Abstract: Liquid egg was fermented with a mixed starter culture of Lactococcus lactis, Streptococcus thermophilus and Moniliella mellis before being used to make custard tart. The effects of different fermentation conditions (inoculum amount, fermentation time and temperature) on the flavor and texture of custard tart were studied by one-factor-at-atime and orthogonal array design methods. The results showed that the optimum fermentation conditions were as follows: inoculum size 2%, temperature 42 ℃, and time 42 h. The prepared custard tarts were intact in shape without any crack and the custard was solidified with bright yellow color, moderate sweetness and the best organoleptic quality. The textural properties were determined as follows: firmness 87.8 g, adhesion force 18.3 g, cohesiveness 74.3 g·mm, and gel strength 730.6 g·mm. Nutrient composition analysis showed that the crude protein in fresh liquid egg displayed a decreasing trend after fermentation while the contents of total amino acids, essential amino acids and umami amino acids were increased from 7.55%, 3.26%, and 3.08% to 9.13%, 4.01%, and 5.15%, respectively. In addition, the pH value changed from neutral (7.6) to acidic (5.1) condition. Analysis by GC-MS showed that a total of 24 and 46 volatile components were identified in the fermented egg liquid and the prepared egg tarts, which significantly increased compared to the unfermented egg (15) and the corresponding egg tarts (31), respectively. The characteristic flavor components of the fermented egg tarts were mainly hexanal, furfural, acetoin, butyl-butyryllactate and 2,5-dimethylpyrazine, exhibiting a unique aromatic flavor. In conclusion, the egg tarts prepared with fermented liquid egg were richer in flavor and nutrients. This study provides a theoretical basis for the application of fermented liquid egg in baked foods.

Key words: liquid egg, fermentation, custard tart, flavor