Antimicrobial and antioxidant activities of tea polyphenols from green tea waste using ultrasonic-assisted extraction
- Pathum Thani, Thailand : Asian Institute of Technology, 2011
- 70 leaves : ill. (some col.)
- Thesis ; no. no.FB-11-12 .
- Asian Institute of Technology. Thesis ; no. no.FB-11-12 .
A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering in food Engineering and Bioprocess Technology
Thesis (M. Eng.) - Asian Institute of Technology, 2011
Tea polyphenols were extracted from green tea waste by using three different met oos, namelyliot water extraction (HWE)~-microwave~assistedHextraction-tMAE]-and----ultrasonic- assisted extraction (UAE). The optimal condition of each method was selected based on the yield of tea polyphenols extracted and the percentage of DPPH. radical inhibitory. The optimal condition of UAE was 45 min. when temperature was controlled to be less than 60°C. The highest· tea polyphenols and %DPPH radical scavenging activity compared with MAE (85°C for 8 min.) and HWE (85°C for 60 min.) was obtained with these conditions. The other factor that was optimized was the concentration of solvent ethanol. The concentration of ethanol solvent was varied from 100%, 80%, 50%, 20% ethanol and 0% (water) and the UAE method applied. At 80%ethanol levels excellent tea polyphenols extraction was obtained. The extraction yield was 109.91 mg/g, while with 100%, 50%, 20% and water 41.85, 64.25, 60.63 and 50.32 mg/g respectively were obtained. The percentage of DPPH radical scavenging activity was related to tea polyphenols contents. The higher the tea polyphenols contents, higher of DPPH activity were obtained. Tea polyphenols was found tobe-17timesmore powerful tharicliemical-- - - antioxid~nt BHA in DPPH activity. Because of the presence of tea polyphenols in green tea waste, antimicrobial and antioxidant activity was also found. A dose of tea polyphenols of at least 8 mg/ml could inhibit Staphylococcus aureus as demonstrated by well agar diffusion assay inhibition zone. On the other hand, the same doses of tea polyphenols could not inhibit the growth of Salmonella typhimurium and Escherichia coli. The utilization of tea polyphenols as antioxidant was studied in lard. Lard deteriorated in 9 days of storage period without any antioxidant. At 200ppm (0.02% Tea polyphenols) levels could inhibit lipid oxidation and prolong shelf life over 14 days compared to the control (lard without tea polyphenols). Color measurement was done to see appearance of final products. At levels of 0.02%, 0.05%, and 0.10% tea polyphenols greenness increased in lard while the lightness decreased. Thus the tea polyphenols antioxidant present in green tea waste can be extracted easily using an ultrasound system and used for a preserving fatty food and a number of other applications.