Drying is important stage in tea manufacturing, because many volatile compounds are formed, transformed, or lost. The effect of different drying temperatures on the volatile composition of black tea has been investigated the first time. Temperature, grade, and temperature–grade interaction showed significant (p < .05) effect on volatile compounds. Aldehydes had the highest share among the volatile compound groups. On average, trans‐2‐hexenal was the most abundant with 14.71% while, linalool was the least abundant with 0.43%. Decanal and 1‐pentene‐3‐one showed no significant (p < .05) difference depending on neither temperature nor grade. Correlation with increasing temperature, 2‐furaldehyde was the strongest positive, whilst trans‐2‐hexenal was the strongest negative (p < .01). Linalool and subsequent volatile flavor compounds (VCF) were grouped as VFC II, volatiles before linalool were grouped as VFC I and also VFC II/VFC I was accepted as flavor index. The highest flavor index value was obtained as 0.214. Practical applications Black tea has a very important place in Turkish culture and it is preferred because of its unique taste. Although the volatile components are small in quantity, it is effective on the flavor of a good tea. In this study, teas graded according to particle size were dried at different temperatures and the change in volatile compounds was investigated. Volatile compounds were extracted by solid phase microextraction (SPME) method and detected by GC–MS. In addition, the flavor index for tea was formed by considering the desired and undesirable volatile components. It can be said that the drying temperature on the volatile components is more effective than the grading.

In this pilot-scale study supercritical carbon dioxide (SCCO) extraction technique was used for decaffeination of black tea. Pressure (250, 375, 500 bar), extraction time (60, 180, 300 min), temperature (55, 62.5, 70 °C), CO flow rate (1, 2, 3 L/min) and modifier quantity (0, 2.5, 5 mol%) were selected as extraction parameters. Three-level and five-factor response surface methodology experimental design with a Box-Behnken type was employed to generate 46 different processing conditions. 100% of caffeine from black tea was removed under two different extraction conditions; one of which was consist of 375 bar pressure, 62.5 °C temperature, 300 min extraction time, 2 L/min CO flow rate and 5 mol% modifier concentration and the other was composed of same temperature, pressure and extraction time conditions with 3 L/min CO flow rate and 2.5 mol% modifier concentration. Results showed that extraction time, pressure, CO flow rate and modifier quantity had great impact on decaffeination yield.

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The aim of the present study was to determine the effects of the addition of green tea powder (GTP) in the production of yogurt on survival of Lactobacillus acidophilus (P) and the yogurt properties. Four yogurt groups (yogurt without P and GTP, Control, C; yogurt with P and without GTP, PC; P + 1% GTP; and P + 2% GTP) were produced. The yogurt samples were stored at 4°C. The addition of GTP into milk did not affect the viability of yogurt bacteria during fermentation. The highest count of L. acidophilus was detected in P + 2% GTP. The L. acidophilus count was high up to the 7 th day (7.54 log cfu/g). Yeast and mold were not counted (<2 log cfu/g) in any yogurt sample during storage. GTP has antioxidant properties that could be attributed to the presence of phenolic and flavonoids compounds. The panelists preferred the PC and P + 1% GTP samples during the storage period. As a result of this research, we can suggest the consumption and production of probiotic yogurt with 1% GTP supplement.