Changes in Physicochemical, Nutritional and Hygienic Properties of ...

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Journal of Food Quality ISSN 1745-4557

CHANGES IN PHYSICOCHEMICAL, NUTRITIONAL AND HYGIENIC PROPERTIES OF CHINESE CABBAGE SEEDS AND THEIR SPROUTS ON GAMMA AND ELECTRON BEAM IRRADIATION JOONG-HO KWON1,4, GUI-RAN KIM1, JAE-JUN AHN1, KASHIF AKRAM1,2, HYE-MIN BAE1, CHAN-HEE KIM1, YURI KIM3 and BUM-SOO HAN3 1

School of Food Science and Biotechnology, Kyungpook National University, Daegu 702-701, Republic of Korea Institute of Food Science and Nutrition, University of Sargodha, Sargodha, Pakistan 3 EB Tech Co. Ltd., Daejeon, Republic of Korea 2

4

Corresponding author. TEL: 82-53-950-5775; FAX: 82-53-950-6772; EMAIL: [email protected] Received for Publication January 14, 2013 Accepted for Publication August 2, 2013 10.1111/jfq.12044

ABSTRACT Seed sprouts are susceptible to microbial contaminations, which might cause foodborne illnesses. In this study, gamma- and electron beam (e-beam)-irradiated (0–3 kGy) Chinese cabbage seeds (Brassica rapa ssp. Pekinensis) and their sprouts were investigated for the physicochemical, functional and microbiological qualities during storage. The irradiated seeds and their sprouts showed better overall microbial quality compared with nonirradiated samples; however, their hygienic quality profiles were same during storage of sprouts. The contents of ascorbic acid, carotenoid, chlorophyll and total phenolics of the seeds increased during germination but negligible changes were found during postharvest storage. Gamma irradiation and e-beam had similar effects on the physicochemical quality of Chinese cabbage seed sprouts with few exceptions (low germination rate of e-beam-treated seeds). These effects should be considered to obtain acceptable hygienic, nutritional and sensory attributes of irradiated Chinese cabbage seeds.

PRACTICAL APPLICATIONS The sprouted seeds widely used for human consumption are the suspect carriers of bacterial pathogens, which can outbreak sprout-related foodborne illnesses. Irradiation treatment is a promising technology to increase shelf life of sprouts and reduce bacterial pathogen contamination with minimum concession of nutritional and sensory aspects. However, it is significant to establish the effect of applied irradiation dose on the seed germination, sprout length, quality parameters and overall acceptability.

INTRODUCTION Fresh sprouts are popular in different cultures because of their high nutritional value and functional properties. They are a rich source of vitamins, minerals, fiber, protein and antioxidants (Waje et al. 2009a,c). Excellent antioxidant and anticancer properties of young sprouts of Korean salad plants have been reported by Kestwal et al. (2012). Chinese cabbage (Brassica rapa ssp. Pekinensis) is a popular green leafy vegetable in Asian countries. It is the main ingredient of the Korean delicacy kimchi, a Korean traditional fer316

mented food and is also gaining popularity in other countries. Chinese cabbage is also recognized to have various functional properties such as antimutagenic and anticancer properties (Park 1995). However, with the importance of sprouts for a healthy lifestyle, a serious threat of foodborne illnesses is also associated with them (Waje et al. 2009b). These sprouts are usually consumed as raw food without any considerable decontamination treatment that makes them a potential source of foodborne illnesses (NACMCF 1999). Raw sprouts are considered responsible for about 30 outbreaks of Journal of Food Quality 36 (2013) 316–323 © 2013 Wiley Periodicals, Inc.

J-H. KWON ET AL.

foodborne illnesses since 2000. Recently (February 2012), sprout-related outbreaks were reported in the U.S.A. in 11 states causing 29 illnesses, in which the shiga toxinproducing Escherichia coli O26 was the culprit microbe (Bites 2012). Innovative techniques to ensure the hygienic safety of fresh produce are highly desired, where food irradiation has shown the widespread application potential in protecting community health (Akram et al. 2012; Tripathi et al. 2013). Irradiation can result in complete sterilization of various foodborne pathogens on seeds. In the U.S.A., the Food and Drug Administration has permitted the irradiation of sprout seeds up to a maximum dose of 8 kGy to improve hygienic safety (CFR 2000). In a previous study, irradiation of broccoli seeds at 5.9 kGy was found effective in achieving a 5-log decrease in the population of different pathogens (Waje 2008). However, a major drawback of irradiation is its detrimental effects on the different seed growth parameters (Waje et al. 2009c). For example, the treatment at 8 kGy can eradicate E. coli O157:H7 from alfalfa seeds, but can also adversely affect the sprout yield (Kim et al. 2006). Waje et al. (2009c) showed that irradiation at a dose of 5 kGy decreased the growth of red radish seeds and the sprouts with reduced carotenoid, chlorophyll, ascorbic acid and total phenol contents were found. Rajkowski et al. (2003) also reported that the irradiation (2 kGy) of broccoli seeds significantly affected the important growth characteristics of the sprouts. However, there are no published results showing the effects of electron beam (e-beam) or gamma ray irradiation on the germination properties of Chinese cabbage seeds. Furthermore, the changes on the physicochemical properties of Chinese cabbage sprouts affected by irradiation of the seeds during growth and during postharvest storage of the sprouts are also important aspects requiring thorough investigation. In this study, the potential application of e-beam and gamma irradiation on Chinese cabbage seeds to improve the hygienic quality of the sprouts was examined. The changes in important seed growth parameters (germination, yield and growth) and physicochemical characteristics (ascorbic acid, carotenoids, chlorophyll and total phenol contents) of the seeds and their sprouts were also investigated.

QUALITY OF IRRADIATED CABBAGE SEEDS

e-beam accelerator (acceleration voltage of 2.5 MeV, ELV-4, EB-Tech., Daejeon, Korea) and gamma irradiator (Co-60, AECL, IR-79, Nordion International Co. Ltd., Ottawa, Canada) at a dose rate of 2.1 kGy/h at the Korean Atomic Energy Research Institute in Jeongeup, Korea. For e-beam irradiation, the seeds were irradiated in a layer of 3 cm, where the dose uniformity (max/min ratio) was 0.9. The applied doses were verified using an alanine dosimeter. The seeds were kept refrigerated at 6 ± 2C prior to use.

Cultivation and Storage The seeds were cultivated in an EasyGreen Automatic Sprouter System (EQMV 110V/60Hz, EasyGreen Factory, Milton, Ontario, Canada). Approximately 20 g of seeds of each treatment were placed in small cartridges and grown for 5 days at 23 ± 2C. A mist generator was turned on for 15 min every 3 h. The sprouts (50 g) were packed in a commercial polyethylene packing container and stored at 6 ± 2C.

Germination, Yield and Shoot Length Determinations The method described by the Association of Official Seed Analysts (AOSA 1965) was used and the results were presented as percent germination. The seeds with 2-mm size of roots or shoots were considered as germinated (Fan et al. 2004). The yield ratio was calculated by dividing the weight of the sprouts with the weight of the seeds used. One hundred seed sprouts were examined for their sprout length with a Digimatic caliper (Mitutoyo Corp., Kawasaki, Japan). The experiments were performed in triplicate.

Chemical Analysis The ascorbic acid contents were examined through the titrimetric method of the Association of Official Analytical Chemists (AOAC 2000). The technique reported by Fan and Thayer (2001) was used to analyze the carotenoids and chlorophyll contents. Total phenolic contents were examined using the Folin–Denis Colorimetric Method (Schanderl 1970). Gallic acid was used to calculate the calibration curve and the contents were reported as gallic acid equivalents (mg) per gram of weight (dried) of sprouts.

MATERIALS AND METHODS Sensory Evaluation Sample Preparation and Irradiation Treatments Chinese cabbage also called kimchi cabbage (Brassica rapa ssp. Pekinensis) seeds were purchased from a local seed company (Daenong Bio, Kyungggido, Korea). The seeds (200 g) were irradiated at doses 0, 1, 2 and 3 kGy using an Journal of Food Quality 36 (2013) 316–323 © 2013 Wiley Periodicals, Inc.

The sprouts were evaluated for color, odor, texture and overall acceptability by 10 sensory panelists comprised of graduated students at Kyungpook National University, Korea. The panelists recorded their ratings on a 5-point (5 = very good; 1 = very bad) hedonic scale (Waje et al. 2009c). 317


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Microbiological Analysis of the Seeds and Sprouts The seeds and sprouts were examined for total plate count, coliforms and yeasts and molds. Five grams of seeds/ sprouts were mixed with 45 mL of sterile peptone water. Further dilutions were performed and plate count agar, desoxycholate agar and potato dextrose agar (acidified with 10% tartaric acid) were used for the total plate count, coliforms and for the yeasts and mold count, respectively. Total microbial count was determined after 24–48 h of incubation at 30C and 37C for the total plate count and coliforms, respectively. The yeast and mold count was determined after incubation for 3 days at 30C.

Statistical Analysis The data analysis was conducted using Origin 6.0 (Microcal Software Inc., Northampton, MA) and the SAS program (version 9.1, SAS Institute, Cary, NC). Results were reported as means ± standard deviations, and Duncan’s multiple range test (P < 0.05) was used to compare the mean values.

severe effect of e-beam irradiation might be attributed due to the high dose rate (Jia et al. 2013). The decrease in length and yield ratio of the sprouts reflected the detrimental effect of irradiation on the seed growth and the results were dependent on the applied irradiation dose. High resistance to irradiation was reported in an earlier study for red radish seeds in terms of its germination ability but a reduced growth rate was observed (Waje et al. 2009c). Rajkowski et al. (2003) also observed that irradiation of broccoli seeds showed a decline in germination percentage and yield ratio with increasing irradiation doses. However, the percent germination was not affected in alfalfa seeds irradiated above 3 kGy, but there was a decrease in yield ratio (Rajkowski and Thayer 2001). The stress response of seeds to irradiation might be the cause of these observations (Fan et al. 2004). Both gamma and e-beam irradiation affected key features of seed viability of Chinese cabbage seeds, which may be unacceptable to sprout producers. Fan et al. (2004) suggested that long cultivation time of irradiated seeds can help to attain the similar yield as that in nonirradiated seeds.

Changes in Ascorbic Acid Content on Irradiation

RESULTS AND DISCUSSION Effect of Irradiation on Seed Viability Table 1 presents the effects of gamma and e-beam irradiation of Chinese cabbage seeds on the percentage germination, yield ratio and sprout length. The nonirradiated seeds had a high germination percentage (98%). Both gamma and e-beam irradiation showed a dose-dependent reduction in germination percentage with the effect being more prominent in the e-beam-irradiated seeds. Waje et al. (2009c) also reported similar findings for red radish seeds; however, the germination percentage of red radish seeds was over 97% for irradiation up to 5 kGy. The yield ratio and sprout length also showed an irradiation dose-dependent decrease. Gamma and e-beam irradiation had a similar effect on sprout length, but the yield ratio was more drastically affected by e-beam irradiation. Comparatively, the more

The ascorbic acid contents of the nonirradiated and irradiated seeds were similar irrespective of the type and dose of irradiation. There was a significant increase in ascorbic acid contents upon germination of both nonirradiated and irradiated seeds (Fig. 1A). Frias et al. (2005) also found that lupin sprouts contain higher amounts of ascorbic acid than the raw seeds. However, a remarkable difference was evident between the sprouts from the nonirradiated and irradiated Chinese cabbage seeds. The effect of the irradiation dose was also clear with a less obvious effect from the source of irradiation. Earlier studies involving alfalfa sprouts presented contrary findings and showed high ascorbic acid contents in treated than that of those grown from nonirradiated seed (Fan et al. 2003, 2004). This might be due to the difference in their stress responses to irradiation resulting in various nutritional changes. Additional

TABLE 1. GERMINATION (%), YIELD RATIO AND SHOOTING LENGTH OF CHINESE CABBAGE SPROUTS GROWN FROM IRRADIATED SEEDS Germination (%)

Yield ratio (g/g seed)

Shooting length (cm)

Dose (kGy)

Electron beam

Gamma ray

Electron beam

Gamma ray

0 1 2 3

98 ± 0.6* 94 ± 1.0by 89 ± 0.6cy 87 ± 1.0dy

98 ± 0.6 96 ± 0.6bx 91 ± 1.0cx 90 ± 1.2cx

9.87 ± 0.26 8.21 ± 0.18by 7.65 ± 0.45bx 4.53 ± 0.29cy

9.87 ± 0.26 8.70 ± 0.15bx 7.86 ± 0.19cx 6.59 ± 0.31dx

ax

ax

ax

ax

Electron beam

Gamma ray

26.27 ± 5.14 21.48 ± 2.96bx 19.72 ± 2.34cx 16.60 ± 2.99dx

26.27 ± 5.14ax 23.19 ± 3.18bx 19.34 ± 3.54cx 16.69 ± 2.27dx

ax

* Means ± standard deviation (n = 100). a–d Means followed by different letters within the column per parameter are significantly different (P < 0.05). x–y Means followed by different letters within the row the parameter are significantly different (P < 0.05).

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Seeds

Germination

Ascorbic content (ppm)

Control E-beam 1 kGy E-beam 2 kGy E-beam 3 kGy Gamma ray 1 kGy Gamma ray 2 kGy Gamma ray 3 kGy

A

80

60

40

Storage

Germination

Seeds

Storage

140

B

16

Carotenoid content (ppm)

160


12

8 Control E-beam 1 kGy E-beam 2 kGy E-beam 3 kGy Gamma ray 1 kGy Gamma ray 2 kGy Gamma ray 3 kGy

4

20

0 0

2

4

6

8

10

12

0

2

4

Day Seeds

C

80

Chlorophyll content (ppm)

Seeds

Storage

Germination

60

40 Control E-beam 1 kGy E-beam 2 kGy E-beam 3 kGy Gamma ray 1 kGy Gamma ray 2 kGy Gamma ray 3 kGy

20

Total phenolic content (ppm)

100

6

8

10

12

Day Storage

Germination

D

300

200


60 55

0 0

2

4

6

8

10

Day

12

0

2

4

6

8

10

12

Day

FIG. 1. ASCORBIC ACID CONTENT (A), CAROTENOID CONTENT (B), CHLOROPHYLL CONTENT (C) AND TOTAL PHENOLIC CONTENT (D) OF CHINESE CABBAGE SPROUTS GROWN FROM IRRADIATED SEEDS DURING GERMINATION (AT 23 ± 2C) AND STORAGE (AT 6 ± 2C)

studies are required to examine the effect of irradiation on the sprouts grown from different varieties of seeds. The decrease in ascorbic acid contents of Chinese cabbage sprouts could be related to the retarded growth of the sprouts. After 4 and 7 days of postharvest storage, the ascorbic acid contents decreased in all the sprouts, where the sprouts from the irradiated seeds showed lower values than that of those from nonirradiated ones. A decline in ascorbic acid contents during postharvest storage was also found in red radish and alfalfa sprouts (Fan et al. 2003; Waje et al. 2009c).

Changes in Total Carotenoid Content on Irradiation Both the sources and doses of irradiation did not affect the total carotenoid contents of the seeds; however, the total carotenoid contents showed significant improvement during sprout growth (Fig. 1B). This shows that sprouting enhances the functional properties of Chinese cabbage Journal of Food Quality 36 (2013) 316–323 © 2013 Wiley Periodicals, Inc.

seeds. Other scientists have also reported that sprouts have higher nutritional and functional components than raw seeds (Randhir et al. 2004; Frias et al. 2005; Waje et al. 2009c). Khattak et al. (2008) reported a noteworthy improvement in the carotenoid content of chickpea seeds with increased germination time. The improvement of the nutritional properties is probably due to the chemical changes during germination, when simple carbohydrates, free amino acids and other essential nutrients are produced (Fernandez-Orozco et al. 2006). The irradiation of Chinese cabbage seeds resulted in a major decrease in carotenoid contents in the sprouts depending on the applied radiation dose. However, Fan et al. (2004) observed no major change in carotenoid content of the sprouts from 3 kGy-irradiated alfalfa seeds, where irradiation had negligible effects on germination characteristics. Irradiation reduced the germination of the Chinese cabbage seeds, which resulted in underdeveloped sprouts with lower carotenoid contents compared with those grown from the nonirradiated ones (Waje et al. 2009a). However, all sprouts were found with a 319


Changes in Total Chlorophyll Content on Irradiation In seeds, the chlorophyll content was unaffected upon irradiation irrespective of the dose and source used. However, germination caused a substantial increase in the chlorophyll content (Fig. 1C). In sprouts, there was a decrease in the chlorophyll content with increasing irradiation doses irrespective of the source of irradiation, which resulted in the sprouts from the nonirradiated seeds being relatively greener than those from the irradiated ones. However, the sprouts from the nonirradiated and irradiated seeds showed similar chlorophyll content during postharvest storage. A low germination rate of the irradiated seeds affected the chlorophyll content. The influence was also visually observed, where the sprouts from the irradiated seeds were less developed and appeared lighter in color compared with those from the nonirradiated ones. The chlorophyll content showed an increase during postharvest storage of the sprouts and the values remained lower in the sprouts from the irradiated seeds than in those from the nonirradiated ones. The findings of this study were in good agreement with the findings for the red radish seed sprouts (Waje et al. 2009c). However, other scientists found that the chlorophyll content of the sprouts from irradiated alfalfa seeds were similar to nonirradiated ones, where the postharvest storage of sprouts showed reduced chlorophyll content (Fan et al. 2003).

from the 1 and 2 kGy-irradiated seeds. The effect of irradiation on germination may have had an influence in the reduction of the phenol content in the sprouts. Contradictory results were reported by Fan et al. (2003) showing that alfalfa sprouts grown from irradiated (up to 4 kGy) seeds had enhanced antioxidant contents than those grown from the nonirradiated ones. The variation in the stress response of different seeds to irradiation might be responsible for these findings as the results from irradiated broccoli seeds also showed reduced carotenoid and phenol contents (Waje et al. 2009a).

Effect of Irradiation on Hygienic Quality Irradiation reduced the total plate count in Chinese cabbage seeds, with the effect of e-beam irradiation being more pronounced. However, it increased exponentially during germination (Fig. 2) and after 5 days of germination, the counts were about 107–109 cfu/g in all sprouts irrespective of the irradiation dose and source. Comparatively higher total

Total aerobic 8

6

Log c fu /g

significantly higher carotenoid content during storage with overall better values for the sprouts from the nonirradiated seeds. Earlier studies have reported red radish (Waje et al. 2009c), broccoli (Waje et al. 2009a) and alfalfa (Randhir et al. 2004) seeds with variable responses in their germination and nutritional properties on irradiation. Therefore, sprout seeds require thorough investigation before application of irradiation technology.

J-H. KWON ET AL.

320


2

0.00 Seeds

0

Storage

Germination

2

4

6

8

10

12

Time (day)

Coliforms

Changes in Total Phenol Content on Irradiation

6

Log c fu/ u /g

Similar to the other contents (mentioned above), irradiation did not change the total phenol content of the Chinese cabbage seeds (Fig. 1D). However, there was a sharp increase in total phenol contents upon germination. Similarly, Lopez-Amoros et al. (2006) and Kestwal et al. (2012) reported an increase in phenolic compounds upon sprouting of peas and beans. Fenugreek (Frias et al. 2005), mungbean (MacCue and Shetty 2002) and Cassia hirsuta (Vadivel et al. 2011) sprouts also showed increased phenol contents and antioxidant activity compared with their raw seeds. Total phenol contents were higher in the sprouts from the nonirradiated seeds upon germination, but their stability during postharvest storage was prominent in the sprouts

4


4

0

Seeds 0

Storage

Germination 2

4

6

8

10

12

Time (day) FIG. 2. TOTAL PLATE COUNT AND COLIFORMS OF CHINESE CABBAGE SPROUTS GROWN FROM IRRADIATED SEEDS DURING GERMINATION (AT 23 ± 2C) AND STORAGE (AT 6 ± 2C)


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plate counts of the sprouts from the nonirradiated seeds was observed during postharvest storage. It has been observed that fresh sprouts typically have total plate counts as high as 108–109 cfu/g because of the intrinsic microflora of the seeds and the sprout growth environment (Waje et al. 2009c). The coliforms were retarded by irradiation at the start of germination, but a similar trend/count was obvious in the sprouts from nonirradiated and irradiated seeds as the germination period proceeded and during postharvest storage. Previously, comparable results were reported for the sprouts from irradiated red radish and broccoli seeds (Waje 2008).

ing, but irradiation retarded the growth of Chinese cabbage seeds, which resulted in a significant reduction in the carotenoid, chlorophyll, ascorbic acid and total phenol contents. The overall acceptability of the sprouts was also affected by irradiation. Most of the nutritional attributes remained stable during the postharvest storage of Chinese cabbage seed sprouts. Further investigation is required to examine whether increasing the growth time of irradiated Chinese cabbage seeds will enhance the yield ratio and nutritional quality of the sprouts. Irradiation at optimum doses in combination with other treatments, such as chemical treatments, should be devised to achieve improved hygienic quality with no/minimal effects on key quality parameters of the sprouts.

Sensory Properties Sensory evaluation of sprouts showed that sprouts grown from gamma-irradiated seeds had a significantly lower acceptability than those from the nonirradiated seeds (Table 2). The results were different in e-beam irradiation, which showed higher acceptability, but this acceptability level decreased and became lower than those from the nonirradiated seeds during postharvest storage. The effects of irradiation on the color and texture score was more clear during the storage of the sprouts, where the sprouts from e-beam-irradiated seeds exhibited lower color scores compared with those from gamma-irradiated seeds. It is well established that irradiation treatment can eradicate foodborne pathogens in sprout seeds resulting in improved hygienic quality of the seed sprouts (Bari et al. 2004). However, this study found that irradiation affected the germination, yield ratio and sprout length depending upon the applied irradiation dose, with the effect of e-beam irradiation being more evident. It was also observed that the nutritional properties of the seeds increased upon sprout-

CONCLUSIONS Germination improved the nutritional value of the Chinese cabbage seeds. E-beam and gamma irradiation of the seeds showed comparable effects on the nutritional quality of the seed sprouts; however, in some cases, the effects of e-beam irradiation were more pronounced. The ascorbic acid, carotenoid, chlorophyll and phenol contents of the sprouts decreased depending on the applied irradiation dose. Irradiation improved the microbial quality of the seeds. However, the effect of irradiation was not observed during germination and postharvest storage, where the sprouts from the irradiated and nonirradiated seeds had about same hygienic quality. The sensory quality of the sprouts decreased with storage, where the effect of irradiation became clearer. Further research is required to obtain acceptable physicochemical and microbial quality characteristics using effective combination treatments with low dose irradiation.

TABLE 2. SENSORY PROPERTIES* OF E-BEAM AND GAMMA RAY-IRRADIATED CHINESE CABBAGE SPROUTS STORED AT 6 ± 2C FOR 7 DAYS

Parameter Color

Odor

Texture

Overall acceptability

Storage (day) 1 4 7 1 4 7 1 4 7 1 4 7

Electron beam (kGy) 0

Gamma ray (kGy)

1

4.6 ± 0.7 3.7 ± 0.5ay 3.8 ± 0.9ay 3.7 ± 0.5ax 3.1 ± 0.3ax 3.0 ± 0.8ax 4.1 ± 0.7ax 3.0 ± 0.6ay 3.4 ± 0.9ay 4.2 ± 0.4ax 3.3 ± 0.7ay 3.3 ± 0.8axy ax

2

4.8 ± 0.4 3.7 ± 0.5by 2.3 ± 0.9bz 3.9 ± 0.9bx 3.1 ± 0.7by 2.6 ± 0.8aby 3.9 ± 0.6abx 3.8 ± 0.4ax 2.6 ± 0.7ay 4.4 ± 0.5ax 3.8 ± 0.4by 2.4 ± 0.5bz ax

3

2.9 ± 0.3 1.9 ± 0.6cy 1.2 ± 0.4cz 3.2 ± 1.0bx 2.7 ± 0.7bxy 2.1 ± 0.6by 3.2 ± 1.2bx 2.5 ± 0.8bx 2.5 ± 0.8ax 3.3 ± 0.7bx 2.5 ± 0.8cy 1.8 ± 0.6bz bx

0

4.7 ± 0.5 4.8 ± 0.4ax 3.7 ± 0.9ay 4.6 ± 0.5ax 4.1 ± 0.3axy 3.4 ± 0.8ay 4.3 ± 0.5ax 4.0 ± 0.8ax 2.9 ± 0.9ay 4.6 ± 0.5ax 4.8 ± 0.4ax 3.3 ± 0.8ay ax

1

4.6 ± 0.7 3.7 ± 0.5ay 3.8 ± 0.9ay 3.7 ± 0.5ax 3.1 ± 0.3ax 3.0 ± 0.8ax 4.1 ± 0.7ax 3.0 ± 0.6ay 3.4 ± 0.9ay 4.2 ± 0.4ax 3.3 ± 0.7ay 3.3 ± 0.8axy ax

2

3.9 ± 0.7 2.8 ± 0.6by 2.6 ± 0.8by 3.3 ± 0.5ax 3.1 ± 0.6ax 2.9 ± 0.7ax 4.2 ± 0.8ax 2.9 ± 0.6aby 2.9 ± 0.9ay 3.7 ± 0.5bx 2.9 ± 0.6ay 2.6 ± 0.7aby bx

3

4.0 ± 0.7 2.9 ± 0.6by 2.8 ± 0.8by 3.0 ± 0.7ax 3.4 ± 0.7ax 3.0 ± 0.9ax 3.7 ± 0.5ax 2.9 ± 0.7aby 2.8 ± 0.8ay 3.7 ± 0.3abx 3.1 ± 0.3ay 2.9 ± 0.9aby abx

3.0 ± 0.7ax 1.4 ± 0.5cy 1.6 ± 0.8cy 3.0 ± 0.8ax 1.9 ± 0.9by 2.5 ± 0.8axy 2.9 ± 0.6bx 2.2 ± 0.6by 2.9 ± 0.6ax 3.0 ± 0.5cx 2.3 ± 0.7by 1.9 ± 0.6by

* Sensory evaluation was conducted by 10 panelists using a 5-point hedonic scale (5 = very good; 1 = very bad). a–c Means followed by different letters within the row per parameter are significantly different (P < 0.05). x–z Means followed by different letters within the column are significantly different (P < 0.05).


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ACKNOWLEDGMENT This research was supported by the Technology Development Program for Food, Ministry for Food, Agriculture, Forestry and Fisheries, Republic of Korea.

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