Reducing the Stickiness of Dragon Fruit Skin Extract Powder as Food Colorant by Addition of Maltodextrin During Freeze Drying

摘要

Dragon fruit skin has been previously reported to contain several bioactive materials, such as antioxidant compounds, phenolic compounds, and pigments (betacyanin and anthocyanin). The utilization of dragon fruit skin wastes to produce food colorant that is also rich in bioactive materials is expected to lower agricultural wastes and also provide additional profit for the dragon fruit farmers and juice industry. In this study, dragon fruit skin extract powder was produced by two stages: extraction and freeze drying. This study particularly aims to evaluate how addition of maltodextrin (10-90%-w) affects the quality of dragon fruit skin extract powder during freeze drying. The moisture content, surface morphology, color, and bioactive materials contents, including total phenolic compound, betacyanin, and anthocyanin, of the extract and powder were assessed. This study found that increasing maltodextrin concentration in the freeze-drying feed may reduce the bioactive contents in the materials, but it may reduce the moisture content and the powder stickiness significantly, which is beneficial during application of the colorant. The moisture content of the powder with the addition of 90% maltodextrin was found to be 9.3 + 3.0%, compared with 26.5 + 6.0% for those without maltodextrin addition. Relatively high recoveries of bioactive materials during freeze drying was observed (more than 60%), which suggested that freeze drying is suitable for drying such heat sensitive materials.