Improving sensory characteristics and shelf life of low-quality beef through the application of Sous Vide cooking and Ginger Protease

Low-quality meat, determined by poor tenderness, juiciness, and flavour, is often sold at a reduced price due to limited consumer acceptability and preference. Adding value to this inferior-quality meat to ensure consumer satisfaction offers enormous potential to the beef industry particularly in developing countries where beef is primarily a by-product of the dairy industry. Tenderness is one of the most important eating quality attributes of the meat, driving the consumer’s preference and their willingness to buy meat products at higher prices if the superior quality is warranted. Tenderness is a multifactorial trait ascribed by several live animal factors (the age of the animal, genetics, feeding, and muscle type), post-mortem conditions, and cooking conditions. These factors influence the collagen content and myofibrillar structure that impacts on the toughness of the meat in the carcass. Several post-harvest meat treatments including aging, sous vide cooking, and injection of protease enzyme solutions have shown promising results to enhance the eating quality of the meat. However, the review of the literature presented here clearly suggested limited scientific understanding of time-temperature combinations in sous vide cooking particularly in reference to low-quality meat from older animals. In addition, there is no body of knowledge investigating the combined effect of aging, sous vide cooking and partially-purified ginger powder (zingibain protease) solution on physical parameters, sensory characteristics, and shelf life of the beef from low-value cuts. This thesis aimed to address this by performing a series of experiments presented here in four chapters. The first experiment (Chapter 3) investigated the effect of sous vide cooking and ageing on tenderness and water-holding capacity of bovine biceps femoris (BF) and semitendinosus (ST) acquired from young and older cattle. The results of this chapter demonstrated that tough meat from both BF and ST of older animals required a higher temperature (75 °C) and prolonged cooking (18 h) to achieve comparable tenderness to that of young animals through increased collagen solubility (P < 0.001, in both muscles). However, there was a significant interaction between cooking temperature and cooking time on cooking loss in both muscles (P < 0.001), and the combination of high-temperature and long-time cooking treatments had a negative effect on cooking loss for both muscles. We concluded high-temperature long-time conditions might not be helpful for the beef industry due to lower juiciness and higher production input costs. The next logical question was can we reduce this cooking time by using proteases to achieve the same quality outcome in the final meat product. Therefore, Chapter 4 investigated whether the use of ginger proteases along with sous vide cooking can enhance tenderness and water-holding capacity of BF from older animals that had been finished on a high energy diet. The results of Chapter 4 revealed significant interactions between concentrate feeding, ginger powder injection, cooking temperature, and time on quality traits. Injecting partially-purified zingibain along with sous vide cooking resulted in weakening of myofibrillar and connective tissue proteins to enhance collagen solubility and tenderness in the BF. The results from Chapter 4 demonstrated that zingibain could be used post-harvest to improve the eating quality characteristics of beef but the consumer perception of flavour had not been examined. Chapter 5 evaluated the physical and sensory characteristics, using a trained consumer panel, of zingibain-injected meat combined with sous vide cooking in the BF. Results revealed a significant improvement in tenderness with injection treatment and cooking time as evaluated by trained panelists, as well as reduced Warner Bratzler shear force and hardness (both P < 0.05). The flavour of the meat was not affected by either injection treatment or cooking time. We reported that moderate to high correlations were found between sensory and physical measurements for tenderness and juiciness. The final question relating to the effect of sous vide cooking and protease injection protocol on the shelf life of the meat was evaluated in Chapter 6. This chapter reported an acceptable microbial count obtained for up to four weeks, and two weeks shelf life for lipid oxidation under refrigerated storage. The results of this thesis demonstrate a protocol for using sous vide cooking, with zingibain protease injection that could be used to improve the eating quality and shelf life of low-value meat cuts ensuring a safe and favourable eating experience to consumers.