Effect of Proteolytic Modification on Texture and Mastication of Heat-Treated Egg White Gels.

Raw egg white undergoes sol-gel transition by heat treatment, which changes it to an elastic gel. Here, protease treatment to render a new texture to heated egg white gel was applied. Protease-treated gels exhibited ductile flow without obvious rupture points. Transmission electron microscopy analysis showed that in protease-treated gels, protein aggregates were distributed more homogeneously compared with that observed in the untreated control, probably because ovalbumin was digested into small peptides as revealed by SDS-PAGE. The properties of the gel were evaluated by sensory tests and by measuring the movement of the masseter muscle, using surface electromyography. Results showed that maximum bite force and mastication duration were decreased for the protease-treated gels, which were evaluated as being softer, smoother, less elastic and better textured. Overall, our results indicate that protease-treated egg white gel has superior qualities and is easier to swallow than the untreated gel. PRACTICAL APPLICATIONS: In the food industry, the use of egg white is limited compared with that of egg yolk and whole eggs. In this study, we performed protease treatment to generate a new food material with smoother and softer texture compared with heat treated egg white. Our findings may expand the consumption of egg white, which can be consumed by people with mastication and swallowing disorders, and reduce the waste of egg white as a surplus product.

Application of an Aspergillus saitoi protease preparation to soybean curd to modify its functional and rheological properties.

An Aspergillus saitoi protease preparation, Molsin, was found to contain beta-glucosidase as well as protease activities. Application of Molsin to soybean curd improved its functionality by converting the contained isoflavone glycosides to their aglycones through beta-glucosidase, and also modified the rheological property into a creamy consistency through protease. The enzymatically modified soybean curd was characterized by a ductility flow having no particular rupture point.

Intracellular alkalinization induces Ca2+ influx via non-voltage-operated Ca2+ channels in rat aortic smooth muscle cells.

In smooth muscle, the cytosolic Ca2+ concentration ([Ca2+](i)) is the primary determinant of contraction, and the intracellular pH (pH(i)) modulates contractility. Using fura-2 and 2',7'-biscarboxyethyl-5(6) carboxyfluorescein (BCECF) fluorometry and rat aortic smooth muscle cells in primary culture, we investigated the effect of the increase in pH(i) on [Ca2+](i). The application of the NH(4)Cl induced concentration-dependent increases in both pH(i) and [Ca2+](i). The extent of [Ca2+](i) elevation induced by 20mM NH(4)Cl was approximately 50% of that obtained with 100mM K(+)-depolarization. The NH(4)Cl-induced elevation of [Ca2+](i) was completely abolished by the removal of extracellular Ca2+ or the addition of extracellular Ni2+. The 100mM K(+)-induced [Ca2+](i) elevation was markedly inhibited by a voltage-operated Ca2+ channel blocker, diltiazem, and partly inhibited by a non-voltage-operated Ca2+ channel blocker, SKF96365. On the other hand, the NH(4)Cl-induced [Ca2+](i) elevation was resistant to diltiazem, but was markedly inhibited by SKF96365. It is thus concluded that intracellular alkalinization activates the Ca2+ influx via non-voltage-operated Ca2+ channels and thereby increases [Ca2+](i) in the vascular smooth muscle cells. The alkalinization-induced Ca2+ influx may therefore contribute to the enhancement of contraction.