Physicochemical Characteristics and Functionality of Burdekin Plum During Fruit Maturation

Burdekin plum (Pleiogynium timoriense) is a rich source of phytochemicals with many health benefits, but the effect of maturation on its physicochemical properties and functionality is unknown. To fill this knowledge gap, Burdekin plums harvested at three different maturity stages (mature green, turning and dark maroon) were analysed, including basic physicochemical parameters, bioactive compounds, antimicrobial activity and antioxidant capacity. Results showed that the dietary fibre content decreased from around 50% to 30% during maturation. Three different solvents (water, 80% ethanol and 80% methanol) were used for extraction and tested for bioactive compounds and functionality. Bioactive compounds were identified and quantified using Ultra-High Performance Liquid Chromatography Tandem Mass Spectrometry. Water extracts contained higher content of gallic acid and galloylquinic acid content. However, ethanol and methanol extracts contained higher content of ellagic acid, anthocyanins and catechins. During maturation, most bioactive compounds decreased, except for anthocyanins, quercetin 3-glucoside and epicatechin, which increased. Similarly, the antioxidant capacity reduced during maturation. Regarding the antimicrobial activity, extracts from turning and dark maroon stages demonstrated a stronger inhibition against Staphylococcus aureus (inhibition zone > 8 mm) compared to mature green stage (inhibition zone < 6 mm), while no inhibition against the Escherichia coli and Candida albicans was observed. In conclusion, the physicochemical characteristics and functionality of Burdekin plums changed significantly during maturation, which should be considered when utilising the fruits as a functional food source.