engleski

Influence of different coatings and drying of wet microbeads in vitro release of phenolic compounds

The aim of this study was to investigate the influence of different coatings and drying of wet microbeads on their parameters of shape (circularity, roundness, solidity), size (area, perimeter, feret), and texture (hardness), as well as on the in vitro release of phenolic compounds from dried microbeads. First, hydrogels (wet microbeads) were prepared by encapsulating polyphenol-rich extracts from grape pomace Cabernet Sauvignon variety by ionic gelation with different natural coatings. Sodium alginate (SA) and combinations of SA with maltodextrin DE 4-7 (SA+MD1), maltodextrin DE 16.5-19.5 (SA+MD2), gum arabic (SA+GA), gum tragacanth (SA+GT), or chitosan (SA/CHIT) were used. The prepared hydrogels were air dried, vacuum dried, or freeze dried to produce various dried microbeads. Geometry parameters (shape and size) were analysed using image analysis, while texture parameter (hardness) were analysed using a texture analyzer. The in vitro release of phenolic compounds was monitored for 250 minutes. SA/CHIT hydrogels had the highest values for all size parameters tested, while SA hydrogels had the lowest values. Drying causes the expected shrinkage of the hydrogels. It was found that the size of the hydrogels decreased the most during air drying (83.5-88%), except for the beads coated with SA+GT, which shrank the most during vacuum drying (85.5%). The results show that the vacuum- dried SA+GT microbeads had the smallest size but the most spherical shape. Freeze-drying was causing the smallest change in surface area compared to other drying methods (32.1-62.2%). Considering the hardness of hydrogels and dried microbeads, the results show that hydrogels have the lowest hardness (0.311- 0.445 N) and air-dried microbeads have the highest hardness (28.6-37.9 N). A difference was also observed between the hardness of the dried microbeads, with the freeze- dried ones having the lowest hardness (0.5-3.4 N). In general, in vitro release showed that most phenolic compounds were released from freeze-dried microbeads, with the exception of SA+MD2 microbeads, where most phenolic compounds were released from vacuum-dried microbeads. The highest concentrations of phenolic compounds were released from SA/CHIT freeze-dried microbeads (43.27 mgTPC/gMB), but it was observed that their concentration started to decrease after 143 min of release. A similar behavior was observed in SA and SA+MD1 freeze-dried microbeads, while in freeze- dried microbeads prepared with SA+GA and SA+GT, a steady increase in concentration was observed during release.

drying, encapsulation, geometry parameters and texture, in vitro releasement, phenolic compounds

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