Combining ethanol pre-treatment and ultrasound-assisted drying to enhance apple chips by fortification with black carrot anthocyanin

BACKGROUND An interesting approach to improve dried foods nutritional properties, functionality, and sensorial attributes, is by taking advantage of pre-treatments for incorporating components into the food matrix. Based on this, this work studied the incorporation of black carrot anthocyanins in apple tissue by using ethanol (concentrations 0-300 mL L-1) as a pre-treatment to ultrasound-assisted convective drying. Samples were pre-treated in acidified ethanol solutions, with and without anthocyanins, and then dried (50 degrees C, 1 m s(-1)) by convective and ultrasound-assisted convective (21.77 kHz, 20.5 kW m(-3)) drying. Both the drying process improvement and the obtained product properties were studied. RESULTS The anthocyanins did not influence the drying kinetics. In contrast, time reduction was > 50% by using both ethanol pre-treatments and ultrasound. Ethanol pre-treatments decreased the external resistance to mass transfer, while ultrasound decreased both internal and external resistances. The impregnation increased the anthocyanins (above 947%), which were retained after drying. Colour modifications after pre-treatments and after drying (L*,b*,h degrees decrease, anda* increase), and antioxidant capacity retention were observed in samples with anthocyanin addition. CONCLUSION The results point that ethanol pre-treatments and ultrasound application can accelerate drying, and through the natural colouring incorporation during pre-treatments, the nutritional properties of dried samples were better retained. (c) 2020 Society of Chemical Industry

Automated summary

The study focused on incorporating black carrot anthocyanins in apple tissue using ethanol pre-treatments and ultrasound-assisted convective drying. The results showed that ethanol pre-treatments and ultrasound application significantly accelerated the drying process and helped retain the nutritional properties of the dried samples by naturally incorporating colorants during pre-treatments.