## 2 Results and Discussion
### Application of the HS-SPME/GC-MS Method to Strawberry Jams  
Strawberry is a very delicious fruit, cultivated in nearly all countries of the world. Strawberry has always been a favored raw material for the production of various food products such as jams and juice, due to its unique aroma and attractive color. Aroma is a prerequisite for quality control; thus, its stability and retention in various food products is of great interest due to its strong relationship with consumer's acceptability of foods. During preparation of fruit products, different additives are used that influence food product physicochemical properties, aroma, texture, and color [13]. It is generally known that the aroma and flavor of fruit products changes drastically during manufacturing, processing, and storage. Various compounds have been reported to degrade over time, whereas others are formed. In most cases, these degradation and formation reactions lead to a deterioration of the original aroma of the product. Consequently, the shelf-life of commercially available fruit jams, juices, and nects is not limited by microbial spoilate but by a drastic decrease in the sensory quality of the products due to chemical reactions [44]. In the present work, the nature of the aroma present in strawberry foodstuff such as jam was investigated. A summary of aroma active volatiles from the various strawberry jams analyzed by the SPME/GC-MS technique is shown in Table 1. According to the relative percentage of volatiles present in the analyzed strawberry jams, terpenids were the most abundant class in Jam 2 and Jam 1, accounting for 79.24% and 53.31% of the total volatile composition, respectively, and these results are consistent with a previous report where terpen were found as the most dominant class in jams of cranberry, blueberry, raspberry, and blackberry/blackcurrant [45]. On the other hand, acids and aldehydes were the most abundant classes in Jam 3 (32.03%) and Jam 4 (27.86%), respectively, followed by terpen which accounted for 30.31% and 26.86% of the total volatile fraction, respectively. Nerolidol was the most dominant terpene in Jam 1 (40.99%), Jam 4 (17.92%), and Jam 2 (13.75%), while limonene was the highest terpene in Jam 2 (58.05%). Linalol was detected in a moderate amount in jam 3 (5.18%), and in low levels in Jam 1 (0.70%) and Jam 4 (0.49%), while it was not detected in Jam 2. Terpenes, such as linalol and nerolidol, contributed with floral, and citrus aroma notes. It is worth noting that \(\alpha\)-terpineol was detected in high amounts in all analyzed strawberry jams in a range from 2.09% to 8.75%. \(\alpha\)-Terpineol has been reported as a potential off-flavor metabolite in strawberry juice [28; 34], and it contributes with a \"woody\" and \"piney\" aroma note [45]. Aldehydes such as furfural, benzaldehyde, and 5-hydroxymethylfurfurral were detected in all jam samples. Furfural showed the highest amount, followed by benzaldehyde and 5-hydroxymethylfurfural, and Jam 4 was the richest one in these three aldehydes with concentrations of 17.22%, 9.8%, and 0.5%, respectively. Thermal treatment might further lead to the formation of new volatile structures; for example, 5-hydroxymethylfurfural (HMF) and furfural are heat-induced chemical markers generated during strawberry jam preparation and baking of cereal-based products [16; 17; 28; 41]. Therefore, the high levels of furfural and 5-hydroxymethylfurfural in jams are justified due to heat treatment under jam processing. Similarly, these two compounds were detected only in heat-drying methods such as oven and microwave and not detected in freeze-dried and frozen samples. Esters, imparting important fruity attributes to foods, were not detected in all jam samples except Jam 2 which possessed only traces (0.12%), compared to 36.96% in fresh strawberry fruits. Furthermore, alcohols were totally absent in Jams 3 and 4, while they were found in small amounts or traces in Jam 1 (0.25%) and Jam 4 (0.09%) compared to fresh fruits (17.10%).