kGy was required for the hygienization of yeasts and fungi. Since the dosage 18

was the lowest and significant different from others

6 kGy was required for the hygienization of yeasts and fungi. Since the dosage 18

unirradiated or irradiated POMU. Irradiation treatment resulted in significant changes 2

in THSG content at different doses.

In this database, THSG showed statistically significant decreases from 3.05 mg/g 4

(0 kGy, p <0.05) to 2.60 mg/g after 5 kGy of irradiation (p <0.05), 2.50 mg/g at 10 5

kGy (p <0.05) and 2.13 mg/g at 15 kGy (p <0.01) (Figure 2; N = 3). Therefore, it was 6

indicated that gamma irradiation caused damage to THSG content in POMU.

7 8

4. Discussion

POMU has long been used as a medicinal herb in Asia.

Insect infestation and

microbial contamination are serious problems for POMU storage. Gamma irradiation 11

is able to penetrate deeply, and has been found to be useful for the hygienization of 12

herbal products even when they are already in packages or sacks. The choice of a 13

suitable radiation dosage is particularly important for

decontaminate the microbial

load

of stored POMU. In this research, the optimal dosage for the inactivation of 15

microorganisms in POMU was evaluated.

2 kGy was sufficient for the hygienization of enterobacteria, whereas a dosage of 17

6 kGy was required for the

hygienization of yeasts and fungi. Since the dosage

required removing microbial contamination is higher than that required killing insects, 19

insects would be killed at the same time [35].

Our results confirmed that at the dose of 4 kGy, mold and yeast counts were 2

obviously reduced; and at 6 kGy, neither yeasts nor fungi were observed any longer in 3

POMU specimens. Thus in our research, it was demonstrated that 4~6 kGy of 4

treatment was effective for the inactivation of microorganisms and 8 kGy treatment 5

could induce complete inactivation.

Phenols are regarded as main contributors to antioxidant activities, the 7

measurements are based on radical scavenging. Antioxidant capacity depends on 8

various factors, such as the number and location of hydroxyl groups on the aromatic 9

ring, as well as their mutual positions [36]. Our results demonstrated that the 10

irradiation dosage on POMU (5 kGy, 63.62 ± 0.84

M/mg extract) had both the

highest antioxidative activity and the lowest value in IC50 of DPPH 12

radical-scavenging activity, and as expected, an increase of radiolytic products, which 13

agreed with literary reports for other foods and medicines. In this study, 5 kGy 14

γ-irradiation increased radiolytic products of POMU; however it seemed to increase 15

the antioxidant effect of POMU in the ABTS assay.

The content of total phenols, expressed as

g (+)-catechin equivalent/mg dry

weight value, did not vary distinctively in irradiated POMU samples. The values were 18

slightly lower; however variations were not statistically significant (Table 4). THSG 19

content of POMU had decreased as the γ-radiation increased (Figure 1). However, the 1

total phenolic compounds and antioxidative activities were increased, probably 2

because other phenolic compounds were formed during irradiation. It has to be 3

mentioned that irradiation of aqueous systems containing aromatic compounds can 4

implicate the formation of phenols.

5. Conclusion

The results of this study indicated that 5 kGy of gamma irradiation was effective 8

for the hygienization of POMU. It did not alter the appearance of POMU before and 9

after gamma irradiation. Though, after 5 kGy of irradiation, some

physicochemical

properties were slightly changed or compensated for the improved hygiene of this 11

medicinal herb, such as the decrease in THSG content. However, the total phenolic 12

compounds and antioxidative activities were increased. Therefore gamma irradiation 13

at 5 kGy could be a potential method for decontaminate the microbial load of POMU 14

to prolong shelf life and improve hygienic quality.

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