Starch: Amylose, Amylopectin, Indian Staples and How Cooking Changes It

Starch is the storage carbohydrate of plants and the main source of energy on an Indian plate: long chains of glucose packed into grains of rice, wheat and millets, and into potatoes and pulses. Raw milled rice is 75.7 g starch per 100 g in the Indian Food Composition Tables 2017. ICMR-NIN sets no requirement for starch itself, but its 2024 dietary guidelines ask that cereals and millets supply no more than 45 per cent of the day's energy. This entry belongs to the carbohydrates section of the handbook.

What is starch?

Starch is a polysaccharide made only of glucose units. Plants lay it down as a reserve in seeds, roots, tubers and some fruits, in small, partly crystalline granules whose size and shape depend on the plant. The FAO and WHO expert consultation on carbohydrates calls it the most important and abundant digestible polysaccharide in food. Digestion begins in the mouth with salivary amylase and is completed in the small intestine by pancreatic amylase and the enzymes of the gut lining. The end product is glucose, which is absorbed into the blood.

ICMR-NIN's Dietary Guidelines for Indians, 2024, places starch beside fibre as one of the two complex carbohydrates found in cereals, millets, pulses, vegetables and tubers, and gives carbohydrate an energy value of 4 kcal per gram. The difference between the two is digestion: starch is broken down and absorbed, while dietary fibre is not. A small share of starch also escapes digestion, and that fraction has its own entry on resistant starch.

Amylose and amylopectin compared

Every starch granule is a mixture of two glucose polymers. Amylose is close to a straight chain, with only limited branching. Amylopectin is a much larger molecule and highly branched, with about 5 to 6 per cent of its links forming branch points. According to the FAO and WHO report, most common cereal starches contain 20 to 30 per cent amylose. The ratio shapes how a grain cooks and how its starch behaves afterwards.

How much starch do you need in India?

No Indian or international body sets a requirement for starch as such; the figures are for total carbohydrate. ICMR-NIN's Nutrient Requirements for Indians, 2020, made carbohydrate recommendations for the first time: a minimum of 100 to 130 g a day from the age of one, described as the amount the brain needs for its glucose use, and an acceptable range of 45 to 65 per cent of energy for adults. Cereals and millets are the major sources of carbohydrate in the national guidelines, and nearly all of the carbohydrate in a cereal is starch.

The 2024 guidelines turn the range into food. A balanced diet should draw not more than 45 per cent of its energy from cereals and millets, yet the same document reports that cereals now supply 50 to 70 per cent. Its My Plate for the Day, built for 2,000 kcal, holds 250 g of raw cereals and millets on the vegetarian plate, giving about 843 kcal and 172 g of carbohydrate, with at least half of the grain to be whole. To find your own energy figure, start with the calorie calculator.

Which Indian staples carry the most starch?

Milled rice and maida lead, the millets and whole-wheat atta sit a step lower, pulses lower again, and tubers are mostly water. IFCT 2017 measures total starch separately from sugars. Per 100 g raw, milled rice has 75.70 g, parboiled milled rice 76.14 g, maida 70.03 g, ragi 62.13 g, jowar 59.70 g, atta 56.82 g and bajra 55.21 g. Red gram dal has 48.53 g and whole Bengal gram 35.69 g. A raw potato has only 11.47 g, which fits ICMR-NIN's listing of roots and tubers at 70 to 100 kcal per 100 g against an average of 343 kcal for cereals.

The portions are illustrative raw amounts for one meal, 80 g of grain or flour and 30 g of pulse, and the arithmetic is NNWA's on IFCT values. The ripe banana shows what ripening does: only 5.29 g of its 18.94 g of available carbohydrate is still starch, and 13.65 g is free sugars. NNWA's table of carbohydrate in Indian foods ranks every food in the database, and the pages for milled rice and potato as a tuber give the full nutrient panels.

How do cooking and cooling change starch?

Heat and water make starch digestible, and cooling takes a little of that back. Raw granules do not dissolve. Heated in water they swell and lose their ordered structure at the gelatinisation temperature, which the FAO and WHO report gives as 68 to 78 degrees C for rice and sorghum and 58 to 64 degrees C for wheat. Gelatinised starch is attacked far more easily by amylase, which is why boiled rice, a soft idli or a ragi porridge is digested quickly.

When cooked starch cools, the chains line up again, a change called retrogradation that is rapid for amylose and slow for amylopectin, and some of the realigned starch resists digestion. Form matters as much as temperature. In a 2022 study in the Indian Journal of Medical Research, broken wheat upma had a glycaemic index of 51.7, while wheat flakes chivda scored 72.5 and a stiff ragi ball 98.2, although all three were whole-grain foods. The authors concluded that being whole grain does not by itself mean a lower index: processing and the intactness of the grain decide it.

Too much starch, too little, and who is at risk in India

A shortage of starch is unusual on an Indian diet; the concern runs the other way. In the ICMR-INDIAB national survey of 18,090 adults, carbohydrate supplied 62.3 per cent of daily energy, with 28.5 per cent of energy from refined cereals alone, while protein supplied 12 per cent. Adults with the highest carbohydrate intakes were more likely than those with the lowest to have newly diagnosed type 2 diabetes (odds ratio 1.30), prediabetes (1.20), generalised obesity (1.22) and abdominal obesity (1.15). The survey is cross-sectional, so these are associations and not proof of cause.

City figures point the same way. Among 2,042 adults in the Chennai Urban Rural Epidemiology Study, refined grains averaged 333 g a day, 46.9 per cent of total calories, and the highest quarter of intake had far higher odds of the metabolic syndrome than the lowest (odds ratio 7.83). At the other end, ICMR-NIN's floor of 100 to 130 g of carbohydrate a day is a reason not to strip cereals out altogether. The entry on the low-carbohydrate diet discusses eating patterns that go lower.

What does the evidence say about starch and blood glucose?

It says that the food carrying the starch matters more than the starch total. ICMR-NIN's 2024 guidelines print indicative glycaemic index values, each from ten volunteers: 78.23 for rice, 65.66 for wheat chapatti, 68.69 for idli with sambar and 37.95 for Bengal gram. A separate Chennai study of three everyday rice varieties, Sona Masuri, Ponni and Surti Kolam, found values of 72.0, 70.2 and 77.0, all in the high category and not significantly different from one another. The article on the glycaemic index of Indian foods explains how to read such numbers.

Changing the grain without changing the amount may do less than hoped. In the ICMR-INDIAB analysis, replacing refined cereals with whole wheat or millet flour, with total carbohydrate unchanged, was not associated with a lower risk of type 2 diabetes (odds ratio 0.94, with a confidence interval from 0.57 to 1.56). Modelled replacement of 5 per cent of energy from carbohydrate with plant, dairy, egg or fish protein was associated with lower odds of diabetes and prediabetes.

The WHO's 2023 guidance adds a rule about quality: carbohydrate should come primarily from whole grains, vegetables, fruits and pulses. None of these is a treatment plan, and the diabetes nutrition course teaches how such figures are used alongside medical care.

A worked example: counting the starch in one day

This example is illustrative and the person in it is invented. Take a 31-year-old school teacher in Chennai who eats about 2,000 kcal a day. In raw weights her day holds idlis made from 45 g of parboiled rice and 15 g of urad dal, a lunch of 100 g of rice, 30 g of toor dal and 100 g of potato, and a dinner of rotis from 60 g of atta with 30 g of whole moong. On IFCT 2017 values the starch comes to 34.3 g and 7.2 g at breakfast, 75.7 g, 14.6 g and 11.5 g at lunch, and 34.1 g and 11.8 g at dinner.

The total is about 189 g of starch, roughly 756 kcal at 4 kcal per gram, or 38 per cent of her 2,000 kcal. About three quarters of it, 144 g, comes from 205 g of cereals. At ICMR-NIN's average of 343 kcal per 100 g, those cereals supply about 703 kcal, 35 per cent of her energy and under the 45 per cent ceiling. The useful change is not less rice but better company: count the potato as a starch, and add a katori of vegetables in its place.

Common mistakes and myths about starch

The commonest mistake is to treat potato as a vegetable. ICMR-NIN's plate leaves it out of the vegetable allowance, and the guidelines group potato, sweet potato, tapioca and yam as roots and tubers that are rich in starch. The second is to assume that a brown colour or the word millet settles the matter: a ragi ball scored 98.2 on the glycaemic index in the Chennai study, higher than any of the three rice varieties tested by the same research group.

A related error is to fear starch altogether. The national guidelines still build the plate on cereals and millets and set a minimum for carbohydrate. NNWA's comparison of rice and whole-wheat atta sets the two grains side by side, and the Indian food calorie counter shows what a cooked serving of each dish adds up to.

Starch, safety and when to see a doctor

Starch is a food, not a supplement, and ICMR-NIN's 2020 table of tolerable upper limits has no entry for carbohydrate. The safety questions are about the person eating it and about storage. Cooked rice and other starchy foods spoil: the 2024 guidelines say that cooked food which must be stored should be kept hot, above 60 degrees C, or cooled quickly to below 5 degrees C, and heated thoroughly before it is eaten.

A change in rice or roti does not replace a medicine, and you should not stop or reduce a prescription because your plate has changed. Blood glucose tests are ordered and interpreted by a doctor. The diabetes risk calculator is a screening aid that tells you whether such a visit is worth making soon.

Learning this subject at NNWA

Carbohydrates, the Indian food tables and plate planning are taught at NNWA, a private skill academy in Kolkata that teaches online in English and Hindi. Its courses, beginning with the Certification in Nutrition, train people to coach healthy clients about food and to send medical cases to a doctor. None is a degree or a dietitian qualification.