Change in fruit properties, bioactive contents and individual phenolics of strawberry tree (Arbutus Unedo L.) fruits at different developmental stage

The strawberry tree (Arbutus unedo L.) is a Mediterranean plant that produces fruits containing important components for health. In this study, fruit quality traits and bioactive contents of A. unedo fruits at 4 different fruit developmental stages [Green Stage (GS), Orange Stage (OS), Pink Stage (PS) and Red Stage (RS)] were investigated. Depending on the developmental stages, fruit properties and bioactive contents varied significantly (p < 0.05). Fruit weight, length and width were found to be lower at the GS stage and higher at the other stages. In color parameters, a decrease in L* and b* values was observed as the red color of the fruits increased. The a* value increased with the progress of fruit development. In the taste tests, fruits that turned red were found to be sweeter, and the highest taste score was obtained at the RS. While the SSC content increased with the progress of fruit development, the TA amount decreased. Fruits at the OS stage exhibited the highest vitamin C (312 mg 100 g− 1), whereas those at the GS stage showed the highest titratable acidity (TA). Total phenolics was highest at the RS stage (964.9 mg GAE kg⁻¹), while total flavonoids peaked at the GS stage (244.9 mg QE kg− 1). The highest antioxidant activity was also observed at the GS stage (52.9 mmol TE kg− 1), showing stage-dependent increases or decreases depending on the developmental stages. Catechin was identified as the predominant individual phenolic compound. In general, the highest individual phenolic compounds were recorded at the GS, while the lowest were found at the OS and PS. The PCA analysis results also support these findings. Indeed, RS was associated with total phenolics, soluble solids, protocatechuic acid, trans-ferulic acid, and catechin (major phenolic). GS was related to other phenolic compounds, total flavonoid and antioxidant activity. Physical properties were associated with PS. As a result, different developmental stages markedly alter the physical, chemical and bioactive properties of strawberry tree fruits. The results provide new insights into which fruits at different developmental stages have the highest content of specific bioactive compounds associated with health benefits or functional properties.