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Food extraction is a process to separate and recover a part or dense calories from whole food raw material by squeezing, mashing, crushing, or extracting with a solvent or water and then, heating to remove the residue. The objective of extraction is to recover a part of dense calories such as oil, sugar for consumption by discarding the residue.

Food extracts such as cooking oil or sugar is considered as calories-dense food. It does not or rarely contains valuable nutrients such as protein, vitamins, minerals, antioxidants and fiber. Today people consume more calories by consuming food extracts than their requirement and also without fiber, vitamins, minerals, and antioxidant which are beneficial for health. They should avoid the food extracts like oil and sugar and consume a high proportion plant based whole food providing the nutritive values which include fruits, vegetables, legumes, nuts, sweet potatoes ( starches)” and whole grains. These plant based whole foods provide not only calories but valuable nutrients, especially protein, vitamins, minerals, antioxidants and fiber which are important for healthy living.

The three objectives of food processing and preservation are (1) to cook the food, (2) to make the food more palatable and (3) to help in preventing spoilage of food.

The 2 disadvantages of food processing and preservation are (1) a processed or preservative food may lose the natural nutritional value and (2) a processed or preservative food may be harmful to health.

More details about commonly used extracted food and other health aspects of food extraction is available here for you to get in depth understanding of the concept

All kinds of cooking oils are made from whole food extraction. For examples, for producing coconut oil, the beginning step is grating coconut meat from coconut which is whole food. Then water is poured, mixed together, squeezed to release coconut milk in the form of white suspensions which is filtered to discard the solid residue, the first discarding. Next, coconut oil is extracted from coconut milk by heating which is a mass of yellow-brown residue which is then discarded again. We can use the remaining oil, the result from the final step of the extraction, which is rich in calories. There are 9 calories in 1 gram of virgin oil. Cooking oil is classified as food providing the highest calories among all foods and it is extracted without other valuable nutrients such as protein, vitamins, minerals and fiber because these nutrients are discarded as residue or filtrate. Other oils such as palm oil, soybean oil, rice bran oil and olive oil are extracted by similar processes and by recovering a part of dense calories and discarding the residue. In terms of meat & milk, a part considered as an extracted food is lard oil, cheese, butter (except margarine which is not whole food but it is trans-fat made by adding hydrogen and catalysts into vegetable oil in industrial process).

Sugar is an extract from whole plant of sugarcane. Sugar production starts with initial processes like cutting and blending sugarcane until tender. Squeezing the sugarcane to release sugarcane juice and discarding the sediment which is the first discard. Sugarcane juice which looks like a thick mud is then precipitated, and filtered. The precipitate is the second discarding. Precipitated sugarcane juice is boiled until it becomes syrup, then it is continuously stewed by heating until the syrup crystallize into raw sugar. After that, it is spun to remove water from mud-colored crystalline sugar and spin continually until dry. Dried crystalline sugar is dissolved with limewater into clear-syrup and the colored sediment is filtered by raisin which is the third discarding. Clear-syrup is stewed again until crystallize into white sugar without residue or any nutrients except sweetness providing 4 calories in 1 gram of sugar.

Commercially fruit juice is the extract from fruits which is a whole food. The extraction process removes partially or completely the most of the valuable ingredients and contains high calories and also more calories from added sugars. Whole Fruits contain phytophenols which are very beneficial for health. Analysis of commercially available fruit juices found that fruit juice contained low levels of phytophenols compared to squeezing fruits ourselves or eating whole fruits[213].

Fruit juice lacks fiber which are essential to stay healthy and reduce blood cholesterol. Meanwhile, packaged fruit juice contains high calories from added sugars compared with whole fruit leading to consumption of more calories than required. A prospective epidemiological study was conducted in over 50,000 participants, to examine associations between fruit consumption and the risk of acute coronary syndrome (ACS). The participants were divided into 2 groups. One group took daily fresh whole apple while other group took apple juice. After almost 8- year of follow-up, the result showed that participants who ate daily whole apple had a lower risk of ACS comparing to those who ate neither fresh whole apple nor apple juice. Participants who drank daily apple juice had a higher risk of ACS compared with those who ate fresh whole apple[214].

Similarly in the results from three prospective longitudinal cohort studies, the researchers of Harvard Medical School followed almost 200,000 individuals who were free of major chronic diseases at baseline but 12,198 participants developed type 2 diabetes during years of follow-up. When they analyzed the relationship between fruit consumption and risk of type 2 diabetes, they found that greater consumption of specific whole fruits, particularly blueberries, grapes and apples, was significantly associated with a lower risk of type 2 diabetes, whereas greater consumption of fruit juice was associated with a higher risk [58].. In a controlled trial, obese patients were randomized to receive either a low-fructose diet (< 20 g/day), in the form of added sugar sweetened-beverages and processed foods, with intense energy-restriction or moderate-fructose diet (50-70 g/day), in form of natural fruit , with moderate energy-restriction to compare the effects of both diets on body weight, for 6-weeks. The results showed that weight loss was higher (4.2 kg) in the moderate energy-restriction, moderate natural fructose diet group than the intensity energy-restriction, low-fructose (in form of added sugar sweetened-beverages) diet group (2.8 kg). These finding indicated that the ratio of nutritional value of food to calories was important than a high or low calories consumption in weight loss program, in other words, obese patients should consume energy-restricted diet with a high nutritional value[215].

Another research, a systematic review of 11 cross-sectional studies and epidemiological studies found that low folate, a nutrient from plant, was associated with depression[137].  However, in a controlled trial, conducted in participants, with increased familial risk of mood disorder were randomized to receive folic acid (2.5 mg daily) or identical placebo liquid. The results showed that the incidence of mood disorder in the folic acid and placebo groups had non-significant difference[138].The combination of over hundred thousands of nutrients from natural food may not be compensated with a single nutrient extraction.

The traditional methods used for food processing and preservation in household are refrigeration, irradiation with microwave oven, boiling, steaming, baking or grilling, smoking, pickling and sugaring. Overview of the researches about nutritional value of processed or preserved foods in household concluded that among the traditional methods, refrigeration resulted in the lowest nutritional value loss, followed by irradiation with microwave oven and boiling or steaming, respectively. A research about fresh-cut fruits with refrigerator storage[218]. was published in Journal of Agricultural and Food Chemistry. Fresh fruits such as mangoes, pineapples, kiwifruits, strawberries watermelons, and cantaloupes were chopped and sliced into thin pieces or cubes, capped by plastic and stored for up to 9 days in air at 5 °C, and evaluated the quality changes and nutrient retention. The results showed that loss in nutritional content of fresh-cut fruits were less. For examples, vitamin C which can be lost easily after 6 days at 5 °C , 5% in mango, strawberry, and watermelon pieces, 10% in pineapple pieces, 12% in kiwifruit slices, whereas losses in cantaloupe cubes were the highest at 25%. However, some nutrients in fruits such as carotenoids increased in mango and watermelon cubes in response to light exposure during storage at 5 °C for up to 9 days. Therefore, refrigeration can keep most of nutritional contents although not up to 100% as fresh vegetables and fruits.

Frying with high temperature, baking or grilling with high-temperature, smoking, pickling, and sugaring whole foods are the methods of generating molecules that are harmful to health. For examples, baking/grilling with high- temperature or smoking produced high amounts of carcinogen in meat but low amounts of carcinogen in vegetables. The research about trans-fat formation during high-temperature cooking at 180 ᵒC and 220 ᵒC by using different types of unsaturated vegetable oils (soybean oil, olive oil, rapeseed oil, groundnut oil, and partially hydrogenated vegetable oil) found that all oils subjected to heating/frying demonstrated significant increase in trans-fatty acids ranging between 2.30 g/100 g and 4.5 g/100 g [218]..Thus, you should not use all unsaturated vegetable oils for cooking foods with overheating and use air-fryer or cook by other methods except for frying.

Trans-fats created in an industrial process are harmful for consumers’ health Trans -fats are added to food to supposedly increase shelf life of the food items. In food processing industries, production of artificial trans-fats (or trans-fatty acids) is done by adding hydrogen to liquid vegetable oils to make them more solid. This is a process that is most harmful for consumers’ health because the artificial trans-fats which are solid and greasy, causing disease obviously. Trans-fats can be found in many foods such as non-dairy creamer, margarines laid on bread, cookies, crunchy snack, croissants, doughnuts and cakes.

At present, US Food and Drug Administration (USFDA) has announced to outlaw artificial trans-fat in processed foods. However, trans-fat foods were transited rapidly from Europe and America into developing countries including Thailand where there are no regulations prohibiting trans-fat foods.

Production of hot dogs, bacons and ham contributes to generation of carcinogens In 2015, the World Health Organization (WHO) classified hot dogs, bacons, and ham or processed meat as “carcinogenic to humans” (Group 1) placed in the same category as tobacco smoking because the preservativeslead to formation of carcinogenic chemicals in these foods.