## 3 Results and Discussion
### Volatile Profile of the Samples
However, beetroot powder showed a 29.7% peak area ratio for dimethyl sulfide, which is in accordance with literature data. This compound probably contributes to the pungent odor and flavor of the product, although the distinctive earthy aroma of fresh beetroot is due to the presence of the terpenoid geosmin [61]. Geosmin was not detected in the beetroot powder, likely because it degraded during processing and storage. Nitrogen-containing compounds like pyrazines and acetylimidazole typically occurred in microalgae powders. Pyrazine, 2,5-dimethyl- was present in an exceptionally high peak area ratio of 7.4% in the spirulina powder. Oxygen-containing heterocyclic compounds are widely occurring natural metabolites and can be formed as a result of thermal processing in sugar-rich foods. These components include furans, furanones, and related compounds, which can contribute to the aroma of foods with sweet, baked, and caramel-like notes [62]. Compounds of this chemical class were detected in the headspace of twelve samples. Acerola powder showed an outstanding peak area ratio (14.0%) for 2-furanmethanol, while the greatest variety of oxygen-containing heterocycles was detected in the headspace of goji berry powder. Pyrazines, furan, and furan derivatives are probably formed as a result of thermal treatment. Concerning the benzene-ring compounds, the greatest number of compounds and peak area ratios were detected in spinach, spirulina, and chlorella powders. Frequently detected members of this chemical class were toluene (\(n=12\)) and benzaldehyde (\(n=7\)). The total peak area ratio of alcohols in our samples ranged from 3.0% to 34.8%. At least one isomer of 2,3-butanediol was detected in eleven products. Sea buckthorn powder exhibited the highest peak area ratios for both isomers. 1-pentanol was present in eleven samples with low relative concentrations. Ethyl alcohol and 2,6-dimethylcyclohexanol were also frequently detected. The former was found in the highest proportion in vegetable powders, while the latter was a major component of microalgae powders. Smaller or higher amounts aldehydes were present in each product, except for the lucuma and turmeric powders. In sea buckthorn, wheat grass, and duckweed powders, aldehydes were present at peak area ratios above 14%. Hexanal was the most frequently detected aldehyde, which can be characterized by a fresh, green, and grassy aroma. It was present in duckweed powder in the highest proportion, followed by rosehip, sea buckthorn, chlorella, beetroot, and spirulina powders. Pentanal, another aldehyde with a fresh, green, and grassy aroma, was also present in several products. Sea buckthorn powder showed relatively high peak area ratios for heptanal and nonanal, while in the headspace of wheat grass and moringa powders, butanal, 3-methyl was detected in high proportions. Ketones were identified in the headspace of each sample with varying peak area ratios. This class of compounds contributed only 1-2% to the total volatiles in the beetroot, acerola, and turmeric powders. On the other hand, the headspace of aronia powder showed an outstanding ketone ratio of 51.1%. This product contained five ketones, of which _trans_-3-penten-2-one was predominant (47.5%). The fresh fruit and the juice of aronia are also rich in this volatile ketone [63; 64]; thus, this compound may be a botanical marker. Acetoin was the most frequently detected ketone in our samples, followed by 5-hepten-2-one, 6-methyl-. The latter compound was present in relatively high proportions in the powders of ginger (11.6%), rosehip (9.6%), moringa (7.9%), and duckweed (4.4%). Figure 4: Number of total volatile compounds in each nutraceutical. Figure 5: Contributions of the chemical classes to the total amount volatiles in the samples. Esters accounted for the total volatiles at 0.0 to 31.4% in the samples. A total of 26 esters were detected in at least one sample. Acerola powder showed the highest total peak area ratio for esters (31.4%), which is attributed to its high lactic acid ethyl ester content.