Edward Webb Animal fat paradox.pdf - ICoMST Contact Point

Edward Webb Animal fat paradox.pdf - ICoMST Contact Point

Edward Webb Animal fat paradox.pdf - ICoMST Contact Point


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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


• 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


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)



Lipid content in

meat (g/100 g

wet weight)


Total lipid

P:S *












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


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 /




Lard spread




Lipid droplet

Adipocytes in young animals have a

relatively large cytoplasm that

shrinks and is replaced by lipid over


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




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



Fat content

Fat colour

Fatty acid profile

n3/n6 fatty acid ratio

Conjugated linoliec acid




Large effect

Large effect

Small, but significant effect

Small, but significant effect

Small, but significant effect


Fat soluble vitamins

Water soluble vitamins

Large effect

Negligible effect

Sensory characteristics



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


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


• Ruminants are sensitive to unprotected


• 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


• 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


• 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


• Fatty acids of the trans-configuration – no

significant effect

Sensory properties of fat in meat



of producers,

retailers and


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 /


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



• Meat fat contributes to meat quality

• Fatty acids are essential in the diet

• Consumers’ perceptions of meat fat


• Can manipulate meat fats

• EFA’s, PUFA’s, n-6/n-3 ratio, CLA’s and


• The meat fat paradox is real!

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