Abstract:To make the wheat germ treated with superheated steam better used in bread production，the wheat germ treated with superheated steam stabilization was crushed to obtain wheat germ flour of different particle sizes. The effects of the addition amount and particle size of wheat germ flour on the characteristics of blended flour，bread sensory evaluation score，bread antioxidant properties，and bread staling were investigated. The results showed that with the increase in wheat germ flour addition，the content of wet gluten，lactic acid solvent retention capacity（SRC），gluten performance index，pasting viscosity，and breakdown value of mixed flour decreased. The SRC of water，sucrose and sodium carbonate increased. As the addition amount of wheat germ flour increased，the texture and internal structure of the bread deteriorated，and the specific volume and sensory evaluation score of bread decreased，while the antioxidant property of the bread improved. When the addition amount of wheat germ flour reached 9%，the polyphenol content in bread increased by more than 94% compared with the blank control group. The DPPH and ABTS+?free radical scavenging ability increased by more than 88% and 37% respectively compared with the blank control group. The staling rate of bread showed an increasing trend with more wheat germ flour added. X-ray diffraction（XRD） data also revealed that the wheat germ flour added accelerated the crystallization of starch. With the same addition amount，the fineness of wheat germ flour also had a certain impact on the mixed flour and bread quality. During the gelatinization process，the viscosity indexes values of the blended flour with wheat germ flour sieved through 60 mesh was lower than that with the wheat germ flour sieved through 80 mesh and 120 mesh. Although the bread made of flour with wheat germ flour sieved through 60 mesh was harder，the internal structure of the bread was more even，the loss rate of antioxidant substances was lower，and the sensory evaluation score was higher. The staling rate of bread added with large particle size wheat germ flour was lower，which was also reflected in the starch retrogradation value，starch retrogradation enthalpy，and XRD data. Therefore，the particle size of wheat germ flour used in bread production should not be too small.