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

¹Unité de Biochimie et Technologie des Protéines, Institut National de la Recherche Agronomique, BP 71627, 44316 Nantes cedex 03, France. ²Laboratoire d'Ingénierie Moléculaire et Sensorielle des Aliments, Ecole Nationale Supérieure de la Biologie Appliquée à la Nutrition et à l'Alimentation, Esplanade Erasme, 21000 Dijon, France. ³EUROGERM S.A., 5 rue des Artisans 21800 Quétigny - France. Convention CIFRE n°613-96. ⁴Corresponding author. Phone: +33-2-4067-5059. Fax: +33-2-4067-5025. E-mail: popineau@nantes.inra.fr

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.