A Healthy Snack Food Made from Tapai (Fermented Black Glutinous Rice) under Freeze-Drying: Bioactive and Sensory Properties

Abstract

Tapai, also known as fermented black glutinous rice (FBGR), is a delicacy in Indonesia. It contains healthful compounds such as phenolic and anthocyanins. The short shelf life of around 5-7 days when refrigerated is a key drawback to its use. The objective of this study was to develop a tapai snack employing a foam-mat freeze-drying method and to examine its bioactive and sensory qualities. To manufacture a tapai snack, maltodextrin (MD) (20, 30, and 40% w/w) and whey protein isolate (WPI) (5% w/w) were combined with FBGR juice and stirred for ten minutes for the foaming process. The foamed tapei juice was removed into a 200-mm-thick plastic mold, and freeze-dried for 24 hours (condenser temperature at -55oC, pressure 0.04 mbar). Dietary fibers, total phenolic content, and total monomeric anthocyanins were investigated. Thirty semi-trained panelists rated the sensory qualities (color, flavor, taste, texture, and overall) using a seven-point hedonic scale. MD-40-treated freeze-dried tapai snacks contained the most dietary fiber at 3.75%, followed by MD-20 and MD-30 at 3.55% and 3.60%, respectively. MD-20 contained the most phenolics (65.4 mg/100 g GAE dried matter), followed by MD-30 (46.6 mg/100 g GAE) and MD-40 (39.9 mg/100 g GAE). The freeze-dried tapai snacks had a total of 44.72, 36.34, and 20.8 mg/100 g Cyn-3-Glu for MD-20, MD-30, and MD-40, respectively. The sensory evaluation revealed a statistically significant (p<0.05) variation in texture among all treated samples. The freeze-dried tapai snacks from MD-30 were excellent in color, flavor, and texture.