Extrusion of λ‐carrageenan gum: Physical properties and in vitro bifidogenic effect

Abstract

Extrusion was used as a tool for modifying carrageenan gum. Increased extrusion temperature and shear led to a considerable decrease in dissolution time (DT) (7,200 to 30 s) and faster solubilization (30 to 7 s) when coarse particle sizes (> 212 µm) and hot water were used (p < 0.05). Extrusion process has also altered morphology and white index, in which fines were whiter than larger particles as well as bulk density, crystallinity, and GAB parameters are affected by particle distribution. The apparent viscosity at zero-shear rate of non-extruded gum was 0.10 Pa.s whereas values of extruded particles ranged from 0.17 to 0.55 Pa.s, evidencing that larger particle size corresponded to lower viscosity. Even after carrageenan’s polysaccharide molecular disaggregation by extrusion, it maintained high fiber content (minimum 38%). Both extruded and non-extruded gum stimulated the growth of Bifidobacterium animalis subsp. lactis (Bb 12) in in vitro experiment, suggesting a bifidogenic effect. Practical applications Carrageenan presents poor aqueous dissolution, hindering direct application in liquid foods. Besides, marine-based ingredients are unexploited sources of bioactive compounds. In this context, thermoplastic extrusion was used as a strategy to reduce its high viscosity, modify the physical properties, and increase the gum use. The results showed that extrusion enhanced dissolution properties and extruded λ-carrageenan gum presented high dietary fiber content (>38%), suggesting in vitro bifidogenic effect. In terms of industrial applications, extruded carrageenan is promising as a food supplement fiber product.