# Optimization and Preparation of Tallow with a Strong Aroma by Mild Oxidation
## 1 Introduction  
Tallow is a form of rendered fat and is classically made from beef. When the slaughtered cattle are raised to the slaughter condition, a large amount of adipose tissue will be accumulated under the epidermis, between muscles, in the abdominal cavity, intestinal region, and other parts, and the tallow adipose tissue obtained by segmentation is refined by using an appropriate processing method to obtain edible grease, which is called tallow [1]. Tallow is widely used in food processing because of its good flavor and is often used as the processing raw material of shortening, cakes, and other foods [2]. As the soul of the Sichuan and Chongqing hotpot, tallow played an important role in the formation of the hotpot flavor, both in its own flavor and the flavor changes produced during the cooking process [3]. According to the previous analysis of the aroma of 41 old hot pot allow, it was found that the strong aroma tallow was particularly popular. Therefore, in this experiment, the strong aroma tallow was prepared through the mild oxidation of fat to meet the needs of consumers [4]. Lipid oxidation is an important pathway for the formation of characteristic meat flavor compounds. The research by [PERSON] et al. [5] has shown that the basic meat flavors of all kinds of meat flavors are the same, while the differences in characteristic meat flavors mainly come from the thermal oxidation degradation reaction of fat, in which heating-induced oxidation of unsaturated hydrocarbon chains in lipids is an important pathway and generates a variety of volatile compounds, including fatty aldehydes, ketones, and acids. Oxidation of fat at a normal temperature will produce a rancid taste, while oxidation under heating conditions will produce characteristic flavor substances, which are the main basis for adding fat and regulating fat oxidation in the production processof meat flavor essence. Therefore, in order to obtain the oxidized fat rich in volatile compound components, air heating can be used to regulate fat oxidation. The thermal reaction meat flavor product prepared by adding oxidized fat has the advantages of strong aroma, prominent characteristic flavor, etc. [6]. Due to the complexity of lipid oxidation and the uncertainty of factors, as well as the limitation of analytical methods, the research progress on the regulation of the preparation of flavor precursors from oxidized fat is relatively slow, but some research results have been achieved. The research on the regulation of fat on oxidation is not systematic and it has only been reported in the early patents. For example, [PERSON] and [PERSON] [7] treated tallow with air heating under conditions of 150-170 \({}^{\circ}\)C, and then mixed and heated the obtained oxidized tallow with fermented soy sauce to prepare the roast beef essence. [PERSON] [8] controlled the triglyceride oxidation process by altering the moisture and metal ions in the system and prepared the flavor concentrate by mild oxidation. [PERSON] [9] prepared milk flavor by mildly oxidizing milk fat to increase the content of 3-methylbutanal and 2-nonenal. There were many studies on the regulated oxidation of fats in China. In general, there were mainly two oxidation methods: high-temperature heating-controlled oxidation and enzymatic mild oxidation. There were differences in the fragrance of the products obtained from the thermal reaction of these two kinds of oxidized fats, with the former being the \"barbecue\" flavor, and the latter being the \"stewed\" flavor [10]. For example, [PERSON] [11] oxidized tallow at 160-170 \({}^{\circ}\)C for 40 min and then thermally reacted with fermented soy sauce and cysteine to produce beef essence. [PERSON] and [PERSON] [12] explored the regulation of tallow oxidation by response surface methodology and determined the optimal process conditions as follows: a reaction temperature of 158.2 \({}^{\circ}\)C, a reaction time of 5.28 h, an airflow rate of 1.49 L/min, and an antioxidant V\({}_{\text{E}}\) addition of 0.15%. [PERSON] et al.