## 3 Results and Discussion
### Changes in Color of HHP-Treated Kiwifruit Pulp Beverage  
The color parameters of kiwifruit pulp beverage treated by HHP and heat treatments are presented in Table 2. L* values increased slightly as the pressure increased. Lightness and yellowish of kiwifruit pulp beverage were not affected by HHP and heat treatments since no significant change was found in L* value and b* value after treatments (\(p>0.05\)). [PERSON] et al. [37] reported that HHP at 550 MPa for 5 min showed no effect on b* and L* values of pepper and orange juice blend, which was similar to our results. Furthermore, all treatments had no significant effect on a* values in addition to HT and treatment at 600 MPa for 10 min, indicating that HT and extremely high pressure would have significant impacts on greenness. \(\Delta\)E value refers to the total color difference. In this study, \(\Delta\)E values tended to increase with increasing pressure. HHP-treated pulp beverage showed lower \(\Delta\)E values than heat-treated pulp beverage, which illustrated that HHP maintained the original color of samples better than HT. Previous studies also reported that \(\Delta\)E values of apricot nectars and mango nectar treated by high temperature short time were higher than \(\Delta\)E values of HHP-treated samples [38; 39]. Especially, \(\Delta\)E value of samples processed at 400 MPa for 15 min was found to be significantly lower than those of the other treatments and thence provided better conservation of original color. Figure 2: Changes of vitamin C content in heat-treated and HHP-treated kiwifruit pulp beverage during storage at 4 °C for 40 days. Heat treatment (85 °C for 10 min) (), HHP (high hydrostatic pressure, 400–600 MPa for 5-15 min): 400 MPa/5 min (), 400 MPa/10 min (), 400 MPa/15 min (), 500 MPa/5 min (), 500 MPa/10 min (), 500 MPa/15 min (), 600 MPa/5 min (), 600 MPa/10 min (), 600 MPa/15 min (). All data were expressed as means \(\pm\) SD, \(n=3\). Kiwifruit is likely to undergo browning during storage, which affects the sensory quality of products. As can be observed in Figure 3, L*, a*, b*, and \(\Delta\)E values of kiwifruit pulp beverage changed during 40-day storage. L* value of heat-treated samples changed significantly and the lowest L* value was obtained at day 40 for HT, which was lower than L* values of pulp beverage treated by HHP, illustrating the maintaining effect of HHP in brightness is better than HT with the prolongation of storage period. L* value increased after 20 days of storage, which may be related to decrease of VC content and total polyphenol [34]. Additionally, a* values increased gradually during storage, stating that a gradual loss of green in all treated samples. As shown in Figure 3C, b* values increased first and then reduced after 20 days. HHP-treated samples remained lower b* values in comparison to heat-treated samples during storage, which meant HHP inhibited browning of pulp beverage compared with HT. There was an increase trend in \(\Delta\)E values of kiwifruit pulp beverage over 40 days (Figure 3D). The result was in agreement with previous studies about clear cucumber juice and purple sweet potato nectar, which concluded that \(\Delta\)E values increased during storage [40; 41]. It is obvious that the difference of \(\Delta\)E values between different treatments gradually increased with the storage time. Besides, \(\Delta\)E values of heat-treated samples as well as samples treated at 600 MPa/15 min increased sharply, illustrating that HT, extremely high pressure and long treatment time would significantly change the color of kiwifruit pulp beverage. On the contrary, HHP ranged from 400 MPa to 500 MPa exerted protective effects on color of pulp beverage. Particularly, the significantly lower \(\Delta\)E values in pulp beverage treated at 400 MPa for 15 min during 40-day storage time clearly demonstrated this treatment could retain the fresh-like color and appearance of kiwifruit pulp beverage. A similar trend was also observed in strawberry and blackberry purees, [PERSON] et al.