title: Determination of antioxidant capacity and phenolic content of chocolate by attenuated total reflectance-Fourier transformed-infrared spectroscopy.
abstract: Antioxidant capacity and phenolic content of chocolate, containing different amounts of cacao (35-100%), were determined using attenuated total reflectance (ATR)-Fourier transformed-infrared (FT-IR) spectroscopy (4000-550cm(-1)). Antioxidant capacities were first characterized using DPPH (2,2-diphenyl-1-picrylhydrazyl) and ORAC (oxygen radical absorbance capacity) assays. Phenolic contents, including total phenol and procyanidins monomers, were quantified using the Folin-Ciocalteu assay and high performance liquid chromatography coupled with photodiode array detector (HPLC-DAD), respectively. Five partial least-squares regression (PLSR) models were constructed and cross-validated using FT-IR spectra from 18 types of chocolate and corresponding reference values determined using DPPH, ORAC, Folin-Ciocalteu, and HPLC assays. The models were validated using seven unknown samples of chocolate. PLSR models showed good prediction capability for DPPH [R(2)-P (prediction)=0.88, RMSEP (root mean squares error of prediction)=12.62μmol Trolox/g DFW], ORAC (R(2)-P=0.90, RMSEP=37.92), Folin-Ciocalteu (R(2)-P=0.88, RMSEP=5.08), and (+)-catechin (R(2)-P=0.86, RMSEP=0.10), but lacked accuracy in the prediction of (-)-epicatechin (R(2)-P=0.72, RMSEP=0.57). ATR-FT-IR spectroscopy can be used for rapid prediction of antioxidant capacity, total phenolic content, and (+)-catechin in chocolate.
authors.affiliation: Food, Nutrition and Health Program, Faculty of Land and Food Systems, The University of British Columbia, Vancouver, V6T 1Z4 BC, Canada.
authors.forename: Yaxi
authors.initials: Y
authors.lastname: Hu
authors.affiliation: Food, Nutrition and Health Program, Faculty of Land and Food Systems, The University of British Columbia, Vancouver, V6T 1Z4 BC, Canada; Food Science and Technology Program, Department of Chemistry, National University of Singapore, Singapore 117543, Singapore.
authors.forename: Zhi Jie
authors.initials: ZJ
authors.lastname: Pan
authors.affiliation: Food, Nutrition and Health Program, Faculty of Land and Food Systems, The University of British Columbia, Vancouver, V6T 1Z4 BC, Canada.
authors.forename: Wen
authors.initials: W
authors.lastname: Liao
authors.affiliation: Food, Nutrition and Health Program, Faculty of Land and Food Systems, The University of British Columbia, Vancouver, V6T 1Z4 BC, Canada.
authors.forename: Jiaqi
authors.initials: J
authors.lastname: Li
authors.affiliation: CHOCOLAT NATUREL, 5971 Marine Drive, West Vancouver, V7W 2S1 BC, Canada.
authors.forename: Pierre
authors.initials: P
authors.lastname: Gruget
authors.affiliation: Food, Nutrition and Health Program, Faculty of Land and Food Systems, The University of British Columbia, Vancouver, V6T 1Z4 BC, Canada.
authors.forename: David D
authors.initials: DD
authors.lastname: Kitts
authors.affiliation: Food, Nutrition and Health Program, Faculty of Land and Food Systems, The University of British Columbia, Vancouver, V6T 1Z4 BC, Canada. Electronic address: xiaonan.lu@ubc.ca.
authors.forename: Xiaonan
authors.initials: X
authors.lastname: Lu
mesh_terms: D000975:Antioxidants / Q000494:pharmacology*; D002099:Cacao / Q000737:chemistry*; D002392:Catechin / Q000032:analysis; D016018:Least-Squares Analysis; D010636:Phenols / Q000032:analysis*; D044945:Proanthocyanidins / Q000032:analysis; D017550:Spectroscopy, Fourier Transform Infrared / Q000379:methods*
chemical_list: D000975:Antioxidants; D010636:Phenols; D044945:Proanthocyanidins; D002392:Catechin
keywords: Antioxidant; Chemometrics; Chocolate; FT-IR; PLSR; Phenolic content