title: Effects of steam-microwave blanching and different drying processes on drying characteristics and quality attributes of Thunbergia laurifolia Linn. leaves.
abstract: BACKGROUND
  Dried Thunbergia laurifolia leaves are usually prepared using tray drying, resulting in products that have lost substantial amounts of bioactive compounds and antioxidant activity. The maturity of the raw material, blanching techniques and drying methods were investigated in order to select the best condition to produce high qualities of dried T. laurifolia leaves.
  
  
  RESULTS
  The 1st stage of maturity was selected and steam-microwave blanching (SMB) for 4 min was adequate for blanching leading to the maximum recovery of bioactive compounds. The modified Halsey model was the best desorption isotherm model. A new drying model proposed in this study was the best to fit the drying curves as compared to five common drying models. Moisture diffusivities were increased with the increase of drying temperature when combining SMB and heat pump-dehumidified drying. Microwave heat pump-dehumidified drying (MHPD) provided the shortest drying time, high specific moisture extraction rate (SMER) and could reduce drying time by 67.5% and increase caffeic acid and quercetin by 51.24% and 60.89%, respectively.
  
  
  CONCLUSIONS
  MHPD was found to be the best drying method and provided the highest antioxidant activity and bioactive compounds content, high SMER and short drying time. © 2016 Society of Chemical Industry.
authors.affiliation: Department of Food Technology, Khon Kaen University, Muang, Khon Kaen 40002, Thailand.
authors.forename: Traiphop
authors.initials: T
authors.lastname: Phahom
authors.affiliation: Department of Food Technology, Khon Kaen University, Muang, Khon Kaen 40002, Thailand.
authors.forename: Singhanat
authors.initials: S
authors.lastname: Phoungchandang
authors.affiliation: Department of Food Science and Technology, University of Georgia, Athens, Georgia 30602, USA.
authors.forename: William L
authors.initials: WL
authors.lastname: Kerr
mesh_terms: D027901:Acanthaceae / Q000737:chemistry*; D000975:Antioxidants / Q000032:analysis; D003890:Desiccation; D005419:Flavonoids / Q000032:analysis; D005519:Food Preservation / Q000379:methods*; D008872:Microwaves; D018515:Plant Leaves / Q000737:chemistry*; D013227:Steam / Q000032:analysis
chemical_list: D000975:Antioxidants; D005419:Flavonoids; D013227:Steam
keywords: Thunbergia laurifolia leaves; antioxidant activity; bioactive compounds; drying models; maturity; steam-microwave blanching