## 3 Results and Discussion
### Shelf Life Analysis of Produced Cookies
#### 3.4.5 Sensory Analysis  
The scores (intensity and acceptability) for the sensory characteristics of the cookie samples (control, 4% SCG-added, and 7% SCG-added) on the first day and after 143 days of storage at 25 \({}^{\circ}\)C, 35 \({}^{\circ}\)C, and 45 \({}^{\circ}\)C are presented in Figure 7a-f. The sensory scores were mainly attributed to the changes in cookie color and texture (at the initial storage time). Defatted SCG incorporation increased the darkness and reduced the surface smoothness of the cookies. As the addition level increased, the hardness and density of the cookies significantly increased (\(p<0.05\)), while the color became darker. [PERSON] et al. (2008) reported that the addition of cereal bran to cookies resulted in darker and harder cookies, leading to a decrease in sensory quality regarding the color and texture [47]. The sensory changes produced by the addition of coffee skin to other baked products and their influence on acceptability have also been reported. For instance, [PERSON] et al. (2022) produced vegan biscuits by replacing wheat flour with Coffee Silverskin (CS) at 2%, 4%, and 6% [28]. A decrease in the acceptability of the sensory attributes (appearance, smell, taste, flavor, texture, and general acceptance) with the addition of CS was reported. The authors suggest that the low scores obtained in general acceptability could be attributed to the development of unpleasant non-volatile compounds during Maillard reactions and/or the natural presence of certain compounds in CS. These compounds include caffeine (contributing to bitterness), polysaccharides, humic acids, chlorogenic acids  
Figure 6: Total Phenolic Content (TPC) of (**a**) 4% SCG-added and (**b**) 7% SCG-added cookies stored at 25 \({}^{\circ}\)C, 35 \({}^{\circ}\)C, and 45 \({}^{\circ}\)C for 143 days. (contributing to astringency), and particularly carboxylic acids such as malic, citric, and acetic, which contribute to acidity. Regarding the low acceptability scores of food products enriched with CS [28,59], it is worth exploring strategies to mitigate the undesirable sensory changes that contribute to consumers' rejection related to sensory characteristics induced by the presence of CS (such as dark color, low sweetness, roasted flavor, intense/coffee flavor, burnt/bitter taste). In this study, SCG-added cookies were characterized by a mild and desirable coffee flavor due to the former removal of coffee oil from SCG, which would have caused a very aggressive flavor. The scores for the intensity of coffee flavor were significantly higher for the 7% SCG-added cookies compared to the 4% SCG-added cookies (\(p<0.05\)) (Figure 7a-c). Though the total sensory quality was evaluated as positive, the acceptability scores for all sensory characteristics were more than 7/9 (Figure 7d-f). The sensory quality loss in cookies results from the increase in hardness, the increase in reactivity, and the development of off-odors and off-flavors [52,60]. The scores for characteristics, appearance, crispiness, taste, aftertaste, and rancidity of the control and SCG-added cookies remained constant (based on the scores given for the intensity on a scale of 1 to 9) during storage (143 days). The scores for odor intensity decreased with an increase in storage time, while the scores for hardness increased with an increase in storage time. The scores for color, odor, hardness, and crispiness of 4% SCG-added cookies samples were significantly increased with storage time and temperature (\(p<0.05\)).