Infrared Spectroscopy Study on the Process of Preparing Caramel Pigment from Glucose
The preparation of caramel pigment from glucose was studied using infrared(MIR)spectroscopy and variable temperature MIR spectroscopy techniques.At a temperature of 303 K,the infrared absorption modes of the main functional groups of glucose include free O-H functional group stretching vibration mode(νO-H-free),associative O-H functional group vibration mode(νO-H-associative),CH2 functional group asymmetric stretching vibration mode(νas CH2),C-H functional group stretching vibration mode(νC-H),CH2 functional group sym-metric stretching vibration mode(νs CH2),water molecule O-H functional group bending vibration mode(δO-H-water),coupled with of CH2 functional group bending vibration and several bending vibration of functional groups such as OCH,CCH,COH etc(δCH2+δOCH+δCCH+δCOH),C-O functional groups in COH structure stretching vibration mode(νC-O-COH),C-O functional group on sugar ring structure stretching vibration mode(νC-O-sugar ring),OCH functional group bending vibration(δOCH),C-O-H functional group bending vibration(δC-O-H),sugar ring structure asymmetric stretching vibration mode(νas-sugar ring),C-C-H functional group and O-C-H functional group bending vibration(δC-C-H+δO-C-H),O-C-H functional group with α-ter-minal isomerism structure bending vibration(δO-C-H-α-terminal isomerism structure),sugar ring structure symmetric stretching vibration mode(νs-sugar ring),functional group vibration mode caused by νC-C and νC-O.During the process of glucose transforming into caramel,there is a significant change in the absorption frequency and inten-sity of the main functional groups of glucose.Among them,443～453 K is a critical temperature range,and the mechanism of glucose structure thermal denaturation is further explored.This study expands the research scope of MIR and variable temperature MIR spectroscopy technology in the preparation of caramel pigment from glucose,and has important application value.
GlucoseInfrared spectroscopyVariable temperature infrared spectroscopyStructure
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