# Aromatic Profile of Hydroponically and Conventionally Grown Tomatoes
## 3 Results and Discussion
### Electronic Nose
A similar view is shared by the authors [25], who state that e-nose is a fast and effective technique that does not require special sample preparation to determine the aroma of the  
Figure 2: Categorization of samples with selection of main markers. product and it is therefore widely used for the detection of food adulteration. They further suggest that in the case of some foods, the aroma of the product is specific enough to distinguish the original product from its counterfeit or adulterated product. Several studies have used this fact and thus e-nose has also been used in the context of authentication and adulteration of fresh juices made from cherry tomatoes. Other authors [26] confirmed the possibility of using this device to detect adulterated food. Our results may indicate the possibility of using e-nose in the process of food authentication and in estimating food adulteration, specifically hydroponically grown tomatoes. To confirm this, we recommend working with a larger number of samples in future research. In the past, much research has led to the development of extraction and analytical techniques useful for obtaining a detailed profile of volatiles from tomatoes. A large number of volatiles have been identified and the volatile profile of tomato has been investigated in detail in many studies. Already in 1998 [4], relationships between chemical compounds and sensory properties of tomatoes were established. (Z)-3-hexenal, hexanal, 1-octen-3-one, methional, 1-penten-3-one, and 3-methylbutanal were among the most odor-active aromatic volatiles in fresh tomatoes. The aroma, taste and aftertaste of different tomato varieties were evaluated by quantitative descriptive analysis. Using PCA analysis, they found that the first three components presented 70% of the total variance. According to [5], volatiles characteristic of tomatoes include acyclic, cyclic and heterocyclic hydrocarbons, alcohols, phenols, ethers, aldehydes, ketones, carboxylic acids, esters and lactones, as well as compounds containing nitrogen, sulfur and halogens. Of these, molecules such as 1-penten-3-one, hexanal, cis-3-hexenal, trans-2-hexenal, 1-penten-3-ol, 3-methylbutanol, cis-3-hexen-1-ol, 2-isobutylthiazole, trans-2 heptanal, 6-methyl-5-hepten-2-one, 6-methyl-5-hepten-2-ol, methyl salicate, geranyl acetone, and phenyl ethanol are important. As mentioned earlier, in this study, we focused on the five basic odors that were present in the samples in the highest amount. After the electronic nose divided the odor profile of the evaluated samples into hydroponic (inside the triangle) and conventionally grown, we were able to identify three main odor cues characteristic for hydroponically grown tomatoes (Figure 2). These are substances listed as 15.31.1-A, 26.07.1-A and, marginally, 43.88.1-A. Under the label 15.31.1-A, we are most likely to recognize the chemical organic compound 2-methylpropanol. This substance is responsible for the typical fruity flavor and the green, unripe notes of the fruit. It is highly likely that the compound dimethyl sulphide, presenting fruity and vegetal notes, also completes this set of odors. The odor substance labeled 26.07.1-A is the chemical compound 2,3-pentanedione representing a fruity flavor. This substance also promotes the freshness feeling of the fruit and participates in the formation of the sweet character. The last compound associated with the sensory character of hydroponically grown tomatoes is (Z)-3-hexen-1-ol or 1-hexanol, causing a fruity, grassy, fresh, and unripe flavor or aroma to the fruit. Correlation between (Z)-3-hexen-1-ol and flavor intensity was also proven in the study of contribution of C6 volatiles to taste and aroma [9]. Other authors report that C6 compounds are the most widespread volatiles in tomato fruit and contribute to tomato flavor in various ways. Similar to our study, the presence of (Z)-3-hexen-1-ol in hydroponically grown tomatoes was also detected by those authors [1]. In some studies, this substance is associated with consumer acceptability [27].