Method of Heat Penetration during Thermal Processing

Heat penetration

During processing of food, heat penetration is an important factor and it should be known to ensure that every particle of food within the container receive the required heat treatment. If the cans are heated from outside, larger the can, larger time it will take to heat the center portion of can to any desired temperature. However, there are several factor besides size and shape of can that affect the heat penetration into food within it.

Liquid food such as canned tomato juice can be readily set into convection heating motion after receiving heat by conduction from the wall of the can. On other hand, solid food such as canned beef hash is too viscous to circulate and so it will be completely heated by conduction through the can wall and through itself. A product containing a combination of free liquid and solid such as  can of peas within a sugar syrup will be intermediate and will rise in temperature from the combination of conduction and convection. Convection heating is more rapid than conduction heating.

Methods of heat Penetration

During thermal processing, contents of the can is heated by following methods; Read more


The world is undergoing a significant increase in its industrialized food processing, and this has entailed a close examination of all aspects of modern hygienic food processing. This involves more investment in machinery and while factory owners may only consider saving of time, space and money and the wish to increase output to serve a wider market, there is another consideration, which is the increased risk of food-borne illnesses and the sometimes unbearably high costs of rectifying this post facto.

There are many systems used to eliminate or reduce the risks of contamination which begin with the raw materials from the farm and field and continue throughout the process until packing. Some risks can be eliminated once and for all, such as small stones and insects washed out of a vegetable harvest but there are far more dangerous forms of contamination further down the line before packing, including inside the factory. Read more

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

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 (×704.jpeg )

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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

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

Tea Processing: Drying and Grading


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