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Improvement of quality and antioxidant properties of dried mulberry leaves with combined far-infrared radiation and air convection in Thai tea process

Paper ID Volume ID Publish Year Pages File Format Full-Text
19229 43052 2011 9 PDF Available
Title
Improvement of quality and antioxidant properties of dried mulberry leaves with combined far-infrared radiation and air convection in Thai tea process
Abstract

Combined far-infrared radiation with hot-air convection (FIR–HA) drying was used for improving colour and antioxidant properties of mulberry leaf tea. Antioxidant properties and phenolic compounds of FIR–HA dried mulberry tea were determined and compared with the commercial product and with fresh leaves. We found that a smaller decrease in L and b values of the FIR–HA dried tea than those of commercial tea was observed. FIR–HA tea was found to have similar colour to fresh leaf while the commercial tea had darker colour. A significant decrease in total phenolic acid content (TPC) and total flavonoid content (TFC) was found in hot-air (HA) dried commercial tea compared to fresh leaves, while TPC in FIR–HA dried tea was significantly increased. Similar results were found in 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical activities. However, the results were different for ferric reducing antioxidant power (FRAP). Both teas had lower FRAP values compared to fresh leaves. Eleven phenolic compounds were identified in fresh leaf and in mulberry tea, namely p-coumaric acid, benzoic acid, (+)-catechin, chlorogenic acid, vanillic acid, syringic acid, sinapic acid, protocatechuic acid, ferulic acid, gallic acid and caffeic acid. The total content of phenolic compounds (TPCC) increased in FIR–HA dried samples compared to those of HA dried tea, except for chlorogenic and syringic acids, which were found in greater amounts in HA dried commercial tea. Our results have demonstrated that FIR–HA should be considered as a suitable drying method for mulberry tea with respect to preserving its antioxidant properties and phenolic compounds.

Keywords
Far-infrared radiation; Hot-air convection; Drying; Phenolic compounds; Antioxidant; Mulberry tea
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Improvement of quality and antioxidant properties of dried mulberry leaves with combined far-infrared radiation and air convection in Thai tea process
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Publisher
Database: Elsevier - ScienceDirect
Journal: Food and Bioproducts Processing - Volume 89, Issue 1, January 2011, Pages 22–30
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Bioengineering
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
Online Support
Any Questions? feel free to contact us