Evaluation of Carotenoid Bioaccessibility in Selected Good Dietary Sources of Lutein Using a Modified INFOGEST In Vitro Digestion Protocol

Background/Objectives: This study aimed to evaluate the bioaccessibility (BA) of lutein and other carotenoids in selected fruits (avocado, kiwi, orange) and a leafy green vegetable (lamb's lettuce) using a modified INFOGEST in vitro digestion protocol. The modifications were specifically designed to enhance the release, micellarization, and subsequent quantification of carotenoids. Methods: The standardized static in vitro digestion model proposed by the COST Action INFOGEST was adapted. Key modifications included using a larger sample size (20 g) and optimizing centrifugation conditions (20,000 G for 5 minutes) to efficiently transfer carotenoids to the aqueous-micellar phase. Quantification was done by HPLC. Results: Lamb's lettuce was rich in lutein (4615.03 µg/100g) and β-carotene (2156.42 µg/100g); avocado was a notable source for lutein (171.67 µg/100g); kiwi contained lutein (64.55 µg/100g); and orange was a source of β-cryptoxanthin (73.39 µg/100g) and zeaxanthin (12.85 µg/100g) in the Spanish population. Regarding stability and BA, lutein in avocado showed high recovery (95.84%) and a BA of 55.32%. Kiwi exhibited excellent lutein stability (73-80% recovery) and the highest BA for lutein (71.01%), with β-carotene at 36.39%. Orange had low violaxanthin BA (1.02%) but intermediate values for zeaxanthin (29.96%) and β-cryptoxanthin (18.03%). In contrast, lamb's lettuce showed low recoveries and significant losses, with very low β-carotene BA (5.08%). Conclusions: sample weight and centrifugation speed are crucial modifications for accurate carotenoid BA assessment. Carotenoid BA varies depending on the specific carotenoid and the food matrix. This highlights the importance of adapting in vitro digestion protocols to the characteristics of lipophilic compounds and food matrices.