The combined effects of N2-packaging, heating and gamma irradiation on the shelf-stability of Kimchi, Korean fermented vegetable

Food Control 19 (2008) 56–61 www.elsevier.com/locate/foodcont

The combined eVects of N2-packaging, heating and gamma irradiation on the shelf-stability of Kimchi, Korean fermented vegetable Jae-Hun Kim a, Jin-Gyu Park a, Ju-Woon Lee a, Wang-Geun Kim b, Young-Jin Chung c, Myung-Woo Byun a,¤ a

Department of Radiation Food Science and Biotechnology, Advanced Radiation Technology Institute, Korea Atomic Energy Research Institute, Jeongeup 580-185, Republic of Korea b Department of Application Science and Technology, Chosun University, Gwangju 501-759, Republic of Korea c Department of Food and Nutrition, Chungnam National University, Daejeon 305-764, Republic of Korea Received 22 November 2006; received in revised form 29 January 2007; accepted 5 February 2007

Abstract This study was conducted to evaluate the combined eVects of N2-packaging (N2), mild heating at 60 °C (HT) and gamma irradiation of 20 kGy (IR) on the shelf-stability and quality of Kimchi during storage at 35 °C for 30 days. Total microbes including lactic acid bacteria were sterilized perfectly by the combination treatment of HT–IR or N2–HT–IR, and the acidity of Kimchi was not changed during storage. Irradiation softened textural property of Kimchi. However, combination of N2-packaging with heating and irradiation retarded this softening of Kimchi by high dose irradiation. Organoleptic qualities were improved by the combination treatment during the storage period. © 2007 Elsevier Ltd. All rights reserved. Keywords: Kimchi; Gamma irradiation; N2-packaging; Heating; Combined treatment; Shelf-stability

1. Introduction Kimchi is a Korean fermented vegetable food, which has a sour, hot, salty and characteristically carbonic taste from the lactic acid fermentation of the brined vegetables (Choi, Whang, Kim, & Suh, 2006; Lee, 1997). However, after it reaches a well-aged stage, these microbiological and enzymatic activities continue and result in a sour and bitter taste, oV-odor and softening due to the deterioration of Kimchi (Cheigh & Park, 1994; Chung & Yo, 1995; Lee et al., 2000). Therefore, the control of the fermentation process is needed to preserve the quality of Kimchi and to extend its shelf-life. Chilled storage (2–8 °C) is generally used to maintain the quality of Kimchi. Several studies have been conducted to extend the shelf-life of Kimchi by using heat treatment *

Corresponding author. Tel.: +82 63 570 3200; fax: +82 63 570 3202. E-mail address: [email protected] (M.-W. Byun).

0956-7135/$ - see front matter © 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.foodcont.2007.02.002

(Kang, Ku, Lee, & Kim, 1991), antiseptic (Park & Woo, 1988) and antimicrobial agents (Ahn, 1988; Moon, Byun, Kim, & Han, 1995), herb medicine (Jung, Chung, & Park, 2002; Lee, Cho, Choi, & Kim, 1998) and pH adjuster (Lee & Kim, 2003; Park, Park, Cheong, & Lee, 2002). Even though these methods could be used to retard the aging process, it is diYcult for these processes to control the deterioration of the sensory quality and to maintain the good quality during long storage periods of above one year at room temperature. Gamma irradiation by using low dose irradiation of 5 kGy or less for the microbiological control of Kimchi has been applied in several studies (Byun, Cha, Kwon, Cho, & Kim, 1989; Cha, Kim, Byun, Kwon, & Cho, 1989; Kim, Song, Yook, Ryu, & Byun, 2004; Song et al., 2004). However, the application of low dose irradiation was not suYcient enough to preserve Kimchi without any changes of its quality under the severe environment such as desert or space.

J.-H. Kim et al. / Food Control 19 (2008) 56–61

In previous study (Kim et al., 2006), high dose irradiation of 10 kGy and above or high temperature treatment of 100 °C were used to control the microXora of Kimchi. But, high dose irradiation or heating with high temperature of 70 °C and above on Kimchi results in the softening of the texture, decolorization and development of oV-odor. Meanwhile, modiWed atmosphere packaging (MAP) is largely used for ready-to-use vegetables (Huxsoll & Bolin, 1989; Kader, Zagory, & Kerbel, 1989; Myers, 1989). Combined treatment of irradiation with MAP conditions has been suggested to maintain the sensory quality and to prolong the shelf-life of minimally processed vegetables (Ahn et al., 2005; Kim et al., 2005; Lacroix & Lafortune, 2004). The objective of this study was to investigate the eVects of combined N2-packaging (N2), heating at 60 °C for 30 min (HT) and gamma irradiation of 20 kGy (IR) on the shelfstability and quality of kimchi during storage at 35 °C. 2. Materials and methods 2.1. Preparation of samples Kimchi was supplied from Food Institute, CJ Food Co. Ltd. (Seoul, Korea). The procedure commonly used for manufacturing Kimchi was followed. BrieXy, Oriental cabbages were cut into half heads, dipped in 15% salt solution for 4 h, washed with tap water, drained and mixed with spices and additives. The spices and additives (5.0 g of sliced radish, 3.0 g of red pepper powder, 1.0 g of ground garlic, 0.5 g of ground ginger, 2.5 g of sliced green onion and 2.0 g of fermented anchovy sauce) were added into 100 g of the brined cabbage. Each half head of the blended cabbage was anaerobically packaged in polyethylene vinyl bags and fermented in a refrigerator (R-D303SJ, LG, Seoul, Korea) at 4 °C. During storage for about two weeks, fermentation process was monitored to obtain Kimchi samples of optimum quality with the range of about pH 4.5 and 0.3% of acidity. 2.2. N2-packaging, mild heating and gamma irradiation Optimally fermented Kimchi was cut into about 5 cm in length, and put in an aluminium-laminated low-density polyethylene (Al-LDPE, Sunkyung Co. Ltd., Seoul, Korea). Al-LDPE has the physical properties that water and gas were not transmittable, and melting point and density were 120 °C and 0.92 g/cm3, respectively. Samples were divided into four groups, non-treated control (Control), heating at 60 °C for 30 min (HT), gamma irradiation after mild heating (HT–IR), and gamma irradiation after N2-packaging and heating sample (N2–HT–IR). Control, HT, and HT–IR groups were aerobically packaged and N2–HT–IR group was packaged within 100% of nitrogen gas. Three groups for heating were sunk in a waterbath, heated at 60 °C for 30 min and cooled in ice water. After heating, two groups of HT–IR and N2–HT–IR were irradiated in a cobalt-60

57

gamma irradiator (point source, AECL, IR-79, Nordion, Canada) to obtain absorbed dose of 20 kGy. The source strength was approximately 300 kCi with a dose rate of 70 Gy min¡1 at 15 § 0.5 °C and the actual doses were within 2% of the target dose. The absorbed dose was monitored with both free-radical and ceric/cerous dosimeters. All samples were stored at 35 °C and used in subsequent experiments during storage period. 2.3. Microbial analysis Method of Oh, Choi, and Kim (1998) was used for the determination of the growth of microXora in treatments. BrieXy, 10 g of sample was aseptically prepared, put in a sterilized bag (10 £ 15 cm; Sunkyung Co. Ltd., Seoul, Korea) with 100 mL of peptone water (0.1%) and stomached in a stomacher (Model 400, Tekmar Co., LA, USA) for 2 min. The stomached solution of sample was used to test the growth of the total viable cells (TVC) and the lactic acid bacteria (LAB) in a plate count agar and MRS agar (Difco Lab., St. Louis, USA), respectively. Plates were prepared in triplicate and incubated at 37 °C for 48 h, and viable cell numbers on a plate were determined as colony forming units (log cfu) per gram. 2.4. Measurement of the pH and acidity By the method of Kang, Kim, and Byun (1988), pH and acidity of samples were determined. Ten grams of sample was homogenized within 100 mL of distilled water and Wltered with Whatman No. 2 (Whatman, Kent, England), and the Wltrate was used to determine pH and acidity. The pH was measured with a pH meter (Orion 520A, Boston, MA, USA) and acidity was expressed as a content of lactic acid (weight %) by measuring the titration volume of 0.1 N NaOH to adjust the pH at 8.4. 2.5. Measurement of the texture The texture of the sample was analyzed by the penetrating test by using a texture analyzer (TA-XT2i, Stable Micro Systems, England) system. Square-type samples (3 £ 3 cm) were prepared by cutting the stump of the cabbage at 5 cm distances from the bottom. Operation condition of texture analyzer was as follows: probe (P2, 5 mm cylinder probe), travel distance (65%), pretest speed (5.0 mm/s), test speed (1.0 mm/s) and post test speed (5.0 mm/s). 2.6. Sensory evaluation Sensory acceptances of samples were tested. The panel was composed of 20 general consumers. Five descriptors were employed to grade the quality in terms of the color, texture, taste, Xavor and overall acceptance. Very poor (weak) corresponded to 1.0 and very good (intense) to 7.0. Steamed rice was given as delivery at each test.

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J.-H. Kim et al. / Food Control 19 (2008) 56–61

2.7. Statistical analysis One-way analyses of variance (ANOVA) were used to determine the eVect of combined treatment of Kimchi on the growth of the microorganisms and the quality properties of the four groups by a Statistical Package for Social Sciences (SPSS, 10.0). Duncan’s multiple range test was used to compare diVerences among means at P < 0.05.

LAB appeared to similar tendency with TVC in Control and in HT. No growth of TVC and LAB was observed in HT–IR and N2–HT–IR treatments during storage of 30 days. The results appeared that combined treatment of irradiation of 20 kGy with heating at 60 °C for 30 min could thoroughly inactivate TCV and LAB in fermented Kimchi and it could control the aging process of Kimchi. 3.2. pH and acidity

3. Results and discussion 3.1. Total microbes and lactic acid bacteria The growths of TVC and LAB of the four Kimchi samples during storage are shown in Tables 1 and 2, respectively. At initial stage of storage, the number of TVC of the Control group appeared to about 8 log cfu g¡1. In general, TVC and LAB reach the level of 8–9 log cfu g¡1 after the optimum fermentation (Choi et al., 2006; Hwang, Yu, & Lee, 2004; Kim et al., 2004). These results indicated that all the samples were prepared from well fermented Kimchi and they were adequate to use in this study. TVC of the Control was not signiWcantly changed during storage of 30 day. The numbers of TVC and LAB of the HT was reduced to about 4 log cycle by a mild heating. TVC of HT increased to about 2 log cycles in 10-day storage and the rate of the growth retarded and reached about 8 log cfu g¡1 for a 30day storage. Kim et al. (2006) reported that heating in the range of 50–70 °C could prolong the aging period of Kimchi due to the inactivation of microorganisms related to aging. Table 1 Evaluation of the total microbes of Kimchi combined with N2-packaging, heating and gamma-irradiation during storage at 35 °C Sample

Storage at 35 °C (days)

Control HT2 HT–IR3 N2–HT–IR4

0

10

20

30

8.45 4.95 ND1 ND

8.64 6.87 ND ND

8.97 7.65 ND ND

8.73 8.21 ND ND

1

ND: not detectable. HT: heated at 60 °C for 30 min. 3 HT–IR: gamma irradiated at 20 kGy after heating at 60 °C for 30 min. 4 N2–HT–IR: gamma irradiated at 20 kGy after N2-packaging and heating at 60 °C for 30 min. 2

Table 2 Evaluation of the lactic acid bacteria of Kimchi combined with N2-packaging, heating and gamma-irradiation during storage at 35 °C Sample

Control HT2 HT–IR3 N2–HT–IR4 1 2–4

Storage at 35 °C (days) 0

10

20

30

8.26 4.35 ND1 ND

8.42 6.68 ND ND

8.73 7.29 ND ND

8.51 8.14 ND ND

ND: not detectable. Footnotes, see Table 1.

The changes of pH and acidity of samples during storage are shown in Tables 3 and 4. All treatments showed similar results of pH and acidity at 0 day, and no diVerences from the treatments were observed. And, these results indicated that Kimchi prepared for this experiment was well fermented. In general, Kimchi had the best taste when pH was about 4.2 (Mheen & Kwon, 1984). In Control and HT samples, pH decreased and acidity increased during storage. The result from HT, especially, indicates that surviving microorganisms recovered and grew, the fermentation was progressed and that the changes of pH and acidity were occurred consequently. Results from Tables 1 and 2 support the results of the pH and acidity well. Proliferation of homofermentative Lactobacillus plantarum strains, observed in the late stage of Kimchi fermentation, survived from mild heating of 60 °C, might cause the excessive fermentation, and pH of Kimchi would drop to below 4.0 and consequently could cause the over-fermentation and deterioration Table 3 Evaluation of the pH of Kimchi combined with N2-packaging, heating and gamma-irradiation during storage at 35 °C Sample

Control HT3 HT–IR4 N2–HT–IR5

Storage at 35 °C (days) 0

10

20

30

4.39 § 0.02a1A2 4.37 § 0.02aA 4.36 § 0.01aA 4.40 § 0.01aA

3.96 § 0.02cB 4.04 § 0.03bB 4.41 § 0.02aA 4.38 § 0.02aA

3.75 § 0.02cC 3.86 § 0.03bC 4.37 § 0.01aA 4.41 § 0.02aA

3.61 § 0.02cD 3.65 § 0.03bD 4.39 § 0.02aA 4.42 § 0.01aA

1 a–c

Values with diVerent letters within a column diVer signiWcantly (P < 0.05). 2 A–D Values with diVerent letters within a row diVer signiWcantly (P < 0.05). 3–5 Footnotes, see Table 1. Table 4 Evaluation of the acidity of Kimchi combined with N2-packaging, heating and gamma-irradiation during storage at 35 °C Sample

Control HT3 HT–IR4 N2–HT–IR5

Storage at 35 °C (days) 0

10

20

30

0.33 § 0.02a1D2 0.32 § 0.01bD 0.35 § 0.01aA 0.34 § 0.01aA

1.06 § 0.03aC 0.96 § 0.03bC 0.38 § 0.02cA 0.36 § 0.02cA

1.13 § 0.01aB 1.02 § 0.02bB 0.36 § 0.02cA 0.38 § 0.02cA

1.24 § 0.03aA 1.17 § 0.03bA 0.37 § 0.01cA 0.35 § 0.01cA

1 a–c Values with diVerent letters within a column diVer signiWcantly (P < 0.05). 2 A–D Values with diVerent letters within a row diVer signiWcantly (P < 0.05). 3–5 Footnotes, see Table 1.

J.-H. Kim et al. / Food Control 19 (2008) 56–61

of the sensory quality of Kimchi (Mheen & Kwon, 1984). Cho and Rhee’s report (1991) can be referred to for explaining the co-relationship between the growth of LAB and the decrease of the pH (or increase of acidity). That is, for retarding the fermentation and ensuring the shelf-stability of Kimchi, the control of LAB should be considered. pH and acidity of HT–IR and N2–HT–IR was not signiWcantly diVerent, and it did not change during storage. A further fermentation might not happen in HT–IR and N2–HT–IR due to inactivation of fermentation-related LAB (Table 2). In the previous study (Kim et al., 2006), the combined treatment of irradiation of 15–25 kGy with heating of 55–65 °C could also control the over-fermentation of Kimchi. 3.3. Hardness of the Kimchi Table 5 shows the changes of hardness of Kimchi samples during storage at 35 °C. Heating and irradiation induced the decrease of hardness of fermented Kimchi and the decrease was accelerated by the combination of irradiation. However, N2-packaging did slightly prevent the Table 5 Evaluation of the hardness of Kimchi combined with N2-packaging, heating and gamma-irradiation during storage at 35 °C Sample

Control HT3 HT–IR4 N2–HT–IR5

Storage at 35 °C (days) 0

10

20

30

1694 § 127a1A2 1528 § 105aA 927 § 73cA 1129 § 82bA

1295 § 118aB 1074 § 97bB 695 § 58dB 894 § 61cB

681 § 92aC 792 § 75aC 496 § 52bC 745 § 83aC

485 § 79abD 594 § 95aD 429 § 47bC 653 § 68aC

1 a–d Values with diVerent letters within a column diVer signiWcantly (P < 0.05). 2 A–D Values with diVerent letters within a row diVer signiWcantly (P < 0.05). 3–5 Footnotes, see Table 1.

59

decrease of hardness of Kimchi treated with heating and gamma irradiation. These results were similar to several reports the loss of hardness of Kimchi was one of the major adverse eVect of ionizing radiation (Cha et al., 1989; Kang et al., 1988; Kim et al., 2006). Generally, cellulose Wbers are broken and the Wrmness is softened by ionizing radiation. Powerful radicals generated from ionization of water by radiation react randomly with the molecules in Kimchi, and glycosidic bonds of carbohydrate are cleaved by the reaction of the radicals with ester bond and then the texture of vegetable is tenderized (Nayak, Suguna, Narasimhamurthy, & Rastogi, 2007; Prakash, Manley, DeCosta, Caporaso, & Foley, 2002). Otherwise, several studies reported that treatment of irradiation under modiWed atmosphere packaging (MAP) conditions could maintain the textural properties of minimally processed vegetables (Ahn et al., 2005; Kim et al., 2005). During storage at 35 °C, hardness of all treatments decreased and the decreasing activity was ranked as follows: Control > HT > HT–IR > N2–HT–IR with signiWcant diVerences of P < 0.05 (Table 5). Tenderization of Kimchi by the over-fermentation is relative to the growth of microorganisms and the activity of pectin hydrolysis enzyme, which catalyses the hydrolysis of partially-esteriWed pectin compounds (Buescher, Hudson, & Adams, 1979; Drake & Spayd, 1983; McCready & McComb, 1954). In this study, the combined treatment of heating and irradiation could not thoroughly control the tenderization of Kimchi during storage, because it was not possible to ensure perfect inactivation of pectin hydrolysis enzyme by the combination of heating and irradiation. When conducted at above refrigeration temperatures, irradiation can lead to softening of fresh vegetable products due to hydrolysis of pectins. Irradiation under frozen temperatures could be applied to some vegetables for reducing the adverse eVects of irradiation

Table 6 Sensory evaluation of Kimchi combined with N2-packaging, heating and gamma-irradiation during storage at 35 °C Storage (days)

Sample

Sensory scores Color

Texture

Taste

6.9 § 0.5 6.6 § 0.4a 6.2 § 0.5a 6.5 § 0.6a

6.9 § 0.6 6.6 § 0.8a 5.3 § 0.3b 5.8 § 0.5ab

6.6 § 0.7 6.4 § 0.5a 4.2 § 0.6c 5.2 § 0.4b

6.8 § 0.5 6.7 § 0.8a 5.4 § 0.4b 5.8 § 0.5ab

6.8 § 0.6a 6.4 § 0.5a 4.2 § 0.4b 5.1 § 0.5b

10

Control HT HT–IR N2–HT–IR

6.7 § 0.4a 6.4 § 0.7a 4.9 § 0.5b 5.1 § 0.4b

5.9 § 0.8a 5.4 § 0.4a 4.8 § 0.3a 5.1 § 0.5a

1.5 § 0.3b 2.6 § 0.4b 5.0 § 0.6a 5.7 § 0.5a

1.8 § 0.2b 2.3 § 0.4b 5.2 § 0.8a 5.9 § 0.6a

1.7 § 0.3b 2.4 § 0.5b 5.1 § 0.7a 5.8 § 0.6a

20

Control HT HT–IR N2–HT–IR

6.3 § 0.6a 6.2 § 0.5a 4.1 § 0.3b 4.6 § 0.5b

4.7 § 0.6a 4.5 § 0.3a 4.4 § 0.5a 4.7 § 0.4a

1.4 § 0.4b 2.1 § 0.3b 4.4 § 0.6a 5.3 § 0.5a

1.4 § 0.2b 2.0 § 0.3b 4.7 § 0.6a 5.4 § 0.4a

1.5 § 0.2b 1.9 § 0.4b 4.4 § 0.4a 5.3 § 0.5a

30

Control HT HT–IR N2–HT–IR

6.1 § 0.7a 5.7 § 0.5a 3.9 § 0.3b 4.2 § 0.4b

4.1 § 0.3a 4.2 § 0.2a 3.9 § 0.4a 4.5 § 0.5a

1.1 § 0.3b 1.8 § 0.2b 3.7 § 0.6a 4.9 § 0.5a

1.2 § 0.3b 1.9 § 0.3b 4.5 § 0.6a 4.9 § 0.4a

1.2 § 0.2b 1.3 § 0.4b 3.9 § 0.5a 4.8 § 0.7a

Values with diVerent letters within a column diVer signiWcantly (P < 0.05). Footnotes, see Table 1.

a

Overall acceptance

Control HT2 HT–IR3 N2–HT–IR4

1 a,b

a

Flavor

0

2–4

a1

a

60

J.-H. Kim et al. / Food Control 19 (2008) 56–61

(Farkas, 1997; Niemira, Fan, & Sommers, 2002; Thakur & Singh, 1995; Valdivia, Bustos, Ruiz, & Ruiz, 2002). Therefore, some applications such as irradiation under frozen temperatures should be required to minimize hydrolysis of pectins and to maintain the adequate sensory quality of Kimchi. 3.4. Sensory evaluation Sensory properties of the samples were evaluated during storage (Table 6). Control showed the highest scores for all items in the evaluation at 0 day. Even though HT– IR and N2–HT–IR were evaluated with lower scores than those of the Control and HT, organoleptic acceptance of N2–HT–IR was properly noted by the panel. All the sensory items of the treatments were scored with low grades of 5 and below except for the color of the Control during storage. Song et al. (2004) reported that high dose-irradiated Kimchi had the lower acceptance in terms of color, Xavor and texture than non-irradiated or low dose-irradiated Kimchi. In particular, taste, Xavor and overall acceptance were very lowly evaluated in Control and HT from 10 day. Whereas, these items of HT–IR and N2–HT–IR were scored in the ranges between 3 and 5 during storage, and N2–HT–IR was more eVective. Like in this study, the deterioration of sensory quality, a sour and bitter taste, oVodor and softening, occurred by the over-fermentation (Cheigh & Park, 1994; Chung & Yo, 1995; Lee et al., 2000). In 30 day storage, overall acceptance showed that N2–HT– IR was the highest among the treatments. However, it could be concluded that other food processing technologies should be taken into consideration to reduce the undesirable changes of Kimchi by ionizing radiation, although N2-packaging was eVective as combination process of irradiation. Acknowledgements This research was supported by Korea Science and Engineering Foundation; Ministry of Science and Technology; and Korean Government through its National Nuclear Technology Program. References Ahn, H. J., Kim, J. H., Kim, J. K., Kim, D. H., Yook, H. S., & Byun, M. W. (2005). Combined eVects of irradiation and modiWed atmosphere packaging on minimally processed Chinese cabbage (Brassica rapa L.). Food Chemistry, 89, 589–597. Ahn, S. J. (1988). The eVect of salt and food preservatives on the growth of lactic acid bacteria isolated from Kimchi. Korean Journal of Society of Food Science, 4, 39–50. Buescher, R. W., Hudson, J. M., & Adams, J. R. (1979). Inhibition of polygalacturonase softening of cucumber pickles by calcium chloride. Journal of Food Science, 44, 1786–1789. Byun, M. W., Cha, B. S., Kwon, J. H., Cho, H. O., & Kim, W. J. (1989). The combined eVect of heat treatment and irradiation on the inactivation of major lactic acid bacteria associated with Kimchi fermentation. Korean Journal of Food Science and Technology, 21(2), 185–191.

Cha, B. S., Kim, W. J., Byun, M. W., Kwon, J. H., & Cho, H. O. (1989). Evaluation of gamma irradiation for extending the shelf life of Kimchi. Korean Journal of Food Science and Technology, 21(1), 109–119. Cheigh, H. S., & Park, K. Y. (1994). Biochemical, microbiological and nutritional aspects of Kimchi (Korean fermented vegetable products). Critical Reviews in Food Science and Nutrition, 34, 175–203. Cho, Y., & Rhee, H. S. (1991). EVect of lactic acid bacteria and temperature on Kimchi fermentation (II). Korean Journal of Society of Food Science, 7, 89–95. Choi, Y. M., Whang, J. H., Kim, J. M., & Suh, H. J. (2006). The eVect of oyster shell powder on the extension of the shelf-life of Kimchi. Food Control, 17, 695–699. Chung, D. K., & Yo, R. (1995). Antimicrobial activity of bamboo leaves extracts on microorganisms related to Kimchi fermentation. Korean Journal of Food Science and Technology, 27(6), 1035–1038. Drake, S. K., & Spayd, S. E. (1983). InXuence of calcium testament on golden delicious apple quality. Journal of Food Science, 48, 403–406. Farkas, J. (1997). Physical methods of food preservation. In M. P. Doyle, L. R. Beuchat, & T. J. Montville (Eds.), Food microbiology fundamentals and frontiers (pp. 497–519). Washington, DC: American Society for Microbiology. Huxsoll, C. C., & Bolin, H. R. (1989). Processing and distribution alternatives for minimally processed fruit and vegetables. Food Technology, 43, 124–128. Hwang, J. H., Yu, K. W., & Lee, K. H. (2004). Studies on the pasteurization conditions for long-term storage of Kimchi. Food Engineering Progress, 8(1), 30–39. Jung, H. O., Chung, D. O., & Park, I. D. (2002). A study on sensory characteristics of herb onion Kimchi diVering in herb content. Korean Journal of Culinary Research, 8, 259–265. Kader, A. A., Zagory, D., & Kerbel, E. L. (1989). ModiWed atmosphere packaging of fruits and vegetables. Critical Reviews in Food Science and Nutrition, 28, 1–30. Kang, K. O., Ku, K. H., Lee, H. J., & Kim, W. J. (1991). EVect of enzyme and inorganic acid salts addition and heat treatment on Kimchi fermentation. Korean Journal of Food Science and Technology, 23, 183–187. Kang, S. S., Kim, J. M., & Byun, M. W. (1988). Preservation of Kimchi by ionizing radiation. Korean Journal of Food Hygiene, 3(4), 225–232. Kim, D. H., Song, H. P., Yook, H. S., Ryu, Y. G., & Byun, M. W. (2004). Isolation of enteric pathogens in the fermentation process of Kimchi (Korean fermented vegetable) and its radicidation by gamma irradiation. Food Control, 15, 441–445. Kim, J. K., Jo, C., Kim, H. J., Lee, J. W., Hwang, H. J., & Byun, M. W. (2005). Microbiological safety of minimally processed white radish in modiWed atmosphere packaging combined with irradiation treatment. Korean Journal of Food Science and Technology, 37(1), 11–14. Kim, M. J., Park, J. G., Kim, J. H., Park, J. N., Lee, H. J., Kim, W. G., et al. (2006). Combined eVect of heat treatment and gamma irradiation on the shelf-stability and quality of packaged Kimchi during acceleration storage condition. Korean Journal of Food Preservation, 13, 531–537. Lacroix, M., & Lafortune, R. (2004). Combined eVects of gamma irradiation and modiWed atmosphere packaging on bacterial resistance in grated carrots (Daucus carota). Radiation Physics and Chemistry, 71, 77–80. Lee, C. H. (1997). Lactic acid fermented food and their beneWts in Asia. Food Control, 8(5/6), 259–269. Lee, J. K., Lee, H. S., Kim, Y. C., Joo, H. K., Lee, S. H., & Kang, S. M. (2000). EVects of addition of adipic acid-resistant strains on extending shelf-life of Kimchi. Korean Journal of Food Science and Technology, 32(2), 424–430. Lee, M. Y., & Kim, S. D. (2003). Calcium lactate treatment after salting of chinese cabbage improves Wrmness and shelf-life of Kimchi. Journal of Food Science and Nutrition, 8, 270–277. Lee, S. H., Cho, O. K., Choi, W. J., & Kim, S. D. (1998). The eVects of mixed medicinal herb extracts with antimicrobial activity on the shelflife of Kimchi. Korean Journal of Food Science and Technology, 30, 1404–1408. McCready, R. M., & McComb, E. A. (1954). Pectic constituents in ripe and unripe fruit. Food Resources, 19, 530–534.

J.-H. Kim et al. / Food Control 19 (2008) 56–61 Mheen, T. L., & Kwon, T. W. (1984). EVect of temperature and salt concentration on Kimchi fermentation. Korean Journal of Society of Food Science and Nutrition, 16, 443–450. Moon, K. D., Byun, J. A., Kim, S. J., & Han, D. S. (1995). Screening of natural preservatives to inhibit Kimchi fermentation. Korean Journal of Food Science and Technology, 27, 257–263. Myers, R. A. (1989). Packaging considerations for minimally processed fruits and vegetables. Food Technology, 43, 120–126. Nayak, C. A., Suguna, K., Narasimhamurthy, K., & Rastogi, N. K. (2007). EVect of gamma irradiation on histological and textural properties of carrot, potato and beetroot. Journal of Food Engineering, 79, 765–770. Niemira, B. A., Fan, X., & Sommers, C. H. (2002). Irradiation temperature inXuences product quality factors of frozen vegetables and radiation sensitivity of inoculated Listeria monocytogenes. Journal of Food Protection, 65, 1406–1410. Oh, Y. A., Choi, K. H., & Kim, S. D. (1998). Changes in enzyme activities and population of lactic acid bacteria during the Kimchi fermentation supplemented with water extract of pine needle. Journal of Korean Society of Food Science and Nutrition, 27, 244–251.

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Park, K. J., & Woo, S. J. (1988). EVect of Na-acetate, Na-malate and Ksorbate on the pH acidity and sourness during Kimchi fermentation. Korean Journal of Food Science and Technology, 20, 40–44. Park, W. P., Park, K. D., Cheong, Y. J., & Lee, I. S. (2002). EVect of calcium powder addition on the quality characteristics of Kimchi. Journal of Korean Society of Food Science and Nutrition, 31, 428–432. Prakash, A., Manley, J., DeCosta, S., Caporaso, F., & Foley, D. (2002). The eVects of gamma irradiation on the microbiological, physical and sensory qualities of diced tomatoes. Radiation Physics and Chemistry, 63, 387–390. Song, H. P., Kim, D. H., Yook, H. S., Kim, H. S., Kwon, J. H., & Byun, M. W. (2004). Application of gamma irradiation for aging control and improvement of shelf-life of Kimchi, Korean salted and fermented vegetables. Radiation Physics and Chemistry, 71, 55–58. Thakur, B. R., & Singh, R. K. (1995). Combination processes in food irradiation. Trends in Food Science & Technology, 6, 7–11. Valdivia, M. A., Bustos, M. E., Ruiz, J., & Ruiz, L. F. (2002). The eVect of irradiation in the quality of the avocado frozen pulp. Radiation Physics and Chemistry, 63, 379–382.