De-esterification and Transacylation Reactions of Pectinesterase from Jelly Fig (Ficus awkeotsang Makino) Achenes

Probing the Stoichiometry Dependence of Enzyme-Catalyzed Junction Zone Network Formation in Aiyu Pectin Gel via a Reaction Kinetics Model

We investigate the enzymatic self-catalyzed gelation process in aiyu gel, a natural ion crosslinked polysaccharide gel. The gelation process depends on the concentration ratio (Rmax) of the crosslinking calcium ions and all galacturonic acid binding sites. The physical gel network formation relies on the assembly of calcium-polysaccharide crosslink bonds. The crosslinks are initially transient and through break-up/rebinding gradually re-organizing into long, stable junction zones. Our previous study formulated a reaction kinetics model to describe enzymatic activation, crosslinker binding, and crosslink microstructural reorganization, in order to model the complex growth of elasticity. In this study, we extend the theory for the time-dependent profile of complex moduli and examine the interplay of enzyme conversion, crosslink formation, and crosslink re-organization. The adjusted model captures how the gelation and structural rearrangement characteristic times vary with the polymer and calcium concentrations. Furthermore, we find that calcium ions act as both crosslinkers and dopants in the excess calcium ion scenario and the binding dynamics is determined by Rmax. This study provides perspectives on the dynamic binding behaviors of aiyu pectin gel system and the theoretical approach can be generalized to enzyme-catalyzed ionic gel systems.

Core-Shell Encapsulation of Lipophilic Substance in Jelly Fig (Ficus awkeotsang Makino) Polysaccharides Using an Inexpensive Acrylic-Based Millifluidic Device

The polysaccharides extracted from the achenes of jelly fig, Ficus awkeotsang Makino, were mainly composed of low methyl pectin and used as a novel shell material for encapsulating lipophilic bioactives in the core of microcapsule. The polysaccharide microcapsules with oil core were prepared using a novel acrylic-based millifluidic device developed in this study. To investigate the physiochemical properties of and find the suitable formula of polysaccharide shells, the films casted with jelly fig polysaccharide were thoroughly characterized. For the preparation of microcapsules, the millifluidic device was optimized by controlling the flow rate to obtain uniform spherical shape with a core diameter of 1.4-1.9 mm and the outer diameter of 2.1-2.8 mm. The encapsulation efficiency was around 90%, and the microcapsules displayed a clear boundary between the polysaccharide shell and oil core. Encapsulation of curcumin in the microcapsules was prepared to test the applicability of the device and processes developed in this study, and the results showed that the microencapsulation could enhance the stability of curcumin against external environment. Overall, the results suggested that the jelly fig polysaccharides and the developed millifluidic device can be useful for the preparation of core-shell microcapsules for encapsulation of lipophilic bioactives.

Pectin methyl esterase treatment on high-methoxy pectin for making fruit jam with reduced sugar content

BACKGROUND

Pectin methyl esterase (PME) has been postulated to catalyse the transacylation reaction between pectin molecules. The present study aimed to prove the occurrence of this reaction. The feasibility of applying PME-catalysed transacylation between high-methoxy pectin molecules in making fruit jam with reduced sugar content was also investigated.

RESULTS

PME treatment increased the turbidity and particle size in pectin solution and the molecular weight of pectin, while it decreased the number of methoxy ester linkages and the intensity of the CH₃ absorption peak in the Fourier transform infrared spectrum without changes in the number of total ester linkages in pectin molecules. These findings support the occurrence of PME-catalysed transacylation between pectin molecules. Higher values of hardness, gumminess and chewiness were found in a jam containing PME-treated citrus pectin (10 g L⁻¹) and sugar (350 g L⁻¹) as compared with either a jam containing untreated citrus pectin (10 g L⁻¹) and sugar (350 g L⁻¹) or strawberry jam containing pectin (10 g L⁻¹) from the fruit and sugar (650 g L⁻¹).

CONCLUSION

The demand for sugar in jam making can be greatly reduced by the use of PME-treated high-methoxy pectin.