Effects of putrescine and MAP on quality, phenolics, and organic acids in strawberry tree fruits

Background: Strawberry tree (Arbutus unedo L.) fruits are rich in bioactive compounds but are highly perishable due to their high respiration rate and soft tissue structure, leading to rapid post-harvest quality losses. Therefore, developing sustainable strategies to maintain quality and extend shelf life is of great importance. Methods: In this study, the individual and combined effects of putrescine (1 mM) and modified atmosphere packaging (MAP) on the post-harvest quality and biochemical properties of strawberry tree fruits were investigated. Fruits harvested at full maturity were stored at 4 ± 1 °C and 90 ± 5% relative humidity for 15 days, and key quality parameters including weight loss, decay rate, respiration rate, soluble solids content, titratable acidity, vitamin C, organic acids, and phenolic compounds were periodically analyzed. Additionally, correlation analysis and principal component analysis (PCA) were performed to evaluate the relationships among variables. Results: Storage duration significantly increased weight loss and decay rate, while decreasing organic acids, vitamin C, and phenolic compounds (p ≤ 0.001). At the end of storage, weight loss reached 2.97% in control fruits, whereas it decreased to 1.14% in the Put + MAP treatment, representing a reduction of approximately 61.6%. Similarly, decay rate decreased from 6.55% (control) to 3.34% (Put + MAP). Respiration rate was also significantly suppressed, with the lowest values observed in the combined treatment. Furthermore, malic acid (1.38 vs. 0.80 g/100 g) and vitamin C (36.90 vs. 28.37 mg/100 g) were better preserved in Put + MAP-treated fruits compared to control at day 15. PCA results confirmed that Put + MAP treatment maintained the most balanced profile between quality attributes and biochemical stability. Conclusion: The combined application of putrescine and MAP exhibited a strong synergistic effect by simultaneously reducing respiration, limiting water loss and decay, and preserving bioactive compounds. This study demonstrates that integrating a natural bioregulator (putrescine) with an environmentally friendly packaging system (MAP) represents an innovative and practical approach for extending the shelf life and maintaining the nutritional quality of strawberry tree fruits. This strategy also has high potential for application in other highly perishable soft fruits.