High intensity ultrasound effects on food proteins functionality

K. D. MARTÍNEZ; P. ZEMA; C. ARZENI; A. ARIAS; O.E. PÉREZ; A.M.R. PILOSOF

Granada, España

Congreso; FOOD COLLOIDS 2010; 2010

Universidad de Granada

Soy, egg white and whey proteins are ingredients widely used in food products. b-conglycinin and glycinin globulins are the principal proteins in soy protein, exhibiting differences in their functional properties [1]. Among the proteins contained in the egg white, the major proteins are ovalbumin, conalbumin, ovomucoide and lysozyme [2,3]. The main proteins in whey are b-lactoglobulin, a-lactalbumin and bovine serum albumin [4]. These proteins are responsible for the functional properties of their respective concentrates and isolates. As the ultrasounds of high intensity (HIUS) is being applied in diverse operations in the food processing, the objective of this work was to comparatively explore the impact of US treatment on the functionality of some of the most industrially used food protein sources. Whey protein concentrate (WPC, Milkaut), an isolated commercial soybean protein (500E) and egg white protein powder (EW, Ovoprot) were used as starting material. Solutions (5 and 10%, w/w), at their respective natural pH were submitted to HIUS treatment for 20 min, in Sonics VCX 750 equipment. The operating conditions were: 20 kHz and 20% of amplitude. Before and after the HIUS treatment, the aggregate size of solutions was measured by light scattering using a Mastersizer 2000 with a Hydro 2000MU dispersion unit from Malvern Instruments Ltd, UK. The amount of sulfhydryl groups was determined with Ellman´s reagent. The effects of USAI on samples viscosity were determined by a Brookfield DV-II viscometer. The evolution of the elastic (G´) and viscous (G´´) moduli as well as tan d were registered upon time and temperature by a Phaar Physica MCR 300 rheometer, controlled stress. The temperature was controlled by a Peltier system and a bath (Viscotherm VT2, Phaar Physica). Foaming properties were studied by whipping, 30 mL of protein solutions were foamed at 25ºC in a graduated tube with a Griffin & George stirrer at 3000 rpm for 3 min. In general, HIUS promoted a decrease in the viscosity of protein solutions, mainly on observating  soybean isolate. The dynamic rheology indicated that HIUS induce the WPC gel formation at lower concentrations. In the same way, the solid character of the soy protein gels increased significantly after HIUS. Sonicated EW did not show differences.  HIUS induced an increase on foam capacity for WPC and 500E, while for EW protein no significant difference was observed. At a molecular level, the size of aggregates suffered an overall reduction and sulfhydryl content increased after HIUS application. These results allowed to conclude that HIUS treatment induced molecular modifications in the protein isolates studied: disaggregation and SH increase. Nevertheless the HIUS affected differently the studied functional properties depending on the size and nature of the protein. This technology could be used to obtain improved functional properties in some protein isolates. References [1] Torrezan, R., Tham, W. P., Bell, A. E., Frazier, R. A., Cristianini, M. (2007). Food Chemistry, 104, 140–147. [2]  Pérez, O.E. and Pilosof, AMR .(2004). Food Research International, 37, 102–110. [3]  Weijers, M, van de Velde, F. Stijnman, A., van de Pijpekamp, A. and Visschers,  R. W. (2006). Food Hydrocolloids, 20, 146–159. [4]  Cayot, P., & Lorient, D. (1997). In S. Damodaran, & A. Paraf (Eds.), Food proteins and their applications (pp. 225–256). New York: Marcel Dekker.[5] Ellman, G.L. (1959) Arch. Biochem. Biophys. 82, 70-7.