An investigation of the effects of thermal and nonthermal processing methods on Polyacetylenes from Apiaceae
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2012Author
Rawson, Ashish
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Abstract
Polyacetylenes are a group of phytochemicals that have attracted significant interest
in recent years due to their range of potential health-promoting bioactivities
however, little is known about the effects of food processing on them. In addition,
their low abundance and relative instability requires rapid and very sensitive
methods for analysis and characterization. Therefore the present work demonstrated
the potential of ESI-MS, in multiple reaction monitoring (MRM)-quantitative
methods for characterization of polyacetylenes and polyacetylene degradation.
Polyacetylenes in water immersion cooked carrot disks were significantly
reduced at 50-60°C, but levels were higher at 70-100oC (p < 0.05) than in raw
unprocessed samples. Blanching (95 +/- 3oC) prior to sous-vide (SV) processing
(90oC for 10 min) of parsnip disks showed that blanching had the greatest influence
on the retention of polyacetylenes. Subsequent chill storage (anaerobic conditions)
resulted in a significant decrease in FaOH levels (p < 0.05) although no change in
FaDOH levels was observed (p > 0.05). FaDOH was particularly susceptible to
degradation during aerobic storage following blanching. Oxidized forms of FaOH,
e.g. falcarindione, dehydrofalcarinol, dehydrofalcarinone were detected in thermally
processed samples. Boiling and roasting decreased levels of all polyacetylenes in
fennel bulb. And the presence of hydroxymethylfurfural was confirmed in roasted
samples of fennel. Kinetic analysis of high pressure-temperature (HPT) processing
of carrot disks revealed that FaDOAc was the most barosensitive while FaDOH was
the most thermosensitive. Nonetheless, HPT yielded higher retention of
polyacetylenes than SV-processing. Ultrasound pretreatment followed by hot air
drying (UPHD) was shown to be a promising technique for retention of
polyacetylenes and carotenoids in carrot disks in comparison to blanching followed
by hot air drying.
In fresh cut products unit operations (mainly peeling) decreased
polyacetylene retention, due to the high polyacetylene content of peels. Washing,
after minimal processing, reduced polyacetylene content but retention was relatively
high during storage and higher in parsnips than in carrots. Freezing and frozen
storage of carrot disks revealed that blast frozen carrot disks retain higher amounts of
polyacetylenes compared to their slow frozen counterparts. The texture and colour
were also found to decrease during frozen storage.