Abstract
Tenderness, juiciness, colour, and flavour are the main parameters that consumers use to judge the quality and monetary value of meat. Different processing techniques such as Pulsed Electric Fields (PEF) and sous vide (SV) processing have been explored to enhance the quality and value of tough meat cuts. Beef short ribs, the meat cut investigated in the current study, is an example of a tough meat cut, which has a low monetary value and the additional processing challenge of containing bones. To date, beef short ribs have not been reported as being valorised by any processing methods. The presence of bones in beef short ribs poses a challenge during processing as conventional heating processing can result in the detachment of the meat from the bone, which consumers report not to be visually appealing. The development of a technology, which can increase the tenderness, juiciness, colour, and flavour of short ribs, without causing the bone to detach is of commercial value.
SV processing is the low-temperature long-time cooking method of vacuum-packed meat at a precise temperature for a defined time. SV processing can enhance tenderness without having an adverse effect on meat colour and flavour. However, this process consumes a high amount of energy and takes a long time, which means that commercial-scale applications typically use temperatures of at least 70 0C and this has an undesirable effect on quality. Therefore, the meat-processing industry is seeking a technology that can reduce the temperature and SV processing time required for tough meat cuts. PEF processing, which involves the application of high-voltage electrical energy for a very short time to the food, could be a suitable technology for enhancing meat tenderness and reducing SV processing time. Electric field strength (EFS) and specific energy (SE) are the two main PEF processing parameters that affect meat quality, which need to be optimised. To date, studies assessing the effect of PEF-SV on the quality of bone-in tough meat cuts such as short ribs have not been reported.
This thesis aimed to understand the effect of PEF-SV processing on the quality of short ribs and to explore the possibility of applying PEF processing to reduce SV temperature-time conditions. Initially, the effect of different SV temperature and time combinations on the quality parameters (colour, cooking loss, shrinkage, soluble collagen, myofibrillar fragmentation index (MFI), Warner Bratzler Shear force (WBSF), and Texture Profile Analysis (TPA) parameters) of beef short ribs vacuum packed in different packaging materials were assessed. Subsequently, the effect of PEF pre-treatments on meat quality and best SV temperature-time conditions were determined. In addition, the quality of PEF-SV processed beef short ribs, their degree of lipid and protein oxidation, in vitro digestibility, and changes in microbial numbers during storage of the final processed vacuum-packed meat were assessed.
A three-layer plastic (polyethylene, ethylene vinyl alcohol, and polyamide) - aluminium laminate pouch was determined to achieve a favourable meat colour. SV processing regime of low temperature (60 0C) for a long time (34.06 h) was determined to be the optimum SV processing condition for short ribs. Short ribs with a low electrical conductivity had a significantly higher EFS, pulse energy (PE), and SE compared with those with high electrical conductivity. Higher intensity (Electric Field Strength: 0.55-0.80 kV/cm and Specific Energy: 83.80-110.96 kJ/kg) PEF treatment led to SV short ribs, which had a significantly lower TPA hardness compared to SV short ribs that had not been subjected to PEF processing. The optimum PEF-SV processing conditions for short ribs were EFS of 0.85 kV/cm and SE of 110.96 kJ/kg, followed by SV processing at 600C for 23.96 h. Vacuum packaging was found to work extremely well to preserve the colour during storage and there was no detectable aerobic microbial growth until 21 days and no anaerobic growth was detected until 42 days of storage.
The work presented in this thesis provides technological insight into the ability of PEF-SV processing to enhance the quality of short ribs. This work provides convincing evidence that PEF treatment can ameliorate the biological electrochemical variability inherent to short ribs, and that PEF processing has the potential to be used commercially as means of reducing the SV processing time required to tenderise tough meat cuts.