Color of Green Tea Powder

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1.1 Bulk Density of Green Tea Powder

Bulk density is defined as the mass of particles occupied by a unit volume of bed. Bulk density of the powder variated between 0.3933-0.5014 gmL, the powder with treatment 9 solid concentration in feed and inlet air temperature 180˚C is sample that has the highest bulk density and the powder with treatment 9 solid concentration in feed and inlet air temperature 220˚C has the lowest one. Significant differences were found among the samples. Bulk density values were found in this research to be in range of bulk density values of instant tea produced by using similar technology about 0.298-0,450 gmL Nadeem et al, 2011. Table 7 shows powder bulk density decreases as inlet air temperature increases. This is caused by evaporation rates are faster when inlet temperature increase and the products dry to more porous of fragmented structure. Walton 2000 reported that increasing the drying air temperature generally produces a decrease in bulk and particle to be hollow. Besides, bulk density value also depend on moisture content of the powder, as a product of the higher moisture would tend to have a higher bulking weight caused by the presence of water Chegini and Ghobadian, 2005. Increasing the solid concentration of the feed from 3 to 6 however which be related to increased total solid content, can reduce the moisture content and it causes bulk density value decrease. The highest bulk density value was grained by concentration 9 and inlet air tempe rature 180˚C because of the sample are sticky on the chamber wall, the more stick nature of a powder is associated with a high bulk density, as the particles that tend sticky together leave less interspaces between them and consequently result in a smaller bulk volume Goula Adamopoulos, 2008.

1.2 Color of Green Tea Powder

Color is one of important sensory attributes of food and a major quality parameter in dehydrated food. During drying, color may change because of chemical or biochemical reaction. Enzymatic oxidation, Maillard reactions, caramelization, and ascorbic acid browning are some of the chemical reaction that can occur during drying and storage. The changes in color during air- dried sample was significantly higher compared to freeze-drying of strawberries. Discoloration and browning during air drying may be result of various chemical reactions including pigment destruction Farias and Ratti, 2009. The attributes as indicator in determining color are L, a, b, and hue values. L value indicates the brightness of sample with range 0 black to 100 white. The a value indicates a micture colors of red and green. The +a value indicates red color with range 0-100, while –a value indicates green color with range 0--80. The b value indicates a combination of yellow and blue. +b range for 0-70 indicates yellowness while –b range for 0-- 70 for blueness Francis, 1996. The results of green tea powder color were shown at Table 7. Color of of the powders are variated, for L value between 68.07-74.41, powder with treatment 9 solid concentration in feed and inlet air temperature 200˚C has the highest L value and powder with treatment 6 solid concentration and inlet air temperature 180˚C has the lowest one. For a value variated between 3.50-5.79, powder with treatment 9 solid concentration and inlet air temperature 180˚C has the highest a value and powder with treatment 3 solid concentration and inlet air temperature 180˚C has lowest a value. For b value variated between 30.08-37.37, with treatment 9 solid concentration and inlet air temperature 180˚C has highest b value, while powder with treatment 25 3 solid concentration in feed and inlet air temperature 180˚C has the lowest one. Based on ANOVA, significant differences were found among the samples. According to Nadeem et al 2011 when the inlet air temperature increased, the L values decreased while the b values increased. This implied that the color of the powders became little darker at higher drying temperatures. But, the result in this study is not same with literature, the L value of powder increased significantly as concentration of feed and inlet temperature increase, except on concentration 3, the higher temperature will decrease the L value. The a and b value of powder increased significantly as concentration of feed increase and as inlet temperature decrease. This implied that the different concentrations of feed and inlet temperatures on product resulted the varieted and different color significantly p0.05. The higher of inlet temperature and feed concentration affect the time of drying. Contact of powder with inlet and outlet air temperature made browning reaction occurs faster. Besides, The Maillard reaction may occur in this research because green tea contains carbohydrate about 7 dry weight of tea leaves Chako et al, 2010. However, freeze concentration also give the effect of reducing color in the feed preparation and it resulted different color of origin.

1.3. Solubility of Green Tea Powder