Methodology for characterization of the phenolic profile of
apple, pear and grape juice was developed. It utilized High
Performance Liquid Chromatography (HPLC) for separation of
individual phenolic compounds and Diode Array Detection for
recording the Ultra-violet (UV) spectrum of chromatographic
peaks. The high resolution achieved and the ability of recording
more than one wavelength simultaneously, allowed for
quantitation of phenolic acids (cinnamics and benzoics), flavonol
and dihydrochalcone glycosides, arbutin and hydroxymethylfurfural
(HMF) with minimum sample preparation. Quantitation of
procyanidins, however, required preliminary isolation and
analysis in a separate run. Procyanidin isolation based on
Sephadex IH-20 resulted in high recoveries and degree of
reproducibility.
The methodology was applied to study the influence of
variety, post-harvest storage, SO₂, initial high temperature short time (HTST) heat treatment, enzymatic clarification,
fining, bottling, concentration and storage on the phenolic
composition of apple, pear and grape juice. Processing with SO₂
inhibited extensive phenolic oxidation during pulping and
resulted in increased phenolic yields. Initial HIST treatment
protected phenolics extracted in the juioe from degradation
during processing. Cinnamic hydrolysis occurred during enzymatic
clarification. The hydrolytic activity was removed with fining
or bottling. There was no appcirent reduction of phenolics with
fining. Procyanidins were sensitive to the heat applied during
bottling and concentration. Storage of juice concentrates for
nine months at 25°C resulted in formation of HMF, considerable
degradation of cinnamics and dihydrochaloones and total loss of
procyanidins and flavonols.
The effect of diffusion extraction at different teirperatures
on the phenolic composition of apple juice from different
varieties was also studied. Up to a three-fold increase in
cinnamics and a five-fold increase in dihydrochalcone glycosides
were measured in diffusion extracted juice relative to juice
extracted with conventional pressing. The increase in
procyanidins and flavonols was even higher. / Graduation date: 1989
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/27130 |
| Date | 29 July 1988 |
| Creators | Spanos, George A. |
| Contributors | Wrolstad, Ronald E. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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