The Relationship between Loin Surface Visual Characteristics with Instrumental Colour and Tenderness Characteristics from Five South African Beef Breeds

The study describes the relationship between visual and instrumental measurements for colour and tenderness between 5 South African beef breeds; Bos indicus (Brahman), Sanga type (Nguni), British Bos taurus (Angus), European Bos taurus (Charolais) and the composite (Bonsmara), 10 animals per genotype were used, n=50. The animals were finished off on a feedlot diet for a period of between 90-110 days at the ARC-AP feedlot and were slaughtered at the ARC-AP abattoir when they reached a live weight which would produce a carcass of Class A (no permanent incisors), and fat class 2 to 3 (1-5 mm) (South African Beef Classification System). After exsanguination, the carcasses were split and the right sides were electrically stimulated (ES) and the left sides were not stimulated (NS), but delay chilled. Steaks from both ES and NS treatments were aged until 3 days (d) post mortem (pm) on polystyrene plates at 6°C in a display cabinet and until 9, 14 and 20 d pm in vacuum bags at 1-4°C in a cold room. The steaks were then evaluated by visual analysis for colour, marbling, fibre separation, surface texture and structure integrity using a 10 member trained panel. Instrumental colour was measured using Minolta meter (CIE L*, a*, b*). Instrumental tenderness was measured by shear force using Instron.

Results of the study showed that Nguni breed produced the most tender and darker meat whereas, the Bonsmara breed produced the least tender and lightest meat. Good correlations were observed between the visual colour and L* (r=0.809; P<0.0001), b* (r=0.698; P<0.0001) and hue (r=0.797; P=0.797). There were also correlations between shear force and structure integrity (r=-0.410; P<0.0001) and fibre separation (r=- 0.401; P<0.0001). Very low correlations were observed between visual colour and shear force. Therefore, although a trained eye could judge meat colour by visual analysis, it seems not possible to predict tenderness by colour judgement. Visual texture did not show any potential as a reliable visual tenderness attribute, therefore cannot be used to predict meat tenderness. However, there is potential for an experienced eye in predicting tenderness by observing visual structural properties such as fibre separation and structural integrity.