Production of soluble green tea powder with enriched cathechins content and determination of in vitro release characteristics

In this study, optimization of soluble green tea production which is enhanced functional properties, the determination of drying conditions and the stability of the obtained product in storage and in vitro gastrointestinal conditions were carried out. In the first step of the study, green tea extraction was carried out and the enrichment activities were studied of obtained extract. In the enrichment study, green tea extracts were subjected to ultrafiltration using filters with different cut-off value (50, 30, 10 kDa). Optimum spray drying conditions of the enriched extract that provide the best product using different carrier materials (maltodextrin and whey protein), different inlet (140, 160, 180 ºC) and outlet temperatures (80, 85, 90 ºC) were investigated with Box-Behnken experimental design. The production was carried out by spraying and freeze drying methods under optimum conditions and some physical and chemical properties of the obtained products were determined. Finally, changes in the stability of the soluble green tea produced by two different methods were observed in in vitro gastrointestinal system and during storage at 2 different temperatures (4, 25 ºC). Extracted green tea samples are enriched of catechins by a filter having a cut off value of 10 kDa, in the ultrafiltration process. According to the Box-Behnken experimental design results, the conditions providing the best soluble green tea production in terms of physicochemical properties were determined to be 25.22% maltodextrin addition on dry matter basis, 140 ºC inlet and 90 ºC outlet temperatures. It has been found that optimum conditions exhibit similar qualities to those produced by freeze drying for some properties. Soluble green tea produced by spray and freeze drying methods was examined in the in vitro gastrointestinal system. It was determined that the total amount of catechin during in vitro digestion for both production methods was close to each other. Following simulated gastric and small intestinal digestion, soluble green tea produced by spray and freeze drying, lost approximately 33% and 75% total catechin, respectively. It has been determined that there is generally no effect on turbidity, humidity, water activity, the amount of caffeine and catechins of the temperature during storage but the storage time is significantly effective. It was also observed that during the storage period the amount of major catechins and caffeine decreased gradually while the minor components increased. When the results obtained within the scope of the thesis are evaluated in general, it is possible to produce rich in functional components soluble green tea. In addition, it has been determined that the production of soluble green tea by spray drying in the result of the study may be an alternative to the characteristics investigated by freeze drying.