Thesis (MSc Food Sc (Food Science))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: The aim of this study was to investigate the impact of an extensive (free-range) and intensive
(feedlot) production system on the consumer’s intrinsic preference cues (physical attributes,
chemical composition, fatty acid profile, aroma, flavour, initial juiciness, sustained juiciness, first
bite, residue, instrumental tenderness) for three muscles (Biceps femoris, Longissimus dorsi,
Semimembranosus) of Dohne Merino lambs (8 months). Secondly to investigate the effect of
natural exercise (grazing, extensive production systems) or restrictive movement (intensive
production systems), on the muscle fiber type composition of the same lamb muscles and the
subsequent effect on the meat quality characteristics.
Intensively raised lambs produced carcasses with a significantly higher dressing
percentage, thicker subcutaneous fat layer (13th rib and 3rd/4th lumbar vertebra) and a greater fat
ratio (carcass composition). Meat of intensively raised lambs had a higher (p < 0.050) Homo-glinolenic
(C20:3n6), Eicosapentaenoic (C20:5n3), Docosapentaenoic acid (C22:5n3) content and
n3:n6 ratio. Extensively reared lambs had a higher (p < 0.050) slaughter weight, cold carcass
weight and the meat of these lambs had a higher myoglobin content.
Results of this study indicate that intensively reared lambs produced meat with more
favourable sensory characteristics compared to the extensive production system as well as a
significant increase in sensory tenderness for Biceps femoris muscle. Overall the Biceps femoris
muscle was the muscle that was primarily affected by the treatment (production systems). The
Biceps femoris from intensively raised lambs contained significantly more intramuscular fat and
type IIB muscle fibers whereas the Bicpes femoris of the lambs from the extensive production
system contained more (p < 0.050) insoluble collagen and type I muscle fibers.
During texture profile analysis (instrumental tenderness test) the Longissimus dorsi and
Semimembranosus of extensively raised lambs required a higher (p < 0.050) compression force
during the first cycle of compression, indicating that these muscles are tougher.
The results of this study provided valuable insight into the impact of production systems on
lamb meat quality and that the application of intensive production systems will increase the
sensory characteristics of the selected muscles from Dohne Merino lambs, especially the
tenderness of the Biceps femoris, which has a high retail value. On the other hand health
conscious consumers will prefer extensively produced meat due to the favourable n3:n6 ratio,
intramuscular fat content and the presences of less visible fat (subcutaneous). / AFRIKAANSE OPSOMMING: Hierdie studie was tweedoelig en is uitgevoer op die Biceps femoris, Longissimus dorsi en
Semimembranosus spiere van Dohne Merino lammers (8 maande oud). Die eerste doel van die
studie was om te bepaal wat die effek van ‘n ekstensiewe (weiding) en intensiewe produksie
sisteem sal wees op vleis verbruikers se algemene kwaliteit voorkeure (fisiese eienskappe,
chemiese samestelling, vetsuur profile, aroma, smaak, sappigheid, taaiheid,). Tweedens om te
bepaal tot watse mate natuurlike oefening, verkry deur weiding asook beperkte beweging as
gevolg van voerkraal omstandighede, die spier vesel tipe samestelling sal verander en die direkte
impak van die samestelling op kwaliteit eienskappe van vleis.
Lammers van die intensiewe produksie sisteem het ‘n betekenisvolle verhoging in
uitslagpersentasie, onderhuidse vet dikte (13de rib en 3de/4de lende werwel) en vet ratio (karkas
samestelling) getoon. Die vleis van die lammers het meer (p < 0.050) C20:3n6, C20:5n3 en
C22:5n3 vetsure bevat asook ‘n hoër n3:n6 ratio gehad. Lammers van die ekstensiewe produksie
sisteem het ‘n betekenisvolle hoër slag en koue karkas gewig gehad. Die vleis van die lammers het
meer (p < 0.050) mioglobien bevat as intensiewe lammers.
Resultate van die studie dui aan dat die vleis van lammer van die intensiewe produksie
sisteem meer gunstige sensories karakteristiek produseer in vergelyking met lammers van die
ekstensiewe produksie sisteem, asook ‘n betekenisvolle verhoging in sensoriese sagtheid van die
Biceps femoris spier. Die Biceps femoris was die spier in die studie wat die meeste geaffekteer
was deur die behandeling (produksie sisteme). Die Biceps femoris spier van intensiewe lammers
het meer intramuskulêre vet en tipe IIB spier vesels bevat teenoor die Biceps femoris van
ekstensiewe lammers wat meer onoplosbare kollageen en tipe I spier vesels bevat het.
Gedurende die tekstuur profiel analise (instrumentele sagtheid toets) het die Longissimus
dorsi en Semimembranosus van ekstensiewe lammers a hoër kompressie krag vereis, wat aandui
dat die spiere taaier is as die ooreenstemmende spiere van intensiewe lammers.
Die resultate van die studie voorsien ons met waardevolle insig in die inpak van verskeie
produksie sisteme op die kwaliteit van lams vleis. Die afleiding kan gemaak word dat die
implementering van intensiewe produksie sisteem die sensoriese kwaliteit van die spiere van
Dohne Merino lammers verbeter, veral die sagtheid van die Biceps femoris spier, wat ‘n hoë
kommersiële waarde het. Laastens, gesondheidsbewus verbruikers sal verkies om vleis te koop
van ekstensiewe lammers weens die gunstige n3:n6 ratio, spier vetinhoud en die minder sigbare
vet (onderhuidse vet) op die vleis.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/5385 |
| Date | 12 1900 |
| Creators | Hanekom, Yvette |
| Contributors | Hoffman, L. C., Muller, M., Cloete, J. J. E., University of Stellenbosch. Faculty of Agrisciences. Dept. of Food Science. |
| Publisher | Stellenbosch : University of Stellenbosch |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | Unknown |
| Type | Thesis |
| Format | 144 p. |
| Rights | University of Stellenbosch |
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