Effects of drying methods and maltodextrin on vitamin C and quality of Terminalia ferdinandiana fruit powder, an emerging Australian functional food ingredient.

BACKGROUND Terminalia ferdinandiana [common name: Kakadu plum (KP)] fruit is a valuable source of vitamin C and its concentration can be used as a quality index of KP products such as dried fruit powder. The present study investigated the effects of two drying methods (freeze-drying and oven drying) and the addition of maltodextrin (0 to 25%) on vitamin C, Maillard products and overall quality of Kakadu plum (KP) fruit powder. RESULTS Freeze-drying was a better dehydration technique in retaining vitamin C, reducing the formation of non-enzymatic browning and oxidation products as well as improving powder colour compared to the oven drying (P < 0.05). Non-enzymatic browning products (furfural and 5-hydroxymethyl furfural) were generated in the oven-dried samples as a function of heating and high water activity. Maltodextrin acted as a vitamin C stabilizer in protecting vitamin C from oxidation, and significantly improved the colour attributes of the final dry products. Incorporation of 10-15% maltodextrin could reduce the percentage loss of vitamin C from 8.1 to 3.4% and 18.9 to 11.4% (compared to the control) during freeze-drying and oven drying, respectively. SEM micrographs revealed differences in the microstructures of the KP powder processed by the two drying methods with different levels of maltodextrin. Multivariate data analysis (PCA) showed separation between the oven-dried and freeze-dried samples, and also suggested that addition of maltodextrin between 7.5-10% and 10-15% are effective for preserving vitamin C and other quality properties of the freeze- and oven-dried KP powder samples, respectively. CONCLUSION The obtained results are important for the KP Industry, including Indigenous Enterprises, in selecting the most appropriate drying method for KP fruit in terms of quality and sustainability. This article is protected by copyright. All rights reserved.