Interaction of xanthan gums with galacto- and glucomannans. Part II: Heat induced synergistic gelation mechanism and their interaction with salt

Abstract

In this study the heat induced synergistic gelation of different hydrocolloid solutions, xanthan gum types (XG) in mixture with galactomannans like guar gum (GG), locust bean gum (LBG) and konjac glucomannan (KGM) is investigated. The physical mechanism of the synergy in thickening and gelling of blends depends on the monomer structure, the molecular weight, the charge, the polarity, and the chain stiffness of the hydrocolloids. Particularly the properties of the electrically neutral galacto- and glucomannans mixed in combination with xanthan gum strongly affect the synergistic effects. These are influenced by the number and distribution of mannan side chains and thus their flexibility. While the pure components do not show gelation on their own, they form viscoelastic solutions or even gels when mixed together and heated. In this study, rheological properties of the resulting composite gels of 0.5% (w/w) were examined under different physicochemical and thermal conditions. Focus was laid on thermally induced gels, as these gels showed higher synergistic effects compared to the non-heated ones. The gelation mechanisms were investigated by strain and temperature dependent oscillatory rheological measurements. Blends with XG-GG (20:80) showed the weakest synergism, followed by XG-LBG blends (20:80), whereas XG-KGM (60:40) blends showed the highest increase of the storage modulus. This can be explained by different local interactions in combinations with the flexibility of the various components. Furthermore, the impact of monovalent salt on the interactions was investigated. Addition of sodium chloride at 0.05% and 0.5% (w/w) concentrations influenced the gelling due to Coulomb screening of the negative charges of XG. Consequently, the synergism, in particular the storage modulus, is strongly affected by variation in salt concentration. We propose specific models based on the gel formation in case of XG-LBG and XG-KGM blends, whereas XG-GG shows an entropic phase separation due to flexibility of GG.

Scaffolds for Cultured Meat on the Basis of Polysaccharide Hydrogels Enriched with Plant-Based Proteins

“…The addition of salt can actually lower the viscosity of XLB [ 73 , 74 ]. Hydrogels, composed solely of xanthan, usually require acidic compounds such as citric acid or adipic acidic for initiation of xanthan gelation [ 75 ].…”

Brühwürste und Surrogate

“…Daher müssen Hydrokolloide mit einem zweiten Netzwerk lokal stabilsierend eingreifen. [15] Allerdings sind die Monomere (Galacto-and Glucomannane) der verschiedenen Hydrokolloide mit den Proteinen thermodynamisch unverträglich. Darüber hinaus verläuft die Vernetzungsreaktion des Xanthan-Johannisbrotkermehl mit 10-20 Minuten kinetisch deutlich langsamer, folglich bleiben Hydrokolloid-und Proteinnetzwerke lokal entmischt [16].…”

Keçi̇boynuzu Gami / Ksantan Gami İlavesi̇ni̇n Keçi̇boynuzu Meyvesi̇ Yan Ürünleri̇nden Elde Edi̇lmi̇ş Yeni̇ Nesi̇l Atiştirmalik Tasarimina Etki̇si̇

“…Ghebremedhin et al (2020) states that XN undergoes a conformational change from a rigid ordered helix structure to disordered shape at higher temperatures. Previous studies show intermolecular bonding between the xanthan in its coil conformation and galactomannans such as LBG so LBG could be trapped in helix structure of XN for gelling process forming junction zones (Ghebremedhin et al, 2020). This gel network might have entrapped higher free water leading higher moisture content in fresh F3 samples.…”

“…It also resists to phase separation and increase end product quality (Barak and Mudgil, 2014). Since LBG is a neutral and semiflexible polymer with low mobility (Ghebremedhin et al, 2020), high hardness values in LBG samples were expected. On the other hand, negative side chains in XN could trigger electrostatic repulsions and showed less resistance to applied force in texture measurements.…”

“…The polymer chains are stretched by pulling them apart and firmer network is obtained. It is seen that XN-LBG blends show maximum modulus range referring to maximum synergistic effect around 1:1 blend ratio (Ghebremedhin et al, 2020) and so this was chosen as LBG replacement ratio. Viscoelastic properties of LBG, XN and 1:1 blend support texture results.…”