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David Davis
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Forage Systems Update
Vol 8, No. 4

Meat Quality and Consumer Evaluation
of Pasture Finished Beef

Dr. Fred Martz
Research Professor,
Department of Animal Science

From 1995 through 1997 we conducted field trials at FSRC to evaluate pasture-based beef finishing in comparison to feedlot finishing. This research was funded jointly by the USDA- Sustainable Agriculture Research and Education (SARE) and EPA-Agriculture in Concert with the Environment (ACE) programs. The SARE interest was in assisting producers in capturing more added value for their beef animals and the ACE interest was from the standpoint of dispersing animal waste across the landscape rather than concentrating it at feedlots. For pasture-finished beef to be viable, the beef produced from such systems must be acceptable to the consumer. The final phase of this research has been the determination of meat quality and consumer acceptance of pasture-finished beef.

Experimental procedures: Research in 1995 and 1996 consisted of five feeding treatments including pasture supplemented with 0, 0.5, 1.0, or 1.5% body weight of grain fed daily and a conventional feedlot treatment with two replicates of all treatments. The feedlot pens of cattle finished first, and were harvested 32 days before the PFB cattle in year 1 of the study. In year 2 the pasture- finished steers were harvested 40 days after the feedlot groups. The PFB cattle were harvested at a lighter weight because the supply of pasture was exhausted and we wanted to slaughter the steers directly from pasture without any alterations of ration. All cattle were killed in a small packing plant in southwestern Missouri, hung for three days, then graded by a certified USDA grader.

Beef sampling and sensory analysis: The third day following slaughter, a boneless, strip loin (longissmus muscle) was removed from six randomly selected carcasses of equivalent breed background within each treatment group. Loins were transported to the University Meats Laboratory, frozen, cut into 1.9 cm steaks and individually packaged in vacuum sealed cryovac containers. Three steaks, one from each third of the strip loin, were submitted to the Sensory Laboratory for Descriptive Sensory Analysis and for Acceptance Testing.

Cookery and Serving: Frozen beef steaks were defrosted in a refrigerator at 4^oC for 24 hours prior to each test session. Steaks were cooked and sampled under controlled conditions in the Sensory Laboratory kitchen. Steaks were broiled to 93^oF then turned and broiled to a final temperature of 185^oF. Edges of each beef steak were removed and the remaining portion was cut into 1.27 cm cubes using an electric knife and a plexiglass template. Tooth picks were inserted into the steak cubes and two adjacent pieces were placed into each three-digit randomly coded and heated 30 ml beaker. The beakers had been preheated in sand baths to 170^oF to aid in maintaining the sample temperature. Samples were then served to the panelists. The entire serving procedure was controlled so that it took less than 5 minutes.

Descriptive Analysis: A 10-member panel participated in score sheet development and training sessions for evaluating the beef steaks. The score sheet consisted of 16.4 unit unstructured line scales (0 = not, 16.4 = very) for 25 attributes. Each panelist received two pieces of steak from all steaks. One piece of steak was used when evaluating the aroma and flavor attributes, and the other piece was used when evaluating all other attributes. Steaks were evaluated monodically in individual sensory booths under red lights. A total of 10 sessions were conducted on separate days to complete the descriptive analysis study. Steaks from each steer were randomly assigned to the 10 sessions. Three, 1.2 cm cores from each cooked steak were used for standard Warner-Bratzler shear force measurement.

Acceptance Testing: Eighty-eight panelists participated in the consumer evaluation. Five sessions were conducted with 15 to 20 panelists participating per session. The consumer panelists evaluated the steaks in conditions similar to the Descriptive panelists, with the exception of evaluating the samples under white light instead of red lights. Each panelist indicated their degree of liking, using the 9-point hedonic scale (with categories from 9 = like extremely to 1 = dislike extremely) for 6 samples of steak.

Results and Discussion: Steers were harvested from pasture before they reached target finish weights (1150 lb) because the forage had been consumed and the research protocol was to harvest directly from pasture in order to evaluate meat flavor, aroma, and texture related to the pasture treatments. Hot carcass weights increased with supplement level from 0 to 1.5% body weight (Table 1). Dressing percentage also increased with increasing carcass weight and backfat thickness, indicating that steers with more finish had higher dressing percentage than steers which lacked finish. Marbling score, rib eye area, yield and quality score all increased with increasing supplementation level. Marbling scores for steers finished on pasture were lower than steers finished in the feedlot, probably because steers on the pasture treatments were not taken to equal finish weights as the feedlot steers. Quality scores for the pasture finished steers were progressively lower than the feedlot steers. Sixty percent of the steers in the feedlot treatment graded choice compared to zero animals grading choice in the 0 supplementation treatment.

Table 1. Carcass characteristics for steers finished with grazing plus grain or in feedlot.

Meat quality and Consumer acceptance: The average Hedonic ratings for acceptability (consumer evaluation) of cooked beef from year 1 pasture and feed lot finished steers were 5.75, 6.12, and 6.66 (LSD = 0.47) for treatments 0, 1.5% and Feedlot; and for year 2 were 5.9, 6.0, and 6.5 (LSD = 0.45), respectively. The acceptance evaluation results were as expected based on the results of the descriptive sensory analysis which indicated that as the percentage of grain supplement fed was increased, the steaks were liked more (Table 2). However, there was some overlapping of acceptance among treatments with higher grain feeding levels on pasture producing results more similar to the feedlot treatment. Off-color fat and dark cutters were not associated with any of the pasture-based feeding treatments.

Five consumer acceptance sessions were held and analysis of the data (not shown in this report) indicated that the steaks were rated consistently across the 5 consumer evaluation sessions. Although there were significant difference among the treatments in the consumer acceptance study, all of the steaks were rated at or above "neither like nor dislike" on the 9-point hedonic scale; thus on average, none of the steaks were disliked. These findings are in agreement with other published reports that US customers who ate beef found little difference in eating quality, among cuts of beef from the range of quality grades from high choice to low select.

Table 2. Texture evaluation scores and shear force values of beef from steers finished with grain fed on pasture or in feedlot^a.

^a Score consists of evaluation recorded on a 16.4 unit unstructured line scale with 0=not and 16.4=very.
^b Warner-Bratzler shear force measurement.

Cooked beef was evaluated for 1)aroma or off-aroma; 2) flavor or off-flavor 3)texture: tender (initial bite), juicy (initial bite), tender (average), juicy (average), stringy, mealy, gristle, or aftertaste. For tender (initial bite), juicy (initial bite), tender (average) juicy (average), and mealy texture, the feedlot treatment had significantly larger intensities than the other treatments which were not significantly different from each other. The feed lot treatment had significantly smaller intensities than the other treatments for stringy and gristle, with the 0% grain treatment having the highest intensities. The feedlot treatment had the smallest intensity for aftertaste which was significantly different from the other treatments. Warner-Bratzler shear force measurements agreed in ranking of the treatments with the descriptive tenderness evaluations. These results indicate that the PFB tended to lack tenderness and juiciness. No off-flavors were observed. The higher percentage grain supplemented treatment (1.5%) tended to be more similar to the feedlot treatment than the non-supplemented treatment.

The higher fat content and lower water content of the feedlot and 1.5% grain steers compared to the 0 and 0.5% grain fed steers confirms that the feedlot and 1.5 steers carried more finish than the other treatments (Table 3). Even with this difference the trimmed steaks of the feedlot and 1.5% supplement steers contained less than 5% fat. These data indicate that steers with less than 0.67 inch backfat will cut out lean beef containing less than 5% fat. Cholesterol content of the zero-trim steaks did not increase with increased fat content. These steaks were within a relatively narrow range of fat content but this finding indicates that within a narrow range of fat content and with a relatively low level of fat, cholesterol content of lean beef should be constant and near 45 mg/100g.

Table 3. Nutrient and cholesterol content of zero-trim beef from steers finished with grain fed on pasture or in a feedlot.

In 1997 a similar study was conducted using the same pastures as the study described above. There were two major differences in the 1997 study: 1) stocking rate was held constant across and treatments, and 2) cattle were fed to a common final weight for all treatments. To achieve the same finish weight, grain supplementation was increased on all pasture treatments in mid-September to ensure finishing by the end of the grazing season. In this study carcass weights, finish grade, and all other carcass parameters were similar for pasture-based treatments and the feedlot. The main difference was that pasture finishing required only about 50% the grain input that the feedlot required. While grain prices are presently quite low and reducing grain input may have little economic consequence, as corn price rises above $2.50/bushel price, the profit margin for conventional feedlot finishing rapidly shrinks.

Differences were found among the treatments in both the descriptive analysis and the acceptance evaluation studies. When considering the results from both studies, the information leads to the conclusion that some grass feeding of beef may be possible without detrimentally affecting steak quality. Since several of the significant descriptive analysis attributes were textural (tenderness and juiciness), it is important to consider other factors contributing to steak texture, such as pre and post slaughter conditions. An example of pre-slaughter treatment would be a short intense feeding of grain supplement to enhance the level of finish of the PFB and to bring steers to an equivalent weight compared to feedlot steers. Examples of post-slaughter treatments would be aging of the beef and/or electrical stimulation of the beef. Fat content of zero-trim steaks was lower for steers finished on pasture compared to steers finished in the feedlot probably because the pasture-based steers had lower body weights at harvest and carried less finish than the feedlot finished steers. Zero-trim steaks contained similar levels of cholesterol (44.5 to 45.9 mg/100g) from all treatments. Cholesterol level in raw zero-trim steaks was not related to fat content in this study.

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