Ca2+-Induced Egg White Isolate Gels with Various Microstructure

Abstract

Commercially available egg white isolates (EWI) or concentrates can not be used for ions-induced gelationbecause of high mineral content. In the present research new egg white isolate with reduced minerals content was applied for production of calcium induced gel. At 5.5% critical protein concentration no gel was obtained at the preheating process at 80℃ for 30 min. Increased calcium ions concentration formed more elastic gels with higher hardness, adhesiveness and chewiness. There was a linear correlation between (dynamic viscosity) x (density) of the gels and chewiness, hardness and adhesiveness. Higher calcium ions concentration produced more aggregated gels with higher surface roughness. There was a linear correlation between quadratic mean of the surface roughness and maximum roughness height for the gels with different calcium concentration.Keywords: egg white, gelation, salt induced, rheological properties IntroductionEgg white albumin is probably the most popular gelling protein. Heat-induced gelation process involving aggregation and turning translucent egg white into white gel is observed at boiling eggs. Egg white protein is a complete protein with all essential amino acids (Vanniekerk et al., 1993). Together with whey protein it is used as a source of protein in supplements for physically active people. Egg white protein concentrates and isolates have excellent gelling and foaming properties (Foegeding et al., 2000). Heated dispersions form gels and their properties are dependent on the powder composition, pH and ionic composition of solvent and heating conditions (Sun et al., 2002; Broersen et al., 2000).In the beginning of the 1990s a new method of gelation was invented (Foegeding and Barbut 1993). Heating a dispersion of whey protein isolate leads to unfolding and polymerization of proteins and increase in viscosity (Vardhanabhuti and Foegeding 1999). Protein dispersion pH is above isoelectric point of whey proteins (ca. 5) and the repulsion between negatively charged protein molecules prevents them from forming a gel matrix. After cooling to room temperature some ions are added, which neutralize the charges on the surface of proteins. This "shielding effect" enables more intensive interactions between the proteins molecules and at a critical protein concentration a gel is formed (Barbut and Foegeding 1993;Hongsprabhas and Barbut 1997; Bryant and McClements, 2000). This kind of process was never used for commercial egg white isolates, as they gel at the preheating part of the process at as low as 3% protein solutions (Holt et al., 1984;Croguennec et al., 2002). In some laboratory tests the main M. T.-Mleko et al. 1208 crystallized egg white protein -ovalbumin is used or commercial egg white protein is desalinated (Weijers et al., 2002;Weijers et al., 2006). Arntfield (1996) used calcium and magnesium to obtain "cold set" ovalbumin gels. Increased salt concentration causes formation of stronger gels (Artfield 1996;Savoie et al., 1996). Savoie et al. (1996) reported that the fracture stress sh...

New controlled release material: aerated egg white gels induced by calcium ions

“…There is an optimal concentration of the ions, at which there is the highest value of viscosity and hardness. The increased calcium concentration creates gels with higher hardness and viscosity [19]. Similar tendencies observed for calcium ions were observed for other ions.…”

“…There is a linear correlation between the quadratic mean of the surface roughness (R q ) and the maximum roughness height (R t ) (R 2 = 0.98) (chart inside). Similar correlation was observed for the non-aerated egg white gels [19]. Chen et al [31] observed that whey protein gel obtained without the sodium ions addition had a very smooth surface, with R q and R a (arithmetic average of the collected roughness points) of 0.20 and 0.18 μm, respectively.…”

“…Lately Kewpie Corporation has produced a new low-mineral egg white isolate. Based on this product, Ca-induced egg white protein gels with a various microstructure were obtained [19].…”

Co-Gelation of Pumpkin-Seed Protein with Egg-White Protein

“…Egg-white gel has a very homogenous microstructure with very small particles (Figure 8c'). This phenomenon can be attributed to the fact that the egg-white protein isolate used in the research was an experimental preparation obtained by Kewpie Egg Corporation, which contained a very small concentration of ions [24,25]. Heat-induced gelation in the 0.2 NaCl solution resulted in a fine-stranded gel being obtained (Figure 8c') [26].…”