This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and

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2 Radiation Physics and Chemistry 81 (2012) Contents lists available at SciVerse ScienceDirect Radiation Physics and Chemistry journal homepage: Effect of high-dose irradiation on quality characteristics of ready-to-eat chicken breast Hyejeong Yun a, Kyung Haeng Lee b, Hyun Jung Lee a, Ju Woon Lee c, Dong Uk Ahn d, Cheorun Jo a,n a Department of Animal Science and Biotechnology, Chungnam National University, Daejeon , South Korea b Department of Food Science and Nutrition, Chungju National University, Jeungpyung , South Korea c Radiation Food Science and Biotechnology, Korea Atomic Energy Research Institute, Jeoungeup , South Korea d Department of Animal Science, Iowa State University, Ames, IA , USA article info Article history: Received 2 June 2011 Accepted 30 October 2011 Available online 7 November 2011 Keywords: High-dose irradiation Ready-to-eat chicken Volatile compound Quality abstract High-dose (higher than 30 kgy) irradiation has been used to sterilize specific-purposed foods for safe and long-term storage. The objective of this study was to investigate the effect of high-dose irradiation on the quality characteristics of ready-to-eat chicken breast in comparison with those of the low-dose irradiation. Ready-to-eat chicken breast was manufactured, vacuum-packaged, and irradiated at 0, 5, and 40 kgy. The populations of total aerobic bacteria were 4.75 and 2.26 Log CFU/g in the samples irradiated at 0 and 5 kgy, respectively. However, no viable cells were detected in the samples irradiated at 40 kgy. On day 10, bacteria were not detected in the samples irradiated at 40 kgy but the number of bacteria in the samples irradiated at 5 kgy was increased. The ph at day 0 was higher in the samples irradiated at 40 kgy than those at 0 and 5 kgy. The 2-thiobarbituric acid reactive substance (TBARS) values of the samples were not significantly different on day 0. However, on day 10, the TBARS value was significantly higher in the samples irradiated at 40 kgy than those at 0 and 5 kgy. There was no difference in the sensory scores of the samples, except for off-flavor, which was stronger in samples irradiated at 5 and 40 kgy than control. However, no difference in off-flavor between the irradiated ones was observed. After 10 days of storage, only the samples irradiated at 40 kgy showed higher offflavor score. SPME-GC MS analysis revealed that 5 kgy of irradiation produced 2-methylbutanal and 3-methylbutanal, which were not present in the control, whereas 40 kgy of irradiation produced hexane, heptane, pentanal, dimethly disulfide, heptanal, and nonanal, which were not detected in the control or the samples irradiated at 5 kgy. However, the amount of compounds such as allyl sulfide and diallyl disulfide decreased significantly in the samples irradiated at 5 kgy and 40 kgy. & 2011 Elsevier Ltd. All rights reserved. 1. Introduction Irradiation technology is well known to be the most effective method for sterilization of food products. Recently, research has focused on using irradiation technology for the development of specific-purposed food products, including space, military, elderly, and immuno-compromised patient foods. The food products in this category should be safe to consume even after a long storage period (Bourland, 2008). When developing space foods, approximately kgy of high-dose irradiation is applied to ensure sterilization of radiation-resistant bacteria and fungi (Bourland, 2008; NASA, 2003). However, high-dose irradiation, especially higher than 10 kgy, can lead to physicochemical changes and significantly deteriorate sensory properties of foods, including taste, flavor, texture, and color (Kim et al., 2006). To prevent or minimize quality changes in food products after high-dose irradiation, the combination of n Corresponding author. Tel.: þ ; fax: þ address: cheorun@cnu.ac.kr (C. Jo). ascorbic acid, calcium salt, color agent from paprika, and an advanced packaging method has been introduced (Lacroix and Ouattata, 2004) but not implemented well. Ready-to-eat chicken breast products are popular poultry meat dishes worldwide. However, the hygienic quality and safety of these products during distribution and storage is not well established due to potential contamination of pathogens or spoilage bacteria from fresh vegetables, soy sauce, and raw chicken breast. In this study, low- and high-dose irradiation (5 and 40 kgy) of ready-to-eat chicken breast was performed, and the physicochemical, microbiological, and sensory quality characteristics were compared after storage for 10 day at 4 1C. 2. Materials and methods 2.1. Sample preparation Chicken breast (Orpum Co. Ltd., Sangju, Korea) and ingredients were purchased from a local market. The amount of ingredients X/$ - see front matter & 2011 Elsevier Ltd. All rights reserved. doi: /j.radphyschem

3 1108 H. Yun et al. / Radiation Physics and Chemistry 81 (2012) per 1 kg of chicken breast used were hot pepper paste (75 g), red pepper powder (75 g), soy sauce (100 g), sugar (75 g), garlic (50 g), fresh onion (750 g), and black pepper (2.5 g). All ingredients were mixed with the chicken breast, heated on a preheated pan (approximately 170 1C) for 20 min, and cooled for 1 h at ambient temperature. Approximately 100 g of the sample was vacuum-packaged in a polyethylene/nylon bag (2 ml O 2 /m 2 /24 h at 0 1C, Kuk Young Export Packaging Co., Daejeon, Korea) and irradiated at 5 and 40 kgy using a gamma irradiator (Advanced Radiation Technology Institute, Jeongeup, Korea). Non-irradiated samples were also prepared as a control. Irradiated and nonirradiated control samples were then stored at 4 1C for 10 day Microbiological, chemical, and sensory analyses The experiment was performed in triplicate. Media for the enumeration of total aerobic bacteria was tryptic soy agar (Difco Laboratories, Sparks, MD, USA). For ph, the homogenized samples were measured using a ph meter (Orion520A; Orion Research Inc., Boston, MA, USA). The development of lipid oxidation was measured as 2-thiobarbituric acid reactive substance (TBARS) value using the method described by Jung et al. (2010). Measurements of volatile basic nitrogen were performed according to Kruk et al. (2011). Volatile compounds were measured by solidphase microextraction (SPME) gas chromatograph/mass spectrometry (GC/MS) according to Sohn et al. (2009). Sensory evaluation of irradiated samples for color, odor, taste, texture, and overall acceptance was performed on a 9 point hedonic scale using 15 untrained panelists. The sensory session was carried out 2 times per day Statistical analysis The data were collected and analyzed by SAS software (version 8.02; SAS Institute, Cary, NC, USA). Mean values and standard errors of the mean (SEM) were reported, and the significance was defined at Pr0.05. Differences among mean values were analyzed by Student Newman Keul s multiple range test. 3. Results and discussion After manufacturing the ready-to-eat chicken breast, the initial number of contaminated microorganisms was 4.75 log CFU/g, but 2 log reduction was achieved by irradiation at 5 kgy (Table 1). When the samples were exposed to 40 kgy of irradiation, no viable cells were observed. On day 10, non-irradiated control showed similar levels of microorganisms as day 0. On the other hand, the samples irradiated at 5 kgy showed increase in the number of microorganisms over the 10-day storage, but still 1 log lower than that of the control. The samples irradiated at 40 kgy showed no viable cells even after 10 day at 4 1C. From the results, it can be assumed that specific-purposed foods should be irradiated at a high-dose (40 kgy) due to the observed microbial growth in the samples irradiated at 5 kgy. The ph of the control samples (5.73) were not different from those irradiated at 5 kgy but was statistically different from that irradiated at 40 kgy (5.83). No difference was found in the ph of the chicken breast after storage, which is in agreement with a study by Lee and Kim (2004). Generally, the ph of meat increases as the level of oxidation increases (Holly et al., 1994). When irradiation passes through matters such as solutions or foods, energy is absorbed, leading to ionization or excitation of atoms and molecules and ultimately induce chemical changes (Stewart, 2001). The ph of an aqueous system can affect the end result of irradiation. Acidic medium (excess H þ ) favors the disappearance of aqueous electrons (e aq), whereas alkaline medium favors their formation (Brewer, 2004). The analysis of TBARS values was carried out to assess lipid oxidation development of the samples. On day 0, there was no significant difference found among the treatments (Table 1). However, irradiation at 40 kgy showed a significantly higher TBARS value than other treatments after 10 day of storage. The content of volatile basic nitrogen (VBN) ranged between and mg%, and the samples irradiated at 40 kgy were higher than those at 0 and 5 kgy (Table 1), regardless of storage time. Generally, VBN is used to measure freshness of meat-based foods (less than 20 mg% in packed meats), and high protein foods with high contamination by microorganisms have high VBN values (Davies and Board, 1998). The higher VBN value of the high-dose-irradiated samples was not due to contamination by microorganisms but instead by chemical radiolysis of meat protein molecules to small N-containing molecules. The volatile compounds produced from ready-to-eat chicken breast were identified by SPME GC/MS immediately after irradiation at 5 and 40 kgy (Table 2). Irradiation increased the production of volatile compounds, including hexane, heptane, propanal, 2-methyl-butanal, 3-methyl-butanal, benzene, ally methyl sulfide, pentanal, toluene, dimethyl disulfide, hexanal, heptanal, nonanal, benzaldehyde, and total volatiles, compared to that of the control. After 10 day of storage, the amounts of hexane, heptane, propanal, 2-methyl-butanal, 3-methyl-butanal, benzene, ally methyl sulfide, pentanal, toluene, dimethyl disulfide, and hexanal increased by approximately 2 5 fold. In contrast, the amounts of heptanal and nonanal decreased or not detected in the control and irradiated samples on day 10. Generally, irradiation produced characteristic volatile compounds in meats such as 1-pentene, 1-hexene, 1-heptene, and dimethyl disulfide, which Table 1 Effect of low- and high-dose irradiation on total aerobic bacteria, ph, TBARS, and volatile basic nitrogen of ready-to-eat chicken breast stored at 4 1C for 10 day. Irradiation dose (kgy) Total aerobic bacteria (log CFU/g) ph TBARS (mg/g of malondialdehyde) Volatile basic nitrogen (mg%) Storage day SEM Storage day SEM Storage day SEM Storage day SEM x 4.74x y y y 18.67y yb 3.30ya y y y 20.35y ND 1 z NDz x b 3.67ax x 22.40x SEM Values with different letters (a b) within the same row differ significantly (Po0.05). Values with different letters (x z) within the same column differ significantly (Po0.05). 1 ND: Viable cell was not detected with detection limit at o10 1.

4 H. Yun et al. / Radiation Physics and Chemistry 81 (2012) Table 2 Major volatile compounds (area count 10 4 ) produced from irradiated ready-to-eat chicken breast. Compound name Storage (day) kgy 5 kgy 40 kgy SEM 1 0 kgy 5 kgy 40 kgy SEM Hexane 0.00b 0.00b 36.39ay b 0.00b ax Heptane 0.00b 0.00by 33.04ay b 15.38bx ax Carbon disulfide a by cy a ax bx Propanal 87.60ay 99.37by ay cx bx ax Propanethiol ay by 23.54c ax bx 0.00c Thietane ay by 58.53cy ax bx 88.78cx methyl-Butanal 0.00cy 24.5by 78.92ay cx 43.71bx ax methyl-Butanal 0.00by 27.31by 89.69ay cx 58.46bx ax Benzene 0.00b 0.00b 24.29ay b 0.00b 68.27ax Allyl Methyl Sulfide by ay a bx ax b Pentanal 0.00b 0.00b 22.95ay b 0.00b 58.45ax Toluene by b ay bx b ax Dimethyl disulfide 0.00b 0.00b 30.10a b 0.00b 33.55a Hexanal 9.92b 46.59by ay c bx ax n-propyl trans-1-propenyl sulfide 48.01ay 55.23ay 18.36by bx ax 88.99bx Allyl sulfide ay ay 87.40by bx ax cx Heptanal 0.00b 0.00b 29.82ax y 0 Nonanal 0.00b 0.00b 74.59ax y 0 Allyl propyl disulfide ay 90.56by 40.62cy ax bx cx 9.16 Diallyl disulfide ay by cy ax bx cx Benzaldehyde 3.93c 18.77b ay b 22.51b ax Total ay by cy ax bx cx Values with different letters (a b) within the same day differ significantly (Po0.05). Values with different letters (x y) within the same irradiation dose differ significantly (Po0.05). 1 Standard errors of the mean (n¼15). Table 3 Sensory evaluation of the ready-to-eat chicken breast after low- and high-dose irradiation. Storage (day) Sensory parameter 1 Irradiation dose (kgy) SEM Color Odor Taste Off-flavor 4.1b 5.4a 5.3a Texture Acceptability Color Odor Taste Off-flavor 4.5b 4.4b 6.6a Texture Acceptability Values with different letters (a b) within the same row differ significantly (Po0.05). 1 Standard errors of the mean (n¼30). are found only in irradiated raw meat (Ahn et al., 2000). These volatile compounds of irradiated meat are associated with lipid oxidation products and/or radiolytic degradation of lipids, amino acids, and proteins (Jo and Ahn, 1999). However, the majority of the compounds formed by irradiation disappeared or were reduced to very low levels during 5 day of storage under aerobic conditions. Sensory evaluation revealed that there were no differences in all the sensory parameters determined by irradiation dose or storage time, except for off-flavor (Table 3). On day 0, the intensity of off-flavor was higher in the irradiated samples at both doses than that of the control (Table 3). After 10 day, the flavor difference between the control and the samples irradiated at 5 kgy disappeared, but the samples irradiated at 40 kgy had significantly higher off-odor than control and 5 kgy irradiated ones. Based on the results, it can be assumed that high-dose irradiation of ready-to-eat chicken breast may have impaired sensory quality. However, other sensory parameters, including overall acceptance, were not significantly different. This may have been due to masking flavors derived from different ingredients that were added during the manufacturing process. Nevertheless, some protective measures against off-odor production by the samples treated with high-dose irradiation are necessary. Sohn et al. (2009) reported that the combination of a-tocopherol and charcoal pack reduced the off-odor intensity in ground beef irradiated at 10 kgy during storage at 4 1C for 7 day. Acknowledgment This work was supported by a grant from the Next-Generation BioGreen 21 Program (no. PJ ), Rural Development Administration, Republic of Korea. References Ahn, D.U., Jo, C., Du, M., Olson, D.G., Nam, K.C., Quality characteristics of pork patties irradiated and stored in different packaging and storage conditions. Meat Sci. 56, Bourland, C.T., NASA FTGSC Space Food Insight. Available from: / (accessed May 5, 2008). Brewer, S., Irradiation effects on meat color a review. Meat Sci. 68, Davies, A., Board, R., The microbiology of meat and poultry. Blackie Academic & Professional, London, UK, pp Holly, R.A., Gariepy, D., Delaquis, P., Doyon, G., Gagnon, J., Static controlled atmosphere packaging retail ready pork. J. Food Sci. 59,

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