## 3 Results and Discussion  
### Influence of Heating Techniques on Water Content  
Water present in food shapes its physical properties and also affects its safety and shelf life. As the water content increases, the possibility of microbial growth in food products increases, and their suitability for long-term storage without proper thermal treatment decreases. The extent of physical, biochemical, chemical, and microbiological changes that occur during the storage of food can be significantly reduced by reducing the water content of the product. The most commonly used methods are drying, smoking, freezing, and adding osmoactive substances, which also reduce water activity [21].  
The water content of the raw chicken breast fleet was 65.51% (Table 4). Statistically significant differences in water content in samples cooked with different techniques were shown. The lowest level of water content was reached in group samples of poultry stewed with traditional Br-A catering equipment (54.40%); this was about 10 percentage points lower compared to cooked breasts. The high temperature during the process of frying poultry causes denaturation of the protein and the formation of a barrier on the surface of the product, which limits the absorption of water during stewing [32].  
to microbiological changes. In many other studies, thermal treatment has significantly reduced the water activity to levels that prevent the development of microorganisms responsible for the health and hygiene condition of meat with extended shelf life [34]. There are no studies on the water activity of meat culinary products ready for consumption immediately after production. Due to the nutritional value and sensory quality of the products, the research conducted attempted to use innovative heat treatment procedures (sous-vide) without the need to reduce water activity.  
Chicken fillet samples obtained during the cooking process (heating groups A, B, C) did not differ in the level of water activity (Table 5). The water activity in the sample baked in the convection-steam oven (Ba-B) was 0.97 and this was the lowest of the samples in this group. Other samples, including raw chicken breast, were characterized by water activity at level 0.98. The statistical analysis showed no significant influence of the heat treatment methods applied on the water activity of the culinary samples obtained.  
The water activity of analyzed culinary samples stored for 24 h was varied, as confirmed by statistical inference. Baking sample Ba-A was again characterized by the lowest water activity (0.96). Statistically, significantly lower water activity was also determined in fried samples (F-B--0.97) and braised samples (Br-B--0.97) by heating technique B in the convection-steam furnace. The chicken breast, cooked by the sous-vide technique after 24 h of storage, was characterized by the same water activity as the sample immediately after production (Table 5). A decrease in the value of the test parameter after 48 h (0.97) and a re-increase after 7 days was observed, which may result from storage in a hermetically sealed film.  
The chicken breast cooked in the water vapor environment (C-B) was characterized by constant water activity (0.98) throughout the experiment. All samples showed an activity above 0.95, which indicates a high susceptibility to microbiological changes.