Influences of food processing and preparation on the nutritional qualities

Food processing, preparation and cooking influence the nutritional qualities of foods and these processes can have advantages and disadvantages. The preparation and preservation of foods involve a great number of different processes, most of which have an effect, not always deleterious, on nutritional value[6]. Heat, one of the most used techniques for preparing food, although it usually causes some destruction of vitamins and protein, under certain conditions heat can maintain nutritive value by inactivating enzymes that would other-wise cause damage[6]. Thermal treatment of foods induces several biological, physical and chemical modifications, leading to sensory, nutritional and textural changes[5]. Cooking is also involved in the formation of desired compounds such as flavour compounds, antioxidants and colouring agents. On the other hand, processing can damage food quality, leading to undesired consequences, such as losses of certain nutrients due to chemical reactions, formation of undesired compounds such as acrylamide or molecules with negative effect on flavour perception, loss of texture, and discolouration[5]. For example food cooking has beneficial effects when is improving the digestibility and bioavailability of nutrients, and by enhancing attractiveness to the consumer because of improved texture and taste, and also eliminating deleterious effects due to loss of nutrients or the formation of toxic compounds [3], inactivating heat-labile antinutritional substances as in cassava or in some legumes, killing microbiological pathogens, making edible some foods such as rice, potatoes, or legumes, or by cooking and preservation techniques making year-round the availability of seasonal foods. Between the disadvantages we can mention the decrease, inactivation or destruction by heat of some nutrients such as vitamin C, vitamin B1 (thiamine), vitamin A and another micronutrients; also some nutrients may be lost in the water when they are boiled such as folate, vitamin B1 (thiamine), minerals and phytochemicals that are phytomoles considered as ‘non-nutrient.constituents of food plants with anticipated health promoting/beneficial and/or toxic effects when ingested[5].

Recent studies have shown there are several ways to enhance the availability of healthy nutrients through proper selection of the method of cooking. According to these studies, the most common methods used for cooking legumes and vegetables are: steaming, roasting, boiling, frying, sautéing, sous vide, microwave and pressure-cooking.[1]. The effect of food processing on nutrient content will depend on the sensitivity of the nutrient to the various conditions prevailing during the process, such as heat, oxygen, pH and light[4]. The storage conditions and handling after processing are also important to the nutritive value of the food[4].

Steaming was the cooking technique that has shown to be the best method for cooking vegetables because it has less impact on the bioavaibility of the micronutrients and the phytochemicals compounds. Ordinary heating or boiling of vegetables using water is likely to result in the elution of a high percentage of vitamins and minerals in the vegetables and these nutrients are decreased in ready-to-eat foods compared with traditional foods, while water-free cooking minimizes the elution of nutrients enabling efficient intake of vegetable nutrients [2].

Also, domestic preparations of vegetables and legumes that normally involve washing, peeling and cutting are anothers sources of cooking techniques that have influences on the nutritional properties of food. During food preparation when is used as chopping and trimming, chopping vegetables can alter the bioavailability of bioactive compounds such as carotenoids, polyphenols and flavonoids. Also it is well known that in onions and garlic, when the cells are damaged by chopping or crushing, the enzyme allinase is released and comes in contact with sulfur compounds increasing the pungency and the flavor of onions or converting in garlic the alliin, an odorless compound, to allicin, the bioactive compound responsible for the characteristic odor and flavor of fresh garlic [1][7].

So, at the moment to prepare our food, it is important to think about what is the best cooking technique to use for getting food with better nutritional properties.
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[1]Fabbri, Adriana D.T. and Crosby, Guy A. 2016. A review of the impact of preparation and cooking on the nutritional quality of vegetables and legumes. International Journal of Gastronomy and Food Science 3, 2–11
[2] Mori, Mari et al. 2012. Effects of cooking using multi-ply cookware on absortion of potassium and vitamins: a randomized double-blind placebo control study. International Journal of Food Sciences and Nutrition. 63(5): 530-536.
[3] Hoffman, Richard and Gerber Mariette. 2015. Food processing and the Mediterranean Diet. Nutrients, 7.
[4] Morris, Audrey et al. 2004. Effect of processing on nutrient content of food. Vol 37, Nro. 3
[5] Palermo, Mariantonella et al. 2014. The effect of cooking on the phytochemical content of vegetables. J Sci Food Agric; 94: 1057–1070
[6] Bender A. E. 1966. Nutritional effects of food processing. J. Fd Technol. 1, 251-289.
[7] Cantwell, Marita. 2000. Alliin in garlic. Perishables Handling Quartely Issue No. 102.

How cooking methods affect foods

Steaming, roasting, boiling, frying, sautéing, sous vide, microwave and pressure-cooking are the most common cooking methods used at home. Different methods of cooking can influence on the chemical compositions of vegetables. Choosing the proper method of cooking we can enhance the availability and get less lost of healthy nutrients. Food preparation at home as final step of the chain has also great influence on quality determining parameters like sensory attributes and the content of vitamins and minerals. It can change them both in a positive and negative way[1]. Cooking induces many chemical and physical modifications in foods; among these the phytochemical content can change. Changes in phytochemicals upon cooking may result from two opposite phenomena: (1) thermal degradation, which reduces their concentration, and (2) a matrix softening effect, which increases the extractability of phytochemicals, resulting in a higher concentration with respect to the raw material[2]. Thermal treatment of foods induces several biological, physical and chemical modifications, leading to sensory, nutritional and textural changes. First of all, cooking increases food safety as a result of the destruction of microorganisms and the inactivation of anti-nutritional factors and a second beneficial effect of cooking is the enhancement of the digestibility of food and the bioavailability of nutrients[2]. Among the negative effect of the thermal treatments on food we can mention the formation of acrylamide by roasting, frying and baking, lost of nutrients in the water when boiling vegetables and the effect of cooking on the vitamin C content of all the vegetables as the heating time increases

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[1] Bernhardt, Simone and Schlich, Elmar. 2006. Impact of different cooking methods on food quality: Retention of lipophilic vitamins in fresh and frozen vegetales. Journal of Food Engeneering 77, 327-333.
[2] Palermo, Mariantonella et al. 2014. The effect of cooking on the phytochemical content of vegetales. J Sci Food Agric 94; 1057-1070.