Question 1: This work could be of interest, but in its current form it is difficult to assess. The text is poorly written, and it is difficult to understand the meaning of many phrases. Furthermore, the references are inappropriately placed in the text, which is riddled with inconsistencies. For example: ”At present, there are few types of healthy oils and fats on the market, and the quality is uneven.” Are you sure that there are few healthy oils on the market? Please provide a reference. ”Compared with TAG, DAG has similar energy value, digestibility and antiobesity characteristics. Their calorific value is low, which has a positive effect on lipid metabolism, decreasing total serum cholesterol, low-density lipoprotein cholesterol, and fat accumulation, thereby reducing liver and abdominal fat levels.” If you affirm that TAG and DAG have the same properties, it is not worth carrying out the study that you have carried out…This is a sample of the poverty of expression throughout the entire manuscript.
We sincerely thank the reviewers for their careful reading. We have rewritten lines 49-130 on pages 3-5 of the original manuscript as follows:
Therefore, it is of great significance to further increase the content of DAG in human diet for health. The preparation methods of DAGs are principally chemical and biological enzyme methods. The chemical method has advantages of high reaction rate and simple operation (Zhong et al., 2010). However, it increases the cost incurred in removing organic reagents from the product. The bioenzymatic method using lipase as a catalyst can effectively avoid contamination with organic reagents. At present, the main methods for the preparation of DAGs by bioenzymatic methods are esterification, hydrolysis, glycerolysis, and transesterification. The esterification method uses lipase as a catalyst to esterify free fatty acids (FFAs) and glycerol in water to obtain DAGs. This method requires the use of vacuum, silica gel, molecular sieves, and nitrogen stream to separate the water produced in the reaction (Arcos et al., 1998; Weber & Mukherjee, 2004; Lo et al., 2004). In the hydrolysis method, the fatty acids in TAG are substituted with alcohol hydroxyl groups in the presence of water and lipase to form FFAs, DAGs, monoacylglycerols (MAGs), and glycerol. The disadvantage of this method is that the degree of hydrolysis is difficult to control and often occurs at the oil-water interface (Li et al., 2018). The DAG content obtained by a single method is not high, and the product has to be purified by molecular distillation, solvent crystallization, supercritical CO2 extraction, and silica column chromatography (Huang et al., 2023; Li et al., 2018). Combining multiple methods may be an effective way to prepare samples with high contents of DAG. Li et al. (2021) partially hydrolyzed soybean oil using Lipase DF “Amano” 15 and obtained DAG content of 55.2% by molecular distillation. Other products were combined with PGL AOL-V269 D esterification reaction and molecular distillation to obtain high purity DAG (99.3%). Liu et al. (2020) prepared DAGs rich in α-linolenic acid by a two-step enzymatic method. The combination of Lipase TL100L and Lipase PCL hydrolyzed silkworm pupae oil to obtain 96.51% FFA, and then silkworm pupae oil diglyceride oil with a purity of 97.01% was obtained by molecular distillation after esterification catalyzed by lipase PCL. Based on the above analysis, it is indeed feasible to prepare a high content of DAG by coupling two or more methods.