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such as coffee and tea, as well as various soft drinks. Teaine extract from tea is added to some pain-relief medicines. teaine compound is well known for its stimulant effect and is
present at 2-4 of dried tea leaf weight, depending on the types and quality of teas Yoshida et al
1999. Studies using animal models show that green tea catechins provide some protection against degenerative diseases. Green tea catechins could also act as
antitumorigenic agents Roomi et al, 2007 and as immune modulators in immunodysfunction caused by transplanted tumors or by carcinogen treatment. Green tea
consumption has also been linked to the prevention of many types of cancer, including lung colon, esophagus, mouth, stomach, small intestine, kidney, pancreas, and mammary glands
Koo and Cho 2004. This beneficial effect has been attributed to the presence of high amounts of polyphenols, which are potent antioxidants. In particular, green tea may lower
blood pressure and thus reduce the risk of stroke and coronary heart disease. Some animal’s studies suggested that green tea might protect against the development of coronary heart
disease by reducing blood glucose levels and body weight Tsuneki et al 2004.
B. SPRAY DRYING
Spray drying is one of the drying methods that commonly used to dry food product. There are several reasons why food products are dried. First is lower transport cost, the total
volume of the product decrease considerably if the product has been dried. Second is lower packing cost, also the packing cost become lower by the smaller of volume, but these costs
become also lower because one can be enough with simple packing resources. For liquid products one must apply fluid-dense packing. The last reason is longer durability. Longer
durability has to do with bacterium increase in liquid products. One of the most important factors for bacterium to be able to increase is water. If water has been removed, the bacteria
will no longer grow Weernink 2000.
Spray dryer have been used massively in food industry. Spray dryer can handle product with higher viscosity well. The viscosity stipulates for an important degree the
atomizing system that can be used in a spray dryer. The two most used atomizing systems are wheel atomizing and high pressure systems with nozzle atomizing Weernink 2000.
The spray drying process takes place in a large chamber. The product is atomized in very small drops in hot air. These drops will dry very rapidly, and dry particles fall to the
lower part of dryer. Drying droplets is a physical process, it simply is water evaporation. The speed of evaporation depends on the ability of the air to take up the vapour. The important
items for evaporation are the water absorption capacity of air, the contact area between air and solution, and the temperature of the solution. The water absorption capacity of air can
increase by raising the temperature of air. The contact area between air and solution can be increased by making the droplets as small as possible during atomizing Weernink 2000.
During drying, it is possible to agglomerate the product. This means that particles which have been atomized as small as possible are sticked together again. Because of this
during drying larger particles are formed which have better dissolving properties. The agglomeration takes place in the top of the dryer. By placing the nozzles in a such way that
the particles will hit each other a moment when they are not entirely dry, these particles will stick to each other and agglomerates will be formed. If also the fine particles from the
cyclones or the bag filters are send back to this area, these particles will also stick to the almost dry particles in the top and result a better soluble product will be produced. Small
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particles dissolve difficulty because they float on a water and as a result are difficult to moisten Weernink 2000.
Spray drying is widely used in food industry. There are some studies that have been done to analyze effect of spray drying to quality of the food product. Some changes that are
generally happened during process are decrease in water activity, glass transition, crystallization, melting of fat, and migration or retention of components, whether volatile or
not Bonazzi Dumoulin 2011. A study on spray drying of Roselle extract indicated
that some volatile compounds were lost and some others were generated due to a degradation
process Gonzales-Palomares 2009. Study on tomato powder by Santos de Sousa et al. 2008 showed that
all the samples became significantly darker and less red with an increase of the variables under study. A low atomization speed 25000 rpm and lower inlet air
temperature 220
o
C produced the powders with a higher color index ab and less darkening. Thankitsunthorn et al. 2009 reported that as inlet drying temperature increased,
the moisture content and subsequentlythe water activity of indian goosebery powder decreased significantly at 0.05 level. The results also show that an increase in the inlet drying
temperature results in a lower vitamin C content. Study on Agave angustifolia Haw by Fabela-Moron et al. 2011 indicated that increasing inlet air temperature increases the
particle size, average time of rehydration, and decreases the bulk density and moisture content of the powder. The powder characteristics of agave can be described through the
effect of the dryer operating conditions on physical-chemical properties of powder.
C. FOOD POWDER
