Meat Science 87 (2011) 33–39
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Meat Science j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / m e a t s c i
The use of natural herbal extracts for improving the lipid stability and sensory characteristics of irradiated ground beef Hussein M.H. Mohamed a,⁎, Hayam A. Mansour a, M. Diaa El-Din H. Farag b a b
Department of Food Hygiene and Control, Faculty of Veterinary Medicine, Cairo University, Giza, Egypt Department of Food Irradiation Research, National Centre for Radiation Research & Technology (NCRRT), Egyptian Atomic Energy Authority, Nasr City, Cairo, Egypt
a r t i c l e
i n f o
Article history: Received 13 January 2010 Received in revised form 4 May 2010 Accepted 7 June 2010 Keywords: Ground beef Sensory characteristics Radiation processing Herbal extracts Lipid oxidation
a b s t r a c t Ground Longissimus dorsi of beef were treated with herbal extracts of marjoram, rosemary and sage at concentration of 0.04% (v/w), radiation (2 or 4.5 kGy) or their combination. Treated samples were stored at 5 °C and analyzed periodically for thiobarbituric acid reactive substances (TBARS), sensory characteristics and psychrotrophic bacterial counts during storage for 41 and 48 days for samples treated at 2 and 4.5 kGy respectively. Results demonstrated a significant benefit of the addition of herbal extracts to the ground beef prior to irradiation. All three extracts significantly (P b 0.05) lowered the TBARS values and off-odor scores and significantly (P b 0.05) increased color and acceptability scores in all samples with marjoram being the most effective. The combination treatment with herbal extracts plus irradiation resulted in extension of the shelf life of samples treated with 2 kGy by one week and samples treated with 4.5 kGy by two weeks, over that treated with irradiation alone. In conclusion, the addition of herbal extracts can minimize lipid oxidation, improve color and decrease off-odor production in irradiated ground beef. © 2010 The American Meat Science Association. Published by Elsevier Ltd. All rights reserved.
1. Introduction Radiation is a well-known technology that has the advantages of improving the microbiological safety and extending the shelf life of different kinds of meat and meat products (Ahn & Nam, 2004; Badr, 2004; Nam et al., 2006; Sweetie, Chander, & Sharma, 2006; Al-Bachir & Zeinou, 2009). In the USA, the USFDA has approved the use of ionizing radiation at levels up to 4.5 kGy for chilled meat and 7 kGy for frozen meat (Olson, 1998). However, a major problem associated with irradiation of raw meat is the development of off-odors due to free radical induced lipid oxidation and radiolytic breakdown of proteins and lipids (Patterson & Stevenson, 1995; Murano, Murano, & Olson, 1998; Kim, Nam, & Ahn, 2002). This lipid oxidation and off-odor reduce the sensory quality and consumer acceptability of irradiated meat. Therefore, the interest of industry and researchers recently is directed towards the use of natural ingredients, which can minimize lipid oxidation and off-odors with consequent increase of the acceptability of irradiated meat. Antioxidants are added to fresh and further processed meats to prevent oxidative rancidity, retard development of off-odors, and improve color stability (Xiong, Decker, Robe, & Moody, 1993). Irradiation causes fatty acid oxidation due to it facilitates the initiation
⁎ Corresponding author. Current address: Department of Food, Agricultural and Biological Engineering, The Ohio State University, 590 Woody Hayes Dr., Columbus, OH 43210, USA. Tel.: +1 614 745 5218; fax: +1 614 292 9448. E-mail address:
[email protected] (H.M.H. Mohamed).
of lipid oxidation. Therefore, antioxidants can retard or prevent the oxidation changes and off-odor in irradiated meat by the same mechanism by which they prevent lipid oxidation in untreated meat (Du & Ahn, 2002). Antioxidants can effectively reduce the peroxidation produced due to irradiation of lard and tallow (Kyong, Hong, Ju, Hyun, & Myung, 1998; Kyong, Hong, Ju, Sung, & Myung, 1999). Conventional antioxidants, such as butylated hydroxyanisole, butylated hydroxytoluene, tertiarybutyl hydroquinone and propyl gallate can be used to minimize lipid oxidation in meat effectively. However, their potential health risk restricted their extensive use and increased the interest in using natural antioxidants (Ito, Fukushinma, Hasegawa, Shibata, & Ogiso, 1983; Han & Rhee, 2005). The effectiveness of sesamol, quercetin and rosemary in preventing off-odor in irradiated raw and cooked pork during storage has been reported (Chen, Jo, Lee, & Ahn, 1999). The effect of irradiation on the quality of meat has been extensively studied for more than 50 years. Moreover, the effect of antioxidant on improving sensory attributes and controlling oxidation reactions in meat has been well established. However, selected antioxidants may differ in reducing lipid oxidation and improving sensory characteristics of irradiated meat depending on the type of antioxidant and packaging method used. Therefore, the objective of the present study was to determine the effect of selected herbal extracts on the lipid oxidation, sensory characteristics and bacterial count of aerobically packaged ground beef irradiated and stored at chilling temperatures (5 °C). This work may encourage the meat industry to implement irradiation processing for producing high quality fresh meat.
0309-1740/$ – see front matter © 2010 The American Meat Science Association. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.meatsci.2010.06.026
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2. Material and methods
2.4. Sensory evaluation
2.1. Samples preparation
The odor, color and overall acceptability of ground beef (treated and untreated) were evaluated using 7 points hedonic scale described by (Nam, Prusa, & Ahn, 2002). Seven panelists were chosen from experienced panelists from the staff members of the Department of Food Hygiene and Control at Faculty of Veterinary Medicine, Cairo University. The panelists were also chosen based on their ability to distinguish irradiation odor from other aroma. Furthermore, a preparatory session was conducted prior to testing, so that each panel could thoroughly discuss and clarify each attribute to be evaluated. Panelists were instructed to smell the samples in random order and record the intensity of irradiation odor based on the hedonic scale with 1 (not detectable) and 7 (extremely intensive). Panelists were asked to assign a numerical value between 1 (dislike extremely) and 7 (like extremely) for color of treated and untreated ground beef. They also asked to assign the same values depends on the overall acceptability of odor and color of the ground beef with 1 (extremely not accepted) and 7 (extremely accepted).
Twelve beef loins (Longissimus dorsi) at the level of 11–13th rib of 18 month steers (cross breed between Holstein and Local (or Baladi breed) in percentage of 87.5% and 12.5% respectively) were used. The loins were purchased from local butchery after 24 h of slaughter and storage at chilling temperature (5 °C) and rapidly transported to the laboratory in an ice box in order to minimize the changes. In the laboratory, the external fascia and visible fat were removed then meat blocks were ground through a 3 mm plate. Marjoram, rosemary and sage extracts (essential oils) were obtained from Research Institute of Horticulture, Aromatic and Medicinal Plants Division, belonging to Ministry of Agriculture and Land Reclamation (Dokki, Giza, Egypt). The oils of the air-dried herbs were extracted according to the British Pharmacopoeia (1963) by water distillation method. This method can be summarized as follow: A known weight of dry herb was placed in a 1 L flask for distillation and adequate amount of water was added. A proper essential oil trap and condenser were attached to the flask and the flask placed on an electrically heated bath. The distillation continued for 3 h until no further increase in the oil was observed. After finishing the distillation process the apparatus was left to be cooled and the essential oil was collected. The ground meat was divided into the following treatment groups: (1) non treated controls, (2) irradiated meat (2 or 4.5 kGy), (3) meat treated with herbal extracts of marjoram, rosemary or sage (0.04%, v/w of non-irradiated meat); (4) meat treated with herbal extracts of marjoram, rosemary or sage (0.04%, v/w) plus irradiation at 2 or 4.5 kGy. Each ingredient (0.04%, v/w) was added to ground beef then mixed for Lab blender to ensure uniform distribution of added extract. Ground beef from each treatment group was individually packaged in polyethylene bags (50 g of meat in each bag). The heat sealed aerobically packaged samples were then irradiated. The total numbers of samples used in this study were 448 (224 samples for sensory analysis and 224 samples for TBARS and bacterial counts). 2.2. Irradiation process and storage For irradiation, the packaged ground beef samples were irradiated at National Centre for Radiation Research &Technology (NCRRT), Nasr City, Cairo, Egypt. The irradiation facility used was Egypt's Mega Gamma-1 type- J-6500. The dose rate was 8 kGy per h. The samples in chilled state, received radiation dose in icebox to keep the temperature around 5 °C during irradiation. The applied irradiation doses were 2 or 4.5 kGy, as monitored by FWT-6-00Ô radiochromic film (ASTM, 2002 [ISO/ASTM 51275:2002(E)]). Following irradiation the irradiated and non-irradiated meat samples were immediately stored at 5 °C. Samples were withdrawn periodically for analysis. 2.3. Chemical analysis Both irradiated and non-irradiated beef samples were analyzed for thiobarbituric acid reactive substances (TBARS) according to the method of Du and Ahn (2002) as follow: Five grams of meat were homogenized with 15 mL of deionized distilled water. One milliliter of the meat homogenate was transferred to a test tube and 50 μL of butylated hydroxytoluene (7.2%) and 2 mL of thiobarbituric acid (TBA)–trichloroacetic acid (TCA) (15 mM TBA–15% TCA) were added. The mixture was vortexed and then incubated in a boiling water bath for 15 min to develop color. Then samples were cooled in cold water for 10 min, vortexed again, and centrifuged for 15 min at 2500 ×g. The absorbance of the resulting supernatant solution was determined at 531 nm against a blank containing 1 mL of deionized water and 2 mL of TBA–TCA solution. The amounts of TBARS were expressed as milligrams of malonaldehyde per kilogram of meat.
2.5. Bacteriological examination Ten grams of meat from each bag were separately obtained under aseptic condition and homogenized in sterile stomacher bag with 90 ml of Ringers' solution (Merck) for 1 min using stomacher (Labblender 400, Seward, UAC house Friars Road, London SE 19 UG-model No. 6021) to provide dilution of 10−1. From the original homogenate ten fold serial dilutions were prepared (APHA, 1992). Psychrotrophic bacterial count was estimated by inoculation onto standard plate count agar and incubation at 7 °C for 7 days. 2.6. Statistical analysis Results were expressed as values of four replicate determinations± SD. Statistical data analysis was carried out using the Minitab Statistical Program, version 11 (Minitab, 1996). Analysis of variance (ANOVA) was performed to compare the effect of the treatments. Multiple comparisons of means were done using Tukey's at family error rate 0.05 to show differences among treatments. 3. Results and discussion 3.1. Lipid oxidation The effect of herbal extracts, irradiation at 2 or 4.5 kGy and combinations of herbal extracts plus irradiation after processing and during refrigerated storage at 5 °C is illustrated in Fig. 1. Adding natural herbal extracts to raw ground beef significantly (P b 0.05) reduced the TBARS values during refrigerated storage with no significant (P N 0.05) difference between the three natural herbal extracts (Fig. 1a). It has been reported previously that antioxidant supplementation increased the oxidative stability of non-irradiated minced beef (Formanek et al., 2001). Irradiation alone resulted in dose dependent increase of TBARS post irradiation and during storage at 5 °C (Fig. 1b and c). This observation is in agreement with different authors (Hampson, Fox, Lakritz, & Thayer, 1996; Luchsinger et al., 1996; Lee, Yook, Kim, Lee, & Byun, 1999; Formanek, Lynch, Galvin, Farkas, & Kerry, 2003; Kanatt, Chander, & Sharma, 2005; Chae et al., 2009). The increase of TBARS due to irradiation may be explained by the auto oxidation of fat which is accelerated by presence of oxygen (Nawar, 1985). Addition of herbal extracts significantly (P b 0.05) reduced the dose and time-dependent increase in TBARS in irradiated ground beef (Fig. 1b and c). The TBARS of samples treated with marjoram followed by irradiation were significantly (P b 0.05) lower than that of samples treated with rosemary or sage followed by irradiation during storage
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TBARS values
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especially with samples treated with 4.5 kGy (Fig. 1c). These results are in agreement with Nam and Ahn (2003) who reported reduction in TBARS in both non-irradiated and irradiated pork patties under aerobic conditions after addition of antioxidants. Chen et al. (1999) also reported that phenolic antioxidants were effective in reducing lipid oxidation in aerobically packaged irradiated pork patties. Mahrour, Caillet, Nketsia-Tabiri, and Lacroix (2003) recorded that irradiation of chicken leg marinated in lemon juice, thyme and rosemary in aerobic packaging reduced the oxidation rate of unsaturated fatty acids derived from phospholipids fraction (Linoleic acid and Arachidonic acid). Addition of sesamol to ground beef before irradiation increased the effectiveness of ascorbic acid and tocopherol in reducing lipid oxidation during storage (Ahn & Nam, 2004; Ismail, Lee, Ko, and Ahn (2008). Moreover, it has been observed that rosemary is effective in decreasing TBARS values in irradiated raw pork loins (Nam et al., 2007). Addition of rosemary extract alone and in combination with other antioxidants was effective in controlling lipid oxidation in irradiated frozen beef burger during frozen storage (Trindade, Mancini-Filho, & Villavicencio, 2010). As a function of stored period, irradiation increased the TBARS values during chilled storage. However, TBARS values of samples
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treated with combinations of irradiation and herbal extracts were significantly (P b 0.05) lower than that of samples treated with radiation alone; these results are in good agreement with Nam et al. (2002) and Kanatt et al. (2005). The use of antioxidants stabilized the lipids of ground beef after irradiation and during simulated retail display (Duong et al., 2008). Moreover, the use of herbal extract of mint reduced the TBARS of irradiated lamb meat after irradiation and during chilled storage for 4 weeks (Kanatt, Chander, & Sharma, 2007). Addition of rosemary extracts to irradiated fermented sausage was effective in controlling lipid oxidation during cold storage (Lim, Seol, Jeon, Jo, & Lee, 2008). Different phenolic compounds that have antioxidant activities have been identified from marjoram, rosemary and sage by different authors (Löliger, 1991; Deighton, Glidewell, Deans, & Goodman, 1993; Santos-Gomes, Seabra, Andrade, & Fernandes-Ferreira, 2002; Durling et al., 2007; Fecka & Turek, 2008; Sellami et al., 2009). These compounds may be the cause of the antioxidant activity of these herbal extracts. 3.2. Sensory evaluation It is well established that irradiation of raw meat even at low doses can give rise to a characteristic unpleasant odor (irradiation odor) due to oxidation of polyunsaturated fatty acids, destruction of antioxidants in muscle by free radicals and production of volatile compounds (Thayer, Boyd, & Jenkins, 1993; Lakritz et al., 1995; Giroux & Lacroix, 1998). Lipid oxidation can be promoted even at low doses of irradiation resulting in the undesirable off-odors of meat (Lescano, Narvaiz, Kairiyama, & Kaupert, 1991; Thakur & Singh, 1994). This odor can be described as rotten egg, bloody, fishy, burnt, sulphur, metallic, alcohol or acetic acid and differ according to the type of meat, packaging condition, temperature during irradiation process and availability of oxygen during and/or after irradiation (Brewer, 2009). Results in Fig. 2 revealed that irradiation increased odor intensity thus increasing irradiation odor scores. The addition of herbal extracts to the ground beef prior to irradiation resulted in significant (P b 0.05) reduction of irradiation odor scores in samples treated with 2 or 4.5 kGy post irradiation and during refrigerated storage. The irradiation odor intensity decreased in samples treated with irradiation alone or natural herbal extracts plus irradiation during refrigerated storage. The panelists could not detect the irradiation odor in samples treated with marjoram plus 2 or 4.5 kGy at the 8th day of storage period. Moreover, they could not detect the irradiation odor in samples treated with sage plus 2 kGy or 4.5 kGy at the 5th day and 12th day of storage respectively. However, they could not detect the irradiation odor in samples treated with rosemary plus 2 kGy and 4.5 kGy at the 19th day and 26th day of storage respectively. The lowering of irradiation odor scores during storage may be attributed to volatization of sulphur-containing compounds as mercaptomethane and dimethyldisulfide that are responsible for most of irradiation odor (Ahn, Nam, Du, & Jo, 2001). The reduction of irradiation odor scores that achieved by addition of studied natural herbal extracts may be attributed to the antioxidant activity of these extracts. This antioxidant activity act as scavengers for free radicals so can interrupt free radical chain reactions and chelate catalytic metals therefore, retard oxidative deterioration and minimize off-odor production in meat (Lee et al., 1999; Ahn et al., 1997). The antioxidant activity of rosemary and sage was reported by many researchers (Barbut, Josephson, & Maurer, 1985; Buckley, Morrissey, & Gray, 1995). Marinating chicken legs in lemon juice, thyme and rosemary prior to irradiation significantly improved the odor and flavor of the air packaged irradiated chicken (Mahrour, Lacroix, Nketsa-Tabiri, Calderon, & Gagnon, 1998). Moreover, addition of sesamol + tocopherol effectively reduced the generation of sulphurcontaining compounds responsible for off-odor of irradiated meat (Nam, Min, Park, Lee, & Ahn, 2003). The color of meat is the most important factor for consumer in the decision to buy a certain piece of meat. It is clear that irradiation have
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effectively maintained during storage by adding ascorbic acid and αtocopherol before irradiation (Ismail et al., 2008). The color of ground beef has been also stabilized after irradiation and during simulated retail display by using antioxidants (Duong et al., 2008). The consumer acceptability of food determines the future of that food in the market. Therefore, increasing the consumer acceptance of food processed with the new technologies will accelerate their implementation in food industry. Addition of natural herbal extracts to non-irradiated ground beef resulted in non significant (P N 0.05) change in the acceptability scores of beef during storage period (Fig. 4a). Irradiation of ground beef significantly (P b 0.05) decreased the overall acceptability scores and the reduction of scores was more pronounced in samples treated with 4.5 kGy. However, adding herbal extracts to the ground beef prior to irradiation resulted in significant (P b 0.05) increase in the acceptability scores of irradiated beef post
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an effect on meat color as judged by its surface appearance. The bright red color of ground beef changed to brown color and the intensity of color change increased as the irradiation dose increased. Addition of natural herbal extracts to raw non-irradiated ground beef resulted in non significant (P N 0.05) change in color scores (Fig. 3a). Ground beef samples treated with radiation alone revealed significant (P b 0.05) reduction of color scores post irradiation and during refrigerated storage especially in samples processed at 4.5 kGy. However, addition of natural herbal extracts to ground beef prior to irradiation resulted in significant (P b 0.05) increase of color scores (improvement of color) of samples treated with 4.5 kGy (Fig. 3b and c). The change of color under irradiation is in agreement with Nanke, Sebranek, and Olson (1998) and Kim et al. (2002) who recorded the change of beef color into brown or gray after irradiation. The changes in irradiated meat color may be due to oxidation of myoglobin with the free radicals generated upon irradiation (Giroux et al., 2001). The color changes in the irradiated meat have been also explained by to the formation of carboxy form of haem pigments either carboxymyoglobin or carboxyhaemoglobin (Millar, Moss, & Stevenson, 2000). The applied natural herbal extracts may improve the color of irradiated meat by scavenging free radicals produced by irradiation therefore, protecting myoglobin from oxidation. Ahn and Nam (2004) reported reduction of the redness of irradiated ground beef with changing of the visible color from bright red to green/brown depending on the age of meat. They also reported that the color changes in irradiated beef prevented by addition of ascorbic acid to meat before irradiation and the effect of ascorbic acid increased as the storage time after irradiation increased. The redness of irradiated ground beef can
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Fig. 2. Irradiation odor scores (1, not detectable; 7, extremely intensive) of ground beef treated with radiation or herbal extracts plus radiation during refrigerated storage at 5 °C. (a) Treatments with 2 kGy or herbal extracts plus 2 kGy, M2: marjoram plus 2 kGy, R2: rosemary plus 2 kGy, S2: sage plus 2 kGy. (b) Treatments with 4.5 kGy or herbal extracts plus 4.5 kGy, M4.5: marjoram plus 4.5 kGy. R4.5: rosemary plus 4.5 kGy, S4.5: sage plus 4.5 kGy.
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Storage period (days) Fig. 3. Color scores (1, dislike extremely; 7, like extremely) of ground beef treated with natural herbal extracts, radiation or herbal extracts plus radiation during refrigerated storage at 5 °C. (a) Control and herbal extracts treatments, C, control, M: marjoram, R: rosemary, S: sage. (b) Treatments with 2 kGy or herbal extracts plus 2 kGy. M2: marjoram plus 2 kGy, R2: rosemary plus 2 kGy, S2: sage plus 2 kGy. (c) Treatments with 4.5 kGy or herbal extracts then 4.5 kGy, M4.5: marjoram plus 4.5 kGy, R4.5: rosemary plus 4.5 kGy, S4.5: sage plus 4.5 kGy.
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3.3. Bacteriological quality
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Addition of natural herbal extracts to non-irradiated ground beef did not significantly (P N 0.05) change the psychrotrophic bacterial count during storage. Moreover, the counts reached 108 cfu/g at the 12th day of storage (Fig. 5a) with the appearance of signs of spoilage in the form of change in color, odor and texture. Irradiation of ground beef significantly (P b 0.05) decreased the psychrotrophic bacterial counts and the count reduction was dose dependent. The 2 kGy irradiation caused 3 log cfu/g reductions in bacterial count while treatment with 4.5 kGy resulted in psychrotrophic bacterial counts below the detectable level immediately after irradiation. Irradiation also resulted in extension of shelf life of treated minced beef. The counts reached 108 cfu/g in samples treated with 2 kGy at the 26th day of storage while the counts reached 107 cfu/g in samples treated with 4.5 kGy at the 40th day of storage (Fig. 5b and c). The decrease in total bacterial populations due to irradiation was in agreement with other studies (Naik, Paul, Chawla, Sheriker, & Nair, 1994; Luchsinger et al., 1996; Kanatt, Paul, D'Souza, & Thomas, 1997; Kanatt et al.,
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Storage period (days) Fig. 4. Overall acceptability (1, extremely not accepted; extremely accepted) scores of ground beef treated with natural herbal extracts, radiation or herbal extracts plus radiation during refrigerated storage at 5 °C. (a) Control and herbal extracts treatments, C: control, M: marjoram, R: rosemary, S: sage. (b) Treatments with 2 kGy or herbal extracts plus 2 kGy. M2: marjoram plus 2 kGy, R2: rosemary plus 2 kGy, S2: sage plus 2 kGy. (c) Treatments with 4.5 kGy or herbal extracts then 4.5 kGy. M4.5: marjoram plus 4.5 kGy, R4.5: rosemary plus 4.5 kGy, S4.5: sage plus 4.5 kGy.
irradiation and during storage (Fig. 4b and c). Depending on the above sensory analyses, the improvement in acceptability of irradiated beef by addition of natural herbal extracts may be attributed to oxidative stability, reduction of irradiation off-odor (improvement of odor) and increasing of color scores (improvement of color) of irradiated minced beef. In a study conducted by McAteer, Grant, Patterson, Stevenson, and Weatherup (1995) trained panelists could detect the difference between irradiated (2 and 3 kGy) and non-irradiated meals especially vegetable components. In another study conducted by Stevenson, Stewart, and McAteer (1995) untrained consumers could not differentiate the stored irradiated (2 kGy) from non-irradiated meals containing beef and gravy and they gave high hedonic scores indicating that the consumers liked both irradiated and nonirradiated components. Trindade et al. (2009) reported that the irradiated beef burger formulated with rosemary obtained a better consumer's score in comparison to non-irradiated samples. They also concluded that the rosemary extract presents a good alternative for replacing synthetic ingredients in food industries.
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Storage period (days) Fig. 5. Psychrotrophic counts (cfu/g) of ground beef treated with natural herbal extracts, radiation or herbal extracts plus radiation during refrigerated storage at 5 °C. (a) Control and herbal extracts treatments, C; control, M: marjoram, R: rosemary, S: sage (b) Treatments with 2 kGy or herbal extracts then 2 kGy. M2: marjoram then 2 kGy, R2: rosemary then 2 kGy, S2: sage then 2 kGy. (c) Treatments with 4.5 kGy or herbal extracts then 4.5 kGy. M4.5: marjoram then 4.5 kGy, R4.5: rosemary then 4.5 kGy, S4.5: sage then 4.5 kGy. ****Counts under the detectable level of direct plate count.
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2005). It has been reported that a dose of 1 kGy significantly decreased the total aerobic plate counts in comparison to untreated samples (Lacroix & Ouattara, 2000). The shelf life of ground beef patties was extended to 55 days under storage at 4 °C by irradiation (Murano et al., 1998; Lee et al., 1999). Addition of herbal extracts to the ground beef prior to irradiation did not significantly (P N 0.05) decrease the psychrotrophic bacterial counts of treated samples immediately after irradiation. However, the bacterial counts of these samples became significantly (P b 0.05) lower than samples treated with radiation alone at the 19th day of storage. Moreover, addition of these extracts at the level used (0.04%) extended the shelf life of samples treated with 2 kGy and 4.5 kGy for one week and two weeks respectively more than samples irradiated alone. Several previous reports on the combination of gamma irradiation and other treatments suggested that microorganisms which can survive radiation treatment will probably be more sensitive to environmental conditions (temperature, pH, nutrients, inhibitors, etc.) than untreated cells (Farkas, 1990, Lacroix & Ouattara, 2000). 4. Conclusion Irradiation has the advantage of destroying microorganisms and extending the shelf life of meat. However, it results in oxidation of lipids and changes the quality of meat with consequent decrease in the overall acceptability of irradiated aerobically packaged ground beef. Herbal extracts of marjoram, rosemary and sage have antioxidant effects and can be used at level of 0.04% of sample (v/w) to minimize lipid oxidation, improve color, and decrease irradiation odor production in irradiated ground beef with consequent increase of the overall acceptability. The results of the present study may encourage the application of radiation processing in combination with natural herbal extracts in meat industry. References Ahn, D. U., & Nam, K. C. (2004). Effects of ascorbic acid and antioxidants on color, lipid oxidation and volatiles of irradiated ground beef. Radiation Physics and Chemistry, 71, 149−154. Ahn, D. U., Nam, K. C., Du, M., & Jo, C. (2001). Volatile production in irradiated normal, pale soft exudative (PSE), and dark firm dry (DFD) pork under different packaging and storage conditions. Meat Science, 57, 419−426. Ahn, D. U., Sell, J. L., Jeffery, M., Jo, C., Chen, X., Wu, C., & Lee, J. I. (1997). Dietery vitamin E effects lipid oxidation and total volatiles of irradiated raw turkey meat. Journal of Food Science, 62, 954−958. Al-Bachir, M., & Zeinou, R. (2009). Effect of gamma irradiation on microbial load and quality characteristics of minced camel meat. Meat Science, 82, 119−124. APHA (1992). Compendium of methods for the microbiological examination of foods (pp. 75−77)., 3rd Ed. Washington, D.C. USA: American Public Health Association. ASTM (2002). American Society for Testing Materials. Standard dosimetry for radiation process, ISO/ASTM 51275:2002 (E). Standard practice for use of a radiochromic film dosimetry system. Annual Book of ASTM Standards (pp. 40−44). Philadelphia, PA: ASTM. Badr, H. M. (2004). Use of irradiation to control food borne pathogens and extend the refrigerated market life of rabbit meat. Meat Science, 67, 541−548. Barbut, S., Josephson, D. B., & Maurer, A. J. (1985). Antioxidant properties of rosemary oleoresin in turkey sausage. Journal of Food Science, 50, 1356−1359. Brewer, M. S. (2009). Irradiation effects on meat flavor: A review. Meat Science, 81, 1−14. British Pharmacopoeia (1963). Determination of volatile oil in drugs. London: The Pharmaceutical Press. Buckley, D. J., Morrissey, P. A., & Gray, J. (1995). Influence of dietary vitamin E on the oxidative stability and quality of pig meat. Journal of Animal Science, 73, 3122−3130. Chae, S. H., Keeton, J. T., Miller, R. K., Johnson, D., Maxim, J., & Smith, S. B. (2009). The triacylglycerol preparation of conjugated linoleic acid reduces lipid oxidation in irradiated, cooked ground beef patties. Meat Science, 81, 647−652. Chen, X., Jo, C., Lee, J. I., & Ahn, D. U. (1999). Lipid oxidation, volatiles and color changes of irradiated pork patties as affected by antioxidants. Journal of Food Science, 64, 16−19. Deighton, N., Glidewell, S. M., Deans, S. G., & Goodman, B. A. (1993). Identification by EPR spectroscopy of carvacrol and thymol as the major sources of free radicals in the oxidation of plant essential oils. Journal of the Science of Food and Agriculture, 63, 221−225. Du, M., & Ahn, D. U. (2002). Effect of antioxidants on the quality of irradiated sausages prepared with turkey thigh meat. Poultry Science, 81, 1251−1256.
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