The influence of different time durations of thermal processing on berries quality

Bioactive compounds (polyphenols, flavonoids, flavanols, tannins, anthocyanins and ascorbic acid) and the level of antioxidant activity by ABTS, DPPH, FRAP and CUPRAC of water, acetone and hexane extracts of Chilean 'Murtilla' (Ugni molinae Turcz) and 'Myrteola' berries (Myrtaceae, Myrteola nummularia (Poiret) Berg.), Chilean and Polish blueberries (Vaccinium corymbosum), Chilean raspberries (Rubus idaeus), and Polish black chokeberry (Aronia melanocarpa) were determined and compared. It was found that the contents of the bioactive compounds and the levels of antioxidant activities in used extracts differ significantly (P < 0.05). The correlation between the total polyphenols, flavanols and the antioxidant activities was significantly the highest in water, average in acetone and the lowest in hexane extracts. Fourier transform infrared (FTIR) spectroscopy was applied as an additional tool for the characterization of the water polyphenol extracts. Aqueous extracts of investigated berries were subjected to different times of thermal processing. Bioactive compounds and the levels of antioxidant activities by 2,2-Azino-bis (3-ethyl-benzothiazoline-6-sulfonic acid) diammonium salt (ABTS+); 1,1-Diphenyl-2-picrylhydrazyl method (DPPH); Ferric-reducing/antioxidant power (FRAP) and Cupric reducing antioxidant capacity (CUPRAC) after 10, 20, 40 and 60 min of thermal processing were determined and compared with non processed samples. It was found that the antioxidant activity only of berries subjected to thermal processing for 10 and 20 min did not differ from the non thermally processed studied berries, showing high correlation between the total polyphenols, flavanols and the antioxidant activities. In conclusion, thermal treatment of studied berries influences their quality: only berries after 10 and 20 min of thermal processing preserved their bioactivity.

► Bioactive compounds of berries were extracted with water, acetone and hexane. ► Aqueous extracts contained the highest levels of antioxidants. ► Berries aqueous extracts were subjected to different times of thermal processing. ► Only berries after 10 and 20 min of thermal processing preserved their bioactivity. ► FTIR spectroscopy was used as additional tool for characterization of polyphenols.