Nutritional value of potatoes

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1 Nutritional value of potatoes Bandana Scientist, Division of Crop Physiology and Post Harvest Technology Central Potato Research Institute, Shimla Potato (Solanum tuberosum) is an economical food as they provide a cheap source of available energy irrespective of every age s human diet. Potato does better than rice and wheat as edible energy source. Consuming potatoes just once or twice each day lowers high blood pressure almost the same as oats without resulting in increase in weight. Besides potatoes have more in store than just those unwanted calories, ensuring staying healthy. It is a staple component of the diet in many human cultures and source of many essential nutrients and is available all year round moreover may be cooked with various means (e.g. boiling, baking, and frying) prior to consumption. Carbohydrates Carbohydrate is almost universally the major dietary source of metabolic energy. The main energy-providing nutrient in potatoes is carbohydrate, in the form of starch. Potatoes contain both carbohydrate types i.e. simple and complex carbohydrates that provide primary source of energy for the body and supply at least half of calories for the day. Sucrose, fructose and glucose are the main sugar present in potatoes. The advantage of getting carbohydrates from potatoes is that one can get a considerable amount of certain micronutrients as well. Although, potato starches are less completely digested when fed raw but their digestibility is similar to that of the cereal starches after cooking. Fat When boiled or baked, potatoes are a virtually fat-free food and average fat content of potato is 0.1%. The little fat present in tuber gives palatability. About 60-80% of the fatty acid content is composed of unsaturated fatty acids (linoleic acid). Protein Proteins are important constituents of cellular membranes as well as various cytoplasmic structures. Also the enzymes present in potatoes are made up of proteins. The essential nitrogen fraction in a potato tuber is protein nitrogen. Potatoes are commonly perceived as a carbohydrate source only, but they do contain high quality protein. On a fresh weight basis they contain only about 2% protein; the value increases to about 6-8% on a dry weight basis that makes potatoes comparable to cereals, such as rice or wheat. In countries, where potato consumption is high this vegetable can make a significant contribution to health as a protein source. Potato proteins comprise amino acids present in varying quantities. More than two-thirds of the non-protein nitrogen present in potatoes is present as free amino acids. A number of different amino acids are present in highest quantities in potatoes viz. lysine, aspartic acid, glutamic acid and valine.

2 Vitamins Of all the vitamins, potatoes contain vitamin C in the highest amount. Vitamin C is a water-soluble and its main component is ascorbic acid. However, dehydroascorbic acid has properties similar to vitamin C if it is reduced to ascorbic acid in the organism. It acts as an antioxidant stabilizing free radicals, thus helping prevent cellular damage. It aids in collagen production; assists with iron absorption and help support the body s immune system. Potatoes are a good source of vitamin B6, a water soluble vitamin that plays important roles in carbohydrate and protein metabolism. It helps the body by making amino acids that is later used to manufacture various proteins. There are several different B group vitamins, and potatoes are a source of some of these. A medium serving of boiled potatoes (180 g) contains more than one sixth of the adult daily requirements for vitamins B 1, B 6 and folate. These B group vitamins have many functions in the body including being essential components in the metabolism of carbohydrates to provide energy, and maintaining a healthy skin and nervous system. Folate is needed for cell growth and development. Minerals Various important minerals and trace elements are present in potato. Potatoes are among the top sources of potassium. In fact, potatoes have more potassium per serving than any other vegetable or fruit, including bananas, oranges, or mushrooms. Diets rich in potassium and low in sodium (which together with chloride forms salt) reduces the risk of hypertension and stroke and help lowering blood pressure. Potatoes are a rich source of iron and this, coupled with the presence of high vitamin C content, helps in its absorption. It is also a good source of potassium, phosphorus and magnesium. Zinc is an important trace element found in potato. Because of low phytic acid content of potato zinc availability is very high. Phytochemicals Phenolic acids and flavonoids are the most prominent phytochemical groups present in the potato. Bioactive compounds or phytochemicals are secondary plant metabolites found in the potato have been the subject of interest for researchers due to their promising role as healthmodulators. Potatoes due to its high consumption is considered as the third largest source of phenolic compounds in the human diet after oranges and apples, thus potatoes can act as delivery mechanisms for bioactive compounds. Colored-flesh potatoes are gaining popularity due to the potential health benefits of anthocyanins. Numerous health benefits such as antioxidant activity, anti-cancer and anti-inflammatory properties, have been attributed to consumption of anthocyanin-rich foods. Dietary fibre Potatoes are a good source of fibre, which contributes to the feeling of fullness, and supports healthy digestive functions. A 180 g portion of boiled potatoes provides about 3 grams of fibre, which equates to more than 10% of the daily recommended intake of

3 fibre. Dietary fiber has been shown to have numerous health benefits, including improving lowering the risk of heart disease, diabetes, and obesity, and increasing feelings of fullness, which may help with weight management. Some people enjoy the stronger taste of eating cooked potatoes with skins on, and in this form they contain even more fibre. A small amount of the starch in potatoes resists digestion (this is called resistant starch ). Amount of starch depends upon the time and temperature during processing or cooking and amount of added water. Resistant starch acts in the body in a similar way to fibre, and too aids in the control of blood glucose and blood lipid levels. Potatoes! awesome for good health Potatoes are a very popular food source for human health. Food ranking system qualified potatoes as a good source of vitamin B6 (involved in more than 100 reactions), vitamin C, copper, potassium, manganese, and dietary fiber. Besides that, potatoes also contain a variety of phytonutrients that have antioxidant activity. Among these important health-promoting compounds are carotenoids, flavonoids, and caffeic acid, as well as unique tuber storage proteins, such as patatin, which exhibit activity against free radicals. UK scientists at the Institute for Food Research have identified blood pressurelowering compounds called kukoamines in potatoes. Potatoes are gluten-free and therefore can be consumed freely by people who need to avoid gluten (so cannot eat many common foods including bread, most breakfast cereals). It is a protein which is found in wheat and rye. Therefore, potatoes can be served as very important food for them. Misconceptions There are numerous misconceptions about the nutritional value of the potato. It is often believed that the potato is a high-energy food that provides little else in the way of nutrients. Most people eat potatoes in the form of greasy French fries or potato chips. Preparation and serving potatoes with high-fat ingredients raises the caloric value of the dish. Such treatment can make even baked potatoes a potential contributor to towards fattening. Potatoes are not contributing towards fattening because potato itself contains very low quantity of oil (0.1%) and it is absorbing oil only when deep fried. Nutritional value of potato processed products Demand for processed potato products is increasing and potato products are liked well worldwide. Since potatoes need to be baked, boiled, fried, or otherwise cooked before consumption, it is of interest to determine to what extent exposure to heat affects nutritive value of the potatoes. Losses during chipping and canning are considerable but appear to be minor during boiling and frying. Processing up to some extent, have deleterious effect on nutrients. Because during cooking and processing diffusion of nutrients from the tuber make them low in concentrations. But it does not mean that processed potato products become low source of nutrients. Frying also avoids loss of water-soluble vitamins through leaching into the cooking water. For example, vitamin C concentrations of French fried potatoes can sometimes be as high as in raw potatoes,

4 and thiamine is well retained in fried potato products as well as in fried pork meat. The table listed below indicate the major nutrients present in potato products. Composition of processed form of potatoes (per 100g) Form of Total Dietary Protein (g) Fat (g) Energy potato carbohydrates (g) fibre (g) (kcal) Raw Chips Frozen French fries Flakes Potato flour Granules Conclusion Potato, a starchy tuberous crop and is an essential food item in the recipes of many countries around the world. While no vegetable dish is complete without the presence of potatoes and there are several countries where only potato is the principal food and is an excellent source of energy-rich diet. Potato is very easy to digest as well as contains mild roughage. The vitamin C content in potatoes is far better than most of the vegetables and fruits and is helpful for preventing the dreaded deficiency disease scurvy and frequent viral infections. Well, the fact is that potatoes are filling and nonfattening, contradictory to the popular belief. Potato is such a wholesome food that one can live by eating potato alone. Suggested readings Burton WG The nutritive value of potato, cooked or processed in relation to human requirements. In: WG Burton. Ed. The Potato, 3rd edition. Longman Singapore Publishers (Pte) Ltd, Singapore. Pp Caprara C Potential health promoting properties of potato-derived proteins, peptides and phenolic compounds. In:potatoes production, consumption and health benefits. Nova science Pulishers. Pp

5 Horton, D and Sawyer, RL The potato as a world food crop, with special reference to developing areas. In: Potato physiology. Li, P.H. Ed. Academic Press, Orlando. Pp. 1-34