title: Hydrogen bonding in maltooligomer-glycerol-water matrices: Relation to physical state and molecular free volume.
abstract: We use Fourier Transform Infra Red (FTIR) Spectroscopy to explore the effects of water and glycerol on the hydrogen bonding of low water content maltooligomer matrices by monitoring the shifts in the position of the peak associated with the fundamental stretching vibration of the hydroxyl groups, νOH. Changes in hydrogen bonding are investigated in relation to the physical state and the molecular packing of the maltooligomer matrices, which are measured by Positron Annihilation Lifetime Spectroscopy (PALS). In the concentration range studied (0-20 wt.%), glycerol acts as an anti-plasticizer whereby it reduces the average molecular hole size, vh, while modulating the hydrogen bond network of the carbohydrate matrices. Depending on the level of hydration, water can cause anti-plasticization or plasticization of the maltooligomer-glycerol matrices. For water contents below ∼ 5 wt.%, water acts as an anti-plasticizer, whereby it reduces vh and we measure a reduction νOH. At higher water contents, water acts as a plasticizer, causing a systematic increase in vh, while νOH continues to decrease as a function of increasing water content.
authors: H. H. Wills Physics Laboratory, Tyndall Avenue, Bristol BS8 1TL, United Kingdom. Electronic address: m.roussenova@bristol.ac.uk.
authors: Mina
authors: M
authors: Roussenova
authors: Nestlé Research Center, Vers-Chez-les-Blanc, CH-1000 Lausanne, Switzerland. Electronic address: Jean-Christophe.Andrieux@rdls.nestle.com.
authors: Jean-Christophe
authors: JC
authors: Andrieux
authors: H. H. Wills Physics Laboratory, Tyndall Avenue, Bristol BS8 1TL, United Kingdom. Electronic address: m.a.alam@bristol.ac.uk.
authors: M Ashraf
authors: MA
authors: Alam
authors: H. H. Wills Physics Laboratory, Tyndall Avenue, Bristol BS8 1TL, United Kingdom; Food Concept & Physical Design "The Mill", Mühleweg 10, CH-4112 Flüh, Switzerland. Electronic address: job.ubbink@themill.ch.
authors: Job
authors: J
authors: Ubbink
keywords: Anti-plasticization; Hydrogen bonding; Maltooligomers; Molecular packing; Plasticization; Positron annihilation