Abstract
The present research reports two studies that were conducted on sheep and rat brains with the
aim of understanding the lipidomic of brains and the impact of processing on the lipidomic
profile of sheep brains and feeding on rat brains.
The sheep brains study investigated the fatty acids and phospholipid profile of commercial
New Zealand sheep brains. The total lipid was extracted using a novel lipid extraction method
using an ethanol-hexane mixture (ETHEX), and compared to the traditional Folch and Soxhlet
methods. The ETHEX method was found to be more efficient compared to Folch and soxhlet
methods. A comprehensive lipidomic profile (fatty acids and phospholipid composition) and
lipid fractionation (neutral lipid and polar lipid) composition of raw and cooked sheep brains
were analysed using gas chromatography with flame ionization detection (GC-FID) and
phosphorus-31 nuclear magnetic resonance (31P NMR). Raw sheep brains were found to have
a higher fatty acids composition than cooked sheep brains (Cooked at 80℃ for 2 hours). The
lipid fraction of sheep brains contained saturated fatty acids (SFA, 36.7% and 34.9% for raw
and cooked samples, respectively), monounsaturated fatty acids (33.1% and 29.3%, for raw
and cooked samples, respectively), and polyunsaturated fatty acids (PUFA, 21.9% and 19.0%
for raw and cooked samples, respectively). The n-6 fatty acids (raw 8.21% and cooked 7.13%)
and n-3 fatty acids (raw 13.7% and cooked 11.8%) in sheep brain samples. Raw sheep brains
have a considerable amount of phosphatidylethanolamine (PE) (33.1%), phosphatidylcholine
(PC) (30.8%), phosphatidylethanolamine plasmalogens (PEP) (12.7%) and phosphatidylserine
(PS) (12.4%), and cooked sheep brains have PE (30.7%), PC (31.6%), PEP (13.3%) and PS
(11.7%). Cooking reduced C14:0, C16:0, C17:0, C18:1, C20:4 and C22:6 compared to raw
samples (P < 0.05). This subsequently translated to significantly lower MUFA, PUFA, n-3, and
3
n-6 fatty acids (P < 0.05). Sheep brain could be a good source of phospholipids that could be
of interest commercially to the food and pharmaceutical industries.
The rat brain study investigated the effect of sheep milk or cow milk on the lipid composition
of the brain. The total lipid was also extracted using the ETHEX method, and analysed using
GC-FID and 31P NMR. A total of 20 fatty acids and 10 phospholipids were found in rat brain,
respectively. No significant (P > 0.05) differences among the treatment groups were observed
using analysis of variance (ANOVA). Some limitations of this study and some possible reasons
that resulted in no significant (P > 0.05) difference among groups were discussed in the present
thesis. The n-3 phospholipid level in the milk was too low to modulate the brain lipid
composition compared to fish oil that has a well-documented effect. In addition, the rats in this
research were fed for 28 days, which was probably not a long enough feeding period to show
a significant effect on the brain lipid composition. The brain samples were pooled into three
groups and four groups in study one and study two, respectively, due to the small brain size of
the rats. However, 3 pooled samples might be small, which resulted in a large standard
deviation resulting in masking the treatment effects.