Influence of semolina cream addition on the bioaccessibility of polyphenols in walnut-filled pastry (Şöbiyet)

Walnuts are widely consumed around the world, and are often used as a filling for pastries, especially in East Asia. In this study, a popular pastry called “şöbiyet” was examined to evaluate the interactions between semolina cream and walnuts. The phenolic profile, antioxidant activity, and in vitro bioaccessibility were analyzed. Samples containing 35% (W35%) and 20% (W20%) walnuts (w/w) were prepared with and without the addition of semolina cream. Total phenolic content (TPC) of undigested samples ranged from 417.6 ± 73.11 mg GAE 100 g⁻¹ sample to 726.2 ± 21.66 mg GAE 100 g⁻¹ sample. Although samples with added semolina cream showed higher TPC levels, the differences were not statistically significant (p > 0.05). In contrast, total antioxidant activity (TAC) levels, as measured by the DPPH and CUPRAC assays, indicated that the addition of semolina cream significantly decreased antioxidant activity (p < 0.05). A similar trend was observed in the in vitro bioaccessibility of individual phenolic compounds. In most cases, no significant differences were observed between samples with higher walnut content (W35%) regardless of whether they contained semolina cream (p > 0.05). However, samples with lower walnut content (W20%) lost some of the phenolic compounds, TPC and TAC during intestinal digestion phase when semolina cream was added (p < 0.05). Overall, the results highlighted that adjusting the walnut content and semolina cream composition in pastries can improve the bioaccessibility of polyphenols, suggesting potential applications in the development of functional foods with enhanced health benefits.