Thesis (MSc Food Sc)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: The aim of this study was to determine the proximate composition of five individual body sites of
the Mustelus mustelus shark in order to evaluate the cross carcass variation of the individual
proximate components (moisture, protein, lipid, ash) of the meat. This variation was determined in
order to find a representative sample of the edible part of the shark (fillet and body flap). Secondly,
this sample representing the entire shark fillet was used to investigate the endogenous factors
(gender, size and life cycle stage) and their effects on the individual proximate components and
other meat components (amino acids, fatty acids, minerals, histamine and mercury contents).
Finally, all this data was combined to describe the average chemical composition and nutritional
value of M. mustelus meat.
None of the proximate components showed any variation between the different fillet
positions. This indicated that the fillet is homogenous and samples for chemical analyses can be
taken anywhere on the fillet as representative of the entire fillet.
It was found that all three main effects (gender, size and life cycle stage) did not have major
influences on most of the components of the chemical composition of M. mustelus meat analysed.
Higher fatty acid levels (SFA, MUFA and PUFA) were observed in large females than in large
males as well as in non-pregnant large females compared to pregnant large females. According to
statistical analysis, large males had higher total mercury levels than large females. The only
component affected by size variation was the fatty acids, showing a trend to decrease in quantity
before maturity was reached. Variation due to life cycle stages was mostly evident in the fatty acid
component with some small effects on two mineral components, aluminium and copper, which had
slightly higher levels in pregnant large females than in non-pregnant large females.
M. mustelus meat has an average proximate composition of 75% moisture, 23% protein,
1.6% lipids and 1.4% ash (weight per wet weight). The protein is, however, an over-estimation of
the true protein value as the meat contains significant amounts of non-protein nitrogen (NPN) in
the form of urea which contributes to the N concentration. M. mustelus meat is a good source of
some essential amino acids, especially lysine and threonine (78% of the daily requirements for an
adult in a 100g portion), but low in minerals. The meat has a healthy lipid content with a good ratio
(>0.45) of PUFA:SFA (0.83) as well as a healthy (<4) n-6:n-3 fatty acid ratio of 0.39. The histamine
content was very low or not detectable but some samples contained total mercury values above
the maximum safe limit.
Although further research is needed for some meat components, these results are a
valuable contribution to the new South African Food Composition Tables being compiled. / AFRIKAANSE OPSOMMING: Die doel van hierdie studie was om die proksimale samestelling van die vleis vanaf vyf afsonderlike
posisies op die liggaam van die Mustelus mustelus haai te bepaal. Sodoende is die variasie, met
betrekking tot die verskillende proksimale komponente (vog, proteïen, lipiede en as), in terme van
die totale karkas, bepaal. Die proksimale variasie is bepaal om vas te stel hoe ʼn
verteenwoordigende monster van die totale karkas geneem kan word. Gevolglik is hierdie
verteenwoordigende monster gebruik om die effek van geslag, grootte en die verskillende fases
van die lewens-siklus op die afsonderlike proksimale komponente asook ander vleis komponente
(aminosure, vetsure, minerale, histamien en kwik inhoud) te ondersoek. Laastens is al hierdie
inligting gebruik om die algemene samestelling en voedingswaarde van M. mustelus vleis te
bespreek.
Geen van die proksimale komponente het enige variasie getoon tussen afsonderlike
liggaamsposisies nie. Hierdie resultaat dui daarop dat die vleis van ʼn M. mustelus haai homogeen
is regoor die karkas en dat ʼn vleis monster vanaf enige posisie op die karkas geneem kan word as
ʼn verteenwoordigende monster.
Daar is gevind dat geslag, grootte en fase van die lewens-siklus geen merkwaardige
invloed het op die vleis se samestelling nie. Hoër vetsuur konsentrasies (versadigde, monoonversadigde
en poli-onversadigde vetsure) is gevind in groot vroulike haaie en nie-dragtige
vroulike haaie as in groot manlike haaie en dragtige vroulike haaie onderskeidelik. Statisties, het
groot manlike haaie hoër vlakke van totale kwik as groot vroulike haaie. Die enigste vleis
komponent wat beïnvloed is deur die grootte van die haai, is die vetsure, wat verminder het voor
volwassenheid bereik is en dan weer vermeerder soos die haai groter word. Variasie as gevolg
van die verskillende fases van die lewens-siklus is meestal gevind in die vetsuursamestelling, en
die minimale het ook gevarieer ten opsigte van die elemente aluminium en boor wat effense hoër
vlakke getoon het in dragtige haaie as in nie-dragtige haaie.
M. mustelus vleis het ʼn gemiddelde proksimale samestelling van 75% vog, 23% proteïen,
1.6% lipiede en 1.4% as (nat massa). Die proteïen waarde is ʼn oorskatting van die ware proteïen
waarde as gevolg van hoë nie-proteïen stikstof in die vorm van ureum wat bydra tot die totale
stikstof inhoud. M. mustelus vleis blyk ʼn goeie bron van sommige essensiële aminosure soos lisien
en treonien (78% van die daaglikse aanbevole dosis), maar laag in mineraal inhoud. Die vleis het ʼn
gesonde vet inhoud met ʼn goeie (>0.045) poli-onversadigde:versadigde vetsuur verhouding (0.83)
asook ʼn gesonde (<4) omega 6 tot omega 3 vetsuur verhouding van 0.39. Die histamien inhoud
van die vleis was baie laag of onder die meetbare limiet, maar sekere monsters het ʼn totale kwik
inhoud getoon wat bo die maksimum veilige limiet is.
Hoewel verdere navorsing ten opsigte van sekere van die vleis komponente vereis word,
lewer hierdie resultate ʼn waardevolle bydrae tot die nuwe Suid-Afrikaanse voedsel samestellings
tabelle wat tans opgestel word.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/20261 |
| Date | 03 1900 |
| Creators | Bosch, Adina Cornelia |
| Contributors | Hoffman, Louw, Sigge, Gunnar, Kerwath, Sven, Stellenbosch University. Faculty of AgriSciences. Dept. of Food Science. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | Unknown |
| Type | Thesis |
| Format | 87 p. : ill. |
| Rights | Stellenbosch University |
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