Phytochemicals changes in the postharvest and frozen process of durian 'Mon Thong'

The processing steps of frozen durian include the preparations of the raw material such as trimming, cutting and peeling followed by freezing. These processes may have an effect on the nutrition and bioactive compounds in the fruit. The purpose of this research is to gain the scientific data of the effects of the preparation and freezing steps on the bioactive compound changes in durian produced in the south and east of Thailand. The bioactive compounds were identified in fresh, fresh-cut and frozen durian, these include vitamin E (α-tocopherol), β-carotene, flavonoids, phenolic, ascorbic acid as well as the antioxidant activity of DPPH radical and FRAP radical. Durian were collected from the southern and eastern part of Thailand. Fresh, fresh-cut and frozen durian were sampled to measure the bioactive compound. For the durian from southern area, the results showed that the content of β-carotene, phenolic compounds and antioxidant activity of DPPH and FRAP radical scavenging were higher in fresh-cut durian than fresh durian, while the content of vitamin C is lower in fresh-cut durian. The freezing process increased the vitamin E content and reduced the phenolic and vitamin C content, but it had no effect on the flavonoid content. For the durian from eastern area, the results revealed that the fresh-cut process increased the β-carotene content but it had no effect on the phenolic content and the antioxidant activity of DPPH radical. The freezing process decreased the vitamin C content, but it had no effect on the content of the flavonoid, vitamin E and phenolic compounds and the antioxidant activity of DPPH and FRAP radical. The content of bioactive compound of durian (from both the south and the east) were: 0.21-1.49 mg 100 g-1 of vitamin E, 8.17-29.89 µg 100 g-1 FW of β-carotene, 5.85-20.0 mg g-1 FW of vitamin C, 0.16-0.40 mg 100 g-1 FW of flavonoid, and 41.76-59.82 mg GAE g-1 FW of phenolic compounds. The antioxidant activity of DPPH and FRAP radical was 461.88-834.37 µmol Trolox equiv. g-1 and 13.20-53.81 µmol Trolox equiv. g-1, respectively. A comparison of the bioactive compound of durian from the south and the east of Thailand revealed that the former contained a higher vitamin E, β-carotene, and vitamin C content than the latter. On the other hand the flavonoids, phenolic, and antioxidant activity of DPPH and FRAP radical were less in the former. The fresh-cut and freezing process increased the bioactive compound and antioxidant activity, except for vitamin C ,when compared with fresh durian and frozen durian.