Abstract/Summary

Excessive salt intake is associated with a growing risk of cardiovascular disease. In order to reduce salt levels in food, one of the popular strategies is to use other metallic salts to partially replace salt. However, this often causes a significant loss in saltiness, leads to additional tastes (i.e., bitter) and reduces shelf-life. According to pervious research, lysine and calcium lactate may hold the key to solve this problem, and hence, enable successful salt substitution. This experiment aimed to explore whether lysine and calcium lactate can be used as salt substitutes and their effect on the quality of low-sodium meat products. Since umami taste has been used widely in sodium reduction by enhancing flavour perception, therefore, this thesis first aimed to gain a better understanding of the interaction of the five basic taste sensations (sweetness, sourness, saltiness, bitterness, umami), and especially the role of umami in complex taste systems. A trained sensory panel was used to rate the taste intensity of equi-intense aqueous solutions. The results concluded that umami did not enhance or suppress the perception of any other taste, whereas sweetness, saltiness, sourness and bitterness significantly suppressed the perception of umami. Therefore, the study changed focus to consider whether lysine and calcium lactate could contribute to salty taste. In aqueous solution, calcium lactate did not offer saltiness, but 1% lysine produced weak saltiness. Overall, 1% lysine with or without 0.75% calcium lactate would replace 50% salt (NaCl) in solution system without compromising saltiness perception. The effects of lysine and calcium lactate as substitutes were further tested in a real food matrix (low-salt meat products). Physicochemical characteristics, sensory properties and microbiological analysis were used to evaluate their effectiveness in salt-reduced pork patties. The results concluded that lysine increased the yield and calcium lactate improved shelf-life of a salt-reduced pork patty. Calcium lactate and lysine could offer effective way to reduce salt by 50% without compromising shelf life and eating quality. Because lysine, as a basic reactive amino acid, may be involved in Maillard reaction and modify the flavour profile of meat products during heating processing, thereby affecting the salty taste. So, gas chromatography-mass spectrometry (GC-MS) was used to study the volatile flavour compounds in salt-reduced pork patties in a range of meat pH (5.5 to 6.5). Results showed that Maillard reaction-related volatile flavour compounds were very low in the low salt patties prepared with lysine and calcium lactate under normal meat pH conditions, and the modification to flavour profile of cooked pork patty was minimum. To sum up, the combination of lysine and calcium lactate could be used as a new salt substitute in meat products offering comparable eating quality and shelf life to full salt products.