Original research articleDevelopment of new apple beverages rich in isothiocyanates by using extracts obtained from ultrasound-treated cauliflower by-products: Evaluation of physical properties and consumer acceptance

- New apple juices (AJ) enriched with isothiocyanates (ITC) were obtained.
- Cauliflower by-products (CBP) were used as source of ITC.
- CBP extracts exhibited the highest ITC yield after sonication (20% amplitude, 5 min).
- CBP extracts were included in apple juices at different percentages (0-40%).
- CBP extract inclusion in AJ is appropriate at 10% from a sensorial point of view.

The objective of this study was to develop a new apple juice beverage enriched with isothiocyanates (ITC) - rich extracts obtained from cauliflower by-products. Ultrasound-assisted extraction (UAE) at different amplitudes (20-100%) and extraction times (0-10 min) at a frequency of 24 kHz was employed to obtain ITC-rich extracts. It was found that both amplitude and treatment time had a significant (p < 0.05) effect on the recovery of ITC from cauliflower leaves and stems, obtaining the highest yields of ITC from leaves (≈3000 μM) and stems (≈7000 μM) after UAE (80% amplitude, 3 min) and UAE (20%, 3 min), respectively. Moreover, the highest recovery of total phenolic compounds (TPC) (≈105 mg gallic acid equivalent (GAE)/L) μM) was found after UAE (100% amplitude, 3 min) of TPC from stems. ITC-rich extracts obtained from caulifower by-products at the optimum UAE conditions were added into apple juice (10-40%), thus increasing the ITC content of the juice and observing the highest values in the new beverage when the highest percentage (40%) was added. Significant differences in smell and taste were found in the apple juices containing 20% and 40% cauliflower extracts compared to control (0% UAE cauliflower waste extracts added) samples. However, the results showed that the beverage with 10% extract addition preserved well the sensorial properties with regard to control sample and no total colour differences (TCD < 3) were observed for any new sample compared to control. Therefore, the addition of extracts obtained after UAE of cauliflower wastes can be a useful tool to obtain new beverages rich in ITC although further research dealing with the bioaccessibility and bioavailability of these compounds in the new beverages should be conducted.