Myoglobin in meat.ppt
- 1. B. Myoglobin & Hemoglobin Myoglobin is a complex muscle proteins Hemoglobin is the blood pigment • Hb contains 4 polypeptide chains & 4 heme groups, which are planar collection of atoms with the iron atom at the center. • Heme group function : to combine reversibly with a molecule of O2 carried by the blood from the lungs to the tissues. • Myoglobin a quarter its size compared to Hb; consists of a single polypeptide chain (±150 AA units) attached to a single Hb group; it is contained within the cell tissues & it acts as a temporary storehouse for the O2 brought by the Hb in blood. Hb considered the linking together of 4 myoglobins (the discussion of these pigments can be limited to myoglobin)
- 2. Physical properties • Oxygenation reaction Myoglobin + molecular O2 oxymyoglobin (O2Mb) forms bright red pigment • Myoglobin is part of sarcoplasmic proteins of muscle; soluble in water & dilute salt solution. Chemical Properties • Oxidation reaction Myoglobin oxidation metmyoglobin (MMb) forms brown color • Ferrous covalent complexes of myoglobin (purple) with : - Molecular O2 oxymyoglobin - Nitric oxide nitrosomyoglobin - Carbonmonoxide carboxymyoglobin
- 3. Effect of Handling, Processing & Storage • Cured Meat Pigment In commercial practice, sodium nitrite (NaNO2) is the source of nitrous acid: NaNO2 (salt cure) in water Na+ + NO2 - (nitrite ion) HNO2 (in the curing brine) Or using combustion gas (NO2) to smoke or gas-oven fresh meat: 2 NO2 (gas cure) + H2O (in meat) ---> HNO2 (nitrous acid) + HNO3 (nitric acid) Meat Curing: HNO2 + Mb (myoglobin in meat) NOMb (pink cured meat pigment)
- 4. The formation of cured meat pigments viewed as 2 processes: (1) Biochemical reaction, which reduce nitrite nitric oxide; iron in heme the ferrous state (2) Thermal denaturation of globin heating at 66 C or higher & may involve the coprecipitation of the heme pigment with other protein in meat
- 5. • Packaging Because meat pigment easily reacts with oxygen to produce either an acceptable oxygenated products or unacceptable oxidized products • Carbon monoxide (CO) flushing It was done before sealing of fresh beef very effective for preserving & stabilizing color for 15 days Certain metallic ions (esp. Cu) extremely active in promoting autooxidation of O2Mb to MMb, while Fe, Zn, Al are less active
- 6. C. Anthocyanins A group of reddish water-soluble pigments in plants which exist in the cell sap/juice, i.e. flowers, fruits, vegetables, • An anthocyanin pigment is composed of an aglycone (an anthocyanidin) esterified to 1 or more sugars. Only 5 type of sugars found in it, which are, in order of relative abundance : glucose, rhamnose, galactose, xylose, arabinose • Anthocyanins may also be “acylated” which adds a third component to the molecule, i.e. p-coumaric, ferulic, caffeic, malonic, vanillic, or acetic acids may be esterified to the sugar molecule. Fig. Anthocyanin aglicone
- 7. Stability in Food • The addition of sulfite, sulfite oxide rapid bleaching of the anthocyanins yellowish colors. i.e. in the making of jams, preserves such as dried fruits & vegetables • Anthocyanins show a marked change in color with changed in pH the higher the pH the faster the rate of destruction Chemical Reactions • The reaction with ascorbic acid the degradation of both compounds the intermediate, peroxide produces by ascorbic acid degradation i.e. Cranberry juice cocktail stored at room temperature: 0 days – 9 mg/100 g anthocyanins & 18 mg/100 g ascorbic acid 6 months – ascorbic acid degradation & 80% degradation of anthocyanin
- 8. Group of anthocyanins: – Chalcone – Flavonones – Flavones – Flavonoids – Flavonols – Cathechins – Anthocyanidins
- 9. Anthocyanidins which can be found in food (red violet spectrum): – Pelargonidin – Cynaidin – Delphinidin – Peonidin – Petunidin – Malvidin
- 10. D. Carotenoids A group of mainly lipid soluble compounds responsible of the yellow & red colors of plants & animal products (430 – 480 nm). • Most of produced carotenoids in nature is in form of fucoxanthin in various algae, in green leaves : lutein, violaxanthin, neoxanthin; β- carotene; lycopene in tomatoes; capxanthin in red peppers LUTEIN kiwi, egg yolk, corn, zucchini, red grapes, pumpkin Good for
- 11. • Carotenoids include a class of HC, called carotenes, and their oxygenated derivatives, called xanthophylls. • They consist of 8 isoprenoids units joined in such a manner that the arrangement of isoprenoid units is reversed in the center of the molecule. • Forms of carotenoids : (1) free state in plant tissues (crystals or amorphous solids) (2) solution in lipid media, i.e. capxanthin- lauric acid ester in paprika
- 12. • The association of carotenoids with proteins stabilised the pigment & also change the color, i.e. red carotenoid astaxanthin when complexed with protein blue colorant in lobster shells; ovoverdin, the green pigment in lobster eggs; carotenoid-protein complexes found in fruits, vegetables. • Carotenoids may occur in combination with reducing sugars via a glycosidic bond, i.e. CROCIN - containing 2 molecules of the sugar gentiobiose united with crocetin, found as the main pigment in SAFFRON Fig. Red pigment of astaxanthin Fig. Lobster Fig. Mud crab
- 13. • Beta carotene is precursor of vitamin A, which yields 2 molecules of vitamin A by cleavage at the center of the molecule. • Stability of carotenoids depend on whether the pigment is in vivo or in vitro in environmental condition, i.e. lycopene in tomatoes is quite stable, but the extracted purified pigment is unstable. Chemical Reactions Provitamin A • Alpha carotene is precursor of one molecule of vitamin A; which is half identical to beta carotene. Oxidation reaction • Enzyme degraded carotenoids rapidly, i.e. lypoxygenase. • In processed food heat, light, presence of pro- and antioxidant influence carotenoids degradation.