Gelation Properties of Whey Protein and Dextran Conjugates Obteined fron Malliard Reactions

Abstract

Polysaccharides are widely used in food, pharmaceutical and many other industries. The chemical structure of polysaccharides can be as diverse as their origin, but they generally have a large number of hydroxyl groups, which are highly hydrophilic. Because of this, they can hydrate and form hydrogen bonds, as well as provide sweetness, and impart texture and viscosity. They also have thickening and/or gelling properties, among others (Perduca, Spotti, Santiago, Judis, Rubiolo, & Carrara, 2013). Dextrans are polysaccharides mainly composed of a linear chain of a-(1,6)-D glucosyl residues, with some branching in a-(1-3) position, being structurally diverse because they could have a different quantity and distribution of their links. They are generally produced by cultures of bacteria such as Leuconostoc spp. (Salou, Loubiere, & Pareilleux, 1994). Dextran structure is very flexible in an aqueous solution. Therefore, dextrans are unable to form gel-like structures. This characteristic is suitable for protein gelation studies (Sun et al., 2011). Furthermore, owing to their neutral and reducing nature, they are used to conjugate proteins, inhibiting the formation of electrostatic complexes. The conjugation of proteins and polysaccharides through the Maillard reaction is a widely used method for transforming these macromolecules into better functional ingredients. Conjugates obtained in the early stages of Maillard have had better emulsifying properties (Oliver, Melton, & Stanley, 2006) as well as better foaming properties (Dickinson & Izgi, 1996), increased protein solubility (Katayama, Shima, & Saeki, 2002) and heat stability (Chevalier, Chobert, Genot, & Haertlé, 2001) than their precursors. Moreover, it has also been shown that conjugates in the early Maillard reaction stages of certain proteins have antimicrobial activity (Takahashi, Lou, Ishii, & Hattori, 2000). Other beneficial effects have been associated with the later stages of this reaction, which produce compounds with antioxidant capacity (Wagner, Derkits, Herr, Schuh, & Elmadfa, 2002). In spite of all these findings, there are few studies focusing on the influence of the Maillard reaction on gelation of protein/polysaccharide conjugate systems. Accordingly, this chapter reviews some studies about the rheological and mechanical properties of conjugate systems obtained through the Maillard reaction of whey proteins and dextrans, as compared with mixed system (without reaction). In general, whey protein/dextran conjugates have different gelation kinetics and gel properties with respect to mixed systems, depending on dextran molecular weight and days of reaction.