Physicochemical, antioxidant and microbial stability of Burdekin plum leathers

Abstract

SummaryBurdekin plums (BP) are the fruits of Pleiogynium timoriense (DC.) Leenh, a tree native to Australia. In this study, BP fruit leathers were developed by blending BP puree with apple puree (0%–80% levels) to make five formulations of BP fruit leathers (100BP, 80BP, 60BP, 40BP, 20BP). Physicochemical parameters and microbial stability of fruit leathers were studied during six‐month storage at ambient conditions (temperature 16–25 °C, humidity 60%–77%). Results showed that BP leathers had a water activity from 0.60 to 0.64 and moisture content from 21% to 25%, and both were stable during storage. 20BP had the highest score for all colour parameters measured and had the lowest value in hardness. Reduction in redness and chroma and an increase in hue were observed in all leathers after storage. The total content of cyanidin 3‐galactoside and cyanidin 3‐glucoside decreased from 400–1600 mg/kg DW to 100–500 mg/kg DW after processing into leathers then to 9–70 mg/kg DW after storage. A decrease in catechins was also observed after puree was processed into leather and after the 6 months of storage, whereas an increase in gallic acid, ellagic acid, quercetin 3‐glucoside, trigalloylglucose was observed particularly in 20BP. Total phenolic content (ranging from 6 to 24 mg GAE/g DW) and antioxidant capacity (ranging from 80 to 240 μmol Fe2+/g DW) remained relatively stable after processing and storage with a slight reduction in 80BP and 100BP. Fruit leathers were microbiologically safe and shelf‐stable during the 6 months of storage. These results demonstrated the potential of BP to be processed into shelf‐stable fruit leathers rich in bioactive phenolics.