# Ultrasound for Meat Processing: Effects of Salt Reduction and Storage on Meat Quality Parameters
###### Abstract  
Meat samples (_Longissimus dorsi_) were processed using an ultrasonic (US) probe system (20 kHz) and a US bath (33 kHz), in brine solutions of 15% NaCl or NaCl/KCl. Selected quality parameters, namely hardness (Warner-Bratzler shear force, WBSF), secondary lipid oxidation products (thiobarbituric acid reactive substances, TBARs) and total colour difference (TCD) were analysed at day 0 and day 60. inoculated _E. coli_ and _L. microcua_ cells, total viable counts and lactic acid bacteria were also monitored for 60 days on meat stored at 4 and 10 \({}^{\circ}\)C. US brining could achieve a 25% sodium reduction in a shorter processing time. No changes were observed for WBSF and TBARs values; noticeable colour differences (\(\Delta\)E > 5) were measured in US-treated samples at the end of storage. Whilst no differences were observed in the levels of inoculated and spoilage bacteria on the meat surface, a significant reduction in _E. coli_ in the brine subjected to US treatment indicates the potential of US as a hurdle technology to prevent cross contamination during meat processing. These results suggest that US processing, in combination with KCl, could assist current sodium reduction strategies improving processing time. In addition, the potential effects for decontamination of brining tanks increasing the shelf-life of the brine and preventing processing losses are highlighted. 20  
in addition, some of their limitations. The partial substitution of NaCl by other chloride salts (e.g., KCl, CaCl\({}_{2}\) and MgCl\({}_{2}\)) has been suggested as one of the best alternatives to reduce sodium content in meat and dairy products [1; 6; 7]. In particular, with salt being an important preservative agent against bacterial growth, preliminary tests on the use of potassium chloride (KCI) as its substitute, have confirmed that KCl has an equivalent antimicrobial effect to NaCl and could therefore be a good candidate for salt replacement [8]. The major issue when lower salt levels are used is being able to maintain product quality characteristics without affecting shelf-life and safety of the products [3; 9]. In addition, to achieve the required salt concentrations within the meat, longer brining times are required, which poses higher microbial contamination risks in the case of raw meat [10]. Development of novel technologies for meat processing has attracted attention in the scientific and research community for decades, leading to an increased interest in helping the transition from research to full commercial applications of new technologies in the meat processing sector. The increased demand for \"less processed\" meat products, with a reduced ingredients list and ingredients with less chemical sounding names, has also significantly reduced the number of options for processors and has led the food industry to look for alternative processing treatments [11]. Among the novel technologies, application of ultrasonic (US) processing (20-100 kHz) to meat products has been shown to improve meat tenderisation, meat functional properties and salt diffusion mechanisms, suggesting its potential use to speed up processing time and compensate for quality losses caused by sodium reduction in meat products [10; 12; 13; 14; 15]. Different studies have reported the possible applications of ultrasound technology for microbial inactivation, due to the effects of the sonochemical reactions happening in the liquid media [16; 17; 18; 19]. However, most of the literature available focuses on US applications for bacterial inactivation in liquid foods, and limited information is available on the effects of US processing on bacteria attached to the meat matrix. Thus, the aim of this study was to evaluate the effects of US-assisted brining on selected quality parameters such as texture, colour and lipid oxidation on reduced sodium pork meat.