Effects of gum arabic edible coatings as pretreatments on the quality attributes of dried red raspberry (Rubus idaeus L.) whole fruits

The purpose of this study was to investigate the effects of various concentrations of gum arabic used as pretreatments on the quality attributes of dried whole raspberries. Whole raspberry fruits were dipped in concentrations of gum arabic of 3, 5 and 10% before oven drying at 60±0.1°C until a moisture content less than 8% was achieved. Whole dried raspberries were assessed for colour, firmness, moisture content (MC) and anthocyanin concentration. The obtained results showed that the redness (a*) of the pretreated dried raspberries ranged from 17.38 to 35.84, and there was a significant difference (P<0.05) among all the pretreated samples, with 3% GA having the highest redness of 26.65 (after untreated/wet control of 35.84) and 10% the lowest redness of 17.38. The firmness increased with increasing gum arabic concentration ranging from 8.37 to 21.91 N, showing that a higher concentration of gum arabic (10% concentration) resulted in higher structural integrity (21.91 N) than the control (8.37 N). Anthocyanin concentration showed a significant difference (P<0.05) between untreated and 3% GA, with 3% GA having the highest anthocyanin concentration of 25.51 mg C3gE g^-1 DM and 10% GA having the lowest concentration of 19.48 mg C3gE g^-1 DM. Overall pretreated samples maintain quality attributes by maintaining low moisture content, increased redness and anthocyanin concentration of whole dried raspberries. Fruit pretreated with 3% GA lowered moisture content, maintained redness and increased anthocyanin concentration compared to all other pretreated samples and would best be used in maintaining quality attributes.