Changes in the composition of red meat

Transcription

1 Changes in the composition of red meat Prof HC Schönfeldt & Ms N Hall Institute of Food, Nutrition & Well-being

2 Content Introduction composition of red meat Overview of classification system Case 1: Local lamb & mutton composition Case 2: Beef composition over time Case 3: Variation in fatty acid composition between feeding regimes & age classes

3 Composition of South African red meat The nutritional attributes of meat are continually researched worldwide Many studies reflect the substantial changes over time in the composition of carcass meat Especially reduction in the amount of fat 1. On the carcass itself 2. After trimming 3. Changes in cooking methods Breeding programmes and modification of animal feeds Seam butchery technique in shop or at home Limiting addition of fat during cooking

4 Background There is a decline of red meat in many 1 st world countries Concerns & reasons include: Nutrition & Health (incl. fat content) Sustainability (incl. nutrients produced vs. cost to environment) Others In SA, we have a growing middle class increasing demand for animal source foods

5 Globally, a decrease in fat content of red meat is observed over time Adheres to consumer concerns Increase positive comparison with other animal source foods

6 Reduction in fat content of the carcass Changes in breed selection Changes in feeding regimes QUANTITY Globally research conducted on the TYPE/QUALITY of fat & how this is affected by breed, feeding etc.

7 Reduction in fat content after slaughtering Changes in butchery technique to adhere to consumer demand for leaner meat e.g. seam trimming At home removal of visible fat, prior to cooking Intermuscular fat Subcutaneous fat Intramuscular fat

8 Reduction in fat content during preparation Fat-reducing cooking techniques, e.g. grilling Limiting the addition of oils & fats Limiting fatty basting & serving sauces Remove remaining visible fat after preparation

9 Case 1: Composition of local lamb & mutton No national nutrient composition values for SA sheep meat was available before Previous reference to the nutrients found in lamb and mutton borrowed from USA In the South African Food Composition Table Used as reference source for health professionals, food industry and the media States that Mutton has 25g/100g fat (25% fat) Highest fat percentage of all animal products No values for lamb has been available in SA

10 Borrowed vs. Own science Nutritional quality of South African mutton Previous data 2012 (Untrimmed) 2012 (Trimmed) Fat Cholesterol Protein Iron (mg)

11 Composition of local lamb and mutton Untrimmed Nutrient South African 1 Previous borrowed values 2 USA 3 Australia Lamb Mutton Mutton Lamb Lamb Lamb Protein g Fat g SFA g MUFA g PUFA g Cholesterol mg Iron mg Zinc mg Sodium mg Wolmarans et al., U.S. Department of Agriculture, Agricultural Research Service USDA National Nutrient Database for Standard Reference, Release 26. Nutrient Data Laboratory Home Page, 4 Greenfield, H The nutrient composition of Australian meat and poultry. Food Technology in Australia 39: NUTTAB, 2010.

12 Composition of local lamb and mutton When trimmed Nutrient Unit South African 1 USDA 2 Australia 3 New Zealand 4 Lamb Mutton Lamb Lamb Lamb Protein g Fat g SFA g MUFA g PUFA g Cholesterol mg Iron mg Zinc mg Sodium mg Schönfeldt, Hall & Van Heerden, U.S. Department of Agriculture, Agricultural Research Service, NUTTAB, Massey University, 2011.

13 Case 1 Conclusions: Locally produced sheep meat compares favourable with other animal source foods in fat content (per 100g cooked portion)

14 Case 2 & 3: Beef Beef available in South Africa Ample variety influencing composition: Production system Grass fed Grain fed Mixed Classification system Age Fat code Local breeds Other

15 American production & classification Based on marbling system Fat content between muscles More marbling = higher price incentive Intensive production of beef - fed a diet to induce more marbling USA vs. RSA

16 South African carcass classification system age (by dentition) 0 permanent incisors Usually grain-fed (feedlot) Ensures carcass reaches optimal fatness at young age Purple-blue roller mark 80% of the market

17 South African carcass classification system age (by dentition) 1-2 permanent incisors Usually the youngest animals from grasssystems Green roller mark

18 South African carcass classification system age (by dentition) 3-6 permanent incisors Slightly older grass-fed animals Brown roller mark

19 South African carcass classification system age (by dentition) >6 incisors Usually retired cows Lifetime on grass, rounded off to desired fatness on grain based systems prior to slaughter Often communal animals

20 Case 2: Beef composition changes over time Study methodology Includes beef from 4 age groups (A, AB, B & C) from fat-code 2 3 Cuts have been selected for this study predict carcass composition the best (Schönfeldt, 1998; Naudé, 1994) 1. Rump 2. Prime-rib 3. Shoulder Bonsmara Breed (27% of national stud herd & ~50% cross-breeds at feedlots)

21 Classification of carcasses Screened for fat class Fat class Description Subcutaneous fat (%) Fat thickness (mm) 0 No fat. 0 1 Very lean 3.3 <1 2 Lean to 3 3 Medium 5.2 >3 and <5 4 Fat 6.3 >5 and <7 5 Overfat 7.3 >7 and <10 6 Excessively fat 7.8 >10

22 Sampling Obtained through ARC Meat Industry & University of Pretoria Experimental Farm Slaughtered at the ARC abattoir

23 Sampling cuts Retail cuts were removed from each side by an experienced dissection team Rump Prime-rib Shoulder

24 Sampling Whole cuts were weighed Physically dissected into meat, bone, subcutaneous and intermuscular fat

25 Sampling Each fraction of each cuts was weighed to determine physical composition of each cut The meat from three cuts were combined The fat (sub+interfat) from the same cuts were combined Cuts from 9 sides = 3 composite samples of 3 cuts each

26 Sampling Each composite meat sample was cubed, thoroughly mixed, and minced, first through a 5mm, and then through a 1.5mm plate

27 Sampling Three 500g samples were drawn and vacuum sealed The samples kept frozen at -20C until chemical analysis

28 Main findings Fatness code 2 (according to the current classification system) was used as a controllable factor when beef carcasses were selected for analyses Age Fatness codes are determined by physical evaluation of the subcutaneous fat layer on the beef carcass after slaughter prior to further division into retail cuts (Department of Agriculture, 1990) No significant difference across the age groups was found for dissected subcutaneous fat from the prime rib Starting mass Bone Meat Subcutane ous fat g g g g g A 4.33 a 0.75 a 2.97 a a AB 4.25 b 0.78 a 2.65 a ab B 4.88 b 0.89 b 3.00 ab b C 4.37 ab 0.90 b 2.55 b b p-value > Intramuscular fat

29 Main findings Focus on t the prime rib cut as was found to predict the composition of the carcass the best (Naude, 1972) The fat percentage of South African age A beef (as slaughtered) has decreased from 15% to 11% since the 1990 s The fat percentage of age C carcasses have remained relatively constant at 16% Naude, 1972 Klingbiel, 1984 Schönfeldt, 1990 Current study (prime rib) Age A A AB C A AB C A AB B C Fatcode N/A N/A N/A N/A Bone % Muscle % Fat %

30 Trimming makes a difference in fat content Trimming = low fat red meat options 1. Removal of subcutaneous fat layer (trimmed of external fat) 2. Removal of visible fat between muscles (only muscle & marbling remains)

31 Results when trimming included As cattle ages, changes in composition is observed. No significant differences in the fat and muscle content are observed between the edible portion of age A and age AB animals (untrimmed) When trimmed of sub fat, there was significantly more muscle in A, than in other cuts Differences are also observed between age A, and age B & C animals (muscle decrease and fat content increase) Fat content in the muscle only portion (with all visible fat removed) increased significantly from age AB to age C, and muscle decreased (increase in intramuscular fat / marbling) Cut Primerib Trimmed of All visible fat Untrimmed Age subcutaneous fat removed Muscle Fat Muscle Fat Muscle Fat A 87.1 a 13.3 b 90.4 a 10.0 a 97.1 a 3.37 a AB 80.7 ab 19.6 ab 84.9 b 15.4 ab 96.5 a 3.82 ab B 79.2 b 21.0 a 83.0 b 17.2 b 95.3 ab 4.87 bc C 79.4 b 20.6 a 82.2 b 17.8 b 94.4 b 5.62 c Std error p-value

32 Case 2: Summary Implications / recommendations The current classification system is effective in classifying carcasses according to amount of subcutaneous fat layer for all age groups Changes in the composition of beef observed over time notably a reduction in fat content of target age (age A) beef (untrimmed) Differences in nutrient profile are observed between age groups for edible portions AB B C

33 Case 3: Fatty acid quality of South African beef Objective: To determine the FA profile of beef from all four South African age groups, including all production systems Forms part of a PhD(Nutrition) research project at the University of Pretoria Supported by Red Meat Research & Development South Africa (RMRDSA), the National Research Foundation (NRF), and the Institute of Food, Nutrition & Well-being (IFNuW) at UP

34 Global focus on quality of fat contained in food CLA

35 South African carcass classification system age (by dentition) Grain fed Grass fed All age groups included in current study Grass & grain fed

36 Sampling Similar as Case 1

37 Analysis Meat & fat fractions (cooked & raw) sent for nutritional analysis separately Enables calculation of effect of trimming on nutrient content Analysis: Proximate composition Minerals Fatty acid profile Gas Chromatography New more precise technology

38 Results Visual:

39 Fatty acid composition per 100g fat from prime rib Total Age FA SFA MUFA PUFA n-6 n-3 CLA A a 1.29 a 0.05 a 0.11 a AB b 0.48 b 0.25 b 0.29 b B b 0.54 b 0.23 b 0.30 b C b 0.78 b 0.11 a 0.19 a P-VALUE <0.001 < Total FA SFA A AB B C No significant difference in total FA No significant difference in SFA between age groups / feeding regimes

40 Fatty acid composition per 100g fat Total Age FA SFA MUFA PUFA n-6 n-3 CLA A a 1.29 a 0.05 a 0.11 a AB b 0.48 b 0.25 b 0.29 b B b 0.54 b 0.23 b 0.30 b C b 0.78 b 0.11 a 0.19 a P-VALUE <0.001 < ,5 1 0,5 0 PUFA n6 n3 CLA A AB B C No significant difference in total MUFAs More PUFAs & n-6 in young animals from grain More n-3 & CLA in grass fed animals

41 From a nutrition perspective: We eat meat not fat! As slaughtered Meat+ inside fat + outside fat Trimmed Meat + inside fat (trimmed of outside fat) Muscle only Meat (trimmed of all visible fat)

42 Fatty acid profile 100g cooked edible meat, untrimmed Total fat SFA MUFA PUFA N-6 N-3 CLA unit g g g g g g g A a 0.02 a AB b 0.06 b B b 0.06 b C a 0.04 ab P-value No statistically significant difference in total fat & SFA, although young animals from grain had less No statistically significant difference in PUFAs & n-6 s, although young animals from grain had more Statistically more n-3 & CLA in grass fed beef (age AB & B)

43 Fatty acid profile 100g cooked edible meat, trimmed of outside fat (subcutaneous fat) FAT SFA MUFA PUFA N6 N3 CLA A 14.5 a a 0.02 a AB 16.3 ab b 0.05 b B 19.6 ab b 0.05 b C 19.7 b a 0.04 b P-value Remaining fat after trimming inter- & intramuscular fat (between and within mucles) Total fat increases with age No statistically significant difference in SFA, MUFA & PUFA Statistically more n-6 in grass fed beef (age AB & B) Statistically more CLA in grass fed beef (age AB & B) AND in age C (grain finished) than in age A Possibly due to CLA stored in fat during lifetime of animal prior to grain-finishing

44 Fatty acid profile 100g cooked edible meat portion (Trimmed of all visible fat) FAT SFA MUFA PUFA N-6 N-3 CLA Unit g g g g g g g A 6.96a 2.16a a 0.007a AB 9.77b 3.30b b 0.029c B 10.3b 3.52b b 0.031c C 10.4b 3.22b a 0.020b P-value <0.001 <0.001 Trimmed of all visible fat remaining fat, within muscles More n-3 & CLA in grass fed beef (age AB & B) Young animals (age A), fed on grains, had significantly less Total Fat Young animals (age A), fed on grains, had significantly less SFA incl. Lauric (C12), Mysteric (C14), Palmitic (C16) & Stearic acid (C18)

45 Comparing FA profile of trimmed, lean, meat Effect on blood cholesterol Lauric acid C12:0 LDL raising Myristic acid C14:0 Palmitic acid C16:0 LDL neutral Stearic acid C18:0 Oleic acid C18:1c9 LDL lowering Linoleic acid (n-6) C18:2 Alphalinolenic acid (n-3) C18:3 A grain 0.002a 0.137a 1.04a 0.859a a 0.004a AB grass 0.004b 0.201b 1.64b 1.283b b 0.024b B grass 0.005b 0.244b 1.83b 1.272b b 0.024b C grain 0.002a 0.195ab 1.61b 1.324b ab 0.012a P-value <0.001

46 In summary As slaughtered Meat+ inside fat + outside fat Trimmed Meat + inside fat (trimmed of outside fat) Muscle only Meat (trimmed of all visible fat) More CLA & n-3 in grass fed meat (AB, B) Slightly less total fat & SFA in young, grain fed animals (A) More CLA & n-3 in grass fed meat (AB, B) Total fat increases with age lowest in young grain fed animals (A) More CLA & n-3 in grass fed meat (AB, B) Less total (intramuscle) fat in young, grain fed, animals (A) Lower SFA in young, grain fed, animals (A)

47 Unique: Less total fat More essential omega-3 fatty acids More hearthealthy CLA Higher SFA per 100g fat (but lower per 100g edible product as less total fat) ẋ More total fat More essential omega-3 fatty acids More hearthealthy CLA ẋ Higher SFA per 100g fat AND higher SFA per fully trimmed, edible meat

48 Acknowledgements Co-workers & authors Ms N Hall, Dr B Pretorius, Dr PE Strydom, Dr SM Van Heerden, Ms J Sainsbury, Ms M Smit Red Meat Research and Development South Africa (RMRDSA) National Research Foundation THRIP University of Pretoria, Institute of Food, Nutrition & Well-being Meat & Livestock Australia (MLA)

49 Thank you!