Oil Seeds and Nuts

Introduction

Nuts are seeds or fruits consisting of an edible fat containing kernel and surrounded by a hard or a brittle shell. Nuts have rich flavour and have a great commercial importance.

Nutritive value

Like pulses, oil seeds nuts are rich in protein and in addition they contain a high level of fat. Hence they are not only good sources of protein but are concentrated source of energy. They do not contain an appreciable amount of carbohydrate but contain high level of B-vitamins. Groundnuts are particularly rich in thiamine and nicotinic acid. Oil seeds produced in the country are mostly used for oil extraction.

In India nuts like walnut, cashewnut, coconut, chestnut, almond and oilseeds like groundnut, mustard, soyabean, safflower, are more commonly grown for edible oil purpose.

Coconut

Coconut water is a refreshing drink which also hygienic and nutritive. The white flesh is a calories rich extensively used for cookery in South India. From grated wet coconut kernel good quality oil as well as protein and carbohydrate can be extracted to prepare coconut honey. Undesirable flavour changes in desiccated coconut is due to oxidative rancidity of the oil. The residual cake after the oil has been extracted is used as cattle food.

Groundnut

Groundnuts resemble other pulse in general nutritive value, except that they are rich in fat. The whole seed contains about 40% fat, twice the amount in Soyabean. Groundnuts are boiled or roasted and consumed. But the chief product is the oil, which can be used either as cooking oil or for making margarine and soap. The secondary product is the residue or cake left after the expression of the oil. It is also purified and used in supplementary mix. The major proteins of groundnut are arachin and conarachine which is lacking in lysine and methionine and its quality can be improved by either adding these amino acids or foods rich in the same.

Groundnut products:

• Groundnut milk

Steps involved:

1. Good quality peanut kernels are cleaned of impurities and roasted lightly to and the red skin is removed.
2. The germ is separated by sieving and the spoilt seeds by handpicking.
3. The cleaned kernels are ground to a smooth paste. The paste is mixed with 7 times the weight of water in a blender. Calcium hydroxide solution is added till the pH of the milk is adjusted to 6.8. A mixture of disodium phosphate and acid potassium phosphate having pH 7.0 is added to stabilise the milk.
4. The milk is filtered through a fine cloth and fortified with vitamins A, D, B2, folic acid. B12 and minerals, calcium and iron. Cane sugar is added at 7% level.
5. The milk is hongenised, steamed, bottled and kept in a refrigerator till distributed.

The milk obtained from soybean or peanut can be used as a supplement to the diets of pre-school and school children. Or it can be used as substitute for ordinary milk, if allergic condition develops.

• Peanut Butter

1. Good quality peanut kernel is cleaned it is roasted to a moderate degree till a pleasant aroma develops.
2. Red skin is removed by passing the roasted kernel through a blanching machine. The germs are separated by sieving and the spoilt kernels by hand picking.
3. The kernels are ground in a grinding machine to medium grind. Hydrogenated fat containing vitamin A is added at 5% level as this helps to prevent separation of oil. Sodium chloride is added at 2% level. The mixture is ground to a smooth paste and packed in bottles. Peanut butter can be consumed with chapathi puri on bread.

Soyabean

The protein of Soyabean yields all the essential amino acids in adequate amounts except methionine and cystine, which are deficient. Soyabean is rich in lysine and can be used to supplement a staple rice diet. Studies have established that soyabean reduces blood cholesterol.

Apart from being used as oil, soyabean is used in different forms. It is used in sausages, biscuits, breakfast foods and other cereal products. Textured vegetable proteins and other artificial meat products are made from soyabean. Soya protein is an important constituent in some infant foods and milk substitutes. The biological value of soyabean protein can be increased by autoclaving it in steam at 125⁰ C for 2 hours.

Soyabean products

• Soyabean Milk

Steps involved

1. Soyabean is cleaned and dehulled by passing through a huller.
2. The dehulled soyabean is soaked in cold water for 5 to 10 hours and the excess soak water is rejected.
3. The soaked bean is steamed for 30 minutes to destroy lipoxidase, trypsin and other inhibitors.
4. The steamed bean is ground in a grinder preheated to 100⁰ C by adding 5 parts of boiling water to one part of soaked bean.
5. The milk is filtered using a cloth. Cane sugar is added at a level of 7g. per 100g.milk. The milk is fortified by the addition of calcium salts, sodium and potassium phosphates and all essential vitamins in the same concentrations as in cow’s milk. It is also fortified with iron and vitamin D.
6. The milk is homogenised and steamed for 30 mts, cooled, filled in bottles and kept in refrigerator till distributed.

• Tofu

It is used in eastern countries like Japan and Indonesia.

1. Soyabean is soaked overnight in water, dehulled and ground to a fine paste with water (water to bean ratio of 10:1). The milk is filtered, boiled and cooled.
2. A water suspension of powdered calcium sulphate is added (2.3kg/100 kg soyabean). The proteins are precipitated as a thick curd. The whey is drained of by transferring the materials to perforated aluminimum trays. The curd is washed with water. It is used in 2 to 3 days. This can be used as a substitute for cottage cheese in cookery.

• Other Preparations from Soyabean

1. Soya sauce is made by months of fermentation.
2. Tempeh is prepared by cooking and skinning soyabeans inoculated with a little tempeh from the previous batch. The mixture is mashed and wrapped in banana leaves and allowed to ferment for 24 hours.
3. Natto is a Japanese product. The soyabeans are soaked in water cooked and inoculated with Bacillus Subtilis or previously prepared Natto. They are then wrapped in barks of pines and are allowed to ferment under vacuum conditions at 40⁰ C for 20 hours.
4. Soyabeans can be sprouted, wet ground and added to cereal flour for the preparation of dosa, dhokla after fermentation.
5. Parching of soyabean is done in Nepal.
6. Soyabean meat food science is involved in the making foods that look and taste like meat but are made from soyabean proteins. If soyabean proteins are dissolved in alkali they form a sticky liquid. This liquid may be extracted through tiny holes and then recoagulated in an acid bath in the form of fibres. The fibres then can be spun into ropes with texture approaching the fibres texture of chicken or beef muscle tissue. The fabricated tissue then can be interlaced with fast-food flavorings and food colours. Products are almost indistinguishable from chicken meat, fish, hen or beef. This soyabean meat like products can be used by vegetarians and for patients with special dietary restrictions such as controlled levels of fat.
7. A butter flavoured low fat soya spread is developed by National Dairy Research Institute, Karnal, with soya concentrate and vegetable fat which is half the cost of butter.

Processing of nuts and oilseeds:

Oil extraction: The nuts and oilseeds are cleaned, dehusked and oil is extracted by mechanical pressing, screw pressing prepress solvent extraction and direct solvent extraction.

Protein isolate: After solvent extraction, it is treated with dilute sodium hydroxide at pH8. The proteins are separated by filtration and washing with water and then used for different purposes.

• Forms of nuts used in cookery

For kitchen use the following types of prepared nuts are available

1. Ground- almonds, groundnuts.
2. Nibbed – almonds, peanuts for decorating iced dishes, pastry goods
3. Flaked- almonds for decoration cakes and pastries halwa.
4. Halved- almond, walnuts for salads, in cakes, decorating cakes.
5. Whole- almonds, hazelnuts for decorating cakes and pastries.
6. Desiccated- coconut for flavoring cakes, decorating cakes curries.
7. Essence – almond for flavouring cakes and fillings.

• Role of Nuts and Oilseeds in cookery

1. Nuts are used fresh, raw, roasted or boiled or salted forms and also fried forms.
2. Nuts are used as thickening agents. Coconut, poppy seeds and cashewnut are used as thickening agents in the preparation of gravy.
3. Chutneys can be made and used from nuts, e.g. groundnut and coconut.
4. Sweets are made from nuts, e.g. chikki, burfi, kozhukattai, cashewnut cake.
5. Oil is used as cooking media for frying and seasoning. Oil is also used as preservative in pickles.
6. Powders made out of nuts like groundnut and coconut are used as chutneys and salad dressing.
7. Nuts are also used in ice creams, cakes, pastries, payasams and chocolate.
8. Nuts are also used in beverages, e.g. badam kheer.
9. Peanut butter is used as a topping on the bread or as a side dish along with chapathis.
10. Oil seed cakes are used as weaning food or as thickening agents in vegetables like capsicum.
11. Nuts are used as gramishing material-raw, roasted, salted or boiled forms.