Instron Warner-Bratzler Test: Parameters from the Instron WBS test are presented in Table 2. Interactions of ES with muscles were not significant (P > 0.05). Peak force (WBS value), initial yield force and work done values for ES and NES groups were 6.99, 7.34 kg; 6.50, 6.33 kg and 5.73, 593 mm2, respectively. These parameters were in the direction of increased tenderness for ES samples, as has already been indicated by Rangaiah et al. (1998). However, in this research, they were not large enough to be significantly different at the P < 0.05 level. The lack of significance for each measurement of tenderness probably was due to low numbers of carcasses and lack of cold shortening in this research.
| Table 2. Least square means and standard deviation for the effects of electrical stimulation and muscles on some Instron Warner Bratzler Shear tests of mutton tissue. | ||||||
| Initial Yield Force (kg)5 | Initial Distance (cm)6 | Peak Force (kg)7 | Final Distance (cm)8 | Peak Force Minus Initial Yield Force9 | Work Done (mm2)10 | |
| Electrical Stimulation | NS | NS | NS | NS | NS | NS |
| ES1 | 6.50 ± 0.54 | 1.14 ± 0.04 | 6.99 ± 0.58 | 2.75 ± 0.10 | 0.64 ± 0.24 | 5.73 ± 0.44 |
| NES2 | 6.33 ± 0.51 | 1.08 ± 0.03 | 7.34 ± 0.54 | 2.67 ± 0.10 | 1.02 ± 0.22 | 5.95 ± 0.42 |
| Muscles | * | NS | * | NS | NS | * |
| LD3 | 5.41 ± 0.52 | 1.13 ± 0.03 | 6.18 ± 0.55 | 2.77 ± 0.09 | 0.69 ± 0.22 | 5.14 ± 0.41 |
| SM4 | 7.43 ± 0.54 | 1.09 ± 0.03 | 8.15 ± 0.57 | 2.65 ± 0.10 | 0.97 ± 0.24 | 6.53 ± 0.45 |
| 1ES = Electrically stimulated, 2NES = Not electrically stimulated, 3LD = Longissimus dorsi, 4SM = Semimembranosus, 5Initial yield force = First major inflexion on the force-distance curve (kg), 6Initial distance = The distance, the first registering of force to the initial force point, 7Peak force = Maximum force recorded on force-distance curve (kg), 8Final distance = the distance, the first registering of force to the point where sample finally yielded, 9Peak force minus initial force = Peak force-initial force, 10Work done = Total area under force-distance curve, NS = Treatments are not significantly different (P > 0.05). * Treatments are significantly different (P < 0.05). | ||||||
Muscles had a significant effect on the initial yield force and work done values. The initial yield force values were lower for LD muscles than the SM (5.41 versus 7.43 kg) muscle. It was also the same for peak force (6.18 versus 8.15) and work done values (5.14 versus 6.53 kg). The other parameters were not significantly affected by the muscle type. Bouton et al. (1975) hypothesized that initial yield force value reflects the amount of force required to break myofibrillar structure, which has been coagulated and stiffened by cooking. Also, the peak force value is considered to be influenced by the strength of the connective tissue as well as myofibrillar strength of meat tissue (Rao and Gault, 1990). In this study, peak force value of the SM muscle was significantly (P < 0.05) higher than that of the LD muscle. This result could be due to the higher total and insoluble collagen content of SM muscle (the data not presented). Similar results were also reported by Solomon (1986), who noted that the instron peak force of the LD muscle was different in ES systems, and it was significantly lower than that of the SM muscle.
Instron Compression Test: The results for instron compression test are presented in Table 3. Again, interactions of ES with muscles were not significantly different (P > 0.05). The hardness and chewiness values of the ES samples were numerically lower (improved tenderness) than that of the control, but the differences between the treatments were not statistically significant (P > 0.05).
| Table 3. Least square means and standard deviation for the effects of electrical stimulation and muscles on parameters of Instron Compression Test. | ||||||||
| Chewiness (kg)5 | Peak Force 1 (Hardness) (kg)6 | Peak Force 2 (kg)7 | Peak Force Distance 1 | Peak Force Distance 2 (cm)8 | Work Done 1 (mm2)10 (cm)9 | Work Done 2 (mm2)11 | Cohesiveness12 | |
| Electrical Stimulation | NS | NS | NS | NS | NS | NS | NS | NS |
| ES1 | 1.95 ± 0.11 | 5.21 ± 0.18 | 4.21 ± 0.22 | 0.89 ± 0.01 | 0.58 ± 0.01 | 5.56 ± 0.29 | 2.12 ± 0.17 | 0.36 ± 0.01 |
| NES2 | 2.10 ± 0.11 | 5.51 ± 0.19 | 4.16 ± 0.23 | 0.87 ± 0.02 | 0.54 ± 0.01 | 5.32 ± 0.29 | 2.08 ± 0.17 | 0.37 ± 0.01 |
| Muscles | ** | NS | NS | NS | NS | NS | ** | NS |
| LD3 | 1.68 ± 0.11 | 4.75 ± 0.18 | 3.77 ± 0.21 | 0.88 ± 0.02 | 0.55 ± 0.01 | 5.15 ± 0.30 | 1.71 ± 0.17 | 0.33 ± 0.01 |
| SM4 | 2.38 ± 0.11 | 5.98 ± 0.19 | 4.60 ± 0.23 | 0.87 ± 0.02 | 0.57 ± 0.01 | 5.73 ± 0.29 | 2.49 ± 0.17 | 0.39 ± 0.01 |
| 1ES = Electrically stimulated, 2NES = Not electrically stimulated, 3LD = Longissimus dorsi, 4SM = Semimembranosus, 5Chewiness = Hardness x (second bite area/first bite area), 6Hardness = Peak force of first bite, 7Peak force 2 = Peak force of second bite, 8Peak force distance 1 = Distance from first registering of force to the peak force point of the first bite, 9Peak force distance 2 = Distance from first registering of force to the peak force point of the second bite, 10Work done 1 = Total area under first bite, 11Work done 2 = Total area under second bite, 12Cohesiveness= Second bite area/first bite area, NS = Treatments are not significantly different (P > 0.05), ** Treatments are significantly different (P < 0.01). | ||||||||
In the present study, chewiness and work done 2 values were both highly significantly (P < 0.01) influenced by muscle type (Table 3) demonstrating that the SM muscle was tougher than the LD muscle. SM muscle had a higher chewiness value than those of LD to break up the muscle tissue. Similar assessment was made by Hayward et al. (1980) that the muscles with more connective tissue than LD muscle might have greater compression differences. The data related with Instron compression test (though some of them was insignificant) followed a trend similar to WBS measurements, indicating that the structural strength of myofibrilar and connective tissue components were influenced by the treatments.