Studies on cloud stability of apricot nectar

H.A.I. Siliha

    Research output: Thesisinternal PhD, WU

    Abstract

    <p/>Cloud loss behaviour in pasteurized apricot nectar was found to be different from that of other fruit juices. The cloud particles settled slowly on standing and a gel formed. On standing for a longer period the gel contracts and a clear supernatant layer which can be considered partly as syneresis water is formed. Addition of commercial pectolytic enzyme preparations containing mainly PG activity prevented gel formation and only improved the level of stability. Wide spectrum preparations containing high activities of PE, PG, PL, and also hemicellulases, cellulases, and proteases stabilized the cloud particles completely. Cloud could also be stabilized by the addition of purified polysaccharidedegrading enzymes such as PL, PG + mould PE, and PG + exo-arabinase. Examination of the changes in the chemical composition of serum and cloud particles showed that the cloud stabilizing enzymes almost completely solubilized and degraded the arabinan-rich pectic material. Microscopic examination revealed that in cloud stable nectar the cell walls of the cloud particles were ruptured. Determination of cloud particle density and rheological measurements showed that cloud stabilizing enzymes decreased cloud particle density and that they increased the yield stress of the nectar more than did non-stabilizing enzymes. Literature on pectic substances, pectolytic enzymes, composition of cloud particles of fruit juices and nectars and on cloud stability of citrus juices, non-citrus juices and nectars have been reviewed.
    Original languageEnglish
    QualificationDoctor of Philosophy
    Awarding Institution
    Supervisors/Advisors
    • Pilnik, W., Promotor, External person
    • Voragen, A.G.J., Co-promotor, External person
    Award date23 Apr 1985
    Place of PublicationWageningen
    Publisher
    DOIs
    Publication statusPublished - 23 Apr 1985

    Keywords

    • vegetable juices
    • fruit juices
    • prunus armeniaca
    • apricots
    • food additives
    • prunus persica
    • nectarines

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