ADSC 2010 Lecture 9Outline of Last Lecture I. Meat Color ContinuedA. Deoxy myoglobinB. Oxy myoglobinC. Met myoglobinD. ChartE. Vacuum packaged meatsF. VitaminsG. Cured MeatsOutline of Current Lecture I. Meats – Proteins1. Myofibrillar Proteinsa. Myosin and Actinb. Troponin and Tropomyosin2. Stromal or Connective Tissue Proteinsa. Collagenb. Elastin II. Meat – LipidsA. Muscle FatIII. Meats – Nutritive IV. Meats – Acceptability1. Tenderness2. Juiciness3. Flavor & Aroma4. Appearance5. PriceV. Meat-Value DeterminantsA. Carcass WeightB. Carcass Category and Gradea. Beef1. Yield2. Quality Current LectureI. Meats- Proteins Continued1. Myofibrillar proteins (salt soluble)- Myosin and actin contractile 75%- Make up majority of muscle structure and contraction in meat- Troponin and Tropomyosin – main regulatory proteins - Attach with actin- Reg. actin and myosin interact ion during muscle contraction- Both each make up 5% of myofibrillar- Close contact with actin and myosin filament2. Stromal or Connective tissue proteins (acid soluble)- Fiberglass- Connect/hold various parts of body together and distributed throughout body as components of skeleton Attaches skin/hide  Infections Wound healing- Collagen – major protein in body - 25-30% weight- White color- High tensile strength, highly ordered structure, complex protein- Elastin - Yellow color- Very strong/ELASTIC- Mainly in tendons and ligaments- Repro tract, blood vessels, abdominal wall- Sarcoplasmic  myofibrillar  stromal (biggest effect on tenderness)- Solubility – less- soluble as you go up!II. Meats- Lipids (adipose tissue)A. Muscle Fat- About 50 % of dietary energy comes from fat - Animal fat highly digestible (~97%)- Much of flavor of meat comes from fat (carbonyl compounds) Species flavor - Animal fat generally more saturated than plant Solid at room temp Order of saturation level: pork < beef < lamb- In monogastrics, dietary fat can influence the saturation level of carcass fat Can get soft and oil (i.e. when pigs eat peanuts)III. Meats- Nutritive- In one 3 oz. serving of meat:Calories 10% RDAProtein 40% RDAIron 16% RDAZinc 35% RDAB-Vitamins 40% RDA- Poor source of vitamins: a, d, e, k, & c- Poor Source of Calcium and Magnesium- Meat protein has high Biological value!!!!! - All essential amino acids Most people eat 3.5 Servings Fat/oils1.3 Milk/dairy2.2 Meat/eggs/beans2 Veggies1 Fruit5.1 Breads IV. Meats- Acceptibility - Factors affecting consumer acceptability1. Tenderness: single most important factor- 3 factors that impact tendernessa. Myofibrillar – contractile proteins Contraction due to rigor causes toughening Rigor: stiffening due to death of muscle Aging causes increasing tendernessMuscle enzymes break down proteins and loosen structure 14-21 daysb. Connective- mainly collagen Amount of connective tissue – locomotor muscle ^ Solubility – as animals age ^, solubility ˅c. Marbling – intramuscular fat- keeps tender Lubrication : fat stimulates salivation which eases chewing Dilution: fat dilutes the negative- Methods for improving tenderness- Electrical stimulation 60-500V Speeds rigor formation Blocks cold shortening Cause pH decline Physical disruption- Aging – structural breakdown by muscle enzymes- Marinating- acid solutions to solubilize connective tissues- Tenderizers – (papain, ficin, bromelin) (CaCl2, NaCl, PO4) Papin: pineapple - Mechanical Tenderization – needle or blade tenderizers - Proper cooking- low temperature / long time –solubilizes collagen2. Juiciness: refers to liquid retention during cooking - Three factors that affect juicinessa. Marbling: intramuscular fat contributes to juiciness b. Cooking method: rapid heat : searing / broiling seals in moisturec. Added moisture – “Enhancement”3. Flavor and Aroma- Protein gives meat flavor (nitrogenous compounds_- Fat gives species flavor (beef, pork, lamb – carbonyl components)4. Appearance: major factor at point of purchase- Color (uniformity, correctness) firmness, texture- pH related problems – normal pH of meat 5.6- Dark/Firm/Dry/DFD – predominately in beef- Results in pH of >6.0- Long term stress- Low muscle glycogen at slaughter- Pale/Soft/Exudative/PSE – predominately in pork- Results from low pH < 5.4- Short term stress prior to slaughter 5. Price: Chicken vs. BeefV. Meats- Value determinants- Two main determinants of carcass valueA. Carcass weight- Decreasing percentage = hot carcass weight/ live weight x 100% Hot carcass: no organs, hair, head, feetOP HCW LWPork 70% 196 280Beef 60% 750 1250Sheep 50% 70 140- Factors affecting dressing percentage Fill contents of GI tract at slaughter Finish (fatness) – fatter animals, ^ DP Muscling – Heavier muscled animals have ^ DP Hide, head, feet weightB. Carcass Category or Grade- Beef: Evaluated between 12th and 13th rib- 2 Grades : Yield Grade and quality gradesa. Yield Grades (1-5) - % boneless, closely-trimmed retail product from chuck, round, rib, and loin 12th rib backfat, inch Ribeye area, in2 Kidney, Pelvic, and heart fat (% of carcass weight) Hot carcass weight, poundsb. Quality Grade (Prime, Choice, Select, Standard) Maturity (A-E) – Bone-size, shape, ossification Marbling score- intramuscular fat