## 4 Discussion  
The effect of sugar substitution with SGs on the sensory quality of very-low-sugar apple jams was evaluated in this study. The sensory evaluation results showed that a high amount of sugar substituted with steviol glycosides (up to 90%) reduced the desirability of the very-low-sugar apple jams, even though the amounts used were small. Compared to low-sugar apple products with the addition of steviol glycosides, their sensory quality was better, as demonstrated in previous studies [11]. The low-sugar products were characterized by a more intense sweet taste and a darker color due to the higher sugar content. They also had a higher intensity of responses regarding metallic and \"other\" taste and odors, as well as a sharp odor, a bitter taste, an stringent sensation, and a bland flavor, which consequently influenced the sensory balance of the products [11]. Other authors also point to an increase in the intensity of metallic, licorice, and other negative flavors instead of sweet and fruity flavors [56; 57; 58]. This is associated with a dominant bitter taste and a reduced perception of sweet taste, which is explained by intermolecular cross-suppression between steviol glycosides responsible for sweet and bitter tastes [58; 59]. Therefore, using low levels of steviol glycosides, as in the case of this study, improved the taste, eliminating the bitter taste of licorice. [PERSON] et al. [60] suggest that steviol glycosides should constitute 20-80% of the sweetness, with sucrose accounting for the rest, obtaining characteristics similar to sugar use. The sensory quality of very-low-sugar apple jams with a 50% SG substitution level did not differ significantly from the control sample, i.e., jam with only sugar. It should also be emphasized that adding pectin and citric acid may mask the negative effect of steviol glycosides, increasing the natural flavor of apple products, i.e., the wine or apple flavor, thus allowing for the possibility of increasing the addition of SGs. Similar data are reported by [PERSON] et al. [61] for quinte jam and by [PERSON] et al. [26] for strawberry jam. The Effect of Storage on the Sensory Quality of Very-Low-Sugar Apple Jams with Sugar Substitution by SGs  
For consumers and food producers, the sensory properties of food products are essential because they directly relate to the product's quality and further consumer acceptance. A product's quality assessment is based on sensory indicators such as color, odor, taste, and consistency. In the studied jams, the sugar content was reduced by substituting it with steviol glycosides, which were sensorily accepted by the evaluators. Adding pectin and citric acid to apple jams with added steviol glycosides improves their sensory quality. It stabilizes the color and physicochemical composition, and, as mentioned earlier, it can mask the adverse effects of SGs, thus enhancing the natural flavor properties of apple products, i.e., wine or apple flavors, as demonstrated in previous studies [11]. Storage time did not significantly affect sensory changes in the very-low-sugar jams (overall quality parameters in the range of 8.5-5.5 c.u., depending on the level of substitution and the storage time). The highest overall quality was noted for the jam with a 30% substitution with steviol glycosides. Moreover, after 3 and 6 months of storage, no statistically significant differences were found in terms of bitter, sweet, or apple taste, i.e., characteristic features of apple jams. Similar results were also indicated by other authors who showed high sensory quality scores of jams with SG substitution after the preparation and storage of cherry jams [62] and strawberry jams [63]. After 12 months of storing cherry jams, only a slight decrease in the intensity of the cherry flavor was observed [64]. In all stored jams, the color darkened, and the darkest color was characteristic of samples containing only sucrose. Color changes may result mainly from Maillard reactions and the formation of non-enzymatic browning products.