Effect of storage conditions on the quality of frozen steamed bread

With advantages of long shelf life, high convenience and reliable safety, frozen steamed bread (FSB) is suitable for industrial production. Storage conditions are critical factors influencing the final quality of FSB. In this study, the effects of storage time, storage temperature and freeze-thaw cycles on the quality of FSB were evaluated. Results showed that the water loss of FSB and the retrogradation of the starch occurred during the storage process. The final gelatinization degree of FSB decreased from 88.69% to 86.37%, whereas the crystallinity gradually increased from 16.78% to 18.47%. As storage temperature of -18 degrees C could not kill microorganisms, metabolites of microorganisms caused a decrease in the pH value from 5.41 to 5.10 after the 90 d of frozen storage at -18 degrees C. Re-steaming properties results showed that the specific volume and whiteness of re-steamed FSB decreased significantly with the storage time, as well as the textural properties and sensory evaluation score. Furthermore, freeze-thaw cycles were found to accelerate the quality deterioration of the FSB, and compared with the temperature of -18 degrees C, frozen temperature of -30 degrees C alleviated the quality deterioration of FSB.