The Role of Processing Conditions on the Color and Antioxidant Retention of Jet Tube Fluidized Bed–Dried Blueberries

Abstract

Jet tube fluidized bed drying was investigated as a means of rapidly generating shelf-stable and high-quality sweetened and nonsweetened blueberries. Sugar-infused and noninfused scarified Rabbiteye blueberries (Vaccinium ashei ‘Brightwell’) were dried at 99, 107, and 116°C. Prior scarification of the blueberry surface aided in decreasing the drying time. Increased lightness (L*) values were most notable at higher drying temperatures for sugar-infused blueberries, suggesting loss of pigments. Total monomeric anthocyanins level, initially 7.65 mg cyanidin-3-O-glucoside equivalents (C3G eq)/g extract, decreased as drying temperature increased and ranged between 4.07 down to 1.51 mg C3G eq/g extract for dried blueberries. The total phenolics content increased with drying for noninfused blueberries, with highest levels of 31.6 mg gallic acid equivalents (GAE)/g extract for samples dried at 107°C. With the exception of sugar-infused berries dried at 107 and 116°C, the dried blueberries maintained or demonstrated slightly increased hydrophilic oxygen radical absorbance capacity (H-ORAC_FL) values, indicating that their antioxidant capacity was retained upon drying. Blueberries dried at 107°C possessed the greatest preference scores and best retention of blueberry flavor and required a relatively short drying time.

Keywords:

• Antioxidant
• Blueberries
• Fluidized drying
• Total phenolics

Notes

Means within a column followed by the same letter are not significantly different (p < 0.05).

^a TMA expressed as mg cyanidin-3-O-glucoside equivalents (C3G eq)/g extract or per gram DM; TPC expressed as mg gallic acid equivalents (GAE)/g extract or per gram DM; and H-ORAC_FL expressed as µmol Trolox equivalents (TE)/g extract or per gram DM.

Means within a column followed by the same letter are not significantly different (p < 0.05).