Notes

Sep 03

Cereal Grains: Physical and Thermal Properties

Understanding the physical properties of grain are important for equipment design for handling, storage aeration and processing. Even the simple technique of drying and storage requires knowledge on heat and moisture transport phenomenon. Important properties of cereal grains are grain size, shape, volume, density, porosity, angle of repose, heat capacity, thermal diffusivity and many others. However, these properties of cereal grains largely depends on moisture content, temperature and density of grain itself. Read more

Sep 01

Introduction to Important Cereal Crops

Cereals are the members of monocotyledonous family Gramineae. They are fruits of cultivated grasses. The principal cereal crops are maize, sorghum and the millets. Wheat, rice and corn together contribute three-fourths of the world’s grain production. In general cereal grains provide the bulk energy consumed on earth. The cereal crop that are grown for their edible fruit are generally called grain and are botanically referred as caryopsis. Two major components of cereal seeds are i) endosperm and ii) embryo or germ. The endosperm that forms bulk of seed is the stored food of grain and is source of energy for animals. Read more

Aug 30

Instant Coffee Manufacturing Process

Instant coffee is also called soluble coffee or coffee powder. It is a beverage derived from brewed coffee beans. The major goal is to produce an instant coffee that taste as better as freshly brewed coffee. Modern technology uses methods that does not require addition of carbohydrate component during production. The process includes following steps. Read more

Aug 28

Roasting of Coffee Beans and Adulteration

After natural / wet processing of coffee cherries, de-hulled coffee beans are roasted to give typical flavor and aroma. Roasting is a time temperature dependent process where chemical and physical changes takes place in the green coffee. During roasting, there is also loss of dry matter, primarily as CO2 gas and other volatile products of the pyrolysis. About half of total CO2 generated are retained in the roasted coffee together with a major proportion of the important volatile flavor substances. Roasting is normally carried out under atmospheric pressure with hot air and combustion gases as the primary heating agent. Though heat may also be provided by contact with hot metal surface.

Fig: Different stages of coffee roasting (https://www.lakotacoffee.com/wp-content/uploads/2017/02/Grades-of-coffee-roasting-1024×704.jpeg )

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Aug 27

Important Considerations for Processing of Coffee by Wash/ Wet Process

Processing of coffee by wash/wash process includes various processing steps like harvesting, cleaning, pulping, fermentation, drying and storage. Individual processing steps should be carefully performed to avoid any chances of contamination and to prevent damage during processing.

Harvesting and cleaning:
1. For preparation of coffee by wet process, only ripe coffee beans should be harvested.
2. If over ripe or green cherries are harvested, should be stored out on a clean surface.
3. Clean bags should be used for collection of harvested cherries
4. Where fertilizer or cattle feed bags are used, they should be washed thoroughly in running water many times before being used. Read more

Aug 25

Introduction of Coffee and its Processing

FIg: Coffee cherry (https://i.pinimg .com/originals/4b/62/56/4b62568 fbd68bd7de749154c57afc141.jpg )

Coffee is a climacteric sensitive crop.  Factors like elevation, rainfall, and temperature can influence the crop performance considerably. It requires hot humid climate with intervals of dry weather for proper ripening of fruits. The two commercially important species of coffee are Coffea arabica and Coffea robusta. The coffee plant is a small tree which extends to the height of 5 ft. in case of Coffea arabica and 5.5 to 6 ft. in case of Coffea robusta. Coffee can be grown up to 25 ft. in wild state but is pruned for two reasons; to facilitate harvesting and to maintain optimal tree shape. Read more

Aug 24

Tea Processing: Drying and Grading

Drying:

After completion of fermentation, it has to be stopped as soon as possible to avoid the over fermentation. Drying of the mass with hot air stop fermentation process. Drying reduce the moisture content of fermented leaves from 50 – 70 % moisture content to 3 %. In dry black tea, it also allows development of tea aroma. Drying is physically achieved by blowing hot air through fermented leaves as they are conveyed in chains. The temperature of hot air in the inlet is 100 – 120°C conveyed while that at the outlet is 56°C. Drying process takes about 15 to 30 minutes. The principle biochemical process involves conversion of chlorophyll to pheophytin and pheophorbide responsible for the black appearance in the manufactured tea. The high temperature during drying also cause loss of low volatile compounds, continuation of few reaction of fermentation stage and the formation of new compounds like β-ion and theaspirone which play an important role in the formation of aroma. Read more