Abstract
The increasing demand for functional foods with added health benefits has driven the development of innovative food products. This study aimed to develop a functional snack made from Granny Smith apples enriched with hydrolyzed collagen using impregnation technologies, including vacuum impregnation (VI), ultrasound (US), and moderate electric field (MEF), and pretreatment with CO(2) laser microperforations (MPs) combined with drying methods, including conventional drying (CD) and refractance window drying (RW). The collagen content increased significantly across treatments, with MP-I achieving the highest retention (79.86 g/100 g db). Compared with VI-CD (3.8 mg GAE/g db), MP-RW drying resulted in more total polyphenols (up to 7.2 mg GAE/g db), which was attributed to its shorter drying time (55 min vs. 160 min). The RW treatments also better-preserved color quality, with higher a* (red tones) and b* (yellow tones) values, especially in the MP-RW and US-RW treatments, highlighting their advantages in maintaining visual appeal. Texture analysis revealed that RW drying produced slices with reduced hardness and increased crispness, with MP-RW resulting in the highest sensory crispness score (8.3). In vitro digestion demonstrated that the (VI) treatment resulted in the highest degree of collagen bioaccessibility (~90%), underscoring the effectiveness of this method in improving nutrient delivery compared with the 65% MP, ~70% US, and ~74% methods. The ~90% bioaccessibility is particularly noteworthy, as it indicates that a significant portion of the impregnated collagen remains available for absorption, reinforcing the potential of VI as a strategy for developing functional foods with enhanced nutritional benefits.