**Abstract**

One of the most important polysaccharides in the vegetal kingdom is pectin. This class of natural polysaccharide is found primarily in citrus fruits and apple pomace. Pectin has been used in different sectors of the industry, among which the food, pharmaceutical, cosmetic, and paper industries stand out. Today, there is a growing demand for this type of hydrocolloid, where both the scientific and industrial fields have focused on using new sources of pectin and developing novel extraction methods. This chapter describes the chemical structure of pectin and its main chemical characteristics. Then, the conventional sources from which pectin is obtained are exposed as well as its main industrial applications. Subsequently, the physicochemical and functional properties of pectins obtained from unconventional sources are described and analyzed as well as the main technologies used for their extraction. Finally, the most recent advances in the role played by pectin in the industrial sector are described.

**Keywords:** pectin, extraction, functional properties, husks, hulls, Cactaceae, new applications

### **1. Introduction**

Pectin is considered one of the main polysaccharides found in plant sources; it participates in the constitution of cell walls of higher plants, impacting the physical and nutritional contribution of products of plant origin. Pectin is a globally recognized polysaccharide with great relevance in the global biopolymer market due to its inherent functional properties and vast applications in the food, pharmaceutical, and biomedical industries [1]. It is a macromolecule capable of forming flexible polymer chains that lead to forming hydrogel-type structures [2]. Its functional properties are associated with the extraction conditions and influenced by the source used. The primary sources of commercial pectin are citric fruits and apples; however, non-conventional sources have been investigated, such as agro-industrial sub-products and residues, pulps, husks, hulls, peels, Cactaceae, and vegetables, among others [3]. Furthermore, pectin has been functionalized

through chemical or enzyme reactions that lead to changes and improvements in its physicochemical properties, such as molecular weight, degree of esterification (DE), and surface charge, which in turn contributes to the development of new functional or improved properties, along with new approaches and applications [4].
