## 3 Results and Discussion
### VOC Flavor Profile of Concentrated Apple juice  
Eleven VOCs were detected in the sample of concentrated apple juice (Table 1). MS profiles of the VOCs identified in the apple juice sample are shown in Figure S2. The profile was dominated by seven medium-chain esters that likely contributed substantially to the flavor. All VOCs were detected in the headspace air of the concentrated apple juice with a probability \(>\) 65% and a match factor score higher than 700. Esters represent the main group of volatile compounds detected in commercial apple juice and are listed as pentyl acetate (amyl acetate) (rt = 4.428 min; top-priority three peaks of MS spectrum: 55, 61, 43), ethyl butyrate or ethyl butanoate (rt = 7.898 min; \(m/z\)= 43, 73, 88), butyl butyrate (\(m/z\) = 89, 43, 71; rt = 11.568), tetramethylene diacetate or 1,4-butenedi diacetate (rt = 8.250 min; three most significant peaks: 43, 61, 71), ethyl 2-methyl butyrate (rt = 8.775 min, \(m/z\) = 74, 102, 87), 2-methyl butyl acetate (rt = 9.490 min; three most prominent peaks: 70, 43, 45) and hexyl acetate, known as N-hexyl ethanoate (rt = 11.930 min; top-priority three peaks MS spectrum 69, 43, 61). Other compounds identified by the screening method were trans-2-pentene (rt = 7.562 min; three most significant peaks 55, 70, 42), 2,2-dimethyl-1-pentene (rt = 10.044 min;three most significant peaks 69, 41, 55), 3-furaldehyde (rt = 10.200 min, three most significant peaks 95, 96, 67), and a-Pinene oxide (rt = 12.045 min; \(m/z\) = 67, 82, 55). Pentyl acetate is the most-often used flavor in the beverage industry and has been reported to have a persistent, ethereal banana/apple odor. It was detected in many fruits: blackberries (_Rubus_), pears (_Pyrus pyrifolia_), apples (_Malus pumila_), papaya (_Carica papaya_), and cocoa beans (_Theobroma cacao_) (_Theobroma cacao_) (_Theobroma cacao_) (_Theobroma cacao_) (_Theobroma cacao_) (_Theobroma cacao_). Ethyl butyrate is a flavoring ingredient in food and drinks with a strong sweet taste like pineapple and an intense fruity odor similar to butyl butyrate (_Theobroma cacao_). According to the Human Metabolome Database, ethyl butyrate naturally occurs in many fruits, e.g., apples, apricots, bananas, plums, and tangerines. Butyl butyrate is used most often to prepare alcoholic beverages (_Theobroma cacao_) (_Theobroma cacao_). It is naturally present in several fruits such as bananas, cherries, melons, and plums and in perennial plants such as common myrtle (_Myrtus communis_ L.) (_Theobroma cacao_) (_Theobroma cacao_) (_Theobroma cacao_). Regarding tetramethylene diacetate, there are few known data related to the origin and the flavor it confers. Its presence is confirmed by headspace solid-phase microextraction and analyzed by Headspace-SPME-GC/MS from pineapple fruit (_Theobroma cacao_). The aroma of fruits such as strawberries, which can be among the spectrum of fruity tones, is most commonly associated with the presence of ethyl 2-methyl butyrate found in blueberries, apples, and obviously in strawberries. The profile of sweet aromas is completed by 2-methyl butyl acetate and hexyl acetate with apple and banana flavors. 2-Methylbutyl acetate is naturally found in perennial herbaceous plants such as Myrtus communis and Tagetes minuta and in vines (Vitis vinifera). In contrast, hexyl acetate is found in very high concentrations in blueberries, and is detected but not quantified in pears, oats, and cherries. Two alken are qualitatively identified in commercial apple juice (trans-2-pentene and 2,2- dimethyl-1-pentene). No scientific studies have been conducted regarding these volatile organic compounds' natural origin. However, the formation of trans-2-pentene was observed in a study of thermal degradation via HS-SPME-GC/MS of sugarcane juice (_Theobroma cacao_). This paper can be a source of confirmation of trans-2-pentene in concentrated apple juice from the related alcohol through thermal degradation during the detection process.