## 3 Results and Discussion
### Volatiles Analysis  
#### Changes of Volatiles in Kiwifruit Pulp Beverage after HHP  
Despite high pressure did not directly change the fresh flavor of fruits and vegetables, HHP could change the concentration of volatiles indirectly because of enhancing or slowing down some enzymatic and chemical reactions [43]. A principal component analysis (PCA) was carried out to evaluate effect of different treatments on volatiles of kiwifruit pulp beverage. Figure 4 showed the score plot of the different variables (coefficients of the eigenvectors) for the two first principal components (PC 1 and PC 2). The most important contributions to PC1 were hexanal, (_E_)-2-hexenal, 1-hexanol, \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Treatments** & **L*** & **a*** & **b*** & \(\Delta\)E \\ \hline Control & 75.05 \(\pm\) 3.93 & 0.83 \(\pm\) 0.19 a  & 12.23 \(\pm\) 2.25 & — \\ HT & 79.34 \(\pm\) 0.82 & \(-\)0.04 \(\pm\) 0.02 b  & 8.93 \(\pm\) 0.86 & 5.48 \\  & 5 min & 75.21 \(\pm\) 4.70 & 0.67 \(\pm\) 0.24 a  & 11.24 \(\pm\) 3.78 & 1.02 \\
400 MPa & 10 min & 73.23 \(\pm\) 9.01 & 0.81 \(\pm\) 0.22 a  & 12.04 \(\pm\) 4.30 & 1.83 \\  & 15 min & 75.21 \(\pm\) 0.44 & 0.93 \(\pm\) 0.12 a  & 12.26 \(\pm\) 0.44 & 0.19 \\  & 5 min & 75.08 \(\pm\) 4.60 & 0.65 \(\pm\) 0.23 a  & 10.86 \(\pm\) 2.53 & 1.38 \\
500 MPa & 10 min & 78.32 \(\pm\) 2.56 & 0.67 \(\pm\) 0.33 a  & 9.35 \(\pm\) 3.06 & 4.36 \\  & 15 min & 73.69 \(\pm\) 8.52 & 0.88 \(\pm\) 0.20 a  & 11.44 \(\pm\) 3.68 & 1.57 \\  & 5 min & 77.65 \(\pm\) 0.82 & 0.54 \(\pm\) 0.11 a  & 10.99 \(\pm\) 0.50 & 2.90 \\
600 MPa & 10 min & 78.70 \(\pm\) 0.75 & \(-\)0.10 \(\pm\) 0.01 b  & 9.09 \(\pm\) 1.88 & 4.90 \\  & 15 min & 79.92 \(\pm\) 2.15 & 0.23 \(\pm\) 0.02 a  & 8.39 \(\pm\) 1.80 & 5.41 \\ \hline \hline \end{tabular} Control, kiwifruit pulp beverage treated without HT or HHP. HT, heat treatment (85 °C for 10 min). HHP, high hydrostatic pressure (400–600 MPa for 5–15 min). L*, the brightness value on a black (0) to white (100) scale. a*, hue on a green (–) to red (+) scale. b*, hue on a blue (–) to yellow (+) axis. \(\Delta\)E, the total color difference between treated samples and untreated samples at the initial time. Results were expressed as means \(\pm\)SD, \(n=3\). Different letters indicate the data are different significantly (\(p<0.05\)). Data without superscripts are not significantly different.  
\end{table} 
Table 2: Color of kiwifruit pulp beverage after HHP treatment on day 0. 1-octen-3-ol, 1-octen-3-one, and 1-penten-3-one since they were far from the origin and explained an important part of the variation. The first principal component (PC) explained 69.2% and the second PC explained 20.9%, altogether 90.1% of the variation among the samples. As can be seen in Figure 5, volatiles of kiwifruit pulp beverage were modified by HHP and heat treatments. All treated samples (except samples treated at 400 MPa/10 min and 600 MPa/15 min) were positively correlated with PC1, indicating hexanal, _(E)_-2-hexanal, 1-octen-3-ol, 1-octen-3-one and 1-penten-3-one were enhanced after treatments. However, the content of 1-hexanol was decreased by HHP and heat treatments. GC-MS analysis demonstrated that some of the original volatiles disappeared while some new volatiles appeared after treatments and the content of volatiles changed (Table 3). Alcohols, aldehydes, ketones, esters, and acids were the most numerously represented volatiles classes in kiwifruit pulp beverage. By contrast, the levels of most aldehydes such as hexanal, _(E)_-2-hexanal, nonanal as well as _(E, E)_-2,4-Heptadienal and alcohols such as ethanol and 1-octen-3-ol increased when kiwifruit pulp beverage treated by HHP. In contrast, HHP caused loss in 1-octanol, 1-hexanol and 2-octanol. On the other hand, HHP at 400 MPa/15 min and 500 MPa/5 min retained phenylethyl alcohol while heat-treated samples could not detect this aroma compound. Similarly, the highest 3-octanone content was found in pulp beverage treated at 400 MPa for 10 min while HT caused lowest 3-octanone content.