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Effect of electron beam irradiation on quality and protein nutrition values of spicy yak jerky
Accepted Manuscript Effect of electron beam irradiation on quality and protein nutrition values of spicy yak jerky Liming Zhao, Yin Zhang, Zhongli Pan, Chandrasekar Venkitasamy, Longyi Zhang, Wei Xiong, Siya Guo, Hu Xia, Wenlong Liu PII:
S0023-6438(17)30632-1
DOI:
10.1016/j.lwt.2017.08.062
Reference:
YFSTL 6484
To appear in:
LWT - Food Science and Technology
Received Date: 6 May 2017 Revised Date:
1 August 2017
Accepted Date: 19 August 2017
Please cite this article as: Zhao, L., Zhang, Y., Pan, Z., Venkitasamy, C., Zhang, L., Xiong, W., Guo, S., Xia, H., Liu, W., Effect of electron beam irradiation on quality and protein nutrition values of spicy yak jerky, LWT - Food Science and Technology (2017), doi: 10.1016/j.lwt.2017.08.062. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT
Effect of electron beam irradiation on quality and protein
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nutrition values of spicy yak jerky
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Liming Zhao1,2, Yin Zhang1*, Zhongli Pan3,4, Chandrasekar Venkitasamy3, Longyi
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Zhang1, Wei Xiong1, Siya Guo1, Hu Xia1, Wenlong Liu1
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China
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Key Laboratory of Meat Processing of Sichuan, Chengdu University, Chengdu, 610106,
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State Key Laboratory of Bioreactor Engineering, R&D Center of Separation and Extraction
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Technology in Fermentation Industry, East China University of Science and Technology,
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Shanghai 200237, China
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Shields Avenue, Davis, CA 95616, USA
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800 Buchanan St., Albany, CA 94710, USA
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Department of Biological and Agricultural Engineering, University of California, Davis, One
Healthy Processed Foods Research Unit, Western Regional Research Center, USDA-ARS,
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Yin Zhang, tel.: +86-28-84616805; fax: +86-28-84616805, e-mail: [email protected]
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Corresponding author.
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ACCEPTED MANUSCRIPT Abstract
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To investigate the effect of electron beam irradiation on quality and protein nutrition values of
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spicy yak jerky (SYJ), irradiation doses of 0, 2, 5, 7 and 9 kGy were used to treat SYJ. The
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results showed that the color preference, taste, hardness, and gumminess of SYJ decreased
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with the increase in the irradiation dose, while the drip loss, off- odor of SYJ increased with
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increase in irradiation dose. Free radicals produced by electron beam irradiation might be the
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reason for these quality changes of SYJ. This is supported by the increase in the TBARS and
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decrease in the capsanthin content of SYJ with the increase in irradiation dose. Low dose of
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irradiation didn’t result in obvious changes of the protein biological value of SYJ, but an
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irradiation dose of 9 kGy led to significant (P<0.05) decrease of biological efficiency of
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protein in SYJ.
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Keywords
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Spicy yak jerky; irradiation; sensory attribute; snack foods
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1 Introduction Irradiation has been considered as an effective method to remove micro-organisms, which
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cause food spoilage, and to eliminate disease- causing pathogenic organisms in foods
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(Grolichová, Dvo, Musilová, Grolichová, Dvo & Musilová, 2004), especially for meat and
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meat products (Gants, 1998). Since the FDA approved using irradiation to treat meat in 1997
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(Jouki & Yazdi, 2014), there have been many investigations on irradiation processing of meat
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and meat products, such as bacon, ham (Kiss, Beczner, Zachariev & Kovács, 1990), beef
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burgers (Dempster, Hawrysh, Shand, Lahola-Chomiak & Corletto, 1985), sausages (Kiss,
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Beczner, Zachariev & Kovács, 1990), etc. Recently, ready- to- eat beef jerky (Kim, Chun,
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Song & Song, 2010), cured pork jerky (Kim, Kang & Jo, 2012), Wuxi meat gluten (Zhang,
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Tang & Wu, 2012), hams (Chen & Quan, 2013), and vacuum-packed lamb meat (Fregonesi,
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Portes, Aguiar, Figueira, Gonçalves, Arthur et al., 2014) were irradiated to sterilize bacteria
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and prolong shelf life. However, fewer investigations have been done on the effect of ionizing
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irradiation on quality and protein nutrition values of spicy yak jerky (SYJ).
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SYJ is a typical snack meat product in China; its spicy taste and beautiful color earns wide
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reputation among the consumers. It is often sold as a local specialty and it is becoming more
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and more popular with the rapid development of the tourism industry in China (Church,
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MacIntyre, Archambault, Moote, Cochran, Durance et al., 2013; Xie, Li, Zhang, Jia, Li, Sun
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et al., 2013). Steam processing (121.1 °C, 0.355 MPa) is usually adopted to sterilize SYJ after
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it has been vacuum packed (Wang & Li, 2005; Wang, Li & Lei, 2016). Sterilization by steam
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is a cumbersome process with high energy consumption and it also causes degradation of food
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quality (Huang & Huan, 2016; Tornberg, 2005). Therefore, snack food producers are looking
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for an alternative method for sterilization of SYJ. In this study, electron beam irradiation was
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used to sterilize the SYJ. The irradiation process can cause quality changes of meat products
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(Du, Hur & Ahn, 2002) and modify nutritive values of food (Dionísio, Gomes & Oetterer,
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2009). Therefore, the objective of this research was to investigate the effect of electron beam
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irradiation treatment on quality and protein nutrition values of SYJ.
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2 Material and methods
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2.1 Preparation of SYJ
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Frozen yak meat was thawed in the refrigerator (Haier BCD-460WDGZ, Qingdao, China)
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at 0 to 4 °C for 24 h. The thawed yak meat was pretreated by removing any visible fat, tendon
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muscle membrane, and the color-changed edge meat. The pretreated meat was washed with
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ice and running water at less than 10 °C for 2 h to remove blood and to reduce smell. The
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washed meat was drained for 3 h at 4 to 8 °C in the refrigerator (Haier BCD-460WDGZ,
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Qingdao, China). Four kilograms of the washed yak meat was boiled in a pressure cooker
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(internal pressure 80 kPa, 117 °C -118 ℃) for 1 h. The boiled meat was sliced into length of
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20 mm ±1 mm, width of 10 mm ± 1 mm, and thickness of 5 mm ± 1 mm chops.
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The meat chops were stir-fried in soybean oil (Yihai Kerry Food Marketing Limited,
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Shanghai, China) with a mass ratio of meat to oil of 5:1 at 120 ± 3 °C for 5 min, and then
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mixed with a meat and seasoning mixture in mass ratio of 1:0.425. The seasoning mixture is
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composed of salt, monosodium glutomate (MSG), sugar, red chili pepper powder, and
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Szechuan pepper corns in mass ratio of 14.29%, 7.14%, 57.14%, 10.71%, 10.71%,
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respectively. The obtained product was divided into 20 equal parts. Each part was packaged
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with a DZ-500-2S double chamber vacuum packing machine (Dajiang machinery equipment
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CO., Ltd) and sealed aseptically in polyethylene bags.
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2.2 Irradiation 4
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an energy level of 10 MeV and a power level of 20 kW (Shandong vanform Electron
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Accelerator Technology Co. Ltd., Qingdao, China) at Sichuan Yun Xiang Irradiation
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Technology Co., Ltd. (Meishan, China) at 12 ± 0.5 °C. Beam current of 2.0 mA± 5% and dose
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rate of 5.8kGy/s were used for irradiation of SYJ samples. Four packed samples were treated
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at each dose. The dose was established using 5-mm diameter alanine dosimeters (Bruker
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Instruments, Rheinstetten, Germany). The irradiation doses in this study were 0 (control), 2, 5,
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7, and 9 kGy and the actual doses were within ±0.2 kGy of the target dose. After irradiation,
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the SYJ was stored at 4 to 8 °C in the refrigerator (Haier BCD-460WDGZ, Qingdao, China).
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All analyses were carried out within a week.
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2.3 Sensory Analysis
To analyze any possible negative effects of irradiation on sensory quality of SYJ, the
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sensory attributes of the SYJ was analyzed according to method of Kanatt, Chander and
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Sharma (2005) and Khattak and Simpson (2009). The sensory attributes were evaluated
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within one day after the irradiation treatment. Off-odor, color preference, and taste of SYJ
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were taken as sensory indices, and a 10-point numerical scale was adopted to indicate quality
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changes. To measure off- odor, the scale was 0: normal, 2: little smell, 4: slightly obvious, 6:
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obvious, 8: more obvious, 10: extremely obvious; for color preference, 0: extremely poor, 2:
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very poor, 4: poor, 6: acceptable, 8: good, 10: excellent; regarding taste, 0: normal, 2: little
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changed, 4: slightly changed, 6: poor, 8: very poor, 10: extremely poor. Each panelist received
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five coded samples (one non-irradiated, and four irradiated samples; one at each dose). All the
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SYJ samples were tasted by 25 persons. Before tasting, the SYJ samples were kept in air for 1
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h to allow the temperature of the samples to be consistent with that of the environment. Each
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panelist independently evaluated the SYJ samples.
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2.4 Texture Profile Texture profile of the SYJ was analyzed using a texture analyzer, TA-XT2i (Stable Micro
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Systems, Surrey, U.K.) according to the method reported by Zhang, Zeng, Zhu, Zhou and Han
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(2009) with slight modification. SYJ samples were equilibrated and the texture was measured
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at room temperature (25 °C ~ 30 °C). At least nine SYJ chops (length of 20mm, width of
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10mm and thickness of 5mm) were equilibrated and evaluated at room temperature (25 °C ~
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30 °C). The SYJ sample was axially compressed to 30% of original height with a speed of 2.0
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mm/s by a P45 cylindrical plunger. Force-time deformation curves were derived with a 25 kg
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load cell. Hardness (g) and gumminess were then determined.
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2.5 Drip Loss
Drip loss of the SYJ samples was determined through image analysis. The unopened SYJ
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package was fixed onto a stainless table, and a BenQ S1430 digital camera was used to take
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pictures of the SYJ samples. The distance between the camera and sample was fixed at 300
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mm. According to the pictures, the area of juice around the yak pieces and the area of the yak
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pieces were determined with Adobe Acrobat XI Pro (Adobe, USA). The drip loss (%) was
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calculated using the formula.
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Drip loss (%) =
Sarea of juice around the yak pieces Sarea of the yak pieces
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2.6 Determination of Capsanthin
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There are 11 unsaturated bonds in the capsanthin molecule. The unsaturated bonds in
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capsanthin molecule are the reason for having a maximum light absorption at 460 nm. To
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analyze effect of irradiation on damage of unsaturated bonds in capsanthin, the content of
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capsanthin in the SYJs was determined using the method of Xu, Ma, Gu and Meng (2009)
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with slight modification. Each SYJ sample was manually chopped into volume 1 mm3 and 6
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at pH 9.0, and then extracted at 40 °C for 3 h. Wavelength absorbance of the acetone extract
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was measured at 460 nm. The amount of capsanthin was calculated according to the
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capsanthin standard curve. The content of capsanthin was expressed as mg capsanthin per g of
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SYJ.
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2.7 Measurement of Lipid Peroxidation
TBARS (thiobarbituric acid reactive substances) produced from lipid peroxidation were
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determined according to the method of Alasnier, Meynier, Viau and Gandemer (2000). A 4 g
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portion of each SYJ sample was blended with 16 mL of 5% trichloroacetic acid (TCA) and
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BHT (10 µg BHT•g-1 of lipids). It was then filtered through a Whatman filter (No. 4). The
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same amounts of the filtrate and 0.02 mol•L-1 TBA were heated in a boiling water (95 °C)
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bath for 30 min, cooled, and their absorbance measured at 532 nm. The amount of TBARS
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was expressed as mg malonaldehyde per kg of SYJ.
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2.8 Microbial Analyses
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The chopped SYJ samples (25 g) in duplicate from the irradiated and non-irradiated control
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batches were aseptically homogenized for 1 min with sterile saline (225 mL) in a Stomacher
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(Seward Medical, UK). Appropriate serial dilutions of the homogenate were carried out. Total
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plate count (by pour plate method) was determined using Plate Count Agar incubated at 30 °C
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for 48 h. The Escherichia coli was measured according to ISO 16649-1: 2001 (ISO16649-1,
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2001) and ISO 16649-2:2001 (ISO16649-2, 2001).
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2.9 Amino acid determination According to the method of Jiang, Wang, Li, Wang and Luo (2014), amino acid 7
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pre-column derivation by a Shimadzu LC-15C HPLC system, after the defatted SYJ was
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hydrolyzed with 6 mol·L-1 HCl for 24 h at 110 °C. The contents of individual amino acids
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were expressed as g/100 g of the protein in each sample. Three replicate determinations were
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performed.
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2.10 Nutrition analysis of amino acid
Biological values of protein in SYJ were analyzed by 4 parameters: total amino acid (TAA)
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content, total essential amino acid (TEAA) content, essential amino acid index (EAAI) , and
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protein efficiency ratio (PER) (Alsmeyer, Cunningham & Happich, 1974; FAO/WHO/UNU,
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1985). The specific calculation formulas of these parameters are: n
TAA = ∑ ai
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i =1
n
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TEAA = ∑bi TAA × 100
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(1)
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EAAI = k (aa AA )1 × L ×(aa/AA)k
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PER = −0.468 + 0.454 × Leu − 0.105 ×Tyr
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Where, a - amino acid in SYJ sample; b - essential amino acid in SYJ sample; n - the
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number of amino acids; m - the number of essential amino acids; AA - the content of amino
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acid in reference (FAO/WHO/UNU, 1985) suggested pattern of protein requirement; aa - the
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content of amino acid in SYJ sample; and k - the number of amino acid type (Alsmeyer,
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Cunningham & Happich, 1974; FAO/WHO/UNU, 1985). Leu refers to leucine and Tyr refers
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to tyrosine.
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2.11 Statistical Analysis
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Data variance analysis and mean comparisons were run by Duncan’s multiple range test
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using the SAS system for Windows 9.0 (SAS Institute, Cary, NC). Excel 2010 was used to
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analyze the regression. All experiments were replicated at least three times.
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3 Results and discussion
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3.1 Effect of electron beam irradiation on quality of SYJ
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3.1.1 Effect of electron beam irradiation on sensory attributes of SYJ
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Effect of electron beam irradiation on sensory attributes of SYJ is shown in Fig. 1. The data
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(Fig. 1) indicated that the off-odor of the SYJ increased with the increase in irradiation dose.
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Off-odor of the SYJ irradiated with 5 kGy was significantly (P<0.05) higher than that of SYJ
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treated with 2 kGy; off-odor of the SYJ irradiated with 9 kGy was significantly (P<0.05)
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higher than that of SYJ treated with 5 kGy. There was no significant (P>0.05) difference
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between off-odor of the SYJ irradiated with 0 and 2 kGy, or with 7 and 9 kGy. Similar
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off-odor changes were found for Jinluo ham samples irradiated with
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2013). Both the color preference and taste of the SYJ decreased with the increase in
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irradiation dose. Compared with the control, the color preference of the SYJ decreased
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significantly (P<0.05) when it was irradiated with 5, 7 and 9 kGy. Similar significant
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difference was found as the tastes of the irradiated SYJs were compared with the control.
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Sensory quality is very important to snack foods as it directly influences consumers’
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acceptance (Bower & Whitten, 2007). The data in Fig. 1 suggested that selecting a proper
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irradiation dose is very important to avoid the deterioration of sensory quality of SYJ.
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Cobat (Chen & Quan,
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Irradiation decreased the sensory quality of meat products (Du, Hur & Ahn, 2002). Free
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radical reaction induced by the irradiation process is the major reason for sensory quality
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changes of foods (Al-Bachir, 2013). Low dose irradiation resulted in unremarkable sensory 9
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smell and a brown color (Ahn, Jo, Du, Olson & Nam, 2000; Smulders, Van Laack &
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Eikelenboom, 1991). Therefore, free radical reaction might have resulted in the increase of
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off-odor in SYJ, and decrease of the color preference and taste of SYJ with the increase in
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irradiation dose. Several reasons for the off-odor of irradiated foods were reported. Gray,
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Gomaa and Buckley (1996) concluded that lipid oxidation was the primary reason for
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off-odor as meat products were irradiated. Du, Hur and Ahn (2002) reported that both lipid
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oxidation of products and sulfur-containing volatiles were responsible for meat irradiation
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odor. However, Ahn, Jo and Olson (2000) thought that the radiolytic breakdown of
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sulfur-containing amino acids is the main reason of the off-odor. As consumers’ responses to
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sensory changes of the irradiated meat products are quite negative (Al-Bachir, 2013; Du, Hur
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& Ahn, 2002), irradiation energy should not be higher than 5 kGy for treatment of SYJ.
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3.1.2 Effect of electron beam irradiation on textural properties of SYJ
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Effect of electron irradiation on hardness and gumminess of SYJ is shown in Fig. 2. The
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results (Fig. 2) indicated that both the hardness and gumminess of the SYJ decreased with the
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increase in irradiation dose. Compared with the control, an irradiation dose of 2 kGy resulted
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in no significant (P>0.05) difference to hardness and gumminess of SYJ, but irradiation doses
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of 5, 7, and 9 kGy led to significant (P<0.05) decrease of the hardness and gumminess.
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Similar effects were reported in the irradiation of pork loin (Lee, Yook, Kim, Sohn & Byun,
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1999).
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Both hardness and gumminess reflect the resistance of a meat product to breakage of
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internal texture (Zhang, Wang & Zhang, 2010). Irradiation resulted in textural changes and
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damage of protein in meat products, and it became more serious with the increase in 10
ACCEPTED MANUSCRIPT irradiation energy (Gu, 2013; Henry, 2009). These effects of irradiation on meat products
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might result in the decrease of hardness and gumminess of the SYJ with the increase in
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irradiation dose. Textural properties are important to food product development (Saláková,
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2012), and the results in Fig. 3 further suggest that proper irradiation energy should be chosen
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when using an irradiation process to sterilize SYJ.
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3.1.3 Effect of electron beam irradiation on drip loss of SYJ
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The result of irradiation on drip loss of SYJ is shown in Fig. 3. The data in Fig. 3 indicated
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that the drip loss of SYJ increased with the increase in irradiation dose. The drip loss of the
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SYJ irradiated with 2 kGy was significantly (P<0.05) higher than that of the control and drip
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loss of the SYJ irradiated with 5 kGy was significantly (P<0.05) higher than that of the SYJ
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irradiated with 2 kGy. There was no significant (P>0.05) difference in drip loss as the SYJ
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was irradiated with 5, 7 and 9 kGy. Similar drip loss patterns occurred as pork fillet (GU,
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2013) and pork loins were irradiated (Zhu, Mendonca & Ahn, 2004).
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Drip loss reflects the capability of meat product to hold water and other flowable liquids. It
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indirectly demonstrates lipid oxidation, protein damage, and internal breakage of the net
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structure of meat and meat products (GU, 2013; Ma, Nan & Dai, 2003). The results of drip
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loss shown in Fig. 3 suggested that more serious fat oxidation and meat protein damages
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might have happened with the increase in irradiation dose. This is consistent with the results
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of increased off-odor of SYJ, and the decreased color preference, taste, hardness and
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gumminess of SYJ with the increase in irradiation dose.
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3.1.4 Effect of electron beam irradiation on content of capsanthin of SYJ Effect of irradiation on content of capsanthin of SYJ is shown in Fig. 4. The results (Fig. 4) 11
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The content of capsanthin of SYJ irradiated with dose of 2 kGy showed no significant
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(P>0.05) difference with the control, but the content of capsanthin of the SYJ irradiated with
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doses of 5, 7, and 9 kGy were significantly (P<0.05) lower than the control. There was no
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significant (P>0.05) difference in content of capsanthin of the SYJ irradiated with doses of 5,
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7, and 9 kGy.
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Capsanthin was added to improve the color of SYJ. Capsanthin is the major pigment of red
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chili pepper. It makes the chili pepper powder appear red, and it endows SYJ with beautiful
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red color. There are 11 unsaturated bonds in the capsanthin molecule. Irradiation-induced free
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radical reaction resulted in the breakdown of unsaturated bonds (Al-Bachir, 2013; Du, Hur &
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Ahn, 2002). This may be the possible reason for the decrease of the content of the capsanthin
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of SYJ as it was irradiated with doses of 5, 7, and 9 kGy, and also for the decrease in color
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preference of SYJ with the increase in irradiation dose.
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3.1.5 Effect of electron beam irradiation on content of TBARS of SYJ TBARS is produced by lipid oxidation and is directly related to the amount of volatile
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substances and the sensory quality of meat products (Ahn, Jo & Olson, 2000). A higher
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TBARS value indicated that more lipid oxidation has taken place, and produced more volatile
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substances which decreased the sensory quality of meat products (Jo & Ahn, 1998). The
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TBARS of the SYJs in Fig. 5 indicated that the TBARS of the SYJ increased with an increase
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in irradiation dose. The TBARS of the SYJ irradiated with 5, 7, and 9 kGy were significantly
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(P<0.05) higher than that of the control. There was no significant (P>0.05) difference between
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the TBARS of the SYJ irradiated with 0 and 2 kGy. These results are consistent with the
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off-odor of the SYJ, which increased with the increase in irradiation energy (Fig. 1).
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Lipid is the most sensitive food component to irradiation processes (Khattak & Simpson,
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2009; Venugopal, Doke & Thomas, 1999). The free radicals produced by irradiation initiate
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chemical reactions in irradiated meat (Ahn, Jo, Du, Olson & Nam, 2000; Cava, Tárrega,
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Ramírez & Carrasco, 2009). These chemical reactions lead to undesired organoleptic changes,
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losses of unsaturated chemicals, and damages of meat protein (Ahn, Jo & Olson, 2000;
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Grolichova, Dvořák & Musilova, 2004). Therefore, the results of irradiation dose on content
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of TBARS further supported the increase in off-odor of the SYJ and decrease in the color
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preference, taste, and the content of the capsanthin in SYJ with the increase in irradiation
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dose.
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3.1.6 Effect of irradiation on microbe of SYJ
Changes in plate counts of aerobic bacteria and Escherichia coli in SYJ samples after
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irradiation are shown in Table 1. The plate counts of the aerobic bacteria and Escherichia coli
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decreased with the increase of irradiation dose. This result was consistent with that of Kim,
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Chun, Song and Song (2010). According to the hygienic standard of China for cooked meat
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products (GB2726-2005), plate counts of aerobic bacteria decreased to less than 104 CFU·g-1,
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and plate counts of Escherichia coli decreased to less than 30 MPN·(100g)-1 are safe to eat.
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The data in Table 1 indicated that an irradiation dose of 2 kGy is enough for killing bacterial
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(870 CUF·g-1 < 104 CFU·g-1) and pathogenic bacteria (<30 MPN·(100g)-1) in SYJ.
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However, past studies on the effect of ionizing radiation and anaerobic refrigerated storage
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on clostridium botulinum spores or salmonella enteritidis in vacuum-canned deboned chicken
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meat indicated that the irradiated samples didn’t develop toxin as they were stored at 5 °C, but
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they became toxic within 18 h at 28 °C (Thayer, Boyd & Huhtanen, 1995). Even though the C. 13
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botulinum is relatively rare in meat (Prejean, 2001), further experiments should investigate
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effect of irradiation on C.botulinum or salmonella enteritidis in SYJ.
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3.2 Effect of electron beam irradiation on protein nutrition of SYJ Effect of irradiation on amino acids and protein nutrition values of SYJ is shown in Table 2.
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The total amino acids (TAA) results in Table 2 showed that the amino acids of the SYJ were
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not significantly (P>0.05) changed as the SYJ was irradiated with doses of 0, 2, 5, and 7 kGy,
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but an irradiation dose of 9 kGy resulted in significant (P<0.05) decrease of the TAA of SYJ.
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Similar significant (P<0.05) difference was observed as the total essential amino acids (TEAA)
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of the SYJs were compared. Irradiation resulting in the decrease of amino acids were also
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reported for the irradiation of sea bream and high protein food (Erkan & Özden, 2007;
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Garrison, 1981). The results of the essential amino acid index (EAAI) of children or adult of
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SYJ irradiated samples showed similar difference. Irradiation doses of 2, 5, and 7 kGy led to
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no significant (P>0.05) difference in EAAI compared with the control, but an irradiation dose
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of 9 kGy resulted in significant (P<0.05) decrease of the EAAI. The protein efficiency ratio
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(PER) indicated that irradiation dose of 2 kGy resulted in significant (P<0.05) decrease of the
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PER compared with the control, but it was not significantly (P>0.05) lower than the PER
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value for irradiation dose of 5 kGy. Both irradiation doses of 7 and 9 kGy resulted in
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significant (P<0.05) decrease of the PER compared with the control.
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Irradiation resulted in amino acid loss (Ahn, 2002; Jo & Ahn, 2000). Stadtman and Levine
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(2003) analyzed the effect of irradiation-produced free radicals on free amino acids and their
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residues and found that free radicals resulted in amino acids, like lysine, arginine, proline,
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cysteine, threonine, leucine, and histidine being transferred into carbonyl derivatives and
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other chemicals. Higher irradiation dose resulted in more free radicals, and more amino acids 14
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were lost. These effects of irradiation on amino acids might be the reason why the irradiation
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dose of 9 kGy resulted in significant decrease of TAA, TEAA, PER, and EAAI of children or
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adults.
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4 Conclusions
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The color preference, taste, hardness, and gumminess of SYJ decreased with the increase in
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irradiation dose, while the drip loss, off-odor of SYJ increased with the increase in irradiation
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dose. Free radicals produced by electron beam irradiation might be the reason for the quality
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changes of SYJ. This can be supported by the increase of TBARS and decrease of the content
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of capsanthin of SYJ with the increase in irradiation. Low irradiation didn’t lead to obvious
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changes of the protein biological value of SYJ, but irradiation dose of 9 kGy resulted in
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significant (P<0.05) decrease of the TAA, TEAA, EAAI of children and adults, and PER of
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the SYJ. An irradiation dose of less than 5 kGy is recommended to treat the SYJ.
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Acknowledgment
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The authors thank the financial support provided by the Education Department of Sichuan
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(17ZA0084), the Science and Technology Department of Sichuan Province (No. 2017JY0086),
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China Postdoctoral Science Foundation (No. 2017M612969) and the National Natural Science
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Foundation of China (No. 31501505).
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Table 1. Effect of electron beam irradiation on microbes of SYJ 0 Irradiation dose [kGy]
2
5
280000
870
20
2400
<30
<30
7
9
Counts of aerobic -1
bacteria [CFU·g ] Counts of Escherichia -1
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<10
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2 [kGy]
5 [kGy]
7 [kGy]
9 [kGy]
9.701±0.072
9.626±0.071
9.676±0.071
9.601±0.071
9.228±0.068
Glutamic acid
20.776±0.153
20.526±0.152
20.601±0.152
20.826±0.154
19.875±0.147
Serine
3.800±0.028
3.975±0.029
3.825±0.028
3.750±0.028
3.620±0.027
Glycine
4.750±0.035
4.925±0.036
4.625±0.034
4.450±0.033
4.500±0.033
Histidine
3.575±0.026
3.550±0.026
3.500±0.026
4.075±0.030
4.272±0.032
Arginine
6.525±0.048
6.425±0.047
6.500±0.048
6.250±0.046
5.751±0.042
Alanine
6.050±0.045
6.100±0.045
6.000±0.044
5.775±0.043
5.773±0.043
Proline
4.600±0.034
4.900±0.036
4.425±0.033
3.650±0.027
4.572±0.034
Threonine
4.450±0.033
4.425±0.033
4.450±0.033
4.350±0.032
4.225±0.031
Tyrosine
3.125±0.023
3.075±0.023
3.075±0.023
3.225±0.024
3.322±0.025
Valine
5.025±0.037
4.975±0.037
5.025±0.037
4.800±0.035
4.710±0.035
Methionine
2.475±0.018
2.450±0.018
2.100±0.016
2.250±0.017
2.347±0.017
Cystine
0.800±0.006
0.850±0.006
0.625±0.005
0.800±0.006
0.767±0.006
Isoleucine
4.700±0.035
4.575±0.034
4.625±0.034
4.600±0.034
4.498±0.033
Leucine Phenylalanine
8.625±0.064 4.150±0.031
8.475±0.063 5.400±0.040
8.550±0.063 5.075±0.037
8.275±0.061 5.950±0.044
8.188±0.060 4.150±0.031
Lysine
8.500±0.063
8.100±0.060
8.475±0.063
8.350±0.062
8.079±0.060
Total amino acids (TAA), [g•(100g)-1] Total essential amino acids (TEAA) [g•(100g)-1] *Essential amino acid index (EAAI) **Essential amino acid index (EAAI) Protein efficiency ratio (PER)
101.631±0.751a
102.356±0.756a
101.156±0.747a
100.980±0.746a
97.878±0.723b
37.927±0.280a
38.402±0.284a
38.302±0.283a
38.577±0.285a
36.198±0.267b
0.164±0.001ab
0.165±0.001a
0.162±0.001b
0.164±0.001ab
0.158±0.001c
0.306±0.002ab
0.308±0.002a
0.302±0.002b
0.306±0.002ab
0.295±0.002c
3.057±0.026b
3.091±0.026ab
2.950±0.025c
2.901±0.025c
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Amino acids [g•(100g)-1] Aspartic acid
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Means (n=3) without a common letter differ significantly (P<0.05);
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* Based on amino acid requirements of school children (10-12 years)
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** Based on amino acid requirements of adults
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Fig.1 Effect of electron beam irradiation on sensory attributes of SYJ
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Values are represented as Mean± SD. Significance was tested by Duncan Multiple Range Test at p < 0.05,
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and values with the same superscript were found not significantly different from each other.
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Fig.2 Effect of electron beam irradiation on texture properties of SYJ
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Values are represented as Mean± SD. Significance was tested by Duncan Multiple Range Test at p < 0.05,
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and values with the same superscript were found not significantly different from each other.
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Fig.3 Effect of electron beam irradiation on drip loss of SYJ
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Values are represented as Mean± SD. Significance was tested by Duncan Multiple Range Test at p < 0.05,
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and values with the same superscript were found not significantly different from each other.
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Fig.4 Effect of electron beam irradiation on content of capsanthin of SYJ
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Values are represented as Mean± SD. Significance was tested by Duncan Multiple Range Test at p < 0.05,
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and values with the same superscript were found not significantly different from each other.
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Fig.5 Effect of electron beam irradiation on content of TBARS of SYJ
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Values are represented as Mean± SD. Significance was tested by Duncan Multiple Range Test at p < 0.05,
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ACCEPTED MANUSCRIPT Highlights 1. Spicy yak jerky is a typical snack meat product in China 2. High dose irradiation decrease the quality of spicy yak jerky
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3. High dose irradiation decrease protein biological value
S0023-6438(17)30632-1
DOI:
10.1016/j.lwt.2017.08.062
Reference:
YFSTL 6484
To appear in:
LWT - Food Science and Technology
Received Date: 6 May 2017 Revised Date:
1 August 2017
Accepted Date: 19 August 2017
Please cite this article as: Zhao, L., Zhang, Y., Pan, Z., Venkitasamy, C., Zhang, L., Xiong, W., Guo, S., Xia, H., Liu, W., Effect of electron beam irradiation on quality and protein nutrition values of spicy yak jerky, LWT - Food Science and Technology (2017), doi: 10.1016/j.lwt.2017.08.062. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT
Effect of electron beam irradiation on quality and protein
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nutrition values of spicy yak jerky
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Liming Zhao1,2, Yin Zhang1*, Zhongli Pan3,4, Chandrasekar Venkitasamy3, Longyi
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Zhang1, Wei Xiong1, Siya Guo1, Hu Xia1, Wenlong Liu1
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China
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Key Laboratory of Meat Processing of Sichuan, Chengdu University, Chengdu, 610106,
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State Key Laboratory of Bioreactor Engineering, R&D Center of Separation and Extraction
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Technology in Fermentation Industry, East China University of Science and Technology,
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Shanghai 200237, China
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Shields Avenue, Davis, CA 95616, USA
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800 Buchanan St., Albany, CA 94710, USA
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Department of Biological and Agricultural Engineering, University of California, Davis, One
Healthy Processed Foods Research Unit, Western Regional Research Center, USDA-ARS,
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*
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Yin Zhang, tel.: +86-28-84616805; fax: +86-28-84616805, e-mail: [email protected]
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Corresponding author.
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ACCEPTED MANUSCRIPT Abstract
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To investigate the effect of electron beam irradiation on quality and protein nutrition values of
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spicy yak jerky (SYJ), irradiation doses of 0, 2, 5, 7 and 9 kGy were used to treat SYJ. The
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results showed that the color preference, taste, hardness, and gumminess of SYJ decreased
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with the increase in the irradiation dose, while the drip loss, off- odor of SYJ increased with
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increase in irradiation dose. Free radicals produced by electron beam irradiation might be the
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reason for these quality changes of SYJ. This is supported by the increase in the TBARS and
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decrease in the capsanthin content of SYJ with the increase in irradiation dose. Low dose of
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irradiation didn’t result in obvious changes of the protein biological value of SYJ, but an
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irradiation dose of 9 kGy led to significant (P<0.05) decrease of biological efficiency of
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protein in SYJ.
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Keywords
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Spicy yak jerky; irradiation; sensory attribute; snack foods
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1 Introduction Irradiation has been considered as an effective method to remove micro-organisms, which
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cause food spoilage, and to eliminate disease- causing pathogenic organisms in foods
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(Grolichová, Dvo, Musilová, Grolichová, Dvo & Musilová, 2004), especially for meat and
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meat products (Gants, 1998). Since the FDA approved using irradiation to treat meat in 1997
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(Jouki & Yazdi, 2014), there have been many investigations on irradiation processing of meat
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and meat products, such as bacon, ham (Kiss, Beczner, Zachariev & Kovács, 1990), beef
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burgers (Dempster, Hawrysh, Shand, Lahola-Chomiak & Corletto, 1985), sausages (Kiss,
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Beczner, Zachariev & Kovács, 1990), etc. Recently, ready- to- eat beef jerky (Kim, Chun,
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Song & Song, 2010), cured pork jerky (Kim, Kang & Jo, 2012), Wuxi meat gluten (Zhang,
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Tang & Wu, 2012), hams (Chen & Quan, 2013), and vacuum-packed lamb meat (Fregonesi,
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Portes, Aguiar, Figueira, Gonçalves, Arthur et al., 2014) were irradiated to sterilize bacteria
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and prolong shelf life. However, fewer investigations have been done on the effect of ionizing
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irradiation on quality and protein nutrition values of spicy yak jerky (SYJ).
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SYJ is a typical snack meat product in China; its spicy taste and beautiful color earns wide
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reputation among the consumers. It is often sold as a local specialty and it is becoming more
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and more popular with the rapid development of the tourism industry in China (Church,
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MacIntyre, Archambault, Moote, Cochran, Durance et al., 2013; Xie, Li, Zhang, Jia, Li, Sun
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et al., 2013). Steam processing (121.1 °C, 0.355 MPa) is usually adopted to sterilize SYJ after
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it has been vacuum packed (Wang & Li, 2005; Wang, Li & Lei, 2016). Sterilization by steam
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is a cumbersome process with high energy consumption and it also causes degradation of food
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quality (Huang & Huan, 2016; Tornberg, 2005). Therefore, snack food producers are looking
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for an alternative method for sterilization of SYJ. In this study, electron beam irradiation was
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used to sterilize the SYJ. The irradiation process can cause quality changes of meat products
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(Du, Hur & Ahn, 2002) and modify nutritive values of food (Dionísio, Gomes & Oetterer,
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2009). Therefore, the objective of this research was to investigate the effect of electron beam
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irradiation treatment on quality and protein nutrition values of SYJ.
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2 Material and methods
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2.1 Preparation of SYJ
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Frozen yak meat was thawed in the refrigerator (Haier BCD-460WDGZ, Qingdao, China)
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at 0 to 4 °C for 24 h. The thawed yak meat was pretreated by removing any visible fat, tendon
69
muscle membrane, and the color-changed edge meat. The pretreated meat was washed with
70
ice and running water at less than 10 °C for 2 h to remove blood and to reduce smell. The
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washed meat was drained for 3 h at 4 to 8 °C in the refrigerator (Haier BCD-460WDGZ,
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Qingdao, China). Four kilograms of the washed yak meat was boiled in a pressure cooker
73
(internal pressure 80 kPa, 117 °C -118 ℃) for 1 h. The boiled meat was sliced into length of
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20 mm ±1 mm, width of 10 mm ± 1 mm, and thickness of 5 mm ± 1 mm chops.
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The meat chops were stir-fried in soybean oil (Yihai Kerry Food Marketing Limited,
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Shanghai, China) with a mass ratio of meat to oil of 5:1 at 120 ± 3 °C for 5 min, and then
78
mixed with a meat and seasoning mixture in mass ratio of 1:0.425. The seasoning mixture is
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composed of salt, monosodium glutomate (MSG), sugar, red chili pepper powder, and
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Szechuan pepper corns in mass ratio of 14.29%, 7.14%, 57.14%, 10.71%, 10.71%,
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respectively. The obtained product was divided into 20 equal parts. Each part was packaged
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with a DZ-500-2S double chamber vacuum packing machine (Dajiang machinery equipment
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CO., Ltd) and sealed aseptically in polyethylene bags.
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2.2 Irradiation 4
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an energy level of 10 MeV and a power level of 20 kW (Shandong vanform Electron
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Accelerator Technology Co. Ltd., Qingdao, China) at Sichuan Yun Xiang Irradiation
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Technology Co., Ltd. (Meishan, China) at 12 ± 0.5 °C. Beam current of 2.0 mA± 5% and dose
90
rate of 5.8kGy/s were used for irradiation of SYJ samples. Four packed samples were treated
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at each dose. The dose was established using 5-mm diameter alanine dosimeters (Bruker
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Instruments, Rheinstetten, Germany). The irradiation doses in this study were 0 (control), 2, 5,
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7, and 9 kGy and the actual doses were within ±0.2 kGy of the target dose. After irradiation,
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the SYJ was stored at 4 to 8 °C in the refrigerator (Haier BCD-460WDGZ, Qingdao, China).
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All analyses were carried out within a week.
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2.3 Sensory Analysis
To analyze any possible negative effects of irradiation on sensory quality of SYJ, the
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sensory attributes of the SYJ was analyzed according to method of Kanatt, Chander and
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Sharma (2005) and Khattak and Simpson (2009). The sensory attributes were evaluated
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within one day after the irradiation treatment. Off-odor, color preference, and taste of SYJ
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were taken as sensory indices, and a 10-point numerical scale was adopted to indicate quality
103
changes. To measure off- odor, the scale was 0: normal, 2: little smell, 4: slightly obvious, 6:
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obvious, 8: more obvious, 10: extremely obvious; for color preference, 0: extremely poor, 2:
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very poor, 4: poor, 6: acceptable, 8: good, 10: excellent; regarding taste, 0: normal, 2: little
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changed, 4: slightly changed, 6: poor, 8: very poor, 10: extremely poor. Each panelist received
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five coded samples (one non-irradiated, and four irradiated samples; one at each dose). All the
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SYJ samples were tasted by 25 persons. Before tasting, the SYJ samples were kept in air for 1
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h to allow the temperature of the samples to be consistent with that of the environment. Each
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panelist independently evaluated the SYJ samples.
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2.4 Texture Profile Texture profile of the SYJ was analyzed using a texture analyzer, TA-XT2i (Stable Micro
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Systems, Surrey, U.K.) according to the method reported by Zhang, Zeng, Zhu, Zhou and Han
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(2009) with slight modification. SYJ samples were equilibrated and the texture was measured
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at room temperature (25 °C ~ 30 °C). At least nine SYJ chops (length of 20mm, width of
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10mm and thickness of 5mm) were equilibrated and evaluated at room temperature (25 °C ~
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30 °C). The SYJ sample was axially compressed to 30% of original height with a speed of 2.0
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mm/s by a P45 cylindrical plunger. Force-time deformation curves were derived with a 25 kg
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load cell. Hardness (g) and gumminess were then determined.
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2.5 Drip Loss
Drip loss of the SYJ samples was determined through image analysis. The unopened SYJ
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package was fixed onto a stainless table, and a BenQ S1430 digital camera was used to take
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pictures of the SYJ samples. The distance between the camera and sample was fixed at 300
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mm. According to the pictures, the area of juice around the yak pieces and the area of the yak
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pieces were determined with Adobe Acrobat XI Pro (Adobe, USA). The drip loss (%) was
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calculated using the formula.
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Drip loss (%) =
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2.6 Determination of Capsanthin
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There are 11 unsaturated bonds in the capsanthin molecule. The unsaturated bonds in
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capsanthin molecule are the reason for having a maximum light absorption at 460 nm. To
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analyze effect of irradiation on damage of unsaturated bonds in capsanthin, the content of
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capsanthin in the SYJs was determined using the method of Xu, Ma, Gu and Meng (2009)
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with slight modification. Each SYJ sample was manually chopped into volume 1 mm3 and 6
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at pH 9.0, and then extracted at 40 °C for 3 h. Wavelength absorbance of the acetone extract
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was measured at 460 nm. The amount of capsanthin was calculated according to the
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capsanthin standard curve. The content of capsanthin was expressed as mg capsanthin per g of
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SYJ.
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2.7 Measurement of Lipid Peroxidation
TBARS (thiobarbituric acid reactive substances) produced from lipid peroxidation were
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determined according to the method of Alasnier, Meynier, Viau and Gandemer (2000). A 4 g
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portion of each SYJ sample was blended with 16 mL of 5% trichloroacetic acid (TCA) and
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BHT (10 µg BHT•g-1 of lipids). It was then filtered through a Whatman filter (No. 4). The
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same amounts of the filtrate and 0.02 mol•L-1 TBA were heated in a boiling water (95 °C)
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bath for 30 min, cooled, and their absorbance measured at 532 nm. The amount of TBARS
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was expressed as mg malonaldehyde per kg of SYJ.
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2.8 Microbial Analyses
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The chopped SYJ samples (25 g) in duplicate from the irradiated and non-irradiated control
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batches were aseptically homogenized for 1 min with sterile saline (225 mL) in a Stomacher
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(Seward Medical, UK). Appropriate serial dilutions of the homogenate were carried out. Total
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plate count (by pour plate method) was determined using Plate Count Agar incubated at 30 °C
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for 48 h. The Escherichia coli was measured according to ISO 16649-1: 2001 (ISO16649-1,
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2001) and ISO 16649-2:2001 (ISO16649-2, 2001).
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2.9 Amino acid determination According to the method of Jiang, Wang, Li, Wang and Luo (2014), amino acid 7
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pre-column derivation by a Shimadzu LC-15C HPLC system, after the defatted SYJ was
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hydrolyzed with 6 mol·L-1 HCl for 24 h at 110 °C. The contents of individual amino acids
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were expressed as g/100 g of the protein in each sample. Three replicate determinations were
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performed.
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2.10 Nutrition analysis of amino acid
Biological values of protein in SYJ were analyzed by 4 parameters: total amino acid (TAA)
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content, total essential amino acid (TEAA) content, essential amino acid index (EAAI) , and
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protein efficiency ratio (PER) (Alsmeyer, Cunningham & Happich, 1974; FAO/WHO/UNU,
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1985). The specific calculation formulas of these parameters are: n
TAA = ∑ ai
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i =1
n
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(1)
(2)
EAAI = k (aa AA )1 × L ×(aa/AA)k
(3)
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PER = −0.468 + 0.454 × Leu − 0.105 ×Tyr
(4)
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Where, a - amino acid in SYJ sample; b - essential amino acid in SYJ sample; n - the
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number of amino acids; m - the number of essential amino acids; AA - the content of amino
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acid in reference (FAO/WHO/UNU, 1985) suggested pattern of protein requirement; aa - the
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content of amino acid in SYJ sample; and k - the number of amino acid type (Alsmeyer,
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Cunningham & Happich, 1974; FAO/WHO/UNU, 1985). Leu refers to leucine and Tyr refers
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to tyrosine.
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2.11 Statistical Analysis
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Data variance analysis and mean comparisons were run by Duncan’s multiple range test
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using the SAS system for Windows 9.0 (SAS Institute, Cary, NC). Excel 2010 was used to
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analyze the regression. All experiments were replicated at least three times.
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3 Results and discussion
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3.1 Effect of electron beam irradiation on quality of SYJ
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3.1.1 Effect of electron beam irradiation on sensory attributes of SYJ
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Effect of electron beam irradiation on sensory attributes of SYJ is shown in Fig. 1. The data
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(Fig. 1) indicated that the off-odor of the SYJ increased with the increase in irradiation dose.
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Off-odor of the SYJ irradiated with 5 kGy was significantly (P<0.05) higher than that of SYJ
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treated with 2 kGy; off-odor of the SYJ irradiated with 9 kGy was significantly (P<0.05)
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higher than that of SYJ treated with 5 kGy. There was no significant (P>0.05) difference
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between off-odor of the SYJ irradiated with 0 and 2 kGy, or with 7 and 9 kGy. Similar
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off-odor changes were found for Jinluo ham samples irradiated with
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2013). Both the color preference and taste of the SYJ decreased with the increase in
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irradiation dose. Compared with the control, the color preference of the SYJ decreased
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significantly (P<0.05) when it was irradiated with 5, 7 and 9 kGy. Similar significant
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difference was found as the tastes of the irradiated SYJs were compared with the control.
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Sensory quality is very important to snack foods as it directly influences consumers’
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acceptance (Bower & Whitten, 2007). The data in Fig. 1 suggested that selecting a proper
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irradiation dose is very important to avoid the deterioration of sensory quality of SYJ.
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Cobat (Chen & Quan,
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Irradiation decreased the sensory quality of meat products (Du, Hur & Ahn, 2002). Free
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radical reaction induced by the irradiation process is the major reason for sensory quality
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changes of foods (Al-Bachir, 2013). Low dose irradiation resulted in unremarkable sensory 9
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smell and a brown color (Ahn, Jo, Du, Olson & Nam, 2000; Smulders, Van Laack &
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Eikelenboom, 1991). Therefore, free radical reaction might have resulted in the increase of
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off-odor in SYJ, and decrease of the color preference and taste of SYJ with the increase in
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irradiation dose. Several reasons for the off-odor of irradiated foods were reported. Gray,
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Gomaa and Buckley (1996) concluded that lipid oxidation was the primary reason for
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off-odor as meat products were irradiated. Du, Hur and Ahn (2002) reported that both lipid
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oxidation of products and sulfur-containing volatiles were responsible for meat irradiation
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odor. However, Ahn, Jo and Olson (2000) thought that the radiolytic breakdown of
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sulfur-containing amino acids is the main reason of the off-odor. As consumers’ responses to
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sensory changes of the irradiated meat products are quite negative (Al-Bachir, 2013; Du, Hur
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& Ahn, 2002), irradiation energy should not be higher than 5 kGy for treatment of SYJ.
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3.1.2 Effect of electron beam irradiation on textural properties of SYJ
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Effect of electron irradiation on hardness and gumminess of SYJ is shown in Fig. 2. The
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results (Fig. 2) indicated that both the hardness and gumminess of the SYJ decreased with the
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increase in irradiation dose. Compared with the control, an irradiation dose of 2 kGy resulted
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in no significant (P>0.05) difference to hardness and gumminess of SYJ, but irradiation doses
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of 5, 7, and 9 kGy led to significant (P<0.05) decrease of the hardness and gumminess.
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Similar effects were reported in the irradiation of pork loin (Lee, Yook, Kim, Sohn & Byun,
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1999).
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Both hardness and gumminess reflect the resistance of a meat product to breakage of
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internal texture (Zhang, Wang & Zhang, 2010). Irradiation resulted in textural changes and
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damage of protein in meat products, and it became more serious with the increase in 10
ACCEPTED MANUSCRIPT irradiation energy (Gu, 2013; Henry, 2009). These effects of irradiation on meat products
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might result in the decrease of hardness and gumminess of the SYJ with the increase in
236
irradiation dose. Textural properties are important to food product development (Saláková,
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2012), and the results in Fig. 3 further suggest that proper irradiation energy should be chosen
238
when using an irradiation process to sterilize SYJ.
239 240
3.1.3 Effect of electron beam irradiation on drip loss of SYJ
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The result of irradiation on drip loss of SYJ is shown in Fig. 3. The data in Fig. 3 indicated
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that the drip loss of SYJ increased with the increase in irradiation dose. The drip loss of the
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SYJ irradiated with 2 kGy was significantly (P<0.05) higher than that of the control and drip
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loss of the SYJ irradiated with 5 kGy was significantly (P<0.05) higher than that of the SYJ
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irradiated with 2 kGy. There was no significant (P>0.05) difference in drip loss as the SYJ
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was irradiated with 5, 7 and 9 kGy. Similar drip loss patterns occurred as pork fillet (GU,
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2013) and pork loins were irradiated (Zhu, Mendonca & Ahn, 2004).
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Drip loss reflects the capability of meat product to hold water and other flowable liquids. It
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indirectly demonstrates lipid oxidation, protein damage, and internal breakage of the net
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structure of meat and meat products (GU, 2013; Ma, Nan & Dai, 2003). The results of drip
252
loss shown in Fig. 3 suggested that more serious fat oxidation and meat protein damages
253
might have happened with the increase in irradiation dose. This is consistent with the results
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of increased off-odor of SYJ, and the decreased color preference, taste, hardness and
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gumminess of SYJ with the increase in irradiation dose.
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3.1.4 Effect of electron beam irradiation on content of capsanthin of SYJ Effect of irradiation on content of capsanthin of SYJ is shown in Fig. 4. The results (Fig. 4) 11
ACCEPTED MANUSCRIPT showed that the content of capsanthin of SYJ decreased with the increase in irradiation dose.
260
The content of capsanthin of SYJ irradiated with dose of 2 kGy showed no significant
261
(P>0.05) difference with the control, but the content of capsanthin of the SYJ irradiated with
262
doses of 5, 7, and 9 kGy were significantly (P<0.05) lower than the control. There was no
263
significant (P>0.05) difference in content of capsanthin of the SYJ irradiated with doses of 5,
264
7, and 9 kGy.
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Capsanthin was added to improve the color of SYJ. Capsanthin is the major pigment of red
267
chili pepper. It makes the chili pepper powder appear red, and it endows SYJ with beautiful
268
red color. There are 11 unsaturated bonds in the capsanthin molecule. Irradiation-induced free
269
radical reaction resulted in the breakdown of unsaturated bonds (Al-Bachir, 2013; Du, Hur &
270
Ahn, 2002). This may be the possible reason for the decrease of the content of the capsanthin
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of SYJ as it was irradiated with doses of 5, 7, and 9 kGy, and also for the decrease in color
272
preference of SYJ with the increase in irradiation dose.
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3.1.5 Effect of electron beam irradiation on content of TBARS of SYJ TBARS is produced by lipid oxidation and is directly related to the amount of volatile
276
substances and the sensory quality of meat products (Ahn, Jo & Olson, 2000). A higher
277
TBARS value indicated that more lipid oxidation has taken place, and produced more volatile
278
substances which decreased the sensory quality of meat products (Jo & Ahn, 1998). The
279
TBARS of the SYJs in Fig. 5 indicated that the TBARS of the SYJ increased with an increase
280
in irradiation dose. The TBARS of the SYJ irradiated with 5, 7, and 9 kGy were significantly
281
(P<0.05) higher than that of the control. There was no significant (P>0.05) difference between
282
the TBARS of the SYJ irradiated with 0 and 2 kGy. These results are consistent with the
283
off-odor of the SYJ, which increased with the increase in irradiation energy (Fig. 1).
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Lipid is the most sensitive food component to irradiation processes (Khattak & Simpson,
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2009; Venugopal, Doke & Thomas, 1999). The free radicals produced by irradiation initiate
287
chemical reactions in irradiated meat (Ahn, Jo, Du, Olson & Nam, 2000; Cava, Tárrega,
288
Ramírez & Carrasco, 2009). These chemical reactions lead to undesired organoleptic changes,
289
losses of unsaturated chemicals, and damages of meat protein (Ahn, Jo & Olson, 2000;
290
Grolichova, Dvořák & Musilova, 2004). Therefore, the results of irradiation dose on content
291
of TBARS further supported the increase in off-odor of the SYJ and decrease in the color
292
preference, taste, and the content of the capsanthin in SYJ with the increase in irradiation
293
dose.
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3.1.6 Effect of irradiation on microbe of SYJ
Changes in plate counts of aerobic bacteria and Escherichia coli in SYJ samples after
297
irradiation are shown in Table 1. The plate counts of the aerobic bacteria and Escherichia coli
298
decreased with the increase of irradiation dose. This result was consistent with that of Kim,
299
Chun, Song and Song (2010). According to the hygienic standard of China for cooked meat
300
products (GB2726-2005), plate counts of aerobic bacteria decreased to less than 104 CFU·g-1,
301
and plate counts of Escherichia coli decreased to less than 30 MPN·(100g)-1 are safe to eat.
302
The data in Table 1 indicated that an irradiation dose of 2 kGy is enough for killing bacterial
303
(870 CUF·g-1 < 104 CFU·g-1) and pathogenic bacteria (<30 MPN·(100g)-1) in SYJ.
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However, past studies on the effect of ionizing radiation and anaerobic refrigerated storage
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on clostridium botulinum spores or salmonella enteritidis in vacuum-canned deboned chicken
307
meat indicated that the irradiated samples didn’t develop toxin as they were stored at 5 °C, but
308
they became toxic within 18 h at 28 °C (Thayer, Boyd & Huhtanen, 1995). Even though the C. 13
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botulinum is relatively rare in meat (Prejean, 2001), further experiments should investigate
310
effect of irradiation on C.botulinum or salmonella enteritidis in SYJ.
311 312
3.2 Effect of electron beam irradiation on protein nutrition of SYJ Effect of irradiation on amino acids and protein nutrition values of SYJ is shown in Table 2.
314
The total amino acids (TAA) results in Table 2 showed that the amino acids of the SYJ were
315
not significantly (P>0.05) changed as the SYJ was irradiated with doses of 0, 2, 5, and 7 kGy,
316
but an irradiation dose of 9 kGy resulted in significant (P<0.05) decrease of the TAA of SYJ.
317
Similar significant (P<0.05) difference was observed as the total essential amino acids (TEAA)
318
of the SYJs were compared. Irradiation resulting in the decrease of amino acids were also
319
reported for the irradiation of sea bream and high protein food (Erkan & Özden, 2007;
320
Garrison, 1981). The results of the essential amino acid index (EAAI) of children or adult of
321
SYJ irradiated samples showed similar difference. Irradiation doses of 2, 5, and 7 kGy led to
322
no significant (P>0.05) difference in EAAI compared with the control, but an irradiation dose
323
of 9 kGy resulted in significant (P<0.05) decrease of the EAAI. The protein efficiency ratio
324
(PER) indicated that irradiation dose of 2 kGy resulted in significant (P<0.05) decrease of the
325
PER compared with the control, but it was not significantly (P>0.05) lower than the PER
326
value for irradiation dose of 5 kGy. Both irradiation doses of 7 and 9 kGy resulted in
327
significant (P<0.05) decrease of the PER compared with the control.
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Irradiation resulted in amino acid loss (Ahn, 2002; Jo & Ahn, 2000). Stadtman and Levine
330
(2003) analyzed the effect of irradiation-produced free radicals on free amino acids and their
331
residues and found that free radicals resulted in amino acids, like lysine, arginine, proline,
332
cysteine, threonine, leucine, and histidine being transferred into carbonyl derivatives and
333
other chemicals. Higher irradiation dose resulted in more free radicals, and more amino acids 14
ACCEPTED MANUSCRIPT 334
were lost. These effects of irradiation on amino acids might be the reason why the irradiation
335
dose of 9 kGy resulted in significant decrease of TAA, TEAA, PER, and EAAI of children or
336
adults.
337
4 Conclusions
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The color preference, taste, hardness, and gumminess of SYJ decreased with the increase in
340
irradiation dose, while the drip loss, off-odor of SYJ increased with the increase in irradiation
341
dose. Free radicals produced by electron beam irradiation might be the reason for the quality
342
changes of SYJ. This can be supported by the increase of TBARS and decrease of the content
343
of capsanthin of SYJ with the increase in irradiation. Low irradiation didn’t lead to obvious
344
changes of the protein biological value of SYJ, but irradiation dose of 9 kGy resulted in
345
significant (P<0.05) decrease of the TAA, TEAA, EAAI of children and adults, and PER of
346
the SYJ. An irradiation dose of less than 5 kGy is recommended to treat the SYJ.
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Acknowledgment
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The authors thank the financial support provided by the Education Department of Sichuan
350
(17ZA0084), the Science and Technology Department of Sichuan Province (No. 2017JY0086),
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China Postdoctoral Science Foundation (No. 2017M612969) and the National Natural Science
352
Foundation of China (No. 31501505).
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Table 1. Effect of electron beam irradiation on microbes of SYJ 0 Irradiation dose [kGy]
2
5
280000
870
20
2400
<30
<30
7
9
Counts of aerobic -1
bacteria [CFU·g ] Counts of Escherichia -1
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<10
<10
<30
<30
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2 [kGy]
5 [kGy]
7 [kGy]
9 [kGy]
9.701±0.072
9.626±0.071
9.676±0.071
9.601±0.071
9.228±0.068
Glutamic acid
20.776±0.153
20.526±0.152
20.601±0.152
20.826±0.154
19.875±0.147
Serine
3.800±0.028
3.975±0.029
3.825±0.028
3.750±0.028
3.620±0.027
Glycine
4.750±0.035
4.925±0.036
4.625±0.034
4.450±0.033
4.500±0.033
Histidine
3.575±0.026
3.550±0.026
3.500±0.026
4.075±0.030
4.272±0.032
Arginine
6.525±0.048
6.425±0.047
6.500±0.048
6.250±0.046
5.751±0.042
Alanine
6.050±0.045
6.100±0.045
6.000±0.044
5.775±0.043
5.773±0.043
Proline
4.600±0.034
4.900±0.036
4.425±0.033
3.650±0.027
4.572±0.034
Threonine
4.450±0.033
4.425±0.033
4.450±0.033
4.350±0.032
4.225±0.031
Tyrosine
3.125±0.023
3.075±0.023
3.075±0.023
3.225±0.024
3.322±0.025
Valine
5.025±0.037
4.975±0.037
5.025±0.037
4.800±0.035
4.710±0.035
Methionine
2.475±0.018
2.450±0.018
2.100±0.016
2.250±0.017
2.347±0.017
Cystine
0.800±0.006
0.850±0.006
0.625±0.005
0.800±0.006
0.767±0.006
Isoleucine
4.700±0.035
4.575±0.034
4.625±0.034
4.600±0.034
4.498±0.033
Leucine Phenylalanine
8.625±0.064 4.150±0.031
8.475±0.063 5.400±0.040
8.550±0.063 5.075±0.037
8.275±0.061 5.950±0.044
8.188±0.060 4.150±0.031
Lysine
8.500±0.063
8.100±0.060
8.475±0.063
8.350±0.062
8.079±0.060
Total amino acids (TAA), [g•(100g)-1] Total essential amino acids (TEAA) [g•(100g)-1] *Essential amino acid index (EAAI) **Essential amino acid index (EAAI) Protein efficiency ratio (PER)
101.631±0.751a
102.356±0.756a
101.156±0.747a
100.980±0.746a
97.878±0.723b
37.927±0.280a
38.402±0.284a
38.302±0.283a
38.577±0.285a
36.198±0.267b
0.164±0.001ab
0.165±0.001a
0.162±0.001b
0.164±0.001ab
0.158±0.001c
0.306±0.002ab
0.308±0.002a
0.302±0.002b
0.306±0.002ab
0.295±0.002c
3.057±0.026b
3.091±0.026ab
2.950±0.025c
2.901±0.025c
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Amino acids [g•(100g)-1] Aspartic acid
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Means (n=3) without a common letter differ significantly (P<0.05);
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* Based on amino acid requirements of school children (10-12 years)
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** Based on amino acid requirements of adults
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Fig.1 Effect of electron beam irradiation on sensory attributes of SYJ
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Values are represented as Mean± SD. Significance was tested by Duncan Multiple Range Test at p < 0.05,
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and values with the same superscript were found not significantly different from each other.
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Fig.2 Effect of electron beam irradiation on texture properties of SYJ
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Values are represented as Mean± SD. Significance was tested by Duncan Multiple Range Test at p < 0.05,
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Fig.3 Effect of electron beam irradiation on drip loss of SYJ
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Fig.4 Effect of electron beam irradiation on content of capsanthin of SYJ
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Fig.5 Effect of electron beam irradiation on content of TBARS of SYJ
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ACCEPTED MANUSCRIPT Highlights 1. Spicy yak jerky is a typical snack meat product in China 2. High dose irradiation decrease the quality of spicy yak jerky
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3. High dose irradiation decrease protein biological value