# Nutritional Analysis of Red-Purple and White-Fleshed Pitaya (_Hylocereus_) Species
## 3 Results
### The Difference of Volatile Compounds between Red- and White-Fleshed Pitaya
[73] detected nineteen aroma volatiles such as aldehydes, alcohols, ketones, hydrocarbons using Solid Phase Micro Extraction (SPME) in six _Hylocereus_ cultivars (Cebra, Rosa, Lisa, San Ignacio, Mexicana, and Physical Grafiffi) grown in California. They also found that aldehydes accounted for more than 90% of the total volatile amount. In another study, [PERSON] et al. [78] identified 121 volatiles such as alcohols, terpen, paraffins, acids, esters, and ketones from _H. megalanthus_ using the aroma extract dilution analysis method, and various other compounds using solvent extraction followed by concentration. They also performed aroma extract dilution analysis (AEDA) to identify nine fragrance active compounds that could potentially affect pitaya flavor. There are some similarities and variations between previous studies and our study, and these differences can be explained by differences in the examined pitaya tissues and the variability of the extraction methods applied, plant material type and maturity stage, growing regions and climatic conditions. The previous studies conducted with horticultural plants indicated that biochemical and volatile content greatly varied among cultivars, geographical conditions, growing conditions, etc. [79; 80; 81]. As a result, both SPME fibers could extract most of the volatile compounds such as alcohols, ketones, aldehydes, acids, easter and several other compounds. Here, we also found the different preferences of PDMS and PDMS/DVB fibers in the extraction of volatile compounds in the pitaya fruit; only the PDMS fiber could specially extract the terpen (l-Limonene) in both red- and white-fleshed compared to that of PDMS/DVB. The \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Category**} & PDMS- & PDMS- & PDMS- & PDMS/DVB & PDMS/DVB & \multirow{2}{*}{**PDMS**} & \multirow{2}{*}{**PDMS**} & \multirow{2}{*}{**PDMS/DVB**} & \multirow{2}{*}{**Volatile Compounds Extracted by Both SPME Fibers**} \\  & Red & White & Red & White & & & & \\ \hline Alcohol & 2 & 2 & 3 & 1 & 5 & 4 & Tridecyl alcohol \\ Terpenes & 1 & 1 & 0 & 0 & 1 & 0 & - \\ Ketones & 1 & 1 & 0 & 3 & 1 & 4 & - \\  & & & & & & & (E)-2-Decneal, Hexanal, Nonanal, \\ Aldehydes & 4 & 6 & 9 & 3 & 13 & 9 & Octanal, trans \\  & & & & & & & 2 dodecenal \\ Esters & 0 & 0 & 0 & 1 & 0 & 1 & Hexanoic acid, Nonanoic acid, \\ Acids & 5 & 4 & 4 & 5 & 9 & 9 & Hexanoic acid, Pentadecanoic acid \\  & & & & & & & 2,6-bis(1,1-dimethylethyl)-4- \\  & 2 & 2 & 4 & 1 & 3 & 5 & methyl- Phenol, \\  & & & & & & & Tridecane \\ Total & 15 & 16 & 20 & 14 & 32 & 32 & 13 \\ \hline \hline \end{tabular} Note: PDMS-Red/PDMS/DVB-Blue; volatiles extracted by PDMS and PDMS/DVB fiber in red and white pitaya.  
\end{table} 
Table 4: Volatile profiles of between red and white pulp pitaya varieties detected by PDMS and PDMS/DVB fibers. technique of SPME has been widely used to detect the composition of volatile compounds in foods and drinks because this method is organic solvent-free, time-saving and low cost compared to traditional extraction methods. The method could seperate and quantify cis-and trans-isomers. PDMS (100\(\upmu\)m polydimethylsiloxane) for volatiles and PDMS/DVB (65 \(\upmu\)m polydimethylsiloxane/divinylbenzene). The SPME method suitably recovered most compounds reported to impart characteristic flavors/aromas in pitaya fruits. SPME offers experimental flexibility and the ability to discover more compounds and address flavor quality differences among pitaya species (Tables 3 and 4). The Mann-Whitney U test was used to test the difference between groups. This nonparametric test was chosen due to the small number of observations and the lack of normal data distribution. According to the results, a significant difference was observed in ellagic acid, myricetin and kaempfer between the white and red-fleshed species at a 10% significance level. In detail, ellagic acid was significantly higher in red, and myricetin and kaempfer were higher in White-fleshed pitaya samples.