This brings me back to my early career on valorisation of plant industry co-products...

Pectin if extracted will dissolve in water, if you want to make a water absorbed you need to cross-link it (there is an old article on this topic by an Italian group: Carbohydrate Polymers 27 (1995) 215-220: Gelation of covalently cross-linked pectins. The method wroks great and is not complicated, just some safety issues to consider.

However on the topic of using citrus peel to retain water there is already abundant litterature, look up dietary fiber and hydration capacities. These works are on sugar beet pulp, but the behaviour of citrus peel is much the same and the time frame (early 1990's) is where you'll find lots of reference, it was a hot topic at that time.

Renard C.M.G.C., Crépeau M.-J. & Thibault J.-F.: Influence of ionic strength, pH and dielectric constant on hydration properties of native and modified fibres from sugar-beet and wheat bran. Industrial Crops and Products 3, 75-84 (1994).

Guillon F., Renard C.M.G.C., Hospers J., Thibault J.-F. & Barry J.-L.: Characterisation of residual fibres from fermentation of pea and apple fibres by human colonic bacteria. Journal of the Science of Food and Agriculture 68 (1995) 521-529.

Renard C.M.G.C., Rohou Y., Hubert C., Della Valle G., Thibault J.-F. & Savina J.-P.: Bleaching of apple pomace by hydrogen peroxide in alkaline conditions: optimisation and characterisation of the products. Lebensm.-Wiss. u. - Technol., 30 (1996) 398-405

Massiot P.& Renard C.M.J.C: Composition, Physico-chemical Properties and Enzymatic Degradation of Fibers Prepared from Different Tissues of Apples. Lebensm.-Wiss. u. -Technol. 30 (1997) 800-806

Dronnet V.M., Axelos M.A.V., Renard C.M.G.C. & Thibault J.-F.: Improvement of the binding capacity of metal cations by sugar-beet pulp. I. Impact of cross-linking treatments on composition, hydration and binding properties. Carbohydr. Polym. 35 (1998) 29-37.

Cordially

Catherine