Effect of Steam Addition Frequency on the Quality of Bread Rolls

The effects of steam addition frequency (low, medium, high;steam added every 4, 2, 1 min) on the quality of bread rolls were studied by measuring the heating curve, texture, acrylamide content and flavor substances. It was found that steam addition led to a gradual increase of center temperatures of bread rolls. Compared with the baking process without steam addition, the baking process with steam addition in high or medium frequency led to the decrease of the baking loss of bread rolls (P<0.05). With increase of steam frequency, the L^* value and b^* value of the center of bread rolls increased, while the a^* value decreased. According to the texture measurement, the hardness of the center crust and the whole bread rolls were significantly reduced by steam addition (P<0.05), and the chewiness and resilience tended to decrease and then increase with the increase of steam addition frequency. The addition of steam increased the relative content of alcohols, nonanal and 3-hydroxy-2-butanone, while the relative content of furfural decreased, which made bread rolls with a stronger aroma and less burnt taste. At the same time, the addition of steam changed microstructure, and reduced acrylamide production in the whole bread rolls and its crust. In the crust, the acrylamide content decreased from 350 μg/kg to 218, 141, and 83 μg/kg (high frequency, medium frequency, and low frequency in turn), respectively. And the acrylamide content of the whole bread decreased from 74 μg/kg to 59, 55, and 41 μg/kg (high frequency, medium frequency, and low frequency in turn), respectively. The lysine residual amount of crust was significantly increased (P<0.05), from 0.97 g/kg in the non-steam group to 1.58 g/kg in the high frequency group. Finally, by conducting sensory evaluation, it was found that the color of bread rolls was moderate and the nutritional quality and safety were superior, when the steam addition time interval was 2 min.