## 3 Plant-Based Biopolymers
### Pettin-Based VMAs  
Pectin is among the most complex polysaccharides [64], being known for its unique chemical and functional characteristics [65]. It comprises approximately one-third of the dry substance in the cell walls of higher plants [66], particularly around actively dividing cells, soft plant tissues, cell corners, and middle lamella [64], and is responsible for intercellular adhesion and contributing to the overall plant structure and firmness [67]. Also found at intercellular junctions in cells with secondary walls (xylem and woody fiber cells), pectin is not limited to angiosperms but is also found in gymnosperms, pteridophytes, bryophytes, and Chara (charophycean algae closely related to land plants) [64]. Additionally, commercially pectin is primarily derived from citrus peel (20-30% pectin) and apple pomace (10-15%), which have similar functional properties. Moreover, alternative sources of pectin include sugarbeet waste, sunflower heads, and mango waste [68]. Indeed, pectin, a high-molecular-weight polysaccharide, is known for its biocompatibility, lack of toxicity, and anionic properties [69]. It is characterized by a high content of galacturonic acid (GalA) (Figure 10) [70], which forms the core of three structurally well-characterized polysaccharide motifs: homogalacturonan (HGA), rhamnoman I (RG I), and rhamnoman II (RG II) [69]. On the other hand, pectin serves various industries as a hydrating agent, regulating water movement and stabilizing formulations [67]. In the food industry, pectin is widely used in products like jam and jellies for its gelling, thickening, and stabilizing properties [69], which arise from interactions like bonding with calcium ions, hydrogen bonding, or hydrophobic interactions [67]. However, the properties of pectin can vary significantly depending on its source, molecular size, extraction conditions, location, and degree of esterification [66; 67]. On the other hand, in the realm of construction, pectin has emerged as a biopolymer that enhances the properties of fresh cement-based materials. Indeed, it has been shown to improve both the viscosity of cement suspensions [71; 72] as well as their water retention capacity [71; 73; 72]. However, its viscosity enhancement depends on the concentration of pectin used and that of Ca\({}^{2+}\) ions. For example, when pectin has a reduced number of free galacturonic acid groups, the interactions with calcium ions become more robust, leading to an increase in the viscosity as a result of pectin chains being bound by Ca\({}^{2+}\) ions. However, when the amount of Ca\({}^{2+}\) ions increases, viscosity is reduced, and gel precipitation occurs [71]. These gelling properties occurring as a result of the interaction of pectin and calcium ions were also highlighted in a study [74]. In addition, pectin improves concrete plasticity, reduces water demand [72], and enhances workability [72; 75]. Similarly, it was concluded that the improvement in concrete viscosity and plasticity is mainly due to the binding of calcium ions by pectin, thus promoting intermolecular associations via calcium bridges [72]. In another study [74], pectin-rich cactus extract was shown to increase flexibility and water absorption. This improvement has been proven to occur due to interactions between the polysaccharides or proteins in the extract and the calcium hydroxide generated during cement hydration. Pectin has also demonstrated its potential for improving the hardened properties and durability of concrete [71; 72]. For example, the interactions that occur between the polysaccharide's cactus extract and calcium hydroxide lead to the formation of complexes increasing the water resistance of concrete [74]. Furthermore, in separate studies [73; 75], not only was concrete porosity enhanced but so was resistance to sulfate attack [75]. Additionally, the compressive strength, splitting tensile strength, and deflection of concrete are improved [75]. Regarding the effect of pectin on the hydration kinetics of cementitious suspensions, two trends were observed.