Beef and emu steaks were restructured with 5% fibrinogen/0.25% thrombin (F), 0.5% algin/0.5% calcium lactate (A), or 0.5% phosphate/1.5% salt (P). P and A treatments had higher cooked binding strengths and cook yields than the F treatments (P < 0.05). The pH and cook yields of restructured emu were higher than beef (P < 0.05). Binding strength of emu was lower than beef in all binding systems (P < 0.05). F solution had an aerobic plate count (APC) of 39,000/g and increased the microbial count in restructured emu steaks from 940 to 7500/g (P < 0.05). Cooking to 60 °C reduced APC to < 250/g (P < 0.05) with progressively greater bacterial kill after cooking to 66 °C or 75 °C.

The correlations between water state and the key factors affecting sourdough quality, including cell activity and acidification capacity of lactic acid bacteria (LAB), were established in this study. Results revealed that with the increase of frozen storage time, the cell density (CD), total titratable acidity (TTA), and organic acids content declined, whereas the pH value rose. Further, the freezable water content (FWC) and free water quantity (FWQ) decreased, but the total water loss rate (WLR) and immobilised water quantity (IWQ) increased. The CD showed a highly inversely correlation with WLR, and the pH value was strongly inversely correlated to the FWQ. The confocal laser scanning microscopy (CLSM) observed that the ice crystals had larger volumes during frozen storage. Our data, for the first time, disclosed that the total water content and the FWQ may play a crucial role in maintaining the viability and acidification capacity of LAB in frozen sourdough.