Effect of Chemical Treatments to Reduce the Bitterness and Drying on Chemical Physical and Functional Properties of Dietary Fiber Pomelo Powder from Citrus grandis (L.) Osbeck Albedo

Abstract

The pomelo albedo was selected from three cultivars—Kao Nampung (KNP), Thongdee (TD) and Kao Yai (KY). KNP was a suitable cultivar for preparing dietary fiber powder because it had high crude fiber content and the limonin and naringin contents were lower than for TD and KY. Limonin and naringin are the main bitter components of pomelo albedo which need to be reduced. Three chemicals were used to reduce the bitterness of the pomelo albedo—NaCl (1%, 3%, 5%), CaCO3 (1%, 3%, 5%) as well as various pH levels using 0.1 N NaOH solution (pH 7, 8 and 9). The results showed that all chemicals treatment could reduce the limonin and naringin contents (P ≤ 0.05) but adjusting the organoleptic quality to pH 7 had the highest odor score and the lowest score for bitterness. Two drying methods were studied: freeze drying was conducted at -40 °C for 14 hr and the three conditions for tray drying were 50 °C for 5.5 hr, 60 °C for 4.5 hr and 70 °C for 2 hr. The freeze dried pomelo albedo powder had better physical, chemical and functional properties than the samples that were tray dried (P ≤ 0.05). The water holding capacity and swelling capacity of the dietary fiber pomelo albedo powder were compared with commercial cellulose (carboxymethyl cellulose). It was found that the pomelo albedo dietary fiber powder had better functional properties than the commercial cellulose based on scanning electron microscopy. Thus, dietary fiber pomelo albedo powder can be used as a functional ingredient or in industrial applications using food products.