Determination of protein and lipid denaturation and water holding capacity

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Raising of animals and feedlot procedures:

All the animals received a Revalor® H growth implant in accordance with general feedlot practices in South Africa. The animals were housed in pens holding 10 animals per pen, feed and clean fresh water was available at all times. Each animal was provided 10 m2 and 50 cm of feed-bunk space. A standard type of high concentrate diet was supplied to the animals (12 MJ/kg DM, 13.5% protein), to which they were adapted to in a three-week period, from high levels of hay (15%) to low levels of hay (6%). Animals were weighed at two-weekly intervals and daily health observations about animal morbidity, consistent breathing and manure consistency were made. All these actions were necessary to comply with the rules of the Ethics Committee of the ARC (ARC AEC-I 2010 001).

Procedures on slaughter day (SL-D)

Animals arrived at the abattoir the day before they were slaughtered. Clean water was provided at all times. The animals were slaughtered at an age of 10 to 12 months, so as to produce carcasses in the A-age class and fatness class two to three of the current South African Beef Carcass Classification System. The animals were slaughtered over a period of 10 weeks, according to the experimental layout highlighted in Table 3.1. After stunning and exsanguination, the carcasses were dressed and split in half and the left sides were electrically stimulated (ES), (400 V peak, 5 ms pulses at 15 pulses per second, for 15 seconds) within 30 minutes post-stunning. m.

Sampling and ageing

Sampling was done at 20 hours post mortem. Both the left and right side carcasses were sampled at the m. longissimus dorsi (Figure 3.1) and the muscle was cut in to steaks as shown in Figure 3.2. Two retail procedures were simulated for ageing of the steaks. The steaks were aged for three and nine days post mortem on polystyrene plates, covered with polypropylene cling wrap (PP) at 6°C in a display cabinet (Figure 3.3), and the other steaks were aged for 14 and 20 days post mortem in vacuum bags at 1-4°C in a cold room (Figure 3.4) for Phase 1. Based on the lipid peroxidation results as measured by the TBARS assay, the day nine steaks had higher TBARS and the steaks had already started to develop moulds, discolouration and a bad odour.

Sensory panel analyses

In order for the sensory analysis and other analysis of fresh meat samples not to overlap with the slaughter days, an experimental layout was used (Table 3.1). The samples were evaluated according to the methods described in the Annual book of ASTM Standards (ASTM, 1989). The sensory analysis facilities were constructed with all the elements necessary for an efficient sensory program according to ASTM design guidelines for sensory facilities. Visual analysis was evaluated by a 10 member trained sensory panel at the ARC-Animal Production Institute, Meat Science laboratory using fresh samples (Figure 3.5 shows example of two members of the sensory panel during evaluation).

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Water holding capacity

The water holding capacity (WHC) was determined by calculating the ratio of meat area divided by meat plus expressed juice area (total area) after pressing a 400-600 mg fresh meat sample on a filter paper (Whatman 4) sandwiched between two Perspex plates, and pressed at a constant pressure of 300 psi for 60 seconds according to the method described by Irie et al. (1996). The areas were measured by means of video image analyses (VIA) using Olympus video photo adapter at magnification of two. Image processing and calculations were done by means of Analysis Life Science software package (Soft Imaging Systems Gmbh, Münster, Germany).

TABLE OF CONTENTS :

  • ABSTRACT
  • DECLARATION
  • ACKNOWLEDGEMENTS
  • Journal article
  • Conference papers (full paper and presentation)
  • LIST OF ABBREVIATIONS
  • Table of Contents
  • LIST OF TABLES
  • LIST OF FIGURES
  • CHAPTER
    • 1.1. Project title:
    • 1.1. Project theme:
    • 1.3. Aims:
    • 1.4 . Motivation
    • 1.5. Hypothesis
  • CHAPTER 2 (LITERATURE REVIEW)
    • 2.1. Meat colour
    • 2.1.2. Measurement of meat colour
      • 2.1.2.1. Visual analysis
      • 2.1.2.2. Instrumental colour
  • 2.2. Meat tenderness
  • 2.2.2. Methods to determine meat tenderness
    • 2.2.2.1. Use of objective measurements to assess meat tenderness
    • 2.2.2.2. Use of objective methods to assess meat tenderness
    • 2.2.2.4. The need for other methods to determine meat tenderness
  • 2.3. Chapter summary
  • CHAPTER 3 (MATERIALS AND METHODS)
    • 3.1 Raising of animals and feedlot procedures:
    • 3.2 Procedures on slaughter day (SL-D)
    • 3.3 Sampling and ageing
    • 3.4 Sensory panel analyses
    • 3.5 Determination of protein and lipid denaturation and water holding capacity
    • 3.6 Determination of colour related parameters
      • 3.6.1 Determination of myoglobin derivatives
      • 3.6.2 Metmyoglobin reducing activity in meat
      • 3.6.3 Muscle colour measured with Minolta
      • 3.6.4 Fibre typing and fibre bundles
    • 3.7 Tests related to meat tenderness according to established methods in the ARC-API Meat Science Laboratories
      • 3.7.1 Warner-Bratzler shear force (WBSF) on cooked meat
      • 3.7.2 Sarcomere length at three days post mortem
      • 3.7.3 Myofibril fragmentation
      • 3.7.4 Fibre detachments
      • 3.7.5 Connective tissue characteristics (total collagen and solubility)
        • 3.7.5.1 Soluble and insoluble collagen extractions
        • 3.7.5.2 Total collagen extraction
        • 3.7.5.3 Procedure for determination of soluble, insoluble and total collagen
  • 3.8 Muscle energy metabolism
  • CHAPTER 4 (RESULTS OF PHASE 1)
    • 4.1. Effect of breed on carcass characteristics, visual sensory panel evaluation of meat characteristics, meat colour measurements/evaluations, muscle energy metabolism, protein denaturation, lipid oxidation and meat tenderness
    • 4.1.1. Carcass characteristics
    • 4.1.2. Visual sensory panel evaluations of meat characteristics
    • 4.1.3 Protein denaturation and lipid oxidation
    • 4.1.4. Minolta measured colour and related parameters
    • 4.1.5. Muscle fibre typing
    • 4.1.7. Tenderness related measurements of m. longissimus dorsi (LD)
    • 4.2. Effect of ageing on visual sensory panel evaluation of meat characteristics, on meat
  • CHAPTER 5 (RESULTS OF PHASE 2)
  • CHAPTER 6 (DISCUSSION)
  • CHAPTER 7 (CONCLUSION)
  • CHAPTER 8 (REFERENCES)

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Visual assessments of meat surface structure and meat colour to predict beef tenderness between five South African beef breeds

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