## 1 Introduction  
The market of industrially produced dried mango is steadily growing due to its good taste, unique flavor, attractive color, and nutritional value [1]. To produce high-quality dried mangoes, fruit-drying industries are paying special attention to the activity preservation of enzymes in the dried product. The ultimate challenge for the modern food industry is not only to minimize the degradation of beneficial enzymes, but also to maximize the preservation of these enzymes in the final dried product. As people are becoming more conscious of their diet, the use of enzyme supplements has also increased considerably in recent years. In this regard, raising consumer awareness and specifying a product by its nutrients (enzyme units) could have a substantial effect on increasing its demand. The advantage of producing dried mango, in which a high proportion of the enzymes amylase and invertase is retained, is that it can be used in a wide range of applications such as functional foods, bread making, brewing, food supplements, and animal feed. As enzymes are proteins in nature, they must be characterized with regard to their temperature-dependent behavior. In this study, amylase and invertase were selected as the model enzymes. The selection was based on the enzymes that are most commonly studied in fresh mango of different varieties and are present in a concentration that is easy to measure [2; 3]. In addition, amylase and invertase are the most important carbohydrate digestive enzymes, as they break down complex carbohydrates into simple sugars. Hence, mango flesh can contribute as a source of natural digestive enzymes. Fresh mango is extremely perishable and susceptible to rapid decay due to ripening and biochemical degradation, resulting in a poor shelf life. Thus, in order to consume this fruit all year long, drying is widely used technology in food processing and preservation. To date, several drying methods, such as hot-air convective drying, infrared drying, vacuum drying, microwave drying, and freeze drying have been applied to fruits, vegetables, and herbs to prepare dehydrated products [4; 5; 6; 7; 8]. However, convective-air drying is most commonly used due to its easy operation, as well as low investment and operating costs [9]. It is also well known that hot-air drying is primarily influenced by the drying temperature and air velocity [10; 11; 12], whereas specific humidity has no major influence on the drying rate, except that its higher value decreases the drying rate [13]. Mango and other tropical fruits are commonly dried at temperatures ranging 40 \({}^{\circ}\)C to 80 \({}^{\circ}\)C, and air velocities of 0.2 to 2.0 m s\({}^{-1}\), to a target moisture content of 10-15 g 100 g\({}^{-1}\) wet basis [14; 15; 16; 17]. Several researchers have extensively documented the effects of the selected drying conditions on the physicochemical and nutritional parameters of dried mango [6; 18; 19; 20; 15]. Only a few studies, however, focus on the enzymatic activity in particular. In most of these studies, considerable efforts have been undertaken to understand the inactivation of the enzymes during fruit drying [21; 22; 23]. However, to the best of our knowledge, no study is available dealing with the effect of drying temperature and air velocity on the activity retention of amylase and invertase in dried mango. As enzymes are very diverse in nature, drying at different temperatures and air velocities could contribute to different degradation rates of enzymes due to differences in drying time, exposure to heat, light, and oxidation. Consequently, the activity preservation of the enzymes in the final dried product may be significantly affected under different drying conditions. Therefore, it is highly important to obtain information about the drying operating parameters and its relationship with activity retention of enzymes in dried mango, due to the health benefits of the enzymes.