Thin sheets of bean curd treated by cold plasma: Changes in surface structure and physicochemical properties

Thin sheets of bean curd (TSBC), a favorite food in China, is mostly vacuum packed to maintain the shelf life. However, the vacuum packing processing will cause adhesion between sheets, which is difficult to peel. To solve this problem, a rapid dehydration technique for the TSBC using cold plasma was developed. The surface structure and physicochemical properties of the TSBC treated by cold plasma were evaluated. The results indicated that water contact angle increased from 0 degrees to 66.37 degrees and 66.94 degrees, and adhesion between sheets decreased from 2.81 g. sec to 0.01 g.sec. It was due to the removal of the bulk-phase water from the TSBC. And scanning electron microscopy showed the formation of a dense structure on the TSBC surface. Moreover, surface structure determination revealed that the cold plasma etching led to the depolymerization of protein and the exposure of hydrophobic points without any effect on the primary structure.