Dynamics of Physicochemical Properties and Pigment Content of Quince Leaves (Cydonia oblonga Mill.) in Relation to Cultivar and Growth Stage

Background: Quince (Cydonia oblonga Mill.) is a fruit-bearing tree cultivated primarily for its aromatic fruit, while its leaves are often frequently discarded as agricultural waste. Given the increasing emphasis on sustainability and waste reduction in agriculture, investigating the physicochemical properties and potential of these leaves represents an opportunity to utilize this underutilized resource. Aims: The objective of this study is to evaluate the potential for utilizing the leaves of three Bulgarian quince cultivars as an agricultural by-product, transforming them from agricultural residues into a potential functional industrial resource. Through a comparative assessment of physicochemical and pigment characteristics at two critical phenological stages—peak vegetation (August) and the end of the growth cycle (October)—the research quantifies the dynamics of moisture, ash, water activity, color, and chlorophyll content. By integrating these parameters, the study seeks to determine the optimal time for recovery of the "waste" and the potential of quince leaves. Methods: Comparative analyses were performed to evaluate the physicochemical properties of quince leaf samples, focusing on varietal differences and the influence of the growth period. The investigated parameters included moisture content, water activity, ash content, and color characteristics. Pigment profiles, including total chlorophyll and carotenoids, were quantified spectrophotometrically, while color coordinates were measured to assess chromatic variations across varieties and seasons. Results: The data indicate that leaf characteristics are influenced by variety and growth period, particularly in relation to natural senescence, structural changes, and the accumulation of substances under the impact of climatic factors. Conclusions: The findings highlight the potential for utilizing quince leaves as a viable functional resource, in sustainable practices rather than a waste product. By recognizing their physicochemical properties, these leaves can be valorized for applications in food, cosmetics, and pharmaceuticals, contributing to waste reduction and resource efficiency in agricultural systems.