Physical and sensory characterization and consumer preference of corn and barley-fed beef

Meat Science 80 (2008) 857–863

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Physical and sensory characterization and consumer preference of corn and barley-fed beef W.V. Wismer a,*, E.K. Okine a, A. Stein b,1, M.R. Seibel c,1, L.A. Goonewardene a a

Department of Agricultural, Food and Nutritional Science, 4–10 Agriculture and Forestry Centre, University of Alberta, Edmonton, AB, Canada T6G 2P5 3868 Broadmoore Court, Tyler, TX 75707, USA c Abbott Nutrition, c/o Upper Suite, 1931 49th Avenue SW, Calgary, AB, Canada T2T 2V3 b

a r t i c l e

i n f o

Article history: Received 17 January 2008 Received in revised form 1 April 2008 Accepted 2 April 2008

Keywords: Beef Diet Consumer preference Trained panel Fatty acids

a b s t r a c t Steaks from corn-fed and barley-fed beef were characterized by a trained panel, which rated corn-fed beef higher (p < 0.05) for tenderness attributes and overall flavor intensity. Canadian consumers preferred (p < 0.01) cooked and raw steaks from barley-fed beef, while Mexican consumers showed no preference (p > 0.05) for either type of finished beef. Japanese consumers showed a preference (p < 0.05) for the appearance of raw barley-fed steaks but a preference for cooked corn-fed steaks (p < 0.05). No differences (p > 0.05) were observed for Warner–Bratzler shear, marbling scores, cooking losses or Hunter colorimeter values. There was a trend for higher concentrations (p < 0.08) of the saturated fatty acids in the barley treatment, but no differences (p > 0.10) in mono or polyunsaturated fatty acids. Ó 2008 Elsevier Ltd. All rights reserved.

1. Introduction The province of Alberta contains 42% of Canada’s cattle inventory (AAFC, 2002), making it the most important contributor to the country’s beef industry. In 1999, over 40% of Alberta beef was exported to international markets that included Japan and Mexico (AAFRD, 2002). In western Canada, barley is the primary source of energy in beef finishing diets, primarily because the climate favors the production of barley over other grains. As an example, feeder cattle may consume 10–11 kg of barley per day during the last 120 days before slaughter. Corn is commonly used as the major energy source for these high-energy diets in most parts of the USA. Cattle genetics, feeding and management practices differ across countries and as a result, beef from different countries have unique flavor attributes (Umberger, Feuz, Calkins, & Killinger, 2001). The unique flavor attributes have been ascribed to differences in fat deposition (Maruri & Larick, 1992), which in turn have been attributed to differences in fatty acid profiles of beef due to differences in diet, breed type and sex (Laborde, Mandell, Tosh, Wilton, & Buchanan-Smith, 2001; Siebert, Deland, & Pitchford, 1996; Zembayashi, Nishimura, Lunt, & Smith, 1995). Beef cattle raised in Alberta, * Corresponding author. Tel.: +1 780 492 2923; fax: +1 780 492 4265. E-mail address: [email protected] (W.V. Wismer). 1 This research was performed while A.S. and M.R.S. were employed at the University of Alberta. 0309-1740/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.meatsci.2008.04.002

which are generally finished on a high-energy barley diet, are purported to have a characteristic taste (Basarab, 2000). Indeed, it has been suggested that barley produces more flavorful meat (Miller, Rockwell, Lunt, & Carstens, 1996), is firmer (Basarab, 2000) and has whiter fat than that from corn-fed beef (Jeremiah, Beauchemin, Jones, Gibson, & Rode, 1998). Some studies have found that diet has little effect on the palatability and sensory attributes of beef (Bidner et al., 1986; Jeremiah et al., 1998; Mandell, Gullett, Wilton, Allen, & Osborne 1996; Miller et al., 1996; Nelson, Busboom, Cronrath, Falen, & Blankenbaker, 2000; Shand, McKinnon, & Christensen, 1998). However, these studies have been conducted with trained panels or consumer panels in domestic markets and may not reflect the preferences of consumers in target export markets. For example, Miller et al. (1996) and Kerr, Klein, Hobbs, and Kagatsume (1994) reported that Japanese preferences tend toward well-marbled beef, such as that produced domestically by barley-fed cattle, with whiter fat and a firmer meat consistency. The Canadian Beef Export Federation (CBEF, 2003) reported that Japan imported 23, 982 tonnes of beef in the year 2002 with a goal of reaching 70,000 tonnes in 2010. This represents a valuable export market opportunity for Canada; however it must compete with the US and Australia, who hold about 95% of the Japanese imported beef market share (AAFRD, 2002). A similar scenario holds for Mexico, where Canadian beef exports were 75,000 tonnes in 2002, with a projected growth to 110,000 tonnes in 2010 (CBEF, 2003). Hence, understanding consumer preference for beef in these two global markets is essential.

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The objectives of this study were to characterize the sensory attributes of steaks from steers finished on corn or barley diets, and to determine Canadian, Japanese and Mexican consumer preferences for these steaks. In addition, Warner–Bratzler Shear, Hunter colorimeter, marbling scores, cooking losses and fatty acids profiles, including conjugated linoleic acid, were also compared.

2. Materials and methods All animals through each aspect of this study were cared for under the guidelines established by the Canadian Council on Animal Care (1993) with ethical approval from the Faculty (Agriculture, Life and Environmental Sciences) Animal Policy and Welfare Committee of the University of Alberta in accordance with the CCAC guidelines (Canadian Council on Animal Care, 1993). Written informed consent was obtained from all participants in the trained and consumer sensory panels, and the study protocol was approved by the University of Alberta’s Faculty of Agriculture, Life and Environmental Sciences Research Ethics Board. 2.1. Animals and feeding The study was conducted at a large commercial finishing feedlot in southern Alberta. The cattle used in this study were exotic crossbred beef steer calves purchased from auction markets throughout western Canada from late June to mid July 2001. The cattle were vaccinated, implanted and tagged as per normal feedlot procedures. Approximately 10, 800 exotic crossbred steers, average weight 395 ± 25 kg were placed on study. The cattle were fed one of two diets (barley or corn) for the feeding period. The two diets were formulated to be nutritionally similar with the exception of caloric density. Monensin sodium and tylosin phosphate were provided in the diet at concentrations of 33 mg/kg and 11 mg/kg, respectively, (dry matter basis). Steers were adjusted from a backgrounding (40% rolled barley grain, 35% barley silage, 23% hay, 1% molasses and 1% vitamin/mineral premix) to either the tempered barley - or corn – based finishing diets over a 15 days adjustment period and for the remainder of the feeding period, they received a finishing diet. Feed was provided twice daily to appetite. The tempered barley based finishing diet was approximately 91% barley grain, 7% barley silage and 2% supplement (dry matter basis). The tempered corn based finishing diet was approximately 86% corn, 7% barley silage, 2% supplement, and 5% canola and urea based protein supplement (dry matter basis). The two dietary treatments were fed to fifteen pens (replicates) of cattle per treatment for approximately 140 days. Thirty steers (15 steers in adjacent pens) fed barley based and corn based diets were harvested on December 14, 2001, based on body weight and body fat estimations by ultrasound. After a 24 h chill, carcass cutouts were performed. The strip loins from the right side of each carcass were taken, identified, cut into eleven 3.25 cm thick steaks, cryovac-packaged and stored in the cooler prior to shipment. The samples were then frozen at 30 °C. 2.2. Trained panel All panels were held in the sensory booths in the Agriculture– Forestry Centre at the University of Alberta, Edmonton, Canada. Potential panelists were subjected to a pre-screening questionnaire based on that of Meilgaard, Civille, and Carr (1999). Basic taste identification, ranking of sucrose solutions, and a 6-n-propylthiouracil (PROP) test were used to determine taste capabilities. All panelists were required to read a project information sheet and attend a presentation about the project before reading and signing the consent form. Panelists were informed that the beef was

finished on two different diets, however the actual treatments were not revealed to them until after the study was completed. The panel consisted of four women and three men between 20 and 47 years of age, all employees or students at the University of Alberta. Steaks remained frozen until required for testing. The vacuumsealed steaks were thawed overnight in a 5 °C refrigerator and placed on broiling trays prior to cooking. A thermocouple was inserted into the geometric center of each steak. Steaks were broiled, with top surfaces 15 cm from the broiling element, for 14 min on one side and then turned over. The steaks were then cooked to an internal temperature of 70 °C (AMSA, 1995) and removed from the oven. The steaks were cut into 1.5 cm  1.5 cm  3.2 cm pieces. Lines of fat or connective tissue were avoided. Randomly selected 3-digit codes were used to identify the 2 treatments. Three pieces of beef from each of the feed treatments were placed in coded, covered 250 mL Styrofoam cups and kept in a 55–60 °C water bath until served to the trained panelists. Consumer panelists received 2 pieces of beef. Training sessions took place in a conference style room (training room) adjacent to the preparation lab. Training consisted of attribute generation and selection, determination of definitions and reference standards for each attribute, and training on these attributes (Table 1). Fifteen-centimeter line scales with verbal anchors on each end were used. Panelists were instructed on the procedures for cleansing the palate before tasting each sample, and use of the line scale and reference standards. Evaluation sessions took place in individual sensory booths in a room equipped with positive airflow. The first 2 of the evaluation sessions were used to assess panelist performance; the last 3 sessions were used to evaluate the beef treatments (3 replications). The steaks were evaluated under red light to mask any color differences between the samples. 2.3. Consumer panel Seventy-one Edmonton residents (26 males and 45 females) over the age of 18 years participated in the Canadian consumer panel. Fifteen Japanese men and 55 Japanese women, over the age of 18 years, and who had been in Canada less than one year participated in the Japanese consumer panel. Twenty four Mexican men and eight Mexican women, over the age of 18 years, and who had been in Canada less than two years participated in the Mexican consumer panel. All consumer panelists were required to read a project information sheet and attend a presentation about the project in their native language before reading and signing a consent form. All information was given in the native tongue of the panelist. Demographic information was collected for all panelists. As incentive for participating, panelists entered their names in a draw to win gift certificates to local restaurants and cafés. Cooked beef samples were presented in pairs under red light. Panelists cleansed their palates with distilled water and unsalted soda cracker before starting and between each sample. Randomly selected 3-digit codes were used to identify the 2 treatments. Panelists were invited to write any comments about the steak on the evaluation sheet. Retasting was allowed. For the evaluation of the appearance of raw steaks, 2 steaks taken from the same region of the longissimus dorsi muscle were digitally photographed. The photos were enlarged to a representative size and color and then laminated. The paired pictures of raw steak were evaluated under ‘‘Daylight” in the sensory booths. Questionnaires for the raw steak evaluation contained instructions on the order in which to evaluate the photos. Panelists were invited to write comments on the evaluation sheet.

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W.V. Wismer et al. / Meat Science 80 (2008) 857–863 Table 1 Reference standards and their placement on the 15 cm line scale for flavor and texture attributes for trained panel evaluation of steaks from corn-fed and barley-fed beef Attribute Initial tenderness Beefy Gamey Metallic Livery Chewiness Juiciness Overall tenderness Mouth-coating Overall flavor intensitya a

Reference standard

Placement on line scale (cm) Ò

All beef wiener, boiled (Schneiders , Kitchener, ON) Beef broth powder, dissolved (OxoÒ, Toronto, ON) Halal Goat meat, broth (Superstore, Edmonton, AB) Ferrous sulphate supplement, dissolved (ExactÒ, Sunfresh Ltd., Laval, PQ) Fine Liverwurst (SchneidersÒ, Kitchener, ON) NibsÒ Black licorice (Hershey Canada, Mississauga, Ont.) CockÒ canned bamboo shoots (Thai World Import & Export Co., Bangkok, Thailand) Mozzarella cheese (Kraft CanadaÒ, Don Mills ON) Fine Liverwurst (SchneidersÒ, Kitchener, ON) N/A

13.0 10.5 10.0 13.5 13.0 11.0 8.5 12.5 11.5 N/A

Defined as the total perceived intensity of all flavors combined.

A paired preference test design was used for both the taste and appearance evaluations of this study. A repeating randomized block design was used for presentation of the cooked beef samples with the pictures. 2.4. Meat quality traits All measurements were performed on each day of the trained panel evaluation. To determine if any color differences existed between the two treatments, thawed, raw steaks from each treatment were evaluated by a Hunterlab (Labscan Spectrophotometer) Lab XE Color Difference Meter (Hunter Associates Laboratory, Inc., Reston, VA) using a half-inch port. For marbling score determination, steaks were visually evaluated by comparison to 6 Official USDA Marbling Photographs where 1 represented ‘‘slight marbling” and 6 represented ‘‘moderately abundant” (National Cattlemen’s Beef Association, 1981). Steaks were weighed before and after cooking to determine the drip and evaporative losses (AMSA, 1995). Two pieces from predetermined areas of the steaks were cut from each cooked steak for the Warner–Bratzler shear evaluation. The Warner–Bratzler apparatus was set up on an Instron Universal Testing Machine (Model 4201, Instron Corporation, Canton, MA) using a crosshead speed of 100.00 mm/min and a 50 kg load cell. 2.5. Fatty acid extraction and analyses Meat fat extraction and derivatization of extracted lipid were carried out as follows. Five to 10 mg of fat were excised and weighed into 100  10 mm thimbles and placed in glass thimble holders used to extract fat in the Goldfisch apparatus. The samples were extracted for 6–8 h and the fat concentrated by evaporation of ethyl ether and stored at 20 °C until required for methylation for fatty acid analysis. Extracted lipid was derivatized using tetramethylguanidine (TMG) and methanol, with an internal standard of heptadecanoic acid (C17:0). Briefly, the total lipid extract was redissolved in 2 ml of hexane, and a volume of the mixture was transferred to a test tube so that 10–20 mg of dried lipid extract were in the tube. Once the exact mass was determined, 100 ll of 20 mg/ml C17:0 standard were added to each sample, followed by 400 ll of methanol and 100 ll of TMG. The tubes were flushed with nitrogen, capped and the mixture was heated in boiling water for 10 min. After cooling, 5 ml of saturated NaCl solution and 2 ml of petroleum ether were added to each tube. The tubes were flushed with nitrogen and centrifuged under 4 °C at 350g for 5 min. The organic phase was transferred to a new test tube, dried under nitrogen in a water bath at room temperature, and the contents were resuspended in exactly 5 ml hexane. This mixture was flushed with nitrogen and stored at 20 °C until fatty acid profiles were determined by gas chromatography. The column was a BPX70 (100 m, 0.22 mm i.d., 0.25 micro film; SJE Australia Pty.

Ltd., Victoria, Australia), installed in an HP5830 GC fitted with a 18835B capillary inlet 18850A integrator (Hewlett–Packard, Mississauga, ON, Canada) using a flame ionization detector and split less injection. Initial temperature was 50 °C and was increased to 200 °C at a rate of 25 °C per min and from 200 °C to 220 °C at a rate of 1 °C per min and from 220 °C to 240 °C at a rate of 15 °C per min. Individual fatty acids were expressed as percentages of the total fatty acids detected as fatty acid methyl esters (FAME) with an internal standard of C17:0. 2.6. Proximate composition The proximate composition of three steaks of each feed treatment was determined in duplicate. Samples were analyzed for DM by drying at 110 °C. Lipid extraction from the steaks were carried out according to the procedures of Jiang, Bjoerck, Fonden, and Emanuelson (1996). Briefly, 15 ml of isopropanol were added to a test tube containing 8.0 ± 0.5 g of finely chopped steak. This mixture was then homogenized at high speed for about 15 s. After adding 10 ml of hexane to the homogenate, the mixture was again homogenized at high speed for 15 s, and the homogenized mixture was filtered through a Whatman filter paper (No. 1) into a second test tube. Fifteen ml of hexane:isopropanol solution (10:14) were twice added to the first tube, and both times it was filtered into the second tube after vigorous mixing with a vortex mixer. Finally, the filtrate (filter paper and residue) was rinsed with 5 ml of hexane:isopropanol (10:14). Then 8 ml of aqueous sodium sulfate (66.8 g Na2SO4 per liter distilled H2O) solution were added to the filtrate and thoroughly mixed by inversion for 30 s before centrifuging at 1100 rpm (640g) for 10 min. The hexane layer was collected into a pre-weighed test tube, and evaporated under nitrogen. The residual fat in the pre-weighed test tube was weighed once the tube was completely dried and the fat content of the sample was calculated. Crude protein values were obtained using a Leco Model FP-428 N analyzer (Leco Corp., St. Joseph, MI) and CP was calculated as N  6.25. Ash content was measured after ashing for at least 6 h at 550 °C calculated. 2.7. Statistical analysis SAS statistical software (SAS, 1989) was used for all data analyses. Analysis of Variance (using the General Linear Model) was performed on Warner–Bratzler shear, Hunter Colorimeter, marbling scores, cook loss, and trained panel data to determine differences between barley and corn treatments. For the cook loss data, which included drip and evaporation losses, raw weight was included as a covariate to adjust least square means for differences in raw weight. Chi-square analysis using the categorical response model was performed on the consumer panel data for each of the populations (Canadian, Japanese and Mexican) within their demographic categories to establish relationships among the demographic

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variables, treatments and beef preference. The statistical model for the Canadian data included feed treatment (barley and corn), two levels of age (18–35 and > 35 years), sex (male and female) and consumption pattern (less than once per week and once or more per week). The models for the Japanese and Mexican groups did not include the two consumption patterns. For the beef fatty acid profiles a t-test was performed.

Initial Tenderness* 150

100

Mouth-Coating

3. Results and discussion

50

Chewiness*

0

3.1. Trained panel Steaks from corn-fed and barley-fed beef were perceived similarly for the intensity of all flavor attributes, with the exception of Overall Flavor Intensity, which was higher (p < 0.05) in the corn treatment (66.84) than the barley (58.11) (Fig. 1). Gamey, Metallic, Livery and Beefy flavor intensities were perceived to be similar for both treatments. All flavors in this study were perceived at relatively low levels. The lack of significant effect of cattle diet on flavor characteristics is not limited to this study. In a study conducted by Shand et al. (1998) in which cattle were fed wet brewers’ or distillers’ grains, no differences were observed in beef flavor intensity. Miller et al. (1996) observed no differences between the individual flavor attributes of steaks from barley- and corn-fed steers. Corn and barley treatments differed more on texture than on flavor attributes (Fig. 2). Steaks from corn-fed beef were rated higher (p < 0.05) for both Initial Tenderness and Overall Tenderness, while steaks from barley-fed beef were rated higher (p < 0.05) for Chewiness. By contrast, Jeremiah et al. (1998) did not find a significant difference in Initial Tenderness between steaks from animals fed corn or barley diets. No significant differences were observed between the treatments for Juiciness and Mouth-coating. 3.2. Consumer panel 3.2.1. Cooked steak evaluation Canadian consumers showed a significant overall preference for cooked steaks from barley-fed animals (barley 64.7%; corn 35.2%) (p < 0.01) (Table 2). Younger consumers (18–35 years) had a greater preference (p < 0.01) for steaks from barley-fed animals, and the same preference was observed as a trend (p < 0.06) in consumers above 35 years of age. As the panel consisted primarily of Alberta residents who eat beef on a regular basis, this result was expected. Consumers tend to prefer foods with which they are more familiar

Gamey

150 100 50

Beefy

Metallic

0 corn barley

Livery

Overall Flavor Intensity*

Fig. 1. Spider plot of mean values (mm) for the flavor attributes of steaks from corn- and barley-fed beef as evaluated by trained panel. *Significant at p < 0.05.

corn barley

Overall Tenderness*

Juiciness

Fig. 2. Spider plot of mean values (mm) for the texture attributes of steaks from corn- and barley-fed beef as evaluated by trained panel. *Significant at p < 0.05.

(Raudenbush & Frank, 1999). Canadian females preferred (p < 0.01) steaks from barley-fed cattle and there was a trend (p < 0.09) for males to follow the same preference. Canadian participants who consumed beef less frequently than once a week had a stronger preference (p < 0.01) for the barley-fed treatment than individuals who consumed beef at least once a week (Table 2). Individuals who do not consume beef frequently might find the stronger flavors produced by a corn diet to be unfavorable, whereas those individuals who eat beef more frequently and are familiar with its many flavors, may find the more intense flavors produced by corn to be more acceptable. It has been suggested that milder flavors are produced by a barley diet, compared to a corn diet (Basarab, 2000). That barley-fed beef is milder flavored is supported by the results of our trained panel, which found corn-fed beef to have stronger Overall Flavor Intensity (Fig. 1). According to Grunert (1997), the most important qualities of beef for consumers in general are taste, tenderness, juiciness, freshness, leanness, healthiness and nutrition. Many of the Canadians wrote comments about the beef samples with reference to flavor, juiciness, and tenderness/texture. Twenty-one percent of the participants who commented and preferred steaks from the barley feed treatment thought that they were juicier than the corn-fed sample, while 14% of those who commented and chose steaks from the corn treatment found those steaks to be juicier. These comments are in contrast with the results of the trained panel, which found no difference (p > 0.05) in the juiciness between the two treatments (Fig. 2). Among Japanese consumers, 59% preferred steaks from corn-fed animals and 41% preferred those from barley-fed animals (p < 0.04). This may be explained in part due to the influence of the large amount of US beef imports into the Japanese market and individuals’ tendencies to choose foods with which they are familiar (Raudenbush & Frank, 1999). Very few of the Japanese panelists commented on the samples. Steaks from the barley-fed treatment were described as being more flavorful and/or tasty. Juiciness, tenderness and toughness were mentioned an approximately equal number of times for each of the treatments, suggesting that little difference were perceived between the steak samples on these attributes. Of the 32 Mexicans who participated in the study, 56.3% preferred barley-fed and 43.7% preferred corn-fed cooked beef steaks (p = 0.32) (Table 2). The ‘‘Frequency of Consumption” category was dropped from the analysis of the Mexican data because all but 1 of the Mexican panelists fell into the same category (eat beef at least once per week). Age did not significantly affect preference, how-

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W.V. Wismer et al. / Meat Science 80 (2008) 857–863 Table 2 Number of Canadian, Japanese and Mexican consumer panelists in each demographic category and their preference for cooked steaks from corn-fed and barley-fed beef Demographic categorya Canadian Age

Prefer barley

Prefer corn

P value

Table 3 Number of Canadian, Japanese and Mexican consumer panelists in each demographic category and their preference for pictures of raw steaks from corn-fed and barley-fed beef Demographic categorya

Prefer barley

Prefer corn

P value

18–35 years >35 years

32 16

10 13

<0.01 0.43

Gender

Male Female

20 28

6 17

<0.01 0.02

Weekly beef consumption


10 38

7 16

0.30 <0.01

48

23

<0.01

Male Female

9 31

6 22

0.27 0.08

Weekly beef consumption

< once Once or more

14 26

4 24

<0.01 0.69

Purchases household food

Yes No

5 35

1 27

0.04 0.15

40

28

0.04

18–35 years >35 years

15 4

7 6

0.02 0.37

Gender

Male Female

15 4

9 4

0.09 1.0

Purchases household food

Yes No

14 5

8 5

0.07 1.0

19

13

0.14

18–35 years >35 years

28 18

14 11

<0.01 0.06

Canadian Age

Gender

Male Female

16 30

10 15

0.09 <0.01

Weekly beef consumption


15 31

2 23

<0.01 0.13

46

25

<0.01

Male Female

7 22

8 33

0.31 0.04

< once Once or more

10 19

8 33

0.51 <0.01

29

41

0.04

18–35 years >35 years

11 7

11 3

1.00 0.24

Overall preference

Male Female

15 2

9 5

0.09 0.12

Mexican Age

18

14

0.32

Overall preference Japanese Gender Weekly beef consumption

Overall preference

Overall preference Mexican Age Gender Overall preference a

‘‘Age” for Japanese panelists and ‘‘Weekly beef consumption” for Mexican panelists were not analyzed due to insufficient numbers in each category.

ever there was a trend (p < 0.09) among males for preference of cooked steaks from the barley-fed treatment (Table 2). Approximately half of the Mexican panelists commented on the samples. Juiciness and tenderness were terms mentioned most frequently to describe the barley-fed beef samples, suggesting that Mexican consumers found steaks from the barley-fed treatment to be more juicy and tender than those from the corn-fed treatment. Published studies regarding consumer preference for beef fed different diets are infrequent in the literature; however, as previously mentioned, trained panels have found no differences in the sensory attributes of beef fed different diets (Bidner et al., 1986; Jeremiah et al., 1998; Mandell et al., 1996; Miller et al., 1996; Shand et al., 1998). A possible explanation for this difference between consumer and trained panel evaluations is that consumer panelists evaluate the beef samples as a whole, with all attributes taken together, whereas trained panelists evaluate specific attributes individually. Thus it is possible that the consumer panelists experience potentially enhancing, or masking, interactions between many attributes, while trained panelists focus on one specific attribute at a time and lose these enhancing or masking effects. 3.2.2. Raw steak picture evaluation There was a significant (p < 0.01) overall preference for the appearance of steak from the barley-fed treatment over the cornfed treatment among the Canadian panelists (barley 67.6%; corn 32.4%). Panelists in the younger age category (18–35 years) had a stronger preference (p < 0.01) for the appearance of raw steak from barley-fed animals compared to panelists in the over 35 years age category (Table 3). Both male and female Canadians preferred (p < 0.02) the look of steaks from the barley treatment compared to corn, while the more frequent consumers of beef preferred (p < 0.01) the look of steaks from the barley-fed animals. The ‘‘Purchase” category was dropped from the analysis of the Canadian panelist raw steak evaluation as not all purchase categories were represented by the panelists. The most frequent comment made regarding the pictures of the raw steaks was that the corn-fed treatment had less fat than the

Japanese Gender

Overall preference a

‘‘Purchases household food” for Canadian panelists, ‘‘Age” for Japanese panelists and ‘‘Weekly beef consumption” for Mexican panelists were not analysed due to insufficient numbers in each category.

barley-fed treatment. ‘‘Good color” was mentioned more frequently for barley than for corn. As Grunert (1997) observed, many consumers use fat and color to judge the quality of meat incorrectly; most consumers do not realize that a more marbled piece of beef will generally be more juicy and tender. However in this study, it appeared that Canadians used fat and color correctly as predictors of quality. The majority of Canadian panelists who preferred cooked steaks from barley-fed animals preferred the pictures of raw steaks of this treatment, demonstrating a consistent preference for barley-fed beef steak among the Canadian panelists (Tables 2 and 3). No such trend between cooked and raw steaks was observed for the Japanese and Mexican panelists. For the Japanese panelists, the ‘‘Age” category was omitted from the data analysis as all of the Japanese panelists fell into the same age category (18–35 years). Two of the panelists’ data were dropped from the analysis as their questionnaires were incomplete. Overall, there was a significant preference (p < 0.04) for the appearance of steak from barley-fed animals over the corn-fed treatment among the Japanese panelists (Table 3) although the reverse was seen for cooked steaks (Table 2). There was a strong tendency for participants who consumed beef less than once a week to prefer the appearance (p < 0.01) of the picture of the raw barley treatment steak over the corn (Table 3). The Japanese panelists’ preference for the picture of raw barleyfed beef steak may be due in part to the significant interaction of feed with frequency of consumption. Those individuals who consumed beef less than once a week had a stronger preference for the appearance of the raw steak from the barley treatment than those individuals who consumed beef at least once a week. Few of the Japanese panelists made comments about their choices for raw beef, thus it is difficult to interpret the reasons for their choices. This observed preference for the barley treatment may

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be a function of familiarity since white fat, well-marbled beef is the norm in Japan, and of the few individuals who commented, most made reference to their perception that steaks from the barleyfed animals had more fat. Two panelists mentioned that the corn-fed sample did not look fresh, which is a requirement for quality in Japan (Kerr et al., 1994). With the exception of age, none of the demographic categories were found to affect Mexican panelists’ preferences and there was no significant (p > 0.05) overall preference for the appearance of steaks from either of the feed treatments (Table 3). This is somewhat unexpected as beef in Mexico is raised on corn and it was anticipated that the Mexicans would prefer its appearance and taste. That they did not specifically choose corn-fed over barleyfed for cooked or raw steak samples may have significant implications for Canadian barley exports. If Mexican consumers have no specific preference for corn-fed or barley-fed beef, either raw or cooked, it would seem that barley could serve as an acceptable feed for cattle in Mexico from a sensory perspective. A larger-sized consumer panel, preferably held in Mexico, should be used to verify this observation. In addition to further examination of the sensory acceptance of barley-fed beef exported from Alberta, a knowledge of consumer perceptions of product characteristics (e.g. perceived freshness) (Erikson, Wahl, Jassaume, & Shi, 1998) and requirements for perceived quality (Sasaki & Mitsumoto, 2004) would benefit exporters. 3.3. Quality traits and chemical composition 3.3.1. Hunter colorimeter Raw steaks from either treatment did not differ (p > 0.05) in color (data not shown), which agrees with the findings of Nelson et al. (2000). The trained panel did not evaluate raw steaks, however consumer panelists had the opportunity to comment on the appearance of the raw steaks. Canadian consumer panelists frequently commented that the barley treatment had ‘‘good color”. Canadian and Japanese consumer panelists generally preferred the appearance of barley treatment steaks while Mexicans did not demonstrate a preference (Table 3), however it is unknown if the perceived color of the raw steaks was a determining factor in their selection. 3.3.2. Marbling scores No differences (p > 0.05) in marbling scores were observed in steaks from the two feed treatments (Table 4), however, Miller et al. (1996) observed more extensive marbling in steaks from steers fed barley versus corn for 102 days prior to slaughter (‘modest’ versus ‘small’, respectively). That Overall Flavor Intensity was rated by the trained panel to be higher in corn-fed steaks may be explained by the presence of flavor compounds in the steaks unrelated to fat marbling or to the fatty acid profiles, such as water-sol-

Table 4 Mean values (and standard errors) for quality traits and proximate components of steaks from corn-fed and barley-fed beef Measurement

Barley

Corn

P value

Quality trait USDA marbling score Cooking loss Drip loss (g) Evaporative loss (g) Warner–Bratzler Shear (N)

3.2 (0.11)

3.0 (0.11)

0.32

37.24 (1.99) 82.98 (2.31) 19.03 (1.37)

36.40 (1.68) 81.13 (1.96) 46.09 (1.37)

0.77 0.57 0.054

Proximate component Moisture (%) Fat (%) Protein (%) Ash (%)

71.23 4.35 22.36 1.08

69.05 7.33 21.75 1.05

0.36 0.14 0.43 0.52

(0.53) (0.66) (0.50) (0.01)

(1.62) (0.79) (0.17) (0.04)

uble reducing sugars and amino acids that are known to contribute to meat flavor. 3.3.3. Cooking loss No differences (p > 0.05) were observed between the treatments for cooking loss measurements (drip loss and evaporative loss) (Table 4), suggesting that the amounts of fat and water in the steaks were similar. Studies by Miller et al. (1996) and Jeremiah et al. (1998) also found negligible differences in cooking losses for beef fed corn or barley. 3.3.4. Warner–Bratzler shear Steaks from corn-fed animals tended (p < 0.054) to have lower mean shear force values then steaks from barley-fed animals (Table 4). Other researchers have not found shear force differences in cooked meat from animals fed corn or barley diets (Jeremiah et al., 1998; Miller et al., 1996; Nelson et al., 2000). The trained panel perceived steaks from the corn treatment to be more tender (Initial Tenderness and Overall Tenderness) and steaks from the barley treatment to have greater Chewiness (Fig. 2). Taken together, these results suggest that steaks from corn-fed beef were more tender than those from barley-fed beef in this study. 3.3.5. Proximate components There were no differences in moisture, fat, protein and ash components in the steaks from barley and corn-fed beef cattle (Table 4). 3.3.6. Fatty acid analyses The fatty acids in steaks of beef in response to feeding barley or corn are shown in Table 5. The higher concentrations of the saturated fatty acids C14:0, C16:1, C17:0 and C18:0 (p < 0.05) and the tendency for C16:0 to be higher (p < 0.08) for barley-fed than for cornfed steers may be a reflection of differences in the fatty acid profile of barley and corn (Miller et al., 1996). The higher proportion of saturated fatty acids in barley-fed steers may result in firmer steaks from barley than from corn-fed beef as saturated fatty acids have higher melting points than unsaturated fatty acids. Human diets rich in short and medium chain saturated fatty acids such as C14:0 and C16:0 have been reported to be hypercholesterolemic. However, the ratio of C18:0 + C18:1: C16:0 (indicator of cholesterolemic tendency of the fat source) was not different (p > 0.05) between barley and corn-fed steers (2.2 and 2.1, respectively). The fatty acids of C18:0 and C18:1 fatty acids have cholesterol lowering properties with a higher ratio of C18:0 + C18:1 to C16:0 being deemed to nutritionally superior (Bonanome & Grundy, 1988). Hegsted, McGandy, Myers,

Table 5 Mean values (and standard errors) of fatty acid composition of steaks from corn-fed and barley-fed beef Fatty acid (% of recovered fatty acids)a

Barleyb

Cornb

C14:0 C14:1 C16:0 C16:1 C17:0 C17:1 C18:0 C18:1 C18:2 C18:3 C20:1 CLAc

3.02 0.79 22.80 4.32 2.19 1.44 11.64 38.74 1.91 0.16 0.49 0.31

2.75 0.63 21.01 3.57 1.86 1.15 9.27 35.42 1.95 0.13 0.56 0.30

n 6 n 3 n 9

(0.24) (0.32) (1.23) (0.77) (0.38) (0.12) (2.49) (11.04) (0.21) (0.09) (0.16) (0.09)

P value (0.36) (0.41) (3.58) (1.09) (0.28) (0.33) (4.63) (15.68) (0.50) (0.11) (0.19) (0.12)

0.02 0.22 0.08 0.04 0.004 0.09 0.05 0.51 0.25 0.81 0.38 0.73

a Percentages may not add up to 100% since areas of several small peaks (C4:0 to C13:1 and from C22:2 n 6 to C22:6 n 3 have not been reported. b N for barley and corn is 14 and 18, respectively. c Total conjugated linoleic acid.

W.V. Wismer et al. / Meat Science 80 (2008) 857–863

and Stare (1965) have suggested that C18:1 does not influence low density lipoprotein (LDL) cholesterol, but Mattson and Brundy (1985) reported that it is effective in lowering LDL cholesterol. The level of conjugated linoleic acid (CLA), which has been shown to have anticarcinogenic effects in humans (Pariza, Ashoor, Chu, & Lund, 1979; Pariza, Loretz, Storkson, & Holland, 1985) did not differ (p > 0.05) between the barley and corn-fed steers. However, the level of 0.31% of CLA for barley-fed steers is higher than the range of 0.17–0.18% reported by Mir, Paterson, and Mir (2000). 4. Conclusion Few differences were found between steaks from corn-fed and barley-fed steers based on results from trained panel evaluations, consumer panel evaluations and instrumental analyses. These results tend to support those found in the literature and cannot substantiate any of the suggestions that corn or barley based diets result in unique flavors or texture in beef, or that one feed results in a more highly desired product among Mexican consumers. Although Canadian consumers preferred the barley-fed beef both as a cooked product and in appearance, the preference for barley-fed beef among the Japanese was only for its appearance. For future consumer studies, it would be desirable to perform the consumer study of these populations in their home countries with ‘‘home-use tests” that allow the participants to prepare beef as they normally would rather than according to Canadian cooking methods. Acknowledgements The authors thank the Alberta Barley Commission and Alberta Agriculture, Food and Rural Development (AAFRD) for financial support; J. Bourgois, S. Gibson, M. Gerlat and R. Soofi-Siawash for their technical assistance; and E. Silva, T. Nakano, C. Wendakoon and L Guan for their translation services. References AAFC. (2002). Canada’s international business strategy 2001–2002, Agriculture and Agri-Food Canada. Consulted at http://ats.agr.ca/info/latin/e3204.htm#MEXICO on August 28, 2002. AAFRD. (2002). Japan: Market information, alberta agriculture, food and rural development. Consulted at http://www.agric.gov.ab.ca/marketnews/japan/ japanmktprofile.html#trade on August 28, 2002. AMSA. (1995). Research guidelines for cookery, sensory evaluation and instrumental tenderness measurements of fresh meat. Chicago, IL: American Meat Science Association and National Livestock and Meat Board. Basarab, J. A. (2000). Effects of barley or corn diets on performance and carcass characteristics of feedlot cattle and the palatability attributes of beef. Edmonton, AB: Internal report to Alberta Agriculture, Food and Rural Development. Bidner, T. D., Schupp, A. R., Mohamad, A. B., Rumore, N. C., Montgomery, R. E., Bagley, C. P., et al. (1986). Acceptability of beef from Angus–Hereford or Angus– Hereford–Brahman steers finished on all-forage or a high-energy diet. Journal of Animal Science, 62, 381–387. Bonanome, A., & Grundy, S. M. (1988). Effect of dietary stearic acid on plasma cholesterol and lipoprotein levels. New England Journal of Medicine, 318, 1244–1248. Canadian Beef Export Federation. (2003). Canadian beef and veal product exports (1995–2002). Consulted at http://www.cbef.com on May 16, 2003.

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