There are many reasons why moon cakes do not return oil: the conversion degree of syrup is not enough; When boiling syrup, the fire is too big; Syrup returning to sand; Too much citric acid; The stuffing is mixed with more powder; The filling is too oily; Improper proportion of syrup, oil and scooping water; Flour gluten is too high. Solution: 1, the quality of converted syrup The key to the quality of syrup is its conversion degree and concentration. Conversion degree refers to the degree to which sucrose converts glucose and fructose. The higher the degree of conversion, the better the oil return of cake crust. The main factors affecting the conversion degree are the amount of water added, the amount and type of acid added and the boiling time. Concentration refers to the sugar content, and the commonly used concentration of invert syrup is about 75%. Because the higher the sugar content, the better the oil return, so some manufacturers increase the concentration to more than 85%. 2. Formulation and manufacturing technology of the crust. The formulation and manufacturing technology of the mooncake crust play an important role in whether it returns oil or not. If the flour used in the formula is 100%, it is impossible to add 35% oil because 25%-30% has reached the peak. If only the proportion of syrup, oil and scooping water is considered, the amount of flour is adjusted according to the hardness, so that the flour cap in the dough will not be stable. It is unscientific for many domestic manufacturers not to design the formula into a standard formula. If the moon cake does not return oil, it is probably because of the formula of the material. The dough should be prepared according to the ratio of flour 100%, syrup 75% and oil 25%. If moon cakes are produced according to this idea, the crust will not return to oil, indicating that the quality of invert syrup is too poor. (1) The ingredients of the cake crust should be reasonable: the water content, oil content and syrup dosage of the moon cake crust should be coordinated. Too much syrup, too little oil, poor gloss of cake crust; Too little syrup and too much oil will soften the skin. (2) The hardness and oil content of mooncake fillings should be appropriate: Cantonese mooncakes are characterized by thin skin and thick fillings, and fillings are the main factors to assist in softening. If the water content and oil content of the stuffing are low, or the stuffing with thick skin is less, the moon cake will gradually soften.