Enhanced bioaccessibility of encapsulated red mizuna microgreens: A phytochemical profile approach

Abstract

Microgreens of the Brassicaceae family have garnered considerable interest due to their higher phytochemical content compared to their mature counterparts. These bioactive compounds include phenolic compounds, glucosinolates, and isothiocyanates. This study evaluated their bioaccessibility and antioxidant capacity in red mizuna microgreens, sodium alginate-encapsulated microgreens, and an aqueous reference standard mixture using the standardized INFOGEST digestion model.Alginate capsules exhibited significantly higher bioaccessible antioxidant activity by TPC assay (83.64% ± 9.02%) than raw microgreens (46.28% ± 1.35%, p < 0.005) and aqueous mixture (0%). The DPPH assay showed a bioaccessibility of 19.69% ± 2.26% in raw mizuna and 0% in the aqueous mixture. However, individual phenolic compounds were more bioaccessible in raw microgreens (98.39 ± 3.60 mg 100 g−1 DW) compared to alginate capsules (60.54 ± 1.56 mg 100 g−1 DW) and aqueous mixture (0%), with flavanols predominating. Glucosinolates were 22% bioaccessible in alginate capsules but undetectable in raw red mizuna´s intestinal phase and aqueous mixture. Isothiocyanate concentrations were significantly higher in encapsulated microgreens (248.53 ± 15.57 μg g−1) than in raw microgreens (163.51 ± 4.28 μg g−1, p < 0.005), while none were detected in the aqueous mixture. The reference standard mixture showed no bioaccessible compounds in any assay, highlighting the food matrix´s protective role.These findings suggest alginate encapsulation enhances glucosinolate and isothiocyanate bioaccessibility while protecting compounds during digestion. However, it may not favor the release of certain phenolics. This research provides insights into functional food development, indicating that encapsulation strategies could optimize the bioavailability of microgreen derived phytochemicals.IntroductionMicrogreens have garnered significant attention in recent years as a novel food category. These young seedlings, characterized by fully developed cotyledons and the emergence of initial true leaves (Jambor et al., 2022). Brassica microgreens are particularly notable for their phenolic compounds, glucosinolates (GLSs), and isothiocyanates (ITCs), which offer antioxidant and anti-inflammatory benefits. (Alloggia et al., 2023; Connolly et al., 2021; Prado et al., 2022; D. A. Ramirez et al., 2024).However, despite their presence in food, these bioactive compounds often exhibit low bioaccessibility, limiting their potential health benefits. Bioaccessibility, defined as the proportion of a compound released from its food matrix and available for absorption in the gastrointestinal tract (Wojtunik-Kulesza et al., 2020), is influenced by factors such as food matrix composition, chemical stability, solubility, and interactions between phytochemicals (Shahidi & Pan, 2022; Ubeyitogullari et al., 2022). Additionally, external conditions like light, heat, and pH variations, cooking process can degrade these compounds, reducing their effectiveness (Baenas et al., 2019; D. Ramirez et al., 2020; Statilko et al., 2024).An innovative solution addressing this issue is the encapsulating functional food or bioactive compounds with biopolymers enhancing their bioaccessibility and stability (Hu et al., 2023). Alginate, an environmentally friendly biopolymer, is one such option. Alginate-based capsules can create a protective matrix, resembling an eggshell-like structure, which serves as an additional barrier to enhance the preservation of bioactive compounds (Ubeyitogullari et al., 2022).Red mizuna microgreens (Brassica rapa var. nipposinica), a staple in Asian cuisine, have garnered significant attention globally due to their rich nutritional profile and potential health benefits (Dereje et al., 2023). Like other Brassicaceae microgreens, they are a dense source of bioactive compounds (Bafumo et al., 2024; Gunjal et al., 2024; Park et al., 2020).Despite their nutritional potential, research on GLS and ITC bioaccessibility in red mizuna microgreens is limited. The effects of growth conditions, digestion, and encapsulation on their bioavailability remain largely unknown. Moreover, comprehensive datasets linking phytochemical content, bioaccessibility, and antioxidant activity are scarce.This study evaluated the bioaccessibility of antioxidant activity measured through Total Phenolic Content (TPC), Ferric Reducing Antioxidant Power (FRAP), 2,2-Diphenyl-1-picrylhydrazyl (DPPH), and 2,2′-Azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) as well as key bioactive compounds, including phenolic compounds (PCs), glucosinolates, and isothiocyanates, in red mizuna microgreens. We compared raw microgreens, alginate-encapsulated microgreens, and an aqueous mixture of analytical standards (sinigrin, glucobrassicin, and allyl isothiocyanate) using an in vitro digestion model. Furthermore, multivariate analyses were applied to examine the interactions between digestion phases, encapsulation, and phytochemical bioaccessibility, offering new insights for optimizing red mizuna microgreens in functional food applications.