Title page for ETD etd-01282008-151436


Document Type Doctoral Thesis
Author Van Heerden, Salomina Maria
Email ina@arc.agric.za
URN etd-01282008-151436
Document Title The quality of South African lamb - carcass, nutrient and sensory attributes
Degree PhD(Consumer Science)
Department Consumer Science
Supervisor
Advisor Name Title
Dr P E Strydom Co-Supervisor
Dr R R Kruger Co-Supervisor
Prof H C Schönfeldt Supervisor
Keywords
  • South African lamb
  • quality
  • carcass
  • slaughter groups
  • nutrient
  • wholesale cuts
  • meat
  • bones
  • subcutaneous fat
Date 2007-09-06
Availability unrestricted
Abstract

The aim of the study was to determine the quality of South African lamb, particularly the carcass, nutrient and sensory attributes. To this end the cut composition of SA lamb carcasses with different fat scores was determined and cuts suitable for trimming were identified. Sixty four grain fed Dorper lambs were divided randomly into three slaughter groups of 30, 36 and 42 kg, respectively. After slaughter, electrical stimulation (how much/long) and chilling (how long/temp) the carcass sides were subdivided into seven wholesale cuts. Each cut was dissected into meat, bone and subcutaneous fat (SCF) in order to determine the physical composition per cut and for the whole carcass. It was found that the percentages total fat in the carcass increased with 15.5 % in subcutaneous fat over the five fat classes.

In order to determine and compare the raw and cooked nutrient composition of shoulder, loin and leg cuts of Dorper and Merino lamb carcasses of the A age class of fat class 2 (± 7 % SCF) from three main production areas in South Africa were analysed. Samples were analysed both raw (left side cuts) and cooked (right sides) using accredited methodologies for nutrient content namely proximate composition, vitamin B and minerals. There was no significant difference in the iron and zinc values between the cooked cuts. Results showed differences in both trace elements and B vitamins among different cooked cuts, although the differences were not statistically significant. Cooked SA lamb (A age class, fat class 2) contains an average of 60.5 % less total fat and 5.28 % less protein, resulting in 1891 kJ less per 100 g edible portion energy, if compared to the previous values in the food composition tables.

Quantitative descriptive sensory analyses were performed by a trained panel on the M. longissimus lumborum (loin) from lambs of the same age. Aroma intensity, initial impression of juiciness, first bite, sustained impression of juiciness, muscle fibre and overall tenderness, amount of connective tissue (residue), overall flavour intensity and off-flavour intensity were measured, as well as cooking related measurements and resistance to shear. With the exception of juiciness, the results in this study showed that contrary to expected carcass fatness (in the same age over five fat classes), as portrayed in the South African Classification system, does not have a significant effect on the sensory qualities of M. longissimus lumborum (loin) from lambs of the same age.

This investigation provides important scientific insight into the physical, nutrient and sensory quality of South African lamb. The results obtained show that subcutaneous carcass fat that increased significantly with an increase in fat class can be trimmed to represent leaner cuts to the discerning consumer. This study found unique values for South African lamb cuts, almost 40 % lower in fat content than the previously-believed-to-be-accurate values, as published by the Medical Research Council for health workers. Contrary to expected it was found in this study that increased fatness did not improve lamb tenderness as popularly believed in the United States. Therefore, the study justifies greater scope for further research into all these aspects, as it provides valuable information for the Red Meat Industry.

© University of Pretoria

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  00front.pdf 122.09 Kb 00:00:33 00:00:17 00:00:15 00:00:07 < 00:00:01
  01chapter1.pdf 144.84 Kb 00:00:40 00:00:20 00:00:18 00:00:09 < 00:00:01
  02chapter2.pdf 228.91 Kb 00:01:03 00:00:32 00:00:28 00:00:14 00:00:01
  03chapter3.pdf 222.50 Kb 00:01:01 00:00:31 00:00:27 00:00:13 00:00:01
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