Enhancing Nutritional Value and Shelf Life of Meat

Question 1

What are lipids, roles and 2 structural compartments

Answer 1

= fats, oils and waxes
- major energy source (2.5x carb) 39mj/kg
- Component of animal cell membranes (lipid base, phospholipids)
- Participate in metabolic reactions (steroid hormones)
~ glycerol
~ fatty acids

Tables in folder

Question 2

Triglycerides and other forms of fats

Answer 2

• = simple gycerol attatched to 3 FA
• glycerol and FA connected via ester bonds
• Glycolipid – 2 FA and a carbohydrate
• Phospholipid – 2 fa and phosphate group
• Monoglyceride – one fa
• diglyceride

Question 3

Fatty acids (consist of and types)

Answer 3

consists of

• carboxyl group (COOH)
• Carbon chain (saturated or unsaturated)

Question 4

Saturated FA

• formula
• examples (inc stearic)

Answer 4

= CH3(CH2)n COOH		- n = 0 - 20
- products of rumen fermentation are short chain fatty acids (e.g. acetic acid n=0, propionic n=1)
- Stearic acid (lard)
~ CH3 (CH2)16 COOH
~ C18:0
~ main FA deposited in adipose tissue
- longer the carbon chain = higher melting point
- volatile when shot = low melting point

Question 5

Unsaturated FA

• formula
• examples (oleic acid)

Answer 5

= CH3 (CH2)x CH = CH (CH2)y COOH
- cant pack close together = double bonds kink = low melting point = chemically more reactive
- oleic acid = vegetable oil
~ CH3 (CH2)7 CH = CH (CH2)7 COOH
~ 18 carbons like steric acid (saturated)

Question 6

Nomenculture FA

Answer 6

• Carbon atoms numbered from ether COOH end (Δ delta) or CH3 (n omega) end of the molecule
• Position of first double bond (e.g. n-3 or n-6) different groups with different physiological characteristics
• Cis and trans double bond refers arrangement of H atoms around the double bonds
  ~ cis = h on same side
  ~ trans = h on different sides

Question 7

Fat composition

Answer 7

• Physical and chemical characteristics of fat depend on fatty acids it contains.
• Vegetable and fish oils (contain chains of 20-26 c in FA chains) liquid at room temperature.
  ~ Long chain unsaturated fatty acids
• Animal fat (lard, butter) solid at room temperature.
  ~ Shorter chain saturated fatty acids

Question 8

Cardiovascular disease

• which FA help/worsen
• recomended changes in diet

Answer 8

• major killer in western world
• Coronary heart disease Associated with high intake of saturated fatty acids (SFA) and low intake of polyunsaturated fatty acids (PUFA)
• SFA = Increase risk of CHD
• PUFA = n-3 PUFA Reduce risk of CHD (C20:5 & C22:6)
• To reduce the risk of CHD the Department of Health (1994) recommend changes to diet
  ~ Reduce intake of SFA (< 10% energy intake)
  ~ Maintain intake of n-6 PUFA
  ~ Increase intake of n-3 PUFA (0.2 g/day)

Question 9

Cardiovascular disease

• recomended nutritional indicies in overall diet
• ruminant meet fat content
• factors that influence fat content

Answer 9

• Total fat = < 35 % total energy intake
• P:S ratio = > 0.45
• n-6:n-3 ratio = < 4:1 (at least 25% n3)
• Subcutaneous fat = SFA - Highly variable content
  ~ tend to store adipose tissue as subcut fat
  ~ consumer/butcher can control how much consume
• Intramuscular fat = SFA - 10 – 300 g/kg (typically 50 g/kg)
  ~ marbling flavour/texture
  ~ depends on breed and production system (longer growth period = more marbling)
• Phospholipids = PUFA - 5 – 10 g/kg
• live wt, breed/type, sex, rate of gain

Question 10

Cardiovascular disease

- nutritional indicies for ruminant meat

Answer 10

• Total fat = High and variable
• P:S ratio = < 0.2 (very saturated)
• n-6:n-3 ratio =
  ~ 2:1 (grass fed) beneficial
  ~ 6:1 (concentrate fed)

Question 11

Grass vs concentrates

Answer 11

• Grass finishing enhances the n-3 fatty acid content and reduces n-6:n-3 ratio, but limited effect on P:S ratio (C18:0 increased !).
• Changes reflect fatty acid content of grass and concentrates (oil seeds), but not as great as you might expect.
• Starch based concentrates may result in increased odd and branched chain fatty acids (BCFA). Lower melting point. Sof fat rejected by butchers
• BCFA derived from metabolism of propionic acid (C3) and incorporation of methylmalonyl-Co A in fatty acid synthesis

Question 12

Oilseeds and fish oil

- impact on

Answer 12

(table in folder)

• Fish oil reduced DMI and LWG
• Linseed increased C18:3 (2 x) in muscle and adipose tissue.
• Fish oil increased C20:5 and C22:6 content of muscle and adipose tissue.
• Mixed diet intermediate between linseed and fish oil.
• Feeding linseed or fish oil reduced n-6:n-3 ratio but had little effect on P:S ratio (as with grass feeding).

Question 13

Rumen biohydrogenation

Answer 13

in folder

Question 14

Rumen protection

Answer 14

• Duodenal Supply of n-3 PUFA could be increased by protection from rumen biohydrogenation
• Protection methods:
  ~ Calcium soaps = Inert, high proportion in animal before effect
  ~ Formaldehyde treatment of whole seeds = Protect seed from rumen so UFA reach animal. Formaldehyde banned as its carcinogenic
  ~ Encapsulation = Protect Oil souce with casine
  ~ Poly-phenol oxidase (PPO) = Compound found in clovers, causes browning, protects fa
• protected oilseeds and fish oil study in folder

Question 15

Flavour and shelf life

Answer 15

• Fatty acids composition influences both the flavour and shelf life of meat.
• Perception and favourable taste depends on tradition and previous experience. UK prefer intense flavour
• Grain finished less intense flavour than grass finished.
• Longer chain C20:5 and C22:6 associated with fishy and abnormal flavour.

Question 16

Effect of diet on oxidative stability of sheep muscle

Answer 16

• Indicator of oxidative stability = algae go off more quickly
• Low level vit e when tbars high = prevent oxidation
• vit e supplementation (500 and 1000 mg/d) helps oxidative stability by prolonging lamb meat shelf life compared to controls