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Evaluation of Lamb and Mutton Quality at Retail Level in the Tshwane Metropole

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Evaluation of Lamb and Mutton Quality at Retail Level in the Tshwane Metropole EVALUATION OF LAMB AND MUTTON QUALITY AT RETAIL LEVEL IN THE TSHWANE METROPOLE By STEPHANI DU PLESSIS Submitted in fulfillment of the requirements for the degree of MAGISTER SCIENTIAE CONSUMER SCIENCE Department of Microbial, Biochemical and Food Biotechnology Faculty of Natural and Agricultural Sciences University of the Free State Bloemfontein South Africa Promoter: Prof. A. Hugo Dr. M. Hope-Jones Co-promoters: Dr. P.E. Strydom January 2019 DECLARATION I hereby declare that the thesis, Evaluation of Lamb and Mutton Quality at Retail Level in the Tshwane Metropole, handed in for the qualification of Magister Scientiae Consumer Science (Food Science) at the University of the Free State, is my own work and that I have not previously submitted the same work for a qualification at another University or faculty. I hereby concede copyright of this thesis to the University of the Free State. ______________________________ Stephani du Plessis Student number: 2011054117 January 2019 TABLE OF CONTENTS CHAPTER CHAPTER TITLE PAGE ACKNOWLEDGEMENTS i LIST OF TABLES ii LIST OF FIGURES iv GLOSSARY OF ABBREVIATIONS vi 1 INTRODUCTION 1 2 LITERATURE REVIEW 5 2.1 Introduction 5 2.2 Defining meat quality 6 2.2.1 Muscle structure 7 2.2.2 Determination of meat tenderness 13 2.3 Factors affecting lamb and mutton quality 14 2.3.1 Breed 14 2.3.2 Chronological age 16 2.3.3 Gender 17 2.3.4 Production system/feeding regime (grass-fed vs Karoo vs grain-fed/concentrate) 18 2.3.5 Growth promotants 21 2.3.6 Calcium chloride and vitamin D infusion 23 2.3.7 Stress ante-mortem 24 2.3.8 Slaughter weight 26 2.3.9 Alternative carcass suspension methods 27 2.3.10 Electrical stimulation 27 2.3.11 Post-mortem muscle biochemistry 28 2.3.12 Post-mortem ageing 31 2.3.13 Temperature and pH 32 2.3.14 Lipid fraction 33 2.3.14.1 Marbling 33 2.3.14.2 Fatty acid composition 34 2.3.14.3 Oxidative stability 35 2.3.15 Impact of freezing and thawing 36 2.3.16 Modern retail packaging 37 2.4 What the consumer wants in terms of lamb and mutton quality 38 2.4.1 Point of sale 38 2.4.2 Point of consumption 39 2.5 Other international lamb and mutton quality audits 40 2.6 Conclusions 41 3 MATERIALS AND METHODS 42 3.1 Sourcing of samples 42 3.2 Quality measurements 44 3.2.1 Fat : meat ratio 44 3.2.2 Meat colour 44 3.2.3 Cooking losses 44 3.2.4 Proximate analysis 45 3.2.5 Collagen 45 3.2.6 Intramuscular fat content and Fatty acid analysis 45 3.2.7 Warner Bratzler shear force 46 3.2.8 Myofibrillar Fragment Lengths 46 3.2.9 Thiobarbituric acid reactive substances (TBARS) 47 3.2.10 Sensory analysis 47 3.3 Statistical analysis 48 4 RESULTS AND DISCUSSION 49 4.1 Background to survey 49 4.2 Price 49 4.3 Tissue distribution 50 4.3.1 Meat/Fat/Bone ratio 50 4.4 Proximate composition 53 4.4.1 Muscle protein and moisture content 53 4.4.2 Dissectible and intramuscular fat 56 4.5 Composition of the lipid fraction 58 4.5.1 Saturated fatty acids 58 4.5.2 Unsaturated fatty acids 60 4.5.2.1 Monounsaturated fatty acids 60 4.5.2.2 Polyunsaturated fatty acids 60 4.5.3 Fatty acid ratios 63 4.5.3.1 PUFA : SFA 63 4.5.3.2 n-6 : n-3 66 4.5.3.3 Atherogenicity index 66 4.5.3.4 Desaturase index 67 4.6 Physical characteristics 69 4.5.1 Meat colour 69 4.5.2 Cooking loss 74 4.7 Tenderness characteristics 76 4.7.1 Warner Bratzler shear force and myofibrillar fragment lengths 76 4.7.2 Total collagen and solubility 81 4.8 Lipid stability 83 4.8.1 Fat oxidation (TBARS) 83 4.9 Sensory analysis 85 4.9.1 Aroma and Flavour 85 4.9.2 Texture 88 4.10 Discriminant analysis 91 5 GENERAL DISCUSSION AND CONCLUSIONS 95 6 REFERENCES 99 7 SUMMARY 132 APPENDIX 1 134 ACKNOWLEDGEMENTS I would like to acknowledge the following people and institutions for their contributions in the successful completion of this study: My mother and father (Elma and Jean du Plessis), for all their support throughout my study career. Thank you for giving me this great opportunity in life. I will make you proud in all I do, to the best of my abilities. Thank you for all the unconditional love. Eljean and Thys Mathee, for all their encouragement and support. Kosie Snyman, for his love and support and taking this journey with me. Prof A. Hugo (Department of Microbial, Biochemical and Food Biotechnology, University of the Free State), for giving me the opportunity to study under his supervision and giving me the knowledge for a bright future. Dr M. Hope-Jones and Dr P.E. Strydom (Department of Food Science and Technology, Agricultural Research Council, Irene, Pretoria), for being my co-promoters and giving me such good guidance throughout. Eileen Roodt (Department of Microbial, Biochemical and Food Biotechnology, University of the Free State), for teaching me so much about laboratory work, work ethic and life all together. You truly are a special person. Rita Myburgh, for all her friendship, support and guidance. Anmeri Rautenbach, for being a dear friend whenever needed. Ms Ilze Auld (Department of Microbial, Biochemical and Food Biotechnology, University of the Free State), for assisting with administrative tasks. Agricultural Research Council (ARC), Irene, for the help from their staff and the use of their laboratories for histo-chemical analysis in the Department of Food Science and Technology. The Meat Industry Trust (MIT), for financial support. The National Research Foundation (NRF), for financial support. GOD ALMIGHTY, for blessing me with such wonderful opportunities and people in life. And for giving me endless hope, love and support. i LIST OF TABLES NUMBER DESCRIPTION PAGE 2.2.1 South African Carcass Classification System for cattle and small stock 7 2.3.1 Factors that affect lamb quality 15 2.3.2 Effects of pre-slaughter handling on carcass and meat quality 25 3.1.1 List of products from the different production systems 43 3.2.1 Sensory evaluation attributes and descriptions 48 4.1 Differences in price between the products of the different production systems 50 4.2 Variation between protein and moisture contents of the products from the different production systems 54 4.3 Variation between dissectible fat content and intramuscular fat content of the products from the different production systems 57 4.4 Variation between IMF saturated fatty acid content of the products from different production systems 59 4.5 Variation between IMF saturated fatty acid content of the products from different production systems 61 4.6 Variation in CLA, total n-6 PUFA and total n-3 PUFA content over a range of products sampled across various retailers and butcheries 63 4.7 Variation between FA indexes of the products from three different production systems 64 4.8 Variation in PUFA content over a range of products sampled across various retailers and butcheries 65 4.9 Average lightness (L*), redness (a*), yellowness (b*), chroma and hue angle values of a range of products sampled across various retailers and butcheries 72 4.10 Variation between colour parameters of the products from three different production systems 74 4.11 Variation between cooking loss, evaporation loss, thawing loss and drip loss of the products from three ii different production systems 75 4.12 Difference in MFL and Shear Force between products with different packaging 78 4.13 Number (out of 14) of incidents where the WBSF measured above the Hopkins threshold and the mean WBSF 79 4.14 Variation between Price (ZAR), % meat, % fat, % bone, WBSF values, MFL’s, collagen content and collagen solubility of the products from three different production systems 83 4.15 Variation between TBARS values of the products from three different production systems 85 4.16 Variation between the sensory aroma profiles of the products from three different production systems 86 4.17 Variation between the sensory flavour profiles of the products from three different production systems 87 4.18 Variation between texture attributes (juiciness, first bite, residual mouthfeel) of the products from three different production systems 89 iii LIST OF FIGURES NUMBER DESCRIPTION PAGE 2.2.1 Structure of a muscle 9 2.2.2 A sarcomere 10 2.3.1 The process of obtaining ATP under aerobic conditions 30 2.4.1 Total sheep meat consumption in South Africa from 2012 to 2017 41 4.1 Variation in price over a range of products sampled across various retailers and butcheries 51 4.2 Variation in percentage meat (loin muscle only) over a range of products sampled across various retailers and butcheries 52 4.3 Variation in percentage fat over a range of products sampled across various retailers and butcheries 52 4.4 Variation in percentage bone over a range of products sampled across various retailers and butcheries 53 4.5 Variation in protein content over a range of products sampled across various retailers and butcheries 55 4.6 Variation in moisture content over a range of products sampled across various retailers and butcheries 55 4.7 Variation in IMF content over a range of products sampled across various retailers and butcheries 57 4.8 Variation in percentage phytanic acid over a range of products sampled across various retailers and butcheries 59 4.9 Variation in PUFA : SFA ratios over a range of products sampled across various retailers and butcheries 64 4.10 Variation in Atherogenicity index over a range of products sampled across various retailers and butcheries 67 4.11 Variation in Desaturase index over a range of products sampled across various retailers and butcheries 68 4.12 Principle component analysis bi-plot of the variation between fatty acid compositions of the products from three different production systems 69 4.13 Variation
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