Emulsifying and Foaming Properties of Gluten Hydrolysates with an Increasing Degree of Hydrolysis: Role of Soluble and Insoluble Fractions

Abstract

Cereal Chem. 77(4): [414][415][416][417][418][419][420] Gluten solubility was improved by enzymatic proteolysis at moderate acidic pH level. Reversed-phase HPLC analysis of gluten hydrolysates with a degree of hydrolysis (DH) in the range of 0-5% showed that both hydrophilic and hydrophobic soluble peptides were released. Emulsifying and foaming properties of hydrolysate dispersions at 3.75 mg/mL decreased with the increasing DH at all pH levels and salt conditions investigated.On the other hand, the soluble fractions separated from those hydrolysate dispersions exhibited good functional properties, independently of the initial DH. The proportion of hydrophilic and hydrophobic peptides in the soluble fractions depended on DH, pH level, and salt concentration. Nevertheless, these soluble fractions were characterized by an excellent capacity to stabilize both oil-water and air-water interfaces.The solubility properties of proteins, which depend on intrinsic physicochemical characteristics and on the pH level and salt conditions of the medium, sometimes limit their use in formulated food systems (Panyam and Kilara 1996). The improvement of the functional properties of proteins by enzymatic or chemical modifications has been extensively studied (Hardwick and Glatz 1989, Hamada 1992, Guillerme et al 1993, Guéguen et al 1995, Chobert et al 1996.Wheat gluten, a by-product of the wheat starch industry, is a typical water-insoluble protein. Much research focused on chemical or enzymatic modifications has resulted in the enhancement of its solubility, foaming, and emulsifying properties (Yang and McCalla 1968, Batey 1985, Bollecker et al 1990, Thébaudin 1990, Kato et al 1991, Mannheim and Cheryan 1992, Mimouni et al 1994, Babiker et al 1996. Adler-Nissen (1986) reported that extensive protein hydrolysis produced short peptides unable to form stable films at the oil-water or air-water interfaces. Thébaudin (1990) showed that limited hydrolysis of wheat proteins by various proteases improved solubility and that gluten hydrolysates with a degree of hydrolysis (DH) in the range of 1-2% exhibited good emulsifying and foamforming properties. However, the foam-stabilizing properties of gluten hydrolysates were very limited (Thébaudin 1990, Mannehein andCheryan 1992). Proteolysis of gluten by several enzymes (pepsin, neutrase, alcalase) confirmed these results (Mimouni et al 1994). According to this author, a pepsin hydrolysate with 1.25% DH exhibited a solubility of 80% but poor foam-stabilizing properties at pH 7. This showed that high solubility is not the only requirement to improve other functional properties. It is important to note that many studies were performed with total hydrolysates characterized by high solubility but only a few reported the effect of the insoluble fraction. Only Velev et al (1993) compared the emulsifying properties of tomato seed protein isolate with its water-soluble fraction and noted a positive effect of the insoluble fraction.The objectives of this research were 1) to study the hydrolysis of gl...

Physicochemical characteristics and functional properties of vitabosa (mucuna deeringiana) and soybean (glycine max)

“…The maximum value (56%) was obtained for 0.4 M. Initially, soybean had a reduction in the FS from 22 to 20% from 0.0 to 0.2 M, but at 0.4 M it began to increase reaching a maximum value of 40% for a 0.8 M salt solution. These results are similar to those of previous studies, in which foam stability increases with the addition of salts (WU et al, 2009;LINARES et al, 2000). Furthermore, Akintayo et al (1999) found a measure of the influence of ionic strength on the foam properties on Cajanus cajan concentrates.…”

Foaming Properties of Acylated Rapeseed (Brassica napus L.) Hydrolysates

“…This indicates that lipophilized peptides are preferentially adsorbed at the air/water interface where they form a stable film, whereas native peptides remain in the aqueous solution without participating in foam formation. An equivalent observation has been made in emulsions where only the most hydrophobic peptides contribute to the surface phenomenon (2,19,20). Thus, acylation of the amino groups of small peptides results in amphiphilic compounds that are surface-active.…”

Peptides: Production, bioactivity, functionality, and applications

“…Additionally, the balance of hydrophilic and hydrophobic forces of peptides is also mentioned as an important cause of solubility enhancement (Kristinsson and Rasco, 2000;Gbogouri et al, 2004). Several reported studies have also confirmed that increasing DH increases solubility of protein hydrolysates (Quaglia and Orban, 1987;Chobert et al, 1988a, b;Mutilangi et al, 1996;Linar es et al, 2000;Gbogouri et al, 2004;Klompong et al, 2007;Souissi et al, 2007;Balti et al, 2010;Geirsdottir et al, 2011). The solubility of the hydrolysates is especially improved at the proteins isoelectric point, pI (Chobert et al, 1988b).…”

“…Foam capacity of proteins can be improved by making them more flexible (hydrolysis) and exposing more hydrophobic residues for the adsorption at the air-water interface (Multilangi et al, 1996). Several studies showed decreased foaming stability for protein hydrolysates compared to that of the untreated proteins (Linar es et al, 2000;Klompong et al, 2007;Souissi et al, 2007;Mune, 2015;Zou et al, 2016). Some studies, on the other hand, reported increased foaming capacity of hydrolysates compared to untreated proteins (Kuehler and Stine, 1974;Balti et al, 2010;Mune 2015).…”