Exploring the relationship between plant sterol bioaccessibility and lipolysis of enriched bread in senior digestion conditions

Plant sterol (PS)-enriched foods are considered a valuable tool for the prevention of cardiovascular diseases, especially in senior population (> 65 years). Despite its relevant effect on human health, there are few studies on the fate of food and PS during digestion under senior adult conditions1,2. The aim of this study was to determine the PS bioaccessibility (BA) and lipolysis from a PS-enriched wholemeal rye bread under senior adult conditions. The bread was subjected to in vitro digestion under older adult conditions (reduction of enzyme activity and agitation, modification of pH and increase of digestion time) at (i) gastric step, (ii) gastric and intestinal step, and (iii) INFOGEST 2.0 method with cholesterol esterase as control. The PS content in bread and in the obtained bioaccessible fractions (BF) were determined by gas chromatography-mass spectrometry (GC-MS), in order to calculate the BAs3. The main lipid classes in both the bread and BF were determined by GC-flame ionization detection (FID)4. The total PS content in the bread was 1.6 g/100 g, with b-sitosterol (81.3%) > campesterol and sitostanol (6.8%) > campestanol (1.7%) > stigmasterol, Δ5-avenasterol, Δ5,24-stigmastadienol, Δ7-stigmastenol and Δ7- avenasterol (< 1%). The BA of total PS after the control digestion was 11.6%, with sitostanol as the most bioaccessible sterol (18.5%). The modified gastric step conditions led to a higher BA of total PS (values of 16.1%), with sitostanol remaining as the most bioaccessible sterol (23.1%). The total PS BA obtained with the gastric and intestinal adaptations was not significantly different with respect to that of the control (9.9% of BA), with sitostanol and stigmasterol displaying the highest BA (16.6 and 15.6%, respectively). The lipid profile in the bread confirmed that free sterols were the major lipid class (82.1%, in agreement with the PS enrichment of the bread), followed by triacylglycerols (12.3%), and free fatty acids, diacylglycerols, monoacylglycerols, esterified sterols and tocopherols (< 1.6%). The total lipid profile obtained in all digestion conditions here tested showed a predominant abundance of free fatty acids (43.2–48.2%) and free sterols (47.2–51.2%). In this case, significant differences were observed only in the intestinal phase, where a higher abundance of esterified sterols (8.8%), diacylglycerols (31.7%), and triacylglycerols (67.1%) was found in the modified condition with respect to the control method. Therefore, our study suggests that senior digestion conditions do not significantly affect the BA of PS in PS-enriched bread, despite the decrease in lipolysis. However, further studies are needed to confirm these results for a better understanding of PS fate in aging populations. Authors thank the financial support from project PID2019-104167RB-I00/AEI/10.13039/501100011033, as well as from the Basic Research Funding RFO of the Alma Mater Studiorum-University of Bologna. V. Blanco-Morales holds a grant for the requalification of the Spanish university system from the Ministry of Universities of the Government of Spain (European Union, NextGenerationEU). 1 Makran et al., 2022. Trends Food Sci Technol. 129, 283-295. 2 Poli et al., 2021. Nutrients. 13, 2810. 3 Cuevas-Tena et al., 2017. Lipids. 52, 871-884; 4 Tappi et al., 2020. Foods, 9, 1485.