Coffee is the most popular beverage in the world. Brazil is the source of 50 percent world’s coffee production. In India, coffee is mainly cultivated in south, mainly in the state of Karnataka, Kerala and Tamil Nadu. Coffee powder is made from ground, roasted beans (seeds) of Coffee Arabica and Coffee Robusta species. It is used for preparation of coffee.
Steps involved in making coffee beverage
Green Coffee Beans
Coffee Roasting Machine
Roasted Coffee Beans
Coffee Grinding Machine
Cup of Brewed Coffee
a) Steps in Processing Coffee
It is the important step in the processing of coffee. Roasting is the most important process for the development of characteristic flavour and aroma of the coffee bean. Apart from these benefits, roasting also helps to reduce the moisture content and the amount of a tannin called chlorogenic acid (a non-volatile acid) and the fat content develops, a group of essential oils known as caffeol. The colour of the bean changes from green to brown due to caramelization of the sugar content of the bean. Roasting time depends upon the required variety of coffee.
The bulk of roasted beans is ground to powder and sold as ground coffee. Roasted beans are ground to three sizes, namely, fine, medium, and coarse powder. Coarse ground powder retains aroma and flavour better and longer than fine ground powder. Coarse ground powder is more suitable for preparing coffee decoction by percolation. On the other hand, fine ground coffee gives a decoction with good aroma. Combination of these two grades in the ratio of 90% of fine powder and10% of coarse powder gives an excellent quality coffee.
Two types of coffee powder are marketed, in the name of pure coffee, prepared from coffee beans only and other containing chicory. Strength, flavour, aroma and acidity are the major criteria considered to judge the quality of coffee.
The aroma and flavour in the ground coffee is highly unstable and it should be properly packed under vacuum or can also be fresh roasted and ground before brewing and is practiced even today by several taste experts in households.
The green coffee bean once is ground and exposed to air the bean has limited storage life. This staling of coffee is accompanied by loss of carbon-di-oxide and oxidation of guaicol and changes in unsaturated volatile compounds. The freshness of the ground coffee is maintained commercially by sealing in a container under vacuum. Storing in a cool place will delay staling. Once a can of coffee is opened, contact with atmosphere with moisture should be kept to a minimum.
b) Adulterants in Coffee
☆If chicory is added and not mentioned on the label, it is considered as adulterant.
☆Cherry husk is sometimes used as an adulterant.
☆Burnt sugar, tamarind seed, used coffee powder and saw dust are also used as adulterants.
c) Methods of preparation of coffee
Two level measuring table spoons are added to 3 /4th cup of water in making coffee. To prepare weaker brew hot water can be added after the full strength coffee preparation.
By this method, water filters through the coffee, into a lower compartment of a coffee maker. The drip part consists of an upper compartment which is perforated and a lower compartment which is a receiver for a filtered beverage.
ii) Vaccum Coffee Maker
The upper compartment holding coffee has an open tube and is connected to lower compartment. Coffee is usually prevented from passing into the lower compartment using a piece of cloth covered dish placed over the tube opening. Water is placed in the lower compartment and the pot is heated until water raises into the upper compartment. When the pot is removed from the fire, a vacuum is created in a lower bowl drawing a clear infusion down into the bottom bowl.
Here the heated water is moved upward through a tube onto the coffee compartment. The ground coffee powder kept in a perforated coffee basket. There is a dome at the lower end of the tube which extends from the top of the percolator, and then the tube supports the basket. Steam generates the pressure on the surface of the water under the dome, forces water up the tube onto the coffee. The percolation time depends upon the speed of circulation which is varied from 8-15 minutes.
Water is heated just before it reaches the boiling point, medium ground coffee powder is added. Steeping time is nearly 6-8 minutes. Then the coffee is passed through the strainer. During steeping the coffee part should be lightly covered to prevent losses of flavouring substances.
d) Different Types of Coffee
The different types of coffee are expresso, soluble, decaffeinated and instant coffee.