Effects of Inlet Temperature and Feed Concentration on Quality of Spray Dried Instant Green Tea Powder

Abstract

Tea is a popular drink because of its unique aroma and characteristic flavor which is controlled by key chemical components which are volatile terpenes, teaine, organic acids, and polyphenols. Currently, the quality ofinstant green tea powder has been improved. It has some advantages like increase solubility, shelf life, and flavor. Instant green tea powder is produced trough drying method like spray drying.This process, unfortunately, potentially has deleterious effects on some component in green tea, like polyphenol compounds and volatile compounds. The objective of this research is to study effect of inlet air temperature and feed concentration in feed on quality of green tea powder. Main material used in this research was green tea leaf which was supplied by Boonrod Tea Factory. The drying method used in this research was spray drying. There are three level of inlet temperature used in this research, which were 180 oC, 200 oC, and 220 oC. This research also used three level of feed concentration which were 3%, 6%, and 9%. Parameters studied in this research were volatile compounds, chemical compound, and physical properties of green tea powder. The result shows that inlet temperature and feed concentration significantly affected (p<0.05) the quality of green tea powder. Generally, increased temperature (up to 200 oC inlet temperature) decreases amount and type of volatile compound, particularly ketone, total polyphenol, teaine content, solubility, and bulk density (p<0.05). On the other hand, increased feed concentration increases L value, b value, gallic acid, teaine, and catechin content (p<0.05). The best green tea powder is the one with 6% total solid in feed and 180 0C inlet temperature. It has highest amount of terpene and also contains hydrocarbon and aldehide.It also has low moisture content (4.17 ± 0.02 %), high total polyphenol content (26.42 ± 0.07 %), high teaine content (7.06 ± 0.01 %), and highest catechin content (26.16 ± 0.13 %). Physical properties analysis shows it has low water activity (0.21 ± 0.02), lowest a value (3.80 ± 0.35) low b value (18.87 ± 0.14) high hygroscopicity (9.09 ± 0.94 %) high solubility (98.79 ± 0.53 %) and low bulk density (0.51 ± 0.18 g / mL).