Effects of ultrasound treatment and storage time on the extractability and biosynthesis of nutraceuticals in carrot (Daucus carota)

• Carrots were treated with ultrasound (US).
• US treatment conditions were: frequency 24 kHz, amplitude 100 μm, for 300 s.
• US increased the extractability of carotenoids.
• US induced the biosynthesis of 3-O-caffeoylquinic acid and isocoumarin.
• US increased respiration rate, ethylene production and PAL gene expression.

In the present study, the effect of postharvest ultrasound (US) treatment on the extractability and biosynthesis of carotenoid and phenolic compounds in carrot was investigated. Carrot was submerged in water and treated with US (frequency 24 kHz, amplitude 100 μm) for 300 s at 20 °C. Variables such as total phenolic and carotenoid content, respiration rate, ethylene production, phenylalanine ammonia-lyase (PAL) gene expression and activity were evaluated after US treatment and during storage (0–3 d at 20 °C). Immediately after treatment, the extractability of carotenoids increased, while total phenolic content decreased. Likewise, the respiration rate was increased as well as PAL gene expression. During storage, US treated carrots did not show accumulation of carotenoids, but showed higher levels of 3-O-caffeoylquinic acid, isocoumarin, and ethylene production as compared to the control. Results allowed the elucidation of a hypothetical model explaining the physiological mechanisms governing the ultrasound-induced accumulation of phenolics in carrot.