Unpurified Gelidium-extracted carbohydrate-rich fractions improve probiotic protection during storage

Abstract

The objective of this work was to investigate whether the use of unpurified agar-based fractions extracted from the seaweed Gelidium as microencapsulation matrices has an impact on probiotic protection during storage. Therefore, unpurified and pure agar and agarose-based microcapsules were produced through emulsification/internal gelation for the protection of Bifidobacterium pseudocatenulatum CECT 7765. Initially, agarosebased formulations with other biopolymers were evaluated, given the excellent oxygen barrier properties of this polysaccharide. The optimal combination in terms of probiotic protection was selected for further experiments and this agarose-based formulation was compared with microcapsules produced using both pure and unpurified agar-based fractions. The presence of other compounds (mainly proteins and polyphenols) in the unpurified agar fractions significantly improved the viability of these sensitive probiotic bacteria both at ambient and refrigerated storage conditions. Furthermore, the presence of impurities allowed the increase of solids content in the formulation giving raise to stronger gel particles, which could contribute to limited oxygen diffusion, thus, partly explaining the improved protection. Therefore, this work demonstrates the potential of more cost-effective less purified carbohydrate-based fractions for probiotic protection.

Advanced structural characterisation of agar-based hydrogels: Rheological and small angle scattering studies

“…However, none of the agar-based samples, except for the commercial sample (for which the crossover point was detected at 45 ºC), presented a true solution behaviour (G''>G'); instead they displayed behaviour typical of entangled networks at the initial temperature of 75 ºC, especially the purified alkali-treated samples. This behaviour has been previously observed for agarose (Mohammed, Hember, Richardson, & Morris, 1998) and agar (Alehosseini et al, 2018). Although agarose chains are known to associate by forming ordered helical structures, this observation does not necessarily mean that these helices were already formed at 75 ºC, but it implies the existence of some kind of molecular association.…”

“…The greater molecular weights of all the agar-based extracts, as compared to the commercial agar, may explain the occurrence of more extensive molecular interactions in the former. As we did not observe a true cross-over between G''>G', we defined the apparent gelling temperature by determining the point at which an abrupt rise in G' and G'' took place, in line with other studies (Alehosseini et al, 2018;Russ, Zielbauer, Koynov, & Vilgis, 2013). This transition corresponds to the formation of a well-developed network by aggregation of the agarose helices into larger bundles, which have been previously related to the existence of strong gels (Indovina et al, 1979;Mohammed et al, 1998).…”

“…Alternative extraction protocols based on heating treatments, as well as their combination with sonication, have been recently explored for the production of less purified agar-based extracts with the aim of optimizing industrial processes in terms of time and energy consumption (Martínez-Sanz, Gómez-Mascaraque, et al, 2019). These agar-based extracts were reported to form softer gels with antioxidant capacity, which may be interesting for a wide range of alternative applications such as food additives, food packaging structures and encapsulation of bioactive components (Alehosseini et al, 2018).…”

Production of unpurified agar-based extracts from red seaweed Gelidium sesquipedale by means of simplified extraction protocols

“…Agar is widely used in the food industry area (mainly as texture modifying and thickening agent) and in the microbiology field. However, alternative applications such as the development of biodegradable films (Atef, Rezaei, & Behrooz, 2014;Guerrero, Etxabide, Leceta, Peñalba, & De la Caba, 2014;Kanmani & Rhim, 2014;Phan, Debeaufort, Luu, & Voilley, 2005;Rhim, 2011), hybrid biopolymeric nanofibers (Sousa et al, 2015), encapsulation structures (Alehosseini et al, 2018) or components with bioactive functionalities (such as antioxidant and antitumoral properties) (Chen, H.-M., Zheng, & Yan, 2005), are currently being explored. Depending on its aimed application, agar must possess a different range of properties (i.e.…”

Characterization and gelling properties of a bioactive extract from Ascophyllum nodosum obtained using a chemical-free approach

“…However, the purification of seaweed polysaccharides from raw algal extracts usually involves multiple energy- and time-consuming steps, which also require the use of large volumes of water ( Bixler and Porse, 2011 ; McHugh, 2003 ). Moreover, unpurified seaweed extracts usually contain functional compounds such as polyphenols ( Alehosseini et al., 2018 ; Cardozo et al., 2007 ) that are frequently lost during purification processes ( Martínez-Sanz et al., 2019 ). In this context, using raw seaweed extracts rather than purified polysaccharides could be an advantageous alternative, since apart from the economic savings and environmental benefits, the additional natural and potentially bioactive compounds found in the raw extracts may add extra value to the final products.…”