Enhancing Nutritional Value and Shelf Life of Meat

= 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

• = 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

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

= 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

= 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)

• 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

• 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

• 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)

• 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

• 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)

• 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

(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).

in folder

• 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

• 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.

• 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