The Selection of Optimal Drying and Grinding Techniques to Maximize Polyphenol Yield from Blueberry (Vaccinium corymbosum L.) Powder Extracts

This study investigated the influence of drying techniques such as convection hot-air drying, vacuum drying, and freeze drying with slow and flash pre-freezing on the total phenolic content and the profile of dominant phenolic compounds in cultivated blueberry (Vaccinium corymbosum L.). Although fresh blueberries exhibited higher total phenolic content (1350.85 mg GAE/100 g), total flavonol glycosides (66.20 mg/100 g), and total anthocyanins (218.23 mg/100 g) compared with dried samples, freeze-dried samples, particularly those subjected to flash pre-freezing, retained higher contents of these components in the dried material compared to other drying techniques. This could be attributed to the microstructural preservation of plant tissue during freeze drying. Furthermore, the study demonstrated that subsequent milling of freeze-dried samples, whether using a knife mill or a ball mill, also affects the availability of bioactive compounds in freeze-dried blueberry powders. The combination of flash pre-freezing followed by ball milling yielded the highest availability of bioactive components in the processed blueberry powder.