Edward Webb Animal fat paradox.pdf - ICoMST Contact Point

The animal fat paradox and
meat quality
E.C. Webb & H.A. O’Neill
Dept. Animal and Wildlife Sciences
University of Pretoria
Email: edward.webb@up.ac.za
ICoMST2008, Cape Town

Introduction – Modern meat
consumer
• Taste and nutritional value → important
quality attributes of meat
• Fat in meat contributes to eating quality
of meat
• Tendency to focus on production of
edible lean with minimum visible fat
• Amount and type of fat in meat
influence tenderness and flavour

Consumer demand for lean meat will
determine largely how cattle are fed in
the 21 st century (Spears, 1996)

Modern meat consumer
• Dietary fat hypothesized to increase risk of
colorectal cancer
• Association between animal fats and
cardiovascular disease
• n-3 Fatty acids → cardioprotective and
antiarrhythmetic effects on heart, ↓LDL etc
• Recommendations range from excluding fats
altogether, to a moderate consumption of
fats

Animal fats
• Axungia = axis ‘axle’ + ungere ‘to greece’ or
“axle greece” – (refers to soft perirenal fat in
geese or pigs)
• Blubber – lipid rich vascularised fat (Mucktuk,
Eskimo meal)
• Lard – pig fat, used as cooking fat or spread
(best quality around kidneys) - ‘Schmaltz’
• Tallow – bovine fat (hard), ‘Suet’= ‘loin or
kidney fat from bovine or ovine’
• Salo – “slanina” (Central & East Europe)

Table 1. Lipid content of meat from domesticated
animals (modified from Sinclair & O'Dea, 1990)
Meat
Beef
Lipid content in
meat (g/100 g
wet weight)
2.5
Total lipid
P:S *
0.22
Sheep
3.1
0.26
Goat
2.3
0.36
Pig
1.4
0.75
*
Ratio of polyunsaturated to saturated fatty acids.

Fatty acid composition (w/w%) of subcutaneous adipose tissue and muscle of
loin steaks/chops in pigs, sheep and cattle (Enser et al., 1996)
Adipose Tissue
Muscle
Pigs Sheep Cattle Pig Sheep Cattle
C14:0 1.6 a 4.1 b 3.7 b 1.3 a 3.3 c 2.7 b
C16:0 23.9 b 21. a 9 26.1 c 23.2 b 22.2 a 25.0 c
C16:1cis 2.4 a 2.4 a 6.2 b 2.7 b 2.2 a 4.5 c
C18:0 12.8 a 22.6 b 12.2 a 12.2 a 18.1 c 13.4 b
C18:1cis-9 35.8 b 28.7 a 35.3 b 32.8 a 32.5 a 36.1 b
C18:2n-6 14.3 b 1.3 a 1.1 a 14.2 b 2.7 a 2.4 a
C18:3n-3 1.4 c 1.0 b 0.5 a 0.95 b 1.37 c 0.70 a
C20:4n-6 0.2 ND ND 2.21 b 0.64 a 0.63 a
C20:5n-3 ND ND ND 0.31 b 0.45 c 0.28 a
n-6:n-3 7.6 1.4 2.3 7.2 1.3 2.1
P:S 0.61 0.09 0.05 0.58 0.15 0.11
TOTAL 65.3 70.6 70.0 2.2 4.9 3.8

Blubber /
Mucktuk
Lard
Lard
Lard spread
Suet

Adipocyte
Cytoplasm
Lipid droplet
Adipocytes in young animals have a
relatively large cytoplasm that
shrinks and is replaced by lipid over
time
Cell membrane (mostly phospholipids in the
structural lipid fraction)
Lipid droplet increases in size in older animals
and replaces cytoplasm (mostly TG synthesis and deposition)
The structural lipid fraction is characterised by a relatively high PUFA :
SFA ratio compared to animal fat that consists mainly of
triacylglyceroles. It follows that the proportion of PUFA will decrease
as the carcass fat content increases (Webb et al., 1998)

Figure 1. General relationship between the total fat
content in meat and the relative proportion of
structural and depot fats (modified from Sinclair and O'Dea, 1990)
Increasing meat fat content
Depot fat
Structural fat
Game meat
& fish
Lean
domestic
meats
Fatty meats

Fatty acids (nomenclature - IUPAC)
• Saturated, monounsaturated and
polyunsaturated fatty acids
• Dietary essential fatty acids (n-3 and n-6 fatty
acids: linolenic acid (C18:3n-3), linoleic acid
(C18:2n-6), arachidonic acid (C20:4n-6),
eicosapentaenoic acid (C20:5n-3, EPA), and
C22:6n-3 (docosahexaenoic acid) )
• Non-essential fatty acids – (synthesized from
acetyl CoA )
• Conjugated linoleic acid (CLA)

Factors that influence fat and fatty
acid composition of meat
• Species differences
• Feeding system
• Anatomical location and fat deposition
• Castration
• Genetic differences
• Manipulating the diet and feedstuffs
• Growth promoters

Dietary manipulation of animal fat
• Fairly simple in monogastric animals
• More complex in ruminants
• Fat content depends more on the
degree of maturity of the animal and the
residence period in the feedlot
• Diet affects mainly the profile of fatty
acids deposited, rather than the
amounts deposited

CONSTITUENT
Fat
Fat content
Fat colour
Fatty acid profile
n3/n6 fatty acid ratio
Conjugated linoliec acid
(CLA)
EXTENT OF THE EFFECT
(Ruminants)
Large effect
Large effect
Small, but significant effect
Small, but significant effect
Small, but significant effect
Vitamins
Fat soluble vitamins
Water soluble vitamins
Large effect
Negligible effect
Sensory characteristics
Aroma
Flavour
Small, but generally significant effect
Small, but generally significant effect

Manipulation of meat fat
• ↓Total carcass and meat fat content,
• ↓ [SFA] in meats,
• ↑ [PUFA] in meats,
• ↓ n-6/n-3 LCFA of meat fat,
• Δ cis / trans fatty acid ratio of meat fat,
• ↑ [CLA] of meat fat.

Effect of dietary factors on fat quality
• The kind and nature of the cereals
• The mode of presentation of the cereals
• The kind and presentation of roughage
The extent of these effects depend on
the production system, species, breed,
live mass, gender, season and growth
modifiers

Manipulating n-3 FA’s
• ↑ Pasture fed cattle
• N-3 ↑ 1%:
•fish oil (ca. 0,5-2%)
•fish meal (ca. 150-200 g/DM/d)
•Veg. Oils:
•rapeseed oil (7% C18:3n3),
•canola oil (11% C18:3n3),
•soybean oil (7% C18:3n3)
•wheat germ oil (7% C18:3n3)

Eicosapentaenoic acid (EPA),
Docosahexaenoic acid (DHA)
• Protected dietary oils
• Mixture of soya oil and linseed oil (2:1
ratio)
• Ruminants are sensitive to unprotected
PUFA’s
• Increase the n-6/n-3 ratio

Manipulating CLA’s
• CLA occurs naturally in meat
• ↑ pasture / forage based diets
• dietary supplementation with safflower
seed (CLA 4000⇒8000ppm; 37 % oil
with 79% linoleic acid)
• Commercial CLA supplements

• Aggravated by:
Lipid oxidation
– quest for leaner beef,
– PUFA’s
– n-3 FA’s
– CLA’s
• Vit. E, selenium, Vit. A, particulary in
concentrate fed cattle
• BHT, BHA, ethoxyquin

From Roche brochure on Vitamin E

Fat pigments
Pigments due to
lutein and
zeaxanthin isomers
in feed / grazing
Yellow fat colour perceived as indicative of
old age, disease or dairy-type carcasses
“unacceptable” pigments may contributed to
the typical aroma

Fat composition and sensory
characteristics
• Fats affect palatability either directly as
short-chain volatiles or through the
oxidation, decarboxylation or
dehydration of long-chain fatty acids, or
their physical attributes, e.g. melting
point or texture

Fat composition and sensory
characteristics
• Oxidative rancidity
• 4-methyl- and 4-ethyloctanoic acids
contribute to species-related flavours
• Neg. corr. between SFA in SCF and IMF with
the flavour of meat (beef)
• Oleic acid improved, while both stearic and
palmitic acid reduced the flavour of beef and
lamb
• Fatty acids of the trans-configuration – no
significant effect

Sensory properties of fat in meat
The
and
of producers,
retailers and
consumers
regarding meat
quality differ
(Webb, 2003)

Shift in perceptions ?
Consumers’ perceptions of
meat quality, has changed
considerably over the past
two decades

• Consumers infer some attributes from others
i.e. marbling and tenderness
• Consumers link intrinsic and extrinsic
attributes with physical and psychological
consequences of consumption
Lean meat
Less calories consumed /
slimming
Attainment of life values i.e.
self confidence and
social acceptance!

Animal fat paradox?
Conflict between reducing carcass
fat and SFA content to comply with
the requirements for a more healthy
product, whilst providing a tasty
product and acceptable eating
experience

Conclusions
• Meat fat contributes to meat quality
• Fatty acids are essential in the diet
• Consumers’ perceptions of meat fat
differ
• Can manipulate meat fats
• EFA’s, PUFA’s, n-6/n-3 ratio, CLA’s and
cholesterol
• The meat fat paradox is real!