Notes

Aug 23

Tea Processing: Rolling and Fermentation

Rolling:

The aim of rolling is to establish proper condition for an enzymatic oxidation (fermentation) of catchin and polyphenols by polyphenolase in the presence of atmospheric oxygen. Rolling twist the leaf, break the cell structure and expel the juices, catchin and enzymes. Catchin and enzymes are originally separated in fresh leaf by cell compartment. During rolling, both the polyphenols and enzymes polyphenolases are brought together and are exposed to the atmospheric condition that begins the oxidation process. Read more

Aug 22

Tea Processing: Withering

Withering brings about physical and chemical changes in the shoots and leaves to produce quality tea. It also provides flush to tea leaves for rolling in subsequent step by reducing turgor pressure. Withering is generally achieved by thinly spreading the flush on mats or in thicker layer in trough for 8 – 20 hours, depending on condition of leaf. During this period, the moisture content of leaf drop between 60 – 65 % (in soft withering) and 50 – 55 % (in hard withering). The physical part of withering can be achieved quickly by passing blast of hot air (35°C) through the leaves but this may adversely affect quality of tea because of inhibition of full biochemical changes. Moisture evaporation in leaves takes place through stomata and highly through the epidermis. The rate of loss of moisture not only depends on external condition but also on the leaf standard. Leaves and buds loose moisture more easily than the stalk and shoots. Read more

Aug 21

Manufacturing Technology of Tea, Packaging and Quality Control

Quality of tea is dependent upon the filed to factory. Quality of tea mainly depends on the raw material and method of plucking . So care should be taken both in field and during transportation and within factory  before operating the withering process. Tea leaves are damaged  at various stage from plucking of leaves. Therefore care must be done as follows,
1. There is tendency that the plucker hold the greater quantity of plucked leaves in their hands. This should be avoided.

2. Plucked shoots collected in smaller or larger container such as bamboo basket, sacks and nets should never be compressed compact. It causes burising of tea leaves, generation of excessive heat and early fermentation. Read more

Aug 20

Introduction to Tea: cultivation, composition and classification

Tea is the most popular and important beverage in the world. In China tea is a beverage known about for 3000 years. However, current distribution pattern of tea type originated in the area somewhere near ‘Irrawaddy basin’ from where it dispersed to South- East China, Indonesia and India. Tea grows at latitude  27° South (Argentina) to 42.43° North (Georgia) and from sea level up to altitude of 2500 m. The soil in which tea grow are widely alluvial (in Assam, India), podzols ( in USSR), volcanic ash ( in Japan), andosole (in Indonesia), red yellow podzols (in Taiwan), red soil ( in China) and sedimentary ( in Darjeeling, India). Read more

Aug 19

Post Harvest of Tomatoes

Tomato (Lycopersicon esculentum) was originated in South America. The improved variety of the wild fruit are grown throughout the world. Its high vitamin content and multiple uses make the tomato an important vegetable. Tomatoes are highly perishable and cannot be stored at low temperature and requires special care in handling, transportation and marketing.

 

Read more

Aug 17

Fundamental Principle of ELISA

Enzyme linked immunosorbent essay (ELISA) is a biochemical technique used mainly in immunology to detect the presence of antibody or antigen in a sample. The Elisa has been used as diagnostic tool in medicine and plant pathology as well as quality control check in various industries.

Principle: Unknown amount of antigen (protein) is affixed to the surface and then specific antibody is washed over the surface, so that it can bind to specific antigen. The antibody-antigen complex is flooded with enzyme that can convert the complex to some detectable signal. For example, in case of fluorescence ELISA, when light is shown upon the sample, antigen/antibody complexes will fluoresce so that amount of antigen in the sample can be measured. Read more

Aug 12

Mixing Index and Power Required for Mixing Newtonian and Non-Newtonian Fluid

Newtonian and Non-Newtonian Fluid

Newtonian fluid: For such fluids, viscosity is dependent only on temperature. There is linear increase in shear stress with increasing shear rate. For such fluid, viscosity remain constant no matter how fast they are forced to flow through pipe or channel. Example; water, organic solvent, honey

Read more