Asterisk artifacts appeared on foods surface caused by the makeshift direct method of critical point dry

Whether the asterisk artifacts are appeared on the surface of food specimens prepared by using the makeshift method for SEM are examined. The samples of boiled eggs, steamed eggs after stirring, custard pudding, jelly, milk gels, Tofu, and soybean milk-gels were observed by two different methods of critical point drier, the ordinary method (absolute ethanol -> iso-amyl acetate -> liquid CO2), and the makeshift direct method (absolute ethanol -> liquid CO2). The asterisk structure were appeared in SEM graphs of albumen, steamed eggs, pudding, jelly and Tofu except yolk, milk-gels, soybean milk-gets prepared by the makeshift direct method, but none of them were appeared in SEM graphs of all specimen prepared by the ordinary method. Therefore, the asterisk structures were artifacts caused by supercritical fluid extraction with CO2 transferred from ethanol during critical point dry. The asterisk artifacts were appeared on the surface of some kinds of protein gels of foods whether animal origin or vegetable origin. Accordingly, protein gels of foods should be prepared with the ordinary method using iso-amyl acetate.