15 polyphenols in samples was derived from a standard curve of gallic acid ranging from 10 to
100 µgmL.
C = gallic acid concentration µgmL obtained from calibration curve
V = Volume of tea extract solution mL
DF = Dillution factor
DM = dry matter
W = Weight of tea sample g
3.7. Antioxidant Activity using DPPH
Antioxidant activity DPPH free radical scavenging activity was determined with DPPH scavenging activity and slightly modification according method by Talcott et al 2003.
Pipette extracted sample 50 µL through test tubes, then add with 1950 µL of 1,1-diphenil-2- picrylhydrazil DPPH methanolic solution. The mixture is thoroughly vortex-mixed and kept
in dark for 30 min. The absorbance is measured later, at 517 nm. A calibration curve was prepared using a standard solution of Trolox 0, 200, 400, 600, 800, 1000µM and the results
were expressed on both fresh weight basis fw and dry weight basis dw as mmol Trolox Equivalent100g.
3.8. Caffeine and Catechins Analysis
Preparation of sample Add to the instant tea 0.500±0.001 g in the flask approximately 25 mL of hot water
max 50ºC. The sample was mixed in room temperature. After that, add 5.0 mL acetonitrile and it was mixed again.
Preparation of Standards Use the purity from the certificate to prepare the stock standard solution. The
individual standard solution of GC, EGC, C, EC, EGCG, CF, GCG, ECG, CG were prepared by dissolving them in a small volume of metanol, to generate a stock concentration of 999.0,
313.6, 412.0, 880.0, 911.8, 1036, 1000, 469, 832.0 and 514.8 µgmL respectively. The mixed stock standard solution was prepared by mixing an equal volume of each stock standard.
Working standard solutions were prepared by dilution of the mixed stock solution and then filtered through a 0.45µm PTFE filter before HPLC analysis.
HPLC analysis HPLC analysis of standards and samples was conducted on Water 966 high
performance liquid chromatography comprising vacuum degasser, quaternary pump, auto- sampler, thermostatted column compartment, and photo diode array detector. The column
used was a Platinum EPS C18 reversed phase, 3µm L 53 x i.d 7mm. Mobile phase eventually adopted for this study was wateracetonitrille 87:13 containing 0.05 vv
trifluoroacetic acid TFA with the flow rate of 2 mLmin. Absorption wavelength was
16 selected at 210 nm. The column was operated at 30ºC. The sample injection was 20 µL.
Peaks were identified by comparing their retention times and UV spectra in the 190-400 nm range with standards. The standard was injected before sample for made calibration curves.
The caffeine and catechins content were calculated using their respective calibration curves.
3.9. Product Recovery Sanphakdee, 2007
Product recovery is mainly determined by powder collection efficiency. Material loss in a spray drying system is due mostly to the attachment of sprayed droplets and dry
powder to the wall of the apparatus and the cyclone’s poor efficiency in collecting fine particle. Product recovery was calculated from the total solid content that determined form
moisture content that heat in the oven at 103±2ºC for 6 hours.
Where a g is weight of powder product dry basis, b mL is volume of feed, and c total solid content of tea extract concentrated.
3.10. Energy Consumption Kamaruddin et al, 1989
