Effect of wall materials on physicochemical properties and bitterness masking of freeze-dried navel orange peel powder

Abstract

Navel orange peel has high nutritive value but severe bitterness. To mask bitterness, five wall materials, including gum Arabic (GA), maltodextrin (MD), corn starch (CS), soy isolate protein (SPI), and whey protein (WP) were used to prepared freeze-dried navel orange peel powder (NOPP). The physicochemical characteristics and bitterness masking of NOPP prepared with different wall materials were evaluated. Wall materials reduced the moisture content of the powder and increased their particle size. WP improved the solubility properties of the powder, with a water solubility index of 36.57%. WP improved the flowability of the powder with the lowest Hausner ratio and Carr index of 1.30 and 23.15%, respectively. Compared with other wall materials, WP has the best antioxidant capacity, with a total phenol content of 10.42 mg/g and an ABTS free radical scavenging rate of 55.34%. In terms of taste masking, the wall materials effectively encapsulated the limonin in NOPP and masked the bitterness of NOPP. WP and SPI resulted in a reduction of the determined limonin content to 63.46 and 23.00 μg/g, respectively. Overall, WP can effectively mask the bitterness of NOPP while improving its physicochemical properties, making it the most suitable wall material for microencapsulating NOPP. WP encapsulated NOPP have potential for use as functional food ingredient. This study provides new insights for the full utilization of citrus peels and other bitter agricultural waste.