Thesis (MPhil (Animal Sciences))--University of Stellenbosch, 2011. / Includes bibliography. / ENGLISH ABSTRACT: The proximate composition of food products, and more importantly fat content and fatty acid
composition, is of growing concern to consumers. It is also of concern to fish processors
because of the effects that various levels of proteins, lipids, water and ash have on the cold
storage potential and texture of fish. A total of 17 Seriola lalandi (yellowtail) were harvested
from a net cage production unit off the coast of Port Elizabeth. Proximate, fatty acid and
mineral analysis were conducted on five areas on the fillet, as well as on the whole fillet as a
control. Differences (P < 0.05) were found in the water and fat content between dorsal and
ventral samples. The highest amount (% wet weight) of moisture (71.5 ± 0.4%) was observed
in the caudal region of the fish. This region was also found to contain the lowest levels of fat
(4.3 ± 0.23%). Protein levels did not differ (P > 0.05) between sample regions. The total fat
content (g/100 g wet tissue) of the whole fillet (A; control) was 5.3 ± 0.11 of which saturated
fatty acids (SFA) accounted for 35.5 ± 1.13%, monounsaturated fatty acids (MUFA) for 25.7
± 0.51% and polyunsaturated fatty acids (PUFA) for 38.2±0.88%. The most predominant
saturated fatty acid was palmitic acid (hexadecanoic acid, C16:0) with levels reaching 24.2 ±
1.25% in the mid belly area, sample section E (mid ventral). The data shows that one could
use either section B (anterior dorsal), section D (mid dorsal) or section F (dorsal and ventral
posterior sections combined) as a representative sample of the whole fillet when doing
proximate analysis. The belly sections of the fish differed significantly (P < 0.05) to the
whole fillet. There was too much variation between samples with regards to the mineral and
fatty acid analysis to identify a section that is representative of the whole fillet. The edible
portion of the farmed yellowtail examined in this study contained eicosapentonic acid (EPA)
and docosahexaenoic acid (DHA) levels of 0.24% and 10.90% respectively which is notably
lower than other marine fish species. However, this could be linked to the feed that these
specific yellowtail were fed, as the lipid profile of the diet has been shown to have an effect
on the lipid profile of the fish. / AFRIKAANSE OPSOMMING: Die algemene samestelling van voedsel produkte, asook die vet inhoud en vetsuur
samestelling daarvan, wek deesdae al meer besorgdheid by verbruikers. Dit is ook belangrik
vir vis verwerkers as gevolg van die effek wat verskillende vlakke van proteïene, lipiede,
water en minerale het op die tekstuur van vis asook die potensiaal om vis in verkoelers te
stoor. ‘n Totaal van 17 Seriola lalandi (geelstert) is geöes vanuit ‘n net-hok eenheid op die
kus van Port Elizabeth. Proksimale, vetsuur en mineraal analises was uitgevoer op vyf areas
van die filet sowel as op die heel filet as ‘n kontrole. Verskille (P < 0.05) is opgemerk in die
water en vet inhoud tussen die dorsale en ventrale monsters. Die hoogste voginhoud (71.5 ±
0.4%) was opgemerk in die stert gedeelte van die vis en hierdie gedeelte het ook die laagste
vetinhoud gehad (4.3 ± 0.23%). Proteïen vlakke het nie verskil tussen enige van die monsters
nie (P < 0.05). Die totale vetinhoud (g/100 g nat weefsel) van die heel filet (A, kontrole) was
5.3 ± 0.11 waarvan versadigde vetsure (SFA) 35.5 ± 1.13%, monoönversadigde vetsure
(MUFA) 25.7 ± 0.51%, en polionversadigde vetsure (PUFA) 38.2 ± 0.88% uitgemaak het.
Die oorheersende versadigde vetsuur was palmitiese suur (heksadekanoïese suur, C16:0) wat
vlakke van 24.2 ± 1.25% bereik het in seksie E (middel ventraal). Die data wys dat seksie B
(voorste dorsaal), seksie D (middel dorsaal) of seksie F (agterste ventraal en dorsaal) gebruik
kan word as verteenwoordigende monsters van die heel filet wanneer proksimale analise
uitgevoer word. Die maag gedeeltes van die vis het beduidend verskil (P < 0.05) van die heel
filet. Die resultate van die mineraal en vetsuur analises het te veel gevarieer en daarom kon
geen verteenwoordigende seksie van die heel filet geïdentifiseer word nie. Die eetbare dele
van akwakultuur geelstert wat in hierdie studie ondersoek is, bevat 0.24% EPA en 10.90%
DHA wat heelwat laer is as die van ander marine vis spesies. Hierdie verskil kan moontlik
toegeskryf word aan die voer wat aan die geelstert gegee is aangesien dit voorheen bewys is
dat die lipied profiel van die dieet ‘n uitwerking het op die lipied profiel van vis.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/6614 |
| Date | 03 1900 |
| Creators | Burke, Andrew Brian |
| Contributors | Hoffman, Louw, University of Stellenbosch. Faculty of AgriSciences. Dept. of Animal Sciences. |
| Publisher | Stellenbosch : University of Stellenbosch |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | 35 p. : ill. |
| Rights | University of Stellenbosch |
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