destroying some nutrients in, depending on how long the cooking process lasts. It is recommended to have less fried foods and use little oil in any cooking process.
Generally, nutrients are either denatured or made bioavailable at the presence of heat.
Many other reviews and studies have revealed the cooking options, their effects on the food nutrient composition and their ripple effects on our health. Fried foods have been linked to Cardiovascular diseases, organ failures, obesity, hypertension, stroke, infertility and so on. Grilling or roasting has been linked to cancer risks, caused by a build-up of Advanced Glycation End-products (AGE) when the food nutrient come in contact with dry heat.
Tips to preserve Nutrients in food
Again, we have seen that food nutrients especially in vegetables are lost more in the traditional ways of cooking. Frying, roasting, sun drying destroy most of the food nutrients and puts us at risks of developing other lifestyle diseases.
Cooking in an open fire (roasting/grilling) for a long time, reheating them over and over is a regular practice in many homes which has led to a very significant reduction in the food nutrients. Let us look at a few tips to preserve food nutrients.
A. Steaming, boiling can be used as long as you plan to use the water because nutrients from the vegetables, if not denatured, would be leeched in there.
Vegetables should be steamed slowly to soften and not overcooked. Avoid pre-heating green vegetables and throwing away the water before you use the vegetable in your cuisine.
Try to have as many green vegetables without cooking to get the most of their nutrients.
B. Ensure to wash all leafy vegetables before cutting them. Wash all leafy vegetables under running water before you cut to avoid nutrient losses too. Cutting will expose the plant cells to atmospheric air and water which will denature the water-soluble vitamins and other minerals therein.
C. For vegetables with peel, it is recommended to cook with skin on or peel thinly to reduce nutrient loss to heat or into the liquid used.
D. When you are planning to make fresh vegetable and or fruit salad meals, try to add a little lemon or vinegar to slow down the vitamin C loss on cutting.
Cook food to a tender texture. Avoid food being mushy as it will require a longer cooking time which will denature most nutrients in the food item.
E. Use the smallest amount of water most times when boiling and try to serve all foods for eating immediately after cooking. Washing rice off in hot water or parboiling also causes nutrient loss in them. Use the regular room temperature water rinse once or twice before cooking. Heating and reheating further increases nutrient loss.
References.
Wang L., Manson J.E., Forman J.P., Gaziano J.M., Buring J.E., Sesso H.D. Dietary fatty acids and the risk of hypertension in middle-aged and older women. Hypertension. 2010;56:598–604. doi: 10.1161/HYPERTENSIONAHA.110.154187.
Gadiraju TV, Patel Y, Gaziano JM, Djoussé L. Fried Food Consumption and Cardiovascular Health: A Review of Current Evidence. Nutrients. 2015;7(10):8424-8430. Published 2015 Oct 6. doi:10.3390/nu7105404
Abate G, Marziano M, Rungratanawanich W, Memo M, Uberti D. Nutrition and AGE-ing: Focusing on Alzheimer's Disease. Oxid Med Cell Longev. 2017;2017:7039816. doi:10.1155/2017/7039816
Hinako ITO, Hiroe KIKUZAKI, Hiroshi UENO, Effects of Cooking Methods on Free Amino Acid Contents in Vegetables, Journal of Nutritional Science and Vitaminology, 2019, Volume 65, Issue 3, Pages 264-271