Melting behaviour and quantification of low amorphous levels in sugars and sugar alcohols with DSC techniques

Minna Lappalainen

    Research output: ThesisDoctoral ThesisCollection of Articles

    Abstract

    The present thesis consists of six publications and a summary of the experimental results reviewed together with relevant literature data. The research was divided into three parts: the melting behaviour and the preparation of amorphous samples as well as the development of a method for quantification of low amorphous content. The melting behaviour of sucrose, glucose, fructose and xylose was investigated. The melting peaks were determined with DSC and the start of decomposition was studied with TG at different rates of heating. In addition, melting points were determined with a melting point apparatus and some StepScan DSC measurements were carried out. There were differences between the different samples of the same sugar and the rate of heating had a remarkable effect on the melting behaviour. The main objective of this thesis was to develop a method for quantification of low levels of amorphous content in sugars (sucrose) and sugar alcohols (maltitol). The techniques chosen were HyperDSC and StepScan DSC, some of the newest DSC techniques. The amorphous maltitol was prepared from crystalline material by melting followed by rapid cooling and the amorphous sucrose was prepared by spray drying. In DSC, detection of low concentrations of amorphous components is based on detection of changes in specific heat capacity (∆Cp) associated with the glass transition. The effects of time and temperature of the low-temperature annealing (below Tg) on the ∆Cp of amorphous samples was studied. The annealing had notable effect on the change in specific heat: as the annealing time was increased, the glass transition temperature moved to a higher temperature and the change of the specific heat increased. The ∆Cp was shown to be a good indicator for the degree of amorphicity in sugar and sugar alcohol samples that are mostly crystalline. With both HyperDSC and StepScan DSC methods experimental conditions were found under which the degree of amorphicity linearly depends on ∆Cp and low limit of detection (LOD) and limit of quantification (LOQ) values were achieved. In addition, the effect of mechanical treatment was tested for sucrose and a correlation between grinding time and amorphous content was found.
    Translated title of the contributionMelting behaviour and quantification of low amorphous levels in sugars and sugar alcohols with DSC techniques
    Original languageEnglish
    QualificationDoctor's degree
    Awarding Institution
    • Aalto University
    Supervisors/Advisors
    • Karppinen, Maarit, Supervising Professor
    • Pitkänen, Ilkka, Thesis Advisor
    Print ISBNs978-952-60-3281-8
    Electronic ISBNs978-952-60-3282-5
    Publication statusPublished - 2010
    MoE publication typeG5 Doctoral dissertation (article)

    Keywords

    • amorphous content
    • glass transition
    • HyperDSC
    • StepScan DSC
    • melting behaviour
    • sugar

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