Surface Gelation of Steamed Bread
Surface gelation is a common and troublesome product failure at both commercial production and laboratory testing levels, especially for steamed breads produced with lean formulations. The effect ranged from minor ‘burned skin’ to full gelation (Fig. 7). The phenomenon of surface gelation appears to be related to flour properties and processing, and is very random. It occurs mostly at the moment cold air mixes with hot steam, and always starts at the bread surface. There was no published information related to the mechanism of surface gelation. The return to crystallinity could be the process responsible for the gelation after steam cooking and immediate cooling when the steamer is opened. Amylose forms opaque, partially crystalline, thermo-irreversible gels. Based on this hypothesis, additives which can prevent the crystallization of amylose should be able to reduce or eliminate bread surface gelation. This theory was confirmed by the fact that incorporation of 0.5% monoglycerides (MG) into steamed bread formulations can essentially prevent gelation on the steamed bread surface (Fig. 8).