Original article Functional properties of hydrolysates from Phaseolus lunatus seeds David Betancur-Ancona, 1 Rogelio Martı´nez-Rosado, 1 Alma Corona-Cruz, 1 Arturo Castellanos-Ruelas, 1 Ma Eugenia Jaramillo-Flores 2 & Luis Chel-Guerrero 1 * 1 Facultad de Ingenierı´a Quı´mica, Universidad Auto´noma de Yucata´n, Av. Jua´rez No. 421, Cd. Industrial, C.P. 1288, Apdo. Postal 26, Suc. Las Fuentes, Me´rida, Yucata´n, Me´xico 2 Escuela Nacional de Ciencias Biolo´gicas, Instituto Polite´cnico Nacional, Me´xico, D. F., Me´xico (Received 11 May 2007; Accepted in revised form 17 October 2007) Summary Use of low degree of hydrolysis (DH < 10%) with enzymatic treatment can produce protein hydrolysates with functional properties superior to the raw material. Suspensions of Phaseolus lunatus protein isolate (PPI) were treated with one of two commercial enzymes (Alcalase or Flavourzyme) at 50 °C and pH 8.0. DH with Alcalase was greater than Flavourzyme at 5 or 15 min of reaction. Alcalase-prepared hydrolysates had more peptides than those prepared with Flavourzyme. All the hydrolysates had higher solubility than the PPI, the highest being for the Alcalase-prepared hydrolysate at 15 min reaction time. Overall, the Alcalase- prepared hydrolysates had better solubility characteristics, whereas the Flavourzyme-prepared hydrolysates had better film properties (maximum emulsifying capacity and the highest foam formation values). This is probably because of the greater ease of movement toward the interface as shown by their high surface hydrophobicity values. The Alcalase-prepared hydrolysates had generally low or nonexistent film properties. Keywords Functional properties, hydrolysed proteins, Phaseolus lunatus, Phaseolus protein isolate. Introduction Protein hydrolysis is an effective way of modifying functional properties in that proteins remain highly soluble, even under acidic conditions or thermal treat- ments (e.g. pasteurisation), and depending on their degree of hydrolysis (DH). This can be manipulated by varying the ratio of enzyme to substrate, hydrolysis time and temperature. Functional properties can be adapted to needs by controlling the DH and using the appropri- ate protease (Govindaraju & Srinivas, 2007). Extensive hydrolysates, for example, have the capacity to form solutions with very low viscosity even at high concen- trations (Frøkjaer, 1994), no flavour and good foaming and emulsion properties, all of which are important in food product applications (Van der Ven et al., 2002b; Tardioli et al., 2003a). Hydrolysed proteins can be produced with chemical processes, using acids or alkalis, but they oxidise, destroying or modifying some amino acids and thus reducing protein quality (Manninen, 2004). Given this, enzymatic hydrolysis is preferred as it can improve the physicochemical, functional and sensory properties of native proteins without affecting their nutritional value (Kristinsson & Rasco, 2000); in addition, it avoids difficulties with government regulations for their use in food (Were et al., 1997; Chan & y Ma, 1999). Among the enzymes used for hydrolysis, Alcalase is a promising candidate for industrial hydrolysate production because of its broad specificity endoprotease activity, low cost (Doucet et al., 2003) and high tolerance for alkaline pHs (Tardioli et al., 2003a). Use of the exopeptidase–endo- protease complex Flavourzyme (Novo Nordisk, Novo- zymes, Bagsvaerd, Denmark), alone or sequentially with Alcalase, can produce a very high DH and diminish the bitter off-taste produced in some products (Villanueva et al., 1999; Hamada, 2000). Partial hydrolysis of proteins increases the number of polar and hydrophilic groups, while diminishing the resulting compounds’ molecular weight (MW). This can cause changes in protein globular structure as the hydrophobic regions hidden within the native protein are exposed, and these changes heavily influence a hydrolysed protein’s emulsifying and foaming capacities (Damodaran, 1997; Van der Ven et al., 2001). In addition to their use in modifying technological functionality, enzymatically produced hydrolysates have been used in many other applications, such as reducing *Correspondent: Fax: +52 (999) 9460994; e-mail: cguerrer@uady.mx International Journal of Food Science and Technology 2009, 44, 128–137 128 doi:10.1111/j.1365-2621.2007.01690.x Ó 2008 Institute of Food Science and Technology