Rheology and thermal transitions of complex mixtures of soy protein hydrolysate and polysaccharides, of potential use as foaming agent.

MARTÍNEZ, KARINA D.; PILOSOF, ANA M.R.

Le Mans, Francia

Congreso; FOOD COLLOIDS 2008 . Creating Structure, Delivering Funcionality; 2008

CNRS, INRA, INSERM, University of Le Mans.

One of the most important features of food systems is their multicomponent nature. Due to their interest in food industry mixed protein-polysaccharide systems are being increasingly studied. These systems are usually used to control structure, texture and stability of foodstuffs. In the particular case of this work, the focus is on mixtures of hydrolyzed soy protein (HSP) (4% degree of hydrolysis), k carrageenan (kC) and hydroxypropylmethylcellulose (HPMC). Limited enzymatic treatment of soy proteins can substantially improve foamability but it has been reported that can decrease foam stability. Therefore, because of the decreased foam stability, their use would require the addition of polysaccharides as stabilizers. The complex mixture we studied could be used as a foaming agent under refrigeration or heating conditions because of the presence of one polysaccharide (HPMC) that gels on heating and another (kC) that gels on cooling. The objective of this work was to study the concentration effect of each biopolymer on rheological and thermal behavior of the mixture. For this purpose, a Response Surface Methodology was used. The elastic (G´) viscous (G´´) components of complex moduli and tan d were determined with a Paar Physica MCR 300 dynamic rheometer at 70ºC simulating heating conditions. The thermal transitions of polysaccharides, i.e. HPMC melting temperature and kC gelling temperature were evaluated by G´ and G´´ interception during the cooling of mixtures. The elastic component (G´) and relative viscoelasticity (tan d) of mixed systems on heating (70ºC), were mainly determined by HPMC because this polysaccharide gelled on heating. However, a high HSP or kC concentration prevented HPMC gelation, giving reduced G´ and relative viscoelasticity values. HSP affected HPMC melting temperature only when the last was in a low concentration. In general, all the three components affected this melting temperature showing strong interactions between them. kC gelling temperature was increased by the presence of HPMC, but not by the presence of HSP. The main cause of this synergistic effect would be the thermodynamic incompatibility between the biopolymers in solution. Keywords: Soy protein; Hydrolysates; Polysaccharides, Gelation.