Application of ultrasound technology for functional meat products

Abstract

With increasing consumer awareness of health and nutrition, the meat processing industry is eager to engage in a search for innovative ways of processing and developing novel meat products with potential health benefits. Novel processing technologies including ultrasound (US) technology can offer several benefits for versatile applications in food processing. In relation to meat processing, US technology has previously been investigated for many potential applications including accelerated brining, tenderisation, rapid cooking, faster thawing and decontamination of muscle-based food products. This thesis assesses the feasibility of employing US technology to assist in the development of functional meat products. To achieve this objective, a series of five studies were carried out. The first study investigated the efficacy of high intensity US on the fermentation profile of Lactobacillus sakei (a starter culture used for meat fermentation) in a meat model system. This study observed that both stimulation and retardation of L. sakei is possible, depending on the ultrasonic power and sonication time employed. Furthermore, to underline the fundamental mechanism influencing the behaviour of microorganisms subjected to ultrasonic frequencies of 20, 45, 130 and 950 kHz on growth kinetics, phenotypic behaviour and cell morphology were assessed in study 2. Results presented in this study showed that the physiological response of L. sakei to US is frequency-dependent and US can influence metabolic pathways. The influence of US frequency on the behaviour of L. sakei culture in a meat matrix was also studied. Additionally, this study investigated possible synergistic effects between US and L. sakei addition on drying kinetics, moisture mobility and key nutritional (fatty acid profile, protein, amino acids, and organic acids) in beef jerky samples. Given the complexity and number of parameters involved, a reliable multivariate statistical strategy was adopted. The results presented in this study showed a significant effect of US pre-treatment on various physicochemical properties as a result of employing both L. sakei and US. The individual effects of L. sakei and US were prominent compared to interactive effects. Conversely, the effect of US frequency on L. sakei culture observed in model systems (Chapter 2 and 3) was not evident when assessed in a solid meat matrix. Two specific studies were carried out to investigate US-assisted diffusion of ingredients into meat matrices with the objective of improving the nutritional profile and healthy image of meat. Results from salt diffusion studies showed improved diffusion rates for sodium salt compared to a static brining system can be obtained. However, no significant differences were observed in the case of sodium salt replacers. A second aspect of US-assisted diffusion focused on the incorporation of essential fatty acids (FA) to improve the lipid profile of pork meat. This study has demonstrated the positive effect of US application in improving diffusion of encapsulated FA into meat, thereby resulting in higher levels of essential FA compared to the static diffusion system. It can be concluded from the thesis work conducted that the effectiveness of US technology is application dependent. The commercial utilisation of US technology remains challenging for solid food applications, especially for meat products due to the complex nature of meat. However, further research is needed prior to commercial uptake of US technology for a range of applications