## 1 Introduction  
Exotic fruits are gaining popularity all over the world due to their taste and nutritional value. The edible part of these fruits is the flesh. The wastes resulting from fruit processing--the peel and seeds--may constitute from 5 to 35% of the whole fruit weight and usually remain unused [1; 2]. The lack of commercial utilization of these wastes is associated with insufficient knowledge of their nutritional and functional properties, as well as fear of the presence of antinutrittional compounds in them [3; 4]. The appropriate use of waste could reduce the problem of overconsumption, especially in countries where these fruits are produced on a large scale [5], while fitting in with the \"zero waste\" trend. This idea was created to counter the effects of food waste, and it aims to get consumers to emulate sustainable natural cycles in which all materials used are resources for use by others [6]. There are concerns among consumers about the presence of anti-nutritional compounds in seeds, which is mainly due to the lack of knowledge about their actual amount and the possibility of their elimination. In order to eliminate the presence of antinutrittional compounds, the seeds should be subjected to appropriate treatment, i.e., soaking, cooking, drying or fermentation [3; 7; 8]. In addition, antinutrittional compounds, mainly oxales and phytates, may be present in some seeds--such as those from mangoes--but their content is often described as trace [8; 9; 10].  
Taking into account the available literature data on the high content of bioactive compounds with antioxidant properties in exotic fruits [11; 12; 13], it can be assumed that their seeds can also be a valuable source of these compounds [14; 15]. Antioxidants are characterized by multidirectional effects, and the consumption of products that are sources of antioxidants is essential for maintaining health [4; 16; 17]. One of the most important functions of antioxidants is counteracting the formation of free radicals, whose excessive accumulation in the body translates into accelerated aging processes and decreased efficiency of the immune system. Moreover, free radicals may damage cellular molecules and structures, resulting in their malfunction [18; 19]. A diet rich in antioxidants reduces the risk of diseases such as diabetes, atherosclerosis, hypertension, heart disease, cardiovascular disease and cancer [19; 20; 21]. Food processing methods, especially in the effects of high temperatures and the presence of oxygen, have a significant impact on the content of bioactive ingredients in food. Convection drying, due to the use of high temperatures and long processing times, can contribute to high losses of bioactive components [22; 23; 24]--higher than in the case of sublimation drying, which, due to the use of low temperature and lack of oxygen, allows the preservation of high biological, chemical and physical properties of dried raw materials and causes lower loss of bioactive compounds [25; 26; 27]. Nevertheless, the use of freeze-drying processes is limited mainly due to the higher cost of these processes compared to other commonly used drying methods (convection drying, spray drying) [23; 25].  
The available literature lacks comparative data on the functional properties of exotic fruit seed powders obtained with various drying methods; therefore, this study compares the effects of various drying methods, i.e., convection (CD) and freeze-drying (FD), of fruit seeds on the content of tannins, total polyphenols, antioxidant activity, color and taste profile of powders obtained from mango (_Mangeifera indica_ L.) and rambutan (_Nephelium lampaceum_ L.), originating in Southeast Asia (Malaysia).