Enhancing ascorbic acid delivery and stability by yeast microencapsulation in vitro and food matrices: A comparative study of<i> Candida,</i> and <i>Kluyveromyces</i> species

Ascorbic acid (vitamin C) is highly unstable and susceptible to degradation under heat, oxygen, and moisture, which significantly limits its shelf life and functional efficiency in food and pharmaceutical systems. Therefore, developing natural and efficient delivery systems to improve its protection and controlled release have a critical role in food science. This study aimed to enhance the stability and release behavior of ascorbic acid by entrapping it into plasmolysed (P) and non-plasmolysed (NP) yeast cells of Candida utilis and Kluyveromyces lactis. Within these systems, non-plasmolysed K. lactis (KL-NP) exhibited the highest encapsulation efficiency (61.15 %) and provided elevated ascorbic acid loading (up to 756.7 mg/g), demonstrating a strong influence of yeast species and plasmolysis treatment on encapsulation performance. Antioxidant activity was well retained, with DPPH scavenging of 91.7 % for CU-P and 91.4 % for KL-NP, and an ABTS & sdot;+ scavenging capacity of 660.1 mu mol TE/g for KL-P. FTIR and SEM analyses confirmed efficient entrapment and interactions between ascorbic acid and yeast cell wall components. Release behavior followed the Korsmeyer-Peppas kinetic model, indicating diffusion-controlled mechanisms. When incorporated into real food matrices, CU-NP microcapsules significantly slowed degradation, reducing vitamin C loss from 47.7 % to 6.6 % in soft candy, and from 15.1 % to 0.57 % in apple juice after 24 days. Overall, non-plasmolysed C. utilis microcapsules demonstrated superior bioactive protection and controlled release efficacy, highlighting their potential as a natural, safe, and effective delivery system for vitamin C in functional foods and nutraceutical applications.