- Email: [email protected]
Measurement of Broiler Breast Meat Shear Values
Q1WApplied Poullry Science, Ine.
]LMEASUREMENT OF BROILER BREAST
MEATSHEARVALUES
J. L.HEATH' and S. L.OWENS Depament of Poulby Science, University of Maryland College Park, MD 20742 Phone: (301) 405-5784
FAX: (301) 314-9557
Primary Audience: Quality Assurance Personnel, Researchers
A number of mechanical devices have been developed to measure various aspects of meat texture. One of the more popular methods uses the multi-blade Kramer shear cell mounted on a variety of instruments to measure poultry meat tenderness. Various investigators have studied the effect of friction [l,21, manufacture tolerance [3], cell size [4], number and thickness of blades [5], and sample weight [6] on shear cell performance. However, there is a lack of research describing the effects of sample shape and size, shear rate, load cell size, and sample temperature on 1 To whom correspondence should be addressed
Kramer shear cell or similar devices do not use standard sample or instrument conditions for shear measurement. If sample or instrument conditions affect shear values, comparison of research data will be difficult; consequently, future experimental designs should account for these factors. A literature review found that poultry meat tenderness research has employed a range of sample surface areas (2 to 16.7 cm2), sample thicknesses (0.7 to 1.5 cm), shear rates (10 to 50 cdmin), load cell sizes (100 to 500 kg), and sample test temperatures (2 to 55°C).
Downloaded from http://japr.oxfordjournals.org/ at Adams State University on March 10, 2015
shear values of poultry meat determined using DESCRIPTION OF PROBLEM the Kramer shear cell. Laboratories using the
SHEAR VALUES
186 We performed this study to determine the effects of shear rate, sample size, sample shape, sample temperature, and load cell size on shear values obtained with the multi-blade Kramer shear cell. The study also compared shear values calculated with peak force and yield force.
A meat slicer was used to cut slices 3 mm thick from the Pectoralis superficialis muscle. Slicing was initiated on the side originally attached to the skin and proceeded inward toward the side originally attached to the ribs. With plastic templates as guides, scalpel blades were used to cut samples from the anterior portion of each slice. Sample dimensions were verified using a dial caliper, and the sampleswere weighed. Samples were sealedin plastic bags to prevent moisture loss prior to shear analysis. The samples were oriented in the Kramer shear cell so that the blades would shear perpendicular to surface muscle fiber orientation. Shear parameters are described under each experiment. Data were analyzed statistically [Ausing SAS [SI.
MATERIALS AND METHODS
SHEAR RATE AND SAMPLE SIZE Templates 2 x 2,3 x 3, and 4 x 4 cm were used to measure samples 4,9, and 16 cm2 for removal from the second slice of each cooked breast muscle. Samples were sheared in the 100 kg load cell at shear rates of 20,40,60,80, and 100 cm/min. Shear values were calculated using peak force. Ten samples from each size group (one from each fillet) were tested at each of the shear rates. Results of two experiments conducted on consecutive days were pooled and average values reported because the results did not differ (P > .05) according to ANOVA (n =20).
SAMPLE SIZE AND SHAPE Circular, rectangular, and square samples were removed from the second slice of cooked breast muscles to provide surface areas of 4,9, and 16 cm2. One sample was cut from each fillet. Rectangular samples (1x 4,2 x 4.5, and 6 x 2.66 cm) were cut so that muscle fibers were parallel to the long axis of the sample. Muscle fiber orientation was not taken into account when circles were removed. Squares were cut so that muscle fiber orientation was parallel to one of the sample sides. Muscle fiber length of each sample was oriented perpendicular to the shear cell blades. Shear rates of 40 and 60 cm/& and the 100 kg load cell were used. Peak force was used to calculate shear values. Results of three experiments conducted on consecutive days were not statistically different and thus were pooled and average values reported (n = 30).
Downloaded from http://japr.oxfordjournals.org/ at Adams State University on March 10, 2015
Shear parameters of cooked broiler breast tissue were measured with a Sintech Material Testing System model VG equipped with a standard Kramer Shear Cell ((3-1, Food TechnologyCorp., h4D). The instrument was programmed to calculate shear value (kg of forcehample weight in g) from the force deformation curve using yield force and peak force. Yield force is the point at which an abrupt change in slope of the force deformation curve occurs prior to maximum peak height. A change in slope occurs after sample compression is completed and at the point on the graph where shear is initiated. Peak force (maximum peak height) is the maximum force obtained from the force deformation curve. The 100 or loo0 kg load cell was used depending on experimental design. The size of the load cell may be important to the computer calculation of yield force and peak force because the 100 kg load cell has more stability and maximum long-term balance than the loo0 kg load cell. Mechanically removed, skinlessPectoralis superficialis muscle fillets from the same processing lot of 52-day-old broilers were obtained from a commercial processing plant. The carcasses were aged overnight at 4°C before the breast muscles were harvested in the processing plant. Immediately after removal from the carcasses, the muscles were sealed in plastic bags, placed on ice, and transported to the laboratory (3 hr). At the laboratory, the muscles were repackaged in plastic bags, randomly assigned to experimental groups, and held at -20°C until used. The muscles were thawed at 4°C prior to cooking. The breast muscles were placed on wire racks with the inner side (originally adjacent to the ribs) down. The muscles were covered with aluminum foil before cooking at 177°C to an internal temperature of 82°C in a forced draft oven. They were then cooled at 25°C for 1hr without removing the aluminum foil prior to slicing.
Research Report HEATH and OWENS
LOAD CELL SIZE Samples from cooked broiler breast muscles were cut into circles, rectangles, and squares with areas of 4,9, and 16 cm2 as previously described. The 100 and loo0 kg load cells and shear rates of 20,40,60,80,and 100 d m i n were used to shear the samples. Shear values were calculated usingpeak force; all other shear parameters were as Previously described. lkro experiments were conducted on consecutive days (n = 20). PEAK FORCE VS. YIELD FORCE Shear values from cooked broiler breast tissue were calculated using peak force and yield force. Values were compared for each sample size (4,9, and 16 an2), sample shape (circle, rectangle, and square), and at each and 100 d m i n ) . shear rate (20,40,60,80, The 100kg load cell was used and other shear parameters were as previously described.
Pearson Correlation and the coefficient of variation [Iwere used to compare shear values calculated using peak force and yield force.
RESULTS AND DISCUSSION SHEAR RATE AND SAMPLE SIZE Shear value differences were associated with both shear rate and sample size (Table 1). Shear value differences in the 9-cm2 samples were not linear with respect to increasing shear rate. The 9-cm2 samples sheared at 20 d m i n were 67% smaller than the same size samples sheared at 40 cdmin. In all three sample sizes, the change from a shear rate of 20 to 40 cdmin was associated with an increase in shear value; at shear rates ranging from 40 to 100 cdmin, however, shear value decreased as shear rate increased. This trend in shear value was not statisticallydifferent for 4- and 16-cm2 samples. A difference in the amount of sample compression prior to initiation of shear may have caused some of the differences associated with a change in shear rate. Zang and Mittal [9] used the Warner Bratzler shear press and observed that the same applied force did not compress the sample as much prior to shear at higher vs. lower shear rates. Increasing sample size from 4 to 9 cm2 decreased shear values by 46% at 20 cdmin and 29% at 40 cm/min. At shear rates of 20,40, 60,80,and 100 cdmin, average shear values of 16-cm2samples were 36% lower than those of 4-cm2 samples. Dividing peak force (kg) by sample weight (g) in this experiment did not completely correct for the different sample surface areas (weights) used. Other researchers [lo] have found that peak force was directly proportional to sample weight when an Allo-
TABLE 1. Effect of shear rate and sample size on shear values (kg/g) from cooked broiler &&x&isuoerficialis
muscles
Downloaded from http://japr.oxfordjournals.org/ at Adams State University on March 10, 2015
SAMPLE TEMPERATURE Thirty square samples (3 x 3 cm) were removed from cooked broiler breast muscles as previously described. Prior to shear, the samples were weighed, placed in plastic bags, randomly divided into three groups, and submerged in a water bath at either 4,X, or 46°C. These sample temperatures were chosen to approximate the range of temperatures used by other researchers. AU samples remained in the water bath for 30 min. The samples were allowed to equilibrate to the test temperature and were weighed prior to shear. Samples were sheared in the 100 kg load cell at a shear rate of 40 d m i n . Peak force was used to calculate shear values; all other shear parameters were as described previously. Four experiments were conducted on consecutive days.
187
SHEAR VALUES
188 Kramer shear cell was used. Compression (yield force) accounted for 78.3,85.7, and 96.0% of the maximum force required to shear the 4,9-, and 16-cm2 samples, respectively. This difference may result from more shear cell blades being in contact with the larger samples during compression and shear.
4
LOAD CELL SIZE Variation in shear values associated with the 100 kg vs. the lo00 kg load cell ranged from 0 to 0.9 kg/g across all shear rates (a,@, 60, 80, and 100 cm/min) and from 0.1 to 0.7kg/g for all sample sizes (4,9, and 16 cm2). For all sample weyjhts, and for shear rates above 40 cdmin, the lo00 kg load cell gave larger shear values than the 100 kg load cell. These differences, however, were not statistically (P> .OS) significant in either of the two experiments. PEAK FORCE VS. YIELD FORCE Most researchers use peak force to calculate shear values. Yield force is useful when the amount of sample compression and the force required to initiate shear are important.
TABLE 2. Effect of sample size and shape on shear values (kg/g) from cooked broiler Pectoralismuscles
Downloaded from http://japr.oxfordjournals.org/ at Adams State University on March 10, 2015
SAMPLE SIZE AND SHAPE Changing sample shape caused a difference in shear values in only one comparison (Table 2). At a shear rate of 60 cdmin, the 4-cm2 rectan les had higher shear values than the 4-cm squares. Shapes did not affect shear value at any other sample size. For all three sample shapes and both shear rates, 4-cm2 samples had larger shear values than 9-cm2 samples. Shear rate did not significantly affect shear values. These results agreed with those in Table 1. Each blade made contact with the sample surface at an angle. One end of a blade initiated shear with the sample edge, and the remainder of the blade continued the shear as the blade traveled lower. Each blade has the same angle, but alternate ends of the blade contact the sample frrst. The three sample shapes were chosen to provide different relationships between the sample and the blades in the Kramer shear cell. The circle allowed some of the blades to contact the sample edges at angles other than 90°C and had no effect on shear values. The rectangular shape and perpendicular orientation of sample length to the blades in the shear cell allowed more blades to contact the rectangular samples than the square samples. Shearing was also completed in a shorter length of time for the rectangular samples than for the square samples.
SAMPLE TEMPERATURE No differences (P > .05) in shear values attributable to sample temperature occurred in any of the four experiments. The plastic bags containing the samples during equilibration to the test temperature were closed but not heat sealed. Samples equilibrated to the three temperatures differed (Pc.05) in the amount of weight lost during equilibration. The samples equilibrated to 46°C lost 1.4% of their sample weight to condensation and possible vapor loss, whereas samples equilibrated to 4 and 26°C lost 0.4% of their weight. Although the weight loss of the 46°C samples differed significantly from that of the 4 and 26°C samples, there was no concomitant difference in shear values. If weight loss had been a factor, the samples held at 46°C would have had shear values signilicantly different from those of the samples held at 4 and 26°C.
Research Report HEATH and OWENS
189
Peak force and yield force were correlated (P<.OS) for each sample size (4, 9, and 16 cm2), shape (circle, rectangle, and square), and 100cm/min) and all shear rates (40,60,80, except 20 cm/mh (Table 3). The coefficients of variation calculated from shear values based on yield force were 0.3 to 20% larger than those calculated using peak force. This
I
difference indicated that the calculations made using peak force had a smaller amount of variation and therefore were more precise than the shear values calculated using yield force. The significant correlation between the two calculation methods indicated that peak force and yield force will measure the same trends in shear values.
PEAK FORCE
YIELD FORCE
4
26.2
32.3
0.82.
9
26.3
33.9
0.73.
Circle
29.3
36.1
0.72.
Rectangle
25.2
31.2
0.80.
Square
25.3
29.2
0.77.
20
26.0
46.2
0.35
40
26.4
29.2
0.90.
60 80 100
24.0
26.2
0.70.
31.6
34.0
0.95.'
25.0
25.3
0.93.
PARAMEIER
PFYF
Samule Sham
I
Shear Rate (cm/Min)
CONCLUSIONS ANDAPPLICATIONS 1. Shear rate affected shear values; the variation, however, was not linear. 2. Increased sample size reduced shear values.
3. Sample shape and sample temperature prior to shear had no effect on shear values. 4. Changing load cell size made no statistically significant differencein shear values. 5. Shear values calculated with peak force and yield force showed the same trends in tenderness. Shear values calculated with peak force had a smaller amount of variation, indicating that they will be more precise than those calculated using yield force.
REFERENCES AND NOTES 1. Bourne, M.C., 1972. Standardization of texturemeasuring instrument. J. Texture Stud. 3:379-384. 2. Voisey, P.W.and W.S. Reid, 1974. Effect of friction on the rformance of texture cells. J. Texture Stud. 5239-& 3. VoJsey, P.W., 1 9 n . Effect of blade thickness on readings from the F.T.C. shear compression cell. J. Texture Stud. 7433-440.
4. VoisCy, P.W.and M. Kloek, 1981. Effect of size on the performance of the shearcompression texture test cell. J. Texture Stud. 12133-139. 5. Timbers, G.E and P.W. Voisey, 198.5. Influence of number and thickness of blades on the performance of the Kramer type shear-compressioncell. J. Texture Stud. 16303-311.
Downloaded from http://japr.oxfordjournals.org/ at Adams State University on March 10, 2015
Sample Size (cm5
JAPR 190 6. Szcusnink,AS.,P.R. H~~mbaugb, and H.W.Block, 1WO.Behavior of different foods in the standard shear
compression cell of the shear p r e s and the effect of sample w e i p on g a k area and maximum force. J. TUtureStud. 356-3 7. Data were sub‘ected to analysis of variance (ANOVA) using the hLM procedure of SAS. Significantly (P-z.05) different means were separated with Duncan s multiple range test. Pearson correlation and coefficient of variation were used to compare the 100 kg load cell to the lo00 kg load cell.
SHEAR VALUES 8. SAS Institute, 1985. SAS User’s Guide: Statistics. SAS Institute, Inc., Cary, NC.
9. Zhang, M. And G.S. Mittal, 1993.Measuring tenderness of meat products by Warner Bratzler shear press. J. Food P m . and Pres. 17351-367.
10.I k M q J.M. and B.S. b e l , 1981.Instrumental methoQ of measurin texture of poultry meat. Pa es 157-164 in: Quality off’oult Meat, S iderholt Jubifee Sympia, Apeldoorn, The x t h e r l a n g
Downloaded from http://japr.oxfordjournals.org/ at Adams State University on March 10, 2015
]LMEASUREMENT OF BROILER BREAST
MEATSHEARVALUES
J. L.HEATH' and S. L.OWENS Depament of Poulby Science, University of Maryland College Park, MD 20742 Phone: (301) 405-5784
FAX: (301) 314-9557
Primary Audience: Quality Assurance Personnel, Researchers
A number of mechanical devices have been developed to measure various aspects of meat texture. One of the more popular methods uses the multi-blade Kramer shear cell mounted on a variety of instruments to measure poultry meat tenderness. Various investigators have studied the effect of friction [l,21, manufacture tolerance [3], cell size [4], number and thickness of blades [5], and sample weight [6] on shear cell performance. However, there is a lack of research describing the effects of sample shape and size, shear rate, load cell size, and sample temperature on 1 To whom correspondence should be addressed
Kramer shear cell or similar devices do not use standard sample or instrument conditions for shear measurement. If sample or instrument conditions affect shear values, comparison of research data will be difficult; consequently, future experimental designs should account for these factors. A literature review found that poultry meat tenderness research has employed a range of sample surface areas (2 to 16.7 cm2), sample thicknesses (0.7 to 1.5 cm), shear rates (10 to 50 cdmin), load cell sizes (100 to 500 kg), and sample test temperatures (2 to 55°C).
Downloaded from http://japr.oxfordjournals.org/ at Adams State University on March 10, 2015
shear values of poultry meat determined using DESCRIPTION OF PROBLEM the Kramer shear cell. Laboratories using the
SHEAR VALUES
186 We performed this study to determine the effects of shear rate, sample size, sample shape, sample temperature, and load cell size on shear values obtained with the multi-blade Kramer shear cell. The study also compared shear values calculated with peak force and yield force.
A meat slicer was used to cut slices 3 mm thick from the Pectoralis superficialis muscle. Slicing was initiated on the side originally attached to the skin and proceeded inward toward the side originally attached to the ribs. With plastic templates as guides, scalpel blades were used to cut samples from the anterior portion of each slice. Sample dimensions were verified using a dial caliper, and the sampleswere weighed. Samples were sealedin plastic bags to prevent moisture loss prior to shear analysis. The samples were oriented in the Kramer shear cell so that the blades would shear perpendicular to surface muscle fiber orientation. Shear parameters are described under each experiment. Data were analyzed statistically [Ausing SAS [SI.
MATERIALS AND METHODS
SHEAR RATE AND SAMPLE SIZE Templates 2 x 2,3 x 3, and 4 x 4 cm were used to measure samples 4,9, and 16 cm2 for removal from the second slice of each cooked breast muscle. Samples were sheared in the 100 kg load cell at shear rates of 20,40,60,80, and 100 cm/min. Shear values were calculated using peak force. Ten samples from each size group (one from each fillet) were tested at each of the shear rates. Results of two experiments conducted on consecutive days were pooled and average values reported because the results did not differ (P > .05) according to ANOVA (n =20).
SAMPLE SIZE AND SHAPE Circular, rectangular, and square samples were removed from the second slice of cooked breast muscles to provide surface areas of 4,9, and 16 cm2. One sample was cut from each fillet. Rectangular samples (1x 4,2 x 4.5, and 6 x 2.66 cm) were cut so that muscle fibers were parallel to the long axis of the sample. Muscle fiber orientation was not taken into account when circles were removed. Squares were cut so that muscle fiber orientation was parallel to one of the sample sides. Muscle fiber length of each sample was oriented perpendicular to the shear cell blades. Shear rates of 40 and 60 cm/& and the 100 kg load cell were used. Peak force was used to calculate shear values. Results of three experiments conducted on consecutive days were not statistically different and thus were pooled and average values reported (n = 30).
Downloaded from http://japr.oxfordjournals.org/ at Adams State University on March 10, 2015
Shear parameters of cooked broiler breast tissue were measured with a Sintech Material Testing System model VG equipped with a standard Kramer Shear Cell ((3-1, Food TechnologyCorp., h4D). The instrument was programmed to calculate shear value (kg of forcehample weight in g) from the force deformation curve using yield force and peak force. Yield force is the point at which an abrupt change in slope of the force deformation curve occurs prior to maximum peak height. A change in slope occurs after sample compression is completed and at the point on the graph where shear is initiated. Peak force (maximum peak height) is the maximum force obtained from the force deformation curve. The 100 or loo0 kg load cell was used depending on experimental design. The size of the load cell may be important to the computer calculation of yield force and peak force because the 100 kg load cell has more stability and maximum long-term balance than the loo0 kg load cell. Mechanically removed, skinlessPectoralis superficialis muscle fillets from the same processing lot of 52-day-old broilers were obtained from a commercial processing plant. The carcasses were aged overnight at 4°C before the breast muscles were harvested in the processing plant. Immediately after removal from the carcasses, the muscles were sealed in plastic bags, placed on ice, and transported to the laboratory (3 hr). At the laboratory, the muscles were repackaged in plastic bags, randomly assigned to experimental groups, and held at -20°C until used. The muscles were thawed at 4°C prior to cooking. The breast muscles were placed on wire racks with the inner side (originally adjacent to the ribs) down. The muscles were covered with aluminum foil before cooking at 177°C to an internal temperature of 82°C in a forced draft oven. They were then cooled at 25°C for 1hr without removing the aluminum foil prior to slicing.
Research Report HEATH and OWENS
LOAD CELL SIZE Samples from cooked broiler breast muscles were cut into circles, rectangles, and squares with areas of 4,9, and 16 cm2 as previously described. The 100 and loo0 kg load cells and shear rates of 20,40,60,80,and 100 d m i n were used to shear the samples. Shear values were calculated usingpeak force; all other shear parameters were as Previously described. lkro experiments were conducted on consecutive days (n = 20). PEAK FORCE VS. YIELD FORCE Shear values from cooked broiler breast tissue were calculated using peak force and yield force. Values were compared for each sample size (4,9, and 16 an2), sample shape (circle, rectangle, and square), and at each and 100 d m i n ) . shear rate (20,40,60,80, The 100kg load cell was used and other shear parameters were as previously described.
Pearson Correlation and the coefficient of variation [Iwere used to compare shear values calculated using peak force and yield force.
RESULTS AND DISCUSSION SHEAR RATE AND SAMPLE SIZE Shear value differences were associated with both shear rate and sample size (Table 1). Shear value differences in the 9-cm2 samples were not linear with respect to increasing shear rate. The 9-cm2 samples sheared at 20 d m i n were 67% smaller than the same size samples sheared at 40 cdmin. In all three sample sizes, the change from a shear rate of 20 to 40 cdmin was associated with an increase in shear value; at shear rates ranging from 40 to 100 cdmin, however, shear value decreased as shear rate increased. This trend in shear value was not statisticallydifferent for 4- and 16-cm2 samples. A difference in the amount of sample compression prior to initiation of shear may have caused some of the differences associated with a change in shear rate. Zang and Mittal [9] used the Warner Bratzler shear press and observed that the same applied force did not compress the sample as much prior to shear at higher vs. lower shear rates. Increasing sample size from 4 to 9 cm2 decreased shear values by 46% at 20 cdmin and 29% at 40 cm/min. At shear rates of 20,40, 60,80,and 100 cdmin, average shear values of 16-cm2samples were 36% lower than those of 4-cm2 samples. Dividing peak force (kg) by sample weight (g) in this experiment did not completely correct for the different sample surface areas (weights) used. Other researchers [lo] have found that peak force was directly proportional to sample weight when an Allo-
TABLE 1. Effect of shear rate and sample size on shear values (kg/g) from cooked broiler &&x&isuoerficialis
muscles
Downloaded from http://japr.oxfordjournals.org/ at Adams State University on March 10, 2015
SAMPLE TEMPERATURE Thirty square samples (3 x 3 cm) were removed from cooked broiler breast muscles as previously described. Prior to shear, the samples were weighed, placed in plastic bags, randomly divided into three groups, and submerged in a water bath at either 4,X, or 46°C. These sample temperatures were chosen to approximate the range of temperatures used by other researchers. AU samples remained in the water bath for 30 min. The samples were allowed to equilibrate to the test temperature and were weighed prior to shear. Samples were sheared in the 100 kg load cell at a shear rate of 40 d m i n . Peak force was used to calculate shear values; all other shear parameters were as described previously. Four experiments were conducted on consecutive days.
187
SHEAR VALUES
188 Kramer shear cell was used. Compression (yield force) accounted for 78.3,85.7, and 96.0% of the maximum force required to shear the 4,9-, and 16-cm2 samples, respectively. This difference may result from more shear cell blades being in contact with the larger samples during compression and shear.
4
LOAD CELL SIZE Variation in shear values associated with the 100 kg vs. the lo00 kg load cell ranged from 0 to 0.9 kg/g across all shear rates (a,@, 60, 80, and 100 cm/min) and from 0.1 to 0.7kg/g for all sample sizes (4,9, and 16 cm2). For all sample weyjhts, and for shear rates above 40 cdmin, the lo00 kg load cell gave larger shear values than the 100 kg load cell. These differences, however, were not statistically (P> .OS) significant in either of the two experiments. PEAK FORCE VS. YIELD FORCE Most researchers use peak force to calculate shear values. Yield force is useful when the amount of sample compression and the force required to initiate shear are important.
TABLE 2. Effect of sample size and shape on shear values (kg/g) from cooked broiler Pectoralismuscles
Downloaded from http://japr.oxfordjournals.org/ at Adams State University on March 10, 2015
SAMPLE SIZE AND SHAPE Changing sample shape caused a difference in shear values in only one comparison (Table 2). At a shear rate of 60 cdmin, the 4-cm2 rectan les had higher shear values than the 4-cm squares. Shapes did not affect shear value at any other sample size. For all three sample shapes and both shear rates, 4-cm2 samples had larger shear values than 9-cm2 samples. Shear rate did not significantly affect shear values. These results agreed with those in Table 1. Each blade made contact with the sample surface at an angle. One end of a blade initiated shear with the sample edge, and the remainder of the blade continued the shear as the blade traveled lower. Each blade has the same angle, but alternate ends of the blade contact the sample frrst. The three sample shapes were chosen to provide different relationships between the sample and the blades in the Kramer shear cell. The circle allowed some of the blades to contact the sample edges at angles other than 90°C and had no effect on shear values. The rectangular shape and perpendicular orientation of sample length to the blades in the shear cell allowed more blades to contact the rectangular samples than the square samples. Shearing was also completed in a shorter length of time for the rectangular samples than for the square samples.
SAMPLE TEMPERATURE No differences (P > .05) in shear values attributable to sample temperature occurred in any of the four experiments. The plastic bags containing the samples during equilibration to the test temperature were closed but not heat sealed. Samples equilibrated to the three temperatures differed (Pc.05) in the amount of weight lost during equilibration. The samples equilibrated to 46°C lost 1.4% of their sample weight to condensation and possible vapor loss, whereas samples equilibrated to 4 and 26°C lost 0.4% of their weight. Although the weight loss of the 46°C samples differed significantly from that of the 4 and 26°C samples, there was no concomitant difference in shear values. If weight loss had been a factor, the samples held at 46°C would have had shear values signilicantly different from those of the samples held at 4 and 26°C.
Research Report HEATH and OWENS
189
Peak force and yield force were correlated (P<.OS) for each sample size (4, 9, and 16 cm2), shape (circle, rectangle, and square), and 100cm/min) and all shear rates (40,60,80, except 20 cm/mh (Table 3). The coefficients of variation calculated from shear values based on yield force were 0.3 to 20% larger than those calculated using peak force. This
I
difference indicated that the calculations made using peak force had a smaller amount of variation and therefore were more precise than the shear values calculated using yield force. The significant correlation between the two calculation methods indicated that peak force and yield force will measure the same trends in shear values.
PEAK FORCE
YIELD FORCE
4
26.2
32.3
0.82.
9
26.3
33.9
0.73.
Circle
29.3
36.1
0.72.
Rectangle
25.2
31.2
0.80.
Square
25.3
29.2
0.77.
20
26.0
46.2
0.35
40
26.4
29.2
0.90.
60 80 100
24.0
26.2
0.70.
31.6
34.0
0.95.'
25.0
25.3
0.93.
PARAMEIER
PFYF
Samule Sham
I
Shear Rate (cm/Min)
CONCLUSIONS ANDAPPLICATIONS 1. Shear rate affected shear values; the variation, however, was not linear. 2. Increased sample size reduced shear values.
3. Sample shape and sample temperature prior to shear had no effect on shear values. 4. Changing load cell size made no statistically significant differencein shear values. 5. Shear values calculated with peak force and yield force showed the same trends in tenderness. Shear values calculated with peak force had a smaller amount of variation, indicating that they will be more precise than those calculated using yield force.
REFERENCES AND NOTES 1. Bourne, M.C., 1972. Standardization of texturemeasuring instrument. J. Texture Stud. 3:379-384. 2. Voisey, P.W.and W.S. Reid, 1974. Effect of friction on the rformance of texture cells. J. Texture Stud. 5239-& 3. VoJsey, P.W., 1 9 n . Effect of blade thickness on readings from the F.T.C. shear compression cell. J. Texture Stud. 7433-440.
4. VoisCy, P.W.and M. Kloek, 1981. Effect of size on the performance of the shearcompression texture test cell. J. Texture Stud. 12133-139. 5. Timbers, G.E and P.W. Voisey, 198.5. Influence of number and thickness of blades on the performance of the Kramer type shear-compressioncell. J. Texture Stud. 16303-311.
Downloaded from http://japr.oxfordjournals.org/ at Adams State University on March 10, 2015
Sample Size (cm5
JAPR 190 6. Szcusnink,AS.,P.R. H~~mbaugb, and H.W.Block, 1WO.Behavior of different foods in the standard shear
compression cell of the shear p r e s and the effect of sample w e i p on g a k area and maximum force. J. TUtureStud. 356-3 7. Data were sub‘ected to analysis of variance (ANOVA) using the hLM procedure of SAS. Significantly (P-z.05) different means were separated with Duncan s multiple range test. Pearson correlation and coefficient of variation were used to compare the 100 kg load cell to the lo00 kg load cell.
SHEAR VALUES 8. SAS Institute, 1985. SAS User’s Guide: Statistics. SAS Institute, Inc., Cary, NC.
9. Zhang, M. And G.S. Mittal, 1993.Measuring tenderness of meat products by Warner Bratzler shear press. J. Food P m . and Pres. 17351-367.
10.I k M q J.M. and B.S. b e l , 1981.Instrumental methoQ of measurin texture of poultry meat. Pa es 157-164 in: Quality off’oult Meat, S iderholt Jubifee Sympia, Apeldoorn, The x t h e r l a n g
Downloaded from http://japr.oxfordjournals.org/ at Adams State University on March 10, 2015