향신 채소류의 휘발성 유기성분에 대한 감마선 및 전자선 조사의 영향

Abstract

Spicy vegetables that give unique flavors to food have been developed as the food industry advanced. The effectiveness and effect of substances that promote physiological activity have been ascertained. Thus, use of such substances is on the increase and extensive studies of enhancement of food preservation by gamma ray irradiation and of easiness in distribution are being conducted. In relation to this, we intend to monitor changes induced using gamma ray and electron beam irradiation in major volatile components in spicy vegetables by investigating the change in major volatile components of major spicy vegetables and by investigating the effect of such irradiation at high dose on spicy vegetables.

1. Analysis of changes in volatile components of irradiated spicy vegetables by gamma ray

A. From red pepper, 38 types of volatile organic components were isolated and identified: alcohols(31.4%), aldehydes(35.8%), esters(21.2%), hydrocarbons (4.7%), ketones(4.5%), acids(0.6%) and heterocyclic compounds. Total amount of organic components was 118.98 mg/kg. Major components identified included ethyl acetate, 2-methybutanal, 3-methylbutanal, hexanal, pyridine, 2-pentylfuran, benzaldehyde, linalool, (E,E)-2,4-decadienal, β-ionone, 1-tridecanol, (Z)-9,17-octadecadienal and methyl linolenate. Total amount of volatile organic components showed an increasing trend in radiation dose, exceptionally decreasing at dose of 7 kGy.

B. From ginger, 70 types of volatile organic components were isolated and identified. The 33 types of components that belong to hydrocarbon families accounted for the largest proportion(83.8%), followed by alcohol, aldehyde, ketone and ester families. Major volatile organic components of dried ginseng included α-zingiberene, β-sesquiphellandrene, β-bisabolene (Z,E)-α-farnesene, β-phellandrene, germacrene D, (Z)-citral, camphene, α-zingibereneand, β-sesquiphellandrene, which accounted formost of organic components. The volatile organic component conten to fall irradiated ginseng specimen was higher than that of non-irradiated specimen with highest content observed in the specimen irradiated with a 7 kGy dose.

C. From welsh onion, 45 types of volatile organic components were isolated and identified. According to type of functional group, S-containing compounds accounted for the largest proportion, and aldehydes, alcohols, ketones, furans, esters, hydrocarbons and acids family were identified. Major volatile organic components included 2-methyl-2-pentenal, 2-tridecanone, propanethiol, 3,5-diethyl-1,2,4-trithiolane, dipropyl trisulfide and 2-propen-thiol. The total amount of volatile organic components of dried welsh onion specimen decreased with increasing irradiation doses with the lowest amount observed at irradiation dose of 10 kGy.

D. From garlic, a total of 47 types of volatile organic components were identified with 26 of them being S-containing compounds and accounting for 98.7% of the total volatile organic components. Besides, alcohols, aldehydes and esters family were also identified. Major compounds included large amount of diallyl disulfide, diallyl trisulfide, methyl allyl disulfide, 3-(allylthio)propionic acid and methyl-2-propenyl trisulfide. The total content of volatile organic components of garlic decreased as irradiation doses increase. Consequently, major compound contents also slightly decreased.

E. From onions, a total of 40 types of volatile organic compounds were isolated and identified with 25 of types accounting for 71.5%: aldehydes, ketones and esters families were identified. Major volatile organic components of dried onions included dipropyl trisulfide, propanethiol and 2-methyl-2-pentanal. Among irradiated and non-irradiated groups, total content of volatile organic compound increased with increasing irradiation doses with the lowest content of volatile organic compound observed at 10 kGy. Total content of volatile organic components at irradiation dose of 10 kGy was higher than that at 7 kGy. The proportion of S-containing compounds in the specimen irradiated with dose of 10 kGy was lower than in a control irradiated with dose of 7 kGy, and was higher than in specimen irradiated with different dose of radiation and in non-irradiated groups.

2. Analysis of change in volatile organic components of irradiated spicy vegetables by electron beam

A. From red hot pepper powder irradiated with electron radiation, 39 types of compounds were identified. Major volatile organic components included ethyl acetate, 2-methybutanal, 3-methylbutanal, hexanal, pyridine, 2-pentylfuran, benzaldehyde, linalool, (E,E)-2,4-decadienal, β-ionone, 1-tridecanol, (Z)-9,17- octadecadienal, and methyl linolenate. The total amount of irradiated red hot pepper increased with an increasing dose of radiation although it decreased at 7 kGy. However, the highest amount of volatile organic components of red hot pepper was observed at a radiation dose of 10 kGy.

B. Total content of volatile organic components of dried ginger irradiated with electron radiation increased with increasing irradiation doses until at a dose of 3 kGy, decreased at 5 kGy and 7 kGy, and increased again at 10 kGy. Major volatile organic components included α-zingiberene, β-sesquiphellandrene, β-bisabolene, (Z,E)-α-farnesene, β-phellandrene, germacrene D, (Z)-citraland- camphene, most of them being Terpene family. Irradiation did not affect the over all proportion of hydrocarbon family. The amount of β-bisabolene decreased with increasing dose of irradiation but exceptionally decreased at a dose of 10 kGy. In contrast, the amount of 6-methyl-5-heptene-2-one and camphor decreased with an increasing dose of irradiation.

C. The amount of volatile organic components of welsh onion irradiated with electron radiation decreased with an increasing dose of irradiation. The lowest amount was observed at a dose of 7 kGy, but increased at 10 kGy. The amount of major aromatic substances of welsh onion such as 2-propenthiol, propylene sulfide, 3,5-diethyl-1,2,4-trithiolane increased with an increasing dose of radiation with the amount being highest at irradiation dose of 7 kGy. It showed a decreasing trend at the irradiation dose of 7 kGy or more. The amount of (Z)-propenyl propyl disulfide, (E)-propenyl propyl disulfide and dipropyl trisulfide increased with increasing doses of irradiation and with the highest amount show data dose of 5 kGy. It showed decreasing then data dose of 5 kGy or more.

D. Electron beam irradiated garlic was not considerably different from non-irradiated garlic in terms of proportion of functional groups as S-containing compound accounted for 97.6% to 98.9% of total 48∼54 types of compounds. Major volatile organic components included diallyl disulfide, diallyl trisulfide, methyl allyl disulfide, 3-(allylthio)propionic acid and methyl-2-propenyl trisulfide. Compared with non-irradiated specimen, total content of organic components decreased with increasing doses of irradiation. Consequently, the major compound contents also decreased.

E. The number of types of compounds identified from the onions irradiated with electron radiation was 40, and the proportion of each functional group was found similar between irradiated and non-irradiated specimen. The change in content was not significant. Major volatile organic compounds included dipropyl trisulfide, propanethiol and 2-methyl-2-pentanal. They decreased with an increasing dose of irradiation with the lowest amount observed at 7 kGy but slightly increased at 10 kGy.

3. Effect of irradiation with high doses of each radiation source on volatile organic components of spicy vegetables

Spicy vegetables exposed to high levels of radiation registered changes in their volatile organic component depending on the type of radiation. The total volatile organic components of red pepper and ginger were higher in gamma ray and electron beam irradiated group than in non-irradiated sample, and its rate of increase was higher in electron beam irradiated group than in gamma ray irradiated specimen. The organic compounds of ginger such as α-zingiberene, (Z,E)-α-farnesene, β-myrcene, and limonene rendered similar results. The total content of volatile organic components in welsh onions was higher in non-irradiated group than in gamma ray and electron beam irradiated group, and it registered lowest in group subjected to electron radiation. After exposure to either gamma ray or electron beam, content of 2-methyl-2-pentenal, (Z)-propenyl propyl disulfide, and dipropyl trisulfide in Welsh onions decreased. The total content of volatile organic components in garlic and onion decreased after irradiation with either gamma ray or electron beam, and registered the lowest in gamma ray irradiated group. The garlic’s content of dially trisulfide was the lowest among all gamma ray irradiated control. The content of major S-containing compound registered the highest in electron beam irradiated in onion. The content of aldehydes was lowest in gamma ray irradiated specimen. The content of propanethiol and dipropyl trisulfide decreased after irradiation and was lowest in electron beam irradiated control.

In this study, we found that irradiation with gamma ray or electron beam affected the volatile organic components by analyzing change in volatile aromatic components of spicy vegetables irradiated with gamma ray and electron beam. Although composition of major components changed, no compounds that are specific to irradiation were observed. The sensitivity of spicy vegetables to radiation source and dose differed by types of spicy vegetables although not highly correlated with extraction efficiency of volatile components after irradiation. Based on these results, we consider that more extensive studies are required to determine appropriate radiation source and dose that can be used to sterilize spicy vegetables while considering sterilization, energy efficiency, and extraction efficiency of useful components.