EFFECT OF ROSEMARY EXTRACT ON LIPID OXIDATION AND SENSORY EVALUATION OF FROZEN, PRECOOKED BEEF PATTIES

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1 EFFECT OF ROSEMARY EXTRACT ON LIPID OXIDATION AND SENSORY EVALUATION OF FROZEN, PRECOOKED BEEF PATTIES KINGKARN THONGTAN 1, RAMSES B. TOMA 1,3, WENDY REIBOLDT 1 and AHMED Z. DAOUD 2 1 California State University, Long Beach 1250 Bellflower Boulevard Long Beach, CA Custom Food Products 1117 West Olympic Boulevard Montebello, CA Accepted for Publication October 12, 2005 ABSTRACT This study investigated the effect of refined rosemary extract on lipid oxidation in frozen, precooked beef patties (FBP) stored at -18.0C (0.4F) for 12 weeks. Samples were analyzed for peroxide value (PV) levels, 2-thiobarbituric acid (TBA) values and sensory characteristics on 0 day and after 4, 8, and 12 weeks. Samples with rosemary extract showed lower PV and TBA values. Sensory evaluations of precooked patties with rosemary extract were not significantly different in scores on color, smell/odor, appearance, texture and overall acceptability. Samples with refined rosemary extract reported a significantly higher liking score for flavor (P 0.05), however, there was no significant correlation between PV and sensory scores and TBA and sensory scores for both frozen, precooked patties with/without the addition of refined rosemary extract. INTRODUCTION Consumption of cooked ground beef has increased because of ease of preparation and versatility, and ground beef continues to command a major share of total beef consumption (Anon 2005). The purchase of frozen, precooked, ready-to-eat meats have increased rapidly because of an innovative 3 Corresponding author. TEL: (562) ; FAX: (562) ; rtoma@csulb.edu

2 food industry, which continuously introduces new products to meet the growing consumer demand for quick foodservice (Younathan et al. 1980). Per capita beef consumption in 2004 totaled 66.1 lb, an increase of 1.8% compared to that in These products, however, are susceptible to meat-flavor changes and oxidative rancidity because ground-beef products generally contain 20 30% fat (Egbert et al. 1991). The most likely cause of meat-flavor changes is from lipid oxidation. Lipid oxidation is a major cause of deterioration in the quality of meat products (Love and Pearson 1971; Asghar et al. 1988) because it has detrimental effects on the color, flavor and texture of meat which render these foods less acceptable (Nawar 1996). Oxidative reactions can decrease the nutritional quality of food, and certain oxidation products are potentially toxic. Consequently, it is desirable to eradicate the rancid or stale flavor by eliminating the formation of by-products such as aldehydes, ketones, alcohol and hydrocarbons in meat products. Initially, peroxides are formed, which break down to hydrocarbons, ketones, aldehydes and trace amounts of epoxides and alcohols (Technical Committee of the Institute of Shortening and Edible Oils, Inc. 1994). Aldehydes are significant contributors to the odor of cooked beef (Love and Pearson 1971; Wu and Brewer 1994). Some alternative antioxidant sources are natural such as tocopherols (Anon 1991), Maillard Reaction products, (Bailey 1988) and addition of vegetables like red-onion skin, oregano, garlic and/or rosemary extracts (Rhee 1988). Among herbs, rosemary (Rosmarinus officinalis L.) is the only one that is explored commercially as a natural antioxidant (Jadhav et al. 1996). Both crude and refined rosemary extracts have exhibited excellent antioxidant properties. Rosemary extracts containing phenolic derivatives were reported to have strong antioxidant effects on cooked meat (Younathan 1985; Rhee 1988). Refined rosemary extract has been proposed as a natural antioxidant in several food systems, especially those containing animal fats and vegetable oils (Offord et al. 1997). Addition of rosemary extract prior to cooking (on heatsterilized ground pork) lowered oxidative changes during precooking and storage (Güntersperger et al. 1998). Alterations in food quality as a result of lipid oxidation range from color variations to changes in appearance, odor/ aroma, texture and taste. Sensory evaluations are the most significant methods for predicting oxidative stability, product shelf life and consumer acceptability (Rajalakshmi and Narasimhan 1996). However, limited information on offflavor intensity scores were reported on oxidized meat products (Poste et al. 1986). When frozen beef patties were evaluated for rancid flavor intensity, a lower score resulted compared to refrigerated patties (McMillin et al. 1991). Furthermore, a high positive correlation between thiobarbituric acid (TBA) values and trained panel scores for cooked beef was noted when stored at 4C (39F) for 1 3 days (Younathan et al. 1980).

3 The purposes of this study were to: (1) determine the effects of rosemary extracts on lipid oxidation by measuring 2-TBA and peroxide values (PV) and by conducting sensory evaluation on the acceptability of frozen, precooked beef patties (FBP) with and without the addition of refined rosemary extract (FBPR and FBP, respectively) stored at -18C (0.4F) for 12 weeks; and (2) correlate the TBA value and sensory score of both FBPR and FBP stored at -18C (0.4F) from 0 day to 12 weeks at 4-week intervals. The off-flavor of FBP that develops during the storage period is considered to be a major drawback for marketing the final product. Research findings will be useful for producers of beef products and consumer acceptance to ensure superior-quality products. MATERIAL AND METHODS This study examined the degree of lipid oxidation in FBPR and FBP (5 g/kg fat) stored at -18.0C (0.4F) by assessing PV and 2-TBA levels on 0 day and after 4, 8 and 12 weeks. Sensory evaluations by 35 untrained panelists were performed at these periods of storage conditions to determine the consumer acceptability of both meat samples. Sampling Two hundred FBP (80% meat/20% fat) (~100 g, 10-cm wide and 1-cm thick each) were supplied and prepared by a Southern California commercial meat processor. The patties were formulated to contain 20% fat by weight. These were divided into two groups, one with the addition of refined rosemary extract (labeled FBPR), and the other without refined rosemary extract (labeled FBP). The patties were precooked on an open flame broiler at ~370C (698F) for 7 min until the internal temperature reached 75 77C ( F) for food safety regulations. Finally, these were individually quick-frozen at -101C (-214F) for 15 min and packed in polyethylene bags (Dore 1989). The patties were stored at -18C (0.4F) for evaluations on 0 day and after 4, 8 and 12 weeks. Twenty-five patties were randomly selected from each storage condition to test for lipid oxidation and sensory evaluation. Oxidative stability was evaluated as TBA according to the method outlined by Tarladgis et al. (1960). Moisture content, PV and total fat analyses were conducted in triplicates according to the procedures outlined by the Association of Official Analytical Chemists (AOAC 1990). A 9-point hedonic scale was used to test for overall flavor acceptability by the 35 untrained panelists (Lawless and Heymann 1998). Each frozen, precooked beef patty was reheated in a microwave oven for 2 min on one side and 1 min on the other side at high power. All patties were

4 uniformly cut into six pie-shaped wedges. A 9-point hedonic scale, ranking from 1 = dislike extremely, to 9 = like extremely, was applied to assess the degree of acceptance for color, smell/odor, appearance, texture, flavor and overall acceptability of both FBPR and FBP for sensory evaluation testing. All statistical analyses were performed using the Statistical Package for the Social Sciences (SPSS) software package (SPSS-PC 9) (SPSS 1999). Analysis of variance (ANOVA) was used to find significant differences among samples, and Duncan s post hoc test was performed to detect significant differences among the four storage periods. Independent t-test was used to test for significant differences in mean values of the variables between the two groups. The level of significance was set at P Moisture and Fat Content RESULTS AND DISCUSSION Moisture and fat contents measured for each storage period sample treatment showed no significant differences (Table 1). Lipid Analyses FBPR and FBP were analyzed for lipid oxidation at four storage times on 0 day and after 4, 8 and 12 weeks (Table 2). TABLE 1. COMPARISON OF MOISTURE AND FAT CONTENTS OF FROZEN, PRECOOKED BEEF PATTIES WITH OR WITHOUT THE ADDITION OF ROSEMARY EXTRACT: T-TESTS FOR INDEPENDENT MEANS Measurement FBP mean + SD FBPR mean + SD t-value Moisture content (%) (n = 3) Day ± ± Week ± ± Week ± ± Week ± ± Fat content (%) (n = 2) Day ± ± Week ± ± Week ± ± Week ± ± Fat content was determined based on dried weight of the samples (DWB). FBP, frozen, precooked beef patties without rosemary extract; FBPR, frozen, precooked beef patties with rosemary extract.

5 TABLE 2. COMPARISON OF LIPID OXIDATION IN FROZEN, PRECOOKED BEEF PATTIES WITH AND WITHOUT THE ADDITION OF ROSEMARY EXTRACT Treatment Time (weeks) Duncan s post hoc F analysis A 0 day mean ± SD B 4 weeks mean ± SD C 8 weeks mean ± SD D 12 weeks mean ± SD PV (meq/kg) FBP 4.22 ± ± ± ± *** D A, B, C FBPR 0.77 ± ± ± ± TBA (mg/kg) FBR 6.39 ± ± ± ± ** C B, D FBPR 1.95 ± ± ± ± *** C B A, D n = 2, analyzed in triplicates. Values were reported as: * P 0.05; ** P 0.01; *** P Duncan post hoc analyses used a significance level of P Letters represent which treatments are significantly different. PV, peroxide value (meq/kg sample); TBA, 2-thiobarbituric acid (mg/kg sample); FBP, frozen, precooked beef patties without rosemary extract; FBPR, frozen, precooked beef patties with rosemary extract. One-way ANOVA yielded a significant F-value for PV in FBP, F (3,4) = 314 compared to FBPR. Furthermore, the Duncan s post hoc analysis revealed that the samples stored for 12 weeks exhibited significantly higher PV levels than those stored for 0 day, 4 and 8 weeks. One-way ANOVA was performed to determine TBA values in relation to the length of storage period. The results showed significant differences in TBA values for both FBP and FBPR, F (3,4) = and 19.02, respectively. Subsequently, the Duncan s post hoc analyses revealed that the FBP stored for 8 weeks had a significantly higher TBA value than those stored for 0 day, 4 and 12 weeks. Furthermore, the samples stored for 4 and 12 weeks had significantly greater TBA values than the samples stored for 0 day. The t-tests (Table 3) showed significantly higher differences in both PV and TBA values between FBPR and FBP. Sensory Evaluation There were no significant differences in preference related to color, smell/odor, appearance, texture and overall acceptability between the two sample treatments. The flavor scores, however, were significantly higher in the FBPR compared to FBP (Tables 4 and 5). The results were in agreement with those reported by Güntersperger et al. (1998).

6 TABLE 3. COMPARISON OF PEROXIDE VALUE AND THIOBARBITURIC ACID OF FROZEN, PRECOOKED BEEF PATTIES WITH OR WITHOUT THE ADDITION OF ROSEMARY EXTRACT: T-TESTS FOR INDEPENDENT MEANS Measurement FBP mean ± SD FBPR mean ± SD t-value PV (meq/kg) Day ± ± * Week ± ± * Week ± ± * Week ± ± ** TBA (mg/kg) Day ± ± ** Week ± ± * Week ± ± * Week ± ± ** n = 2, analyzed in triplicates. * P 0.05; ** P PV, peroxide value (meq/kg sample); TBA, 2-thiobarbituric acid (mg/kg sample); FBP, frozen, precooked beef patties without rosemary extract; FBPR, frozen, precooked beef patties with rosemary extract. TABLE 4. SUMMARY ANALYSIS OF VARIANCE TABLE FOR SENSORY ATTRIBUTES FOR FROZEN, PRECOOKED BEEF PATTIES WITH AND WITHOUT THE ADDITION OF ROSEMARY EXTRACT Attribute Effect df F P level Color T W (W T) Smell/Odor T W (W T) Appearance T W (W T) Texture T W (W T) Flavor T * W (W T) Overall T W (W T) * P df, degrees of freedom; F, significance level; P, probability values; T, treatment; W, week.

7 TABLE 5. MEAN VALUES OF SENSORY ATTRIBUTES DURING STORAGE OF FROZEN PRECOOKED BEEF PATTIES WITH AND WITHOUT THE ADDITION OF ROSEMARY EXTRACT Attribute Time (weeks) 0 n = 33 4 n = 33 8 n = n = 31 FBP Color 5.61 ± ± ± ± 1.45 Smell/Odor 6.09 ± ± ± ± 1.54 Appearance 6.03 ± ± ± ± 1.62 Texture 6.18 ± ± ± ± 1.53 Flavor 6.24 ± ± ± ± 1.57 Overall 6.27 ± ± ± ± 1.64 FBPR Color 6.30 ± ± ± ± 1.61 Smell/Odor 6.61 ± ± ± ± 1.62 Appearance 6.48 ± ± ± ± 2.10 Texture 6.42 ± ± ± ± 2.15 Flavor 6.82 ± ± ± ± 1.75 Overall 6.73 ± ± ± ± 1.72 A 9-point hedonic scale was used. FBP, frozen, precooked beef patties without rosemary extract; FBPR, frozen precooked beef patties with rosemary extract. No significant correlations were noted between PV and TBA, PV and sensory scores and TBA and sensory scores of both FBPR and FBP (Tables 6 and 7). Changes in PV and TBA values were compared during storage of both FBPR and FBP. Both PV and TBA values indicated that the frozen, precooked beef patties without antioxidant were considerably less stable compared to those with antioxidant. FBPR were less affected by lipid oxidation during storage. Throughout the storage study, PV and TBA values were significantly higher in FBP compared to those prepared with antioxidants. These results were consistent with studies done by Güntersperger and Escher (1994), who found TBA values to be less in heat-sterilized ground pork with the addition of rosemary extract. The addition of rosemary extract before cooking lowered oxidative changes during cooking and later during storage. This study is in agreement with Bhattacharya et al. (1988) findings where lipid oxidation is greatly affected by storage time and elevated temperature. At 12 weeks of storage, the effect of rosemary extract in retarding lipid oxidation, is evident as determined by both PV and TBA values. PV levels of FBP were considerably higher than those at earlier storage periods; but stable

8 TABLE 6. CORRELATION COEFFICIENT BETWEEN PV AND TBA, PV AND SENSORY SCORES AND TBA AND SENSORY SCORES IN FROZEN, PRECOOKED BEEF PATTIES WITHOUT ROSEMARY EXTRACT n r P PV/TBA PV/Color PV/Odor PV/Appearance PV/Texture PV/Flavor PV/Overall TBA/Color TBA/Odor TBA/Appearance TBA/Texture TBA/Flavor TBA/Overall n, number of pairs of scores; r, Pearson correlation; P, probability values;pv, peroxide value (meq/kg sample); TBA, 2-thiobarbituric acid (mg/kg sample). TABLE 7. CORRELATION COEFFICIENT BETWEEN PV AND TBA, PV AND SENSORY SCORES AND TBA AND SENSORY SCORES IN FROZEN, PRECOOKED BEEF PATTIES WITH ROSEMARY EXTRACT n r P PV/TBA PV/Color PV/Odor PV/Appearance PV/Texture PV/Flavor PV/Overall TBA/Color TBA/Odor TBA/Appearance TBA/Texture TBA/Flavor TBA/Overall n, number of pairs of scores; r, Pearson correlation; P, probability values; PV, peroxide value (meq/kg sample); TBA, 2-thiobarbituric acid (mg/kg sample).

9 for FBPR. TBA values in both treatment samples decreased at 12 weeks of storage. This, however, did not mean that the degree of lipid oxidation was lowered at the last storage period. TBA numbers do not always increase with storage of muscle foods (Tarladgis et al. 1960). TBA test is a common method used for determining rancidity by quantifying malondialdehyde (MDA), a secondary product from lipid oxidation (St. Angelo 1996). Studies by Güntersperger and Escher (1994) stated that during advanced oxidation, the rate of MDA decomposition surpasses that of its formation. The increased decomposition can be attributed to secondary oxidation or polymerization. Although, the TBA values were significantly higher over time in both FBPR and FBP, the TBA values of the precooked beef patties with added antioxidant were relatively low (Table 2). The antioxidant effects of rosemary extract are also noted in a study by Chen et al. (1999) on irradiated, raw pork patties stored at 4C (39F) for 0, 3 and 7 days. The TBA values were reduced by 40% compared to control samples at day 3 of storage (P 0.05). However, at day 7, rosemary oleoresin had no effect on either irradiated or raw pork patties. Our research findings were in agreement with their study (30% lower TBA values were found in beef patties with the addition of rosemary extract stored at -18C [0.4F] for 4 weeks). The results showed a significant difference in flavor attribute between the two sample treatments. The panelists recorded higher flavor scores to the samples with refined rosemary extract. For the other attributes, such as color, smell/odor, appearance and texture, no significant differences were observed. Although there were no significant differences in overall acceptability scores between the two treatments, the results demonstrated that the consumer panelists liked FBPR more than FBP. Therefore, the addition of refined rosemary extract resulted in a more desirable product, and did not adversely affect the other sensory characteristics. This study is in disagreement with Greene and Cumuze (1981), who found a significant correlation between sensory scores and TBA values (P 0.01; r = 0.32, 0.21 and 0.16) because of the variation in methods of preparation. CONCLUSIONS The results of this study demonstrate the beneficial effects of the addition of refined rosemary extract to FBP. It is suggested that addition of both natural and synthetic antioxidants to retard lipid oxidation can prolong the shelf life of precooked meat products, as the development of lipid oxidation is very rapid in cooked meats. It is apparent that with an increase in beef consumption in

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