Effects of dietary n-3 polyunsaturated fatty acids and ... - FINS

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1 st WorkshopXIII International Feed Technology SymposiumTrans isomers of 18:1:Analysis of the different isomers of trans 18:1 (from beef total trans 18:1 purified bypreparative HPLC) by gas-liquid chromatography-mass spectrometry (GLC-MS) clearlyshowed that with a basal diet rich in cereals, lipid supplements can diversely modifiedthe health value of beef trans 18:1 on the basis of the Δ9tr and Δ10tr (detrimental) andΔ11tr 18:1 (beneficial) (Table 3). They had a positive effect when 18:3n-3 was mainlyprovided (diet L) or a rather negative effect when 18:3n-3 was associated to 18:1n-9(diet RL) (Bispo et al., 2009).Table 3. Effects of lipid supplements (L= linseed; R = rapeseed) on the distribution oftrans 18:1 (in % total trans 18:1, mean ± SD) in lipids of bovine LT muscledetermined by GLC-MS (*, P< 0.05) (from Bispo et al., 2009).Trans18:1Diet CDiet LDiet RL6tr 7tr 8tr 9tr 10tr 11tr 12tr 13tr 14tr 15tr 16tr1.3±0.90.6±0.50.5±0.40.5±0.10.4±0.10.6±0.11.9±0.31.6±0.42.3±0.68.5±1.55.0*±0.86.4*±0.933.7±18.615.6*±6.741.1±16.436.1±14.433.2±11.825.0*±12.44.3±1.26.1*±0.34.9±9.23.4±1.08.7*±0.85.8±1.84.0±1.39.1*±0.95.5±1.63.4±1.810.9*±9.05.0±1.82.9±1.98.9*±2.73.1±1.1EFFECTS OF DIETARY AND PHYSIOLOGICAL FACTORS ONPLASMA AND BEEF LIPOPEROXIDATIONBeef having improved nutritional qualities (higher content of n-3 PUFA associated to abetter protection of PUFA by antioxidants) by breeding factors are marketed with a highadded value such as the French Label Rouge procedure. In this context, it is necessary toprecise the impact of specific meat technological treatments to preserve their qualitiesuntil the sale of products. Indeed, technological treatments as storage and processingmay favour peroxidation processes and lipolysis which entail negative consequences onnutritional and sensorial qualities (Min and Ahn, 2005). In this context, PUFA ofphospholipids are the primary substrates of lipid oxidation in muscle foods whereastriacylglycerols would play a minor role. Incorporation of PUFA (from seeds or freshgrass) into bovine muscle lipids did not activate muscle antioxidant enzymes, theprotection against the peroxidation process being strictly dependent on the amount ofdietary antioxidant molecules stored in muscle cells (Durand et al., 2005).The effects of technological treatments on beef lipoperoxidation stability were studiedon PUFA rich beef varying in their antioxidant content (from cows given the L, LE orRLEP diet). The impact of beef ageing and packaging treatments were more especiallyanalyzed.5
1 st WorkshopXIII International Feed Technology SymposiumExperimental aspectsAnimals and dietsThe study was performed with the animals given the same diets (concentrate/straw baseddiet, lipid and antioxidant supplements) and stress breeding conditions than for theanalysis of beef lipids and fatty acids (cf. Part I Effects of n-3 PUFA and antioxidants onbeef FA). Intensity of the animal stress was evaluated by plasma cortisol determined i) atthe end of the finishing period, ii) just after slaughter during the bleeding.Beef technological treatmentsLT and ST muscles were collected just after slaughter, stored under vacuum for 12 d at4°C and finally cut as steaks as on the market and packaged at +4°C in a trayoverwrapped with a film either i) under air for 4 d. (A), ii) under modified atmosphere(70:30, O 2 /CO 2 ) for 7 d. (MA), or in a bag iii) under vacuum for 14 d. (V). Beef sampleswere immediately ground into a powder in liquid N 2 and stored at -80°C until analysis.Methods for lipoperoxidation characterizationThe intensity of lipoperoxidation in plasma (jugular vein) and in beef samples atslaughter was determined by the measurement of malondialdehyde (MDA) production(after its extraction by hexane) by HPLC (fluorescence detection) using atetraethoxipropane calibration curve. Plasma and tissue vitamin E was determined byHPLC (UV detection).The in vitro susceptibility of plasma to lipoperoxidation was evaluated by measuring thekinetic production of conjugated dienes (CD) indicating the degree of resistance tolipoperoxidation (Lag phase), the lipoperoxidation velocity (Tx max) et the maximalamount of produced CD (Q max). The Peroxidizability Index (PI) of beef FA wascalculated from the FA composition of total meat lipids according to the equationreported by Hu et al. (1989) as follows: IP = (% dienoic x1) + (% trienoic x2) + (%tetraenoic x3) + (% pentaenoic x4) + (% hexaenoic x5). This index estimated bis-allylichydrogen atoms in PUFA and therefore their susceptibility to peroxidation. Plasma free4-hydroxy-2-nonenal (HNE) and free 4-hydroxy-2-hexenal (HHE), respective specificmarkers of n-6 and n-3 PUFA oxidation, were evaluated by GC-MS.Effects of dietary n-3 PUFA and antioxidants on plasma and beef lipoperoxidation(Gobert et al., 2008a and b, 2009a to c)Plasma lipoperoxidationDietary n-3 PUFA supplements reduced the resistance capacity of plasma againstlipoperoxidation (-11%) favouring conjugated diene (x 1.75) and MDA (x2) formations(Table 4).Only the combined supply of antioxidants (vit E and PERP) effectively protected plasmalipids against peroxidation (LEP diet) that was favoured by dietary n-3 PUFAsupplements, the plasma MDA and lipoperoxidation velocity Tx being reduced by -80and -33% (P=0.01) respectively in the LEP diet compared to the L diet (Table 4).Such protection by the mixture vitamin E and PERP would act not only during thepropagation phase of the lipoperoxidation reaction (by vitamin E that acts as a chainbreaker), but also during the initiation of the reaction by the uptake of free radicals bythe plant polyphenols (EVRP) as earlier demonstrated in rats and sheep (Gladine et al,2007) and in lactating cows (Gobert et al., 2008c).6
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Effects of dietary n-3 polyunsaturated fatty acids and ... - FINS

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