An investigation of the effects of thermal and nonthermal processing methods on Polyacetylenes from Apiaceae
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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.