meat flavour

FLAVOR DURING COOKING OF MEAT

13FET1003 : MOKSHA CHIB13FET1004: AMEYA PATHAK

Cooking of meat• Meat is cooked using different media for heat transfer like dry heat methods,

moist heat methods, microwave cooking or a combination of both• The cooking method chosen should be appropriate to the type of meat, the

amount of connective tissue and the shape and size of the meat

Core temp increases

from 0°C to as much as

85°C

Proteins get coagulated

Browning begins at

90°C : Concentration of sugars

Water is lost as cooking

lossFat melts and cell

membrane ruptures; fat is

spread throughout the

tissue

Fat becomes available for

chemical reaction

Change in texture and

flavor

Heating Process in meat

• The rate of heating in meat depends upon the coefficient of conductivity in meat the surface temperature of meat: affected by the temperature of the heating

source, air circulation & relative humidity• Increasing air circulation improves heat conduction & increases evaporation from

the surface of meat• Heat absorbed in the meat causes a temp rise by heat conduction through meat

from the surface to the center

Cooking methods• Three main factors differing in cooking techniques:o Temperature at the surface of meato Temperature profile through meato Method of heat transfer (contact, air, steam, microwave)Dry Heat Cooking

Moist Heat Cooking

Combination

Grilling/ broiling Steaming StewingBarbecuing Poaching BraisingRoasting/ baking

Simmering

Sauteing BoilingPan fryingDeep fat frying

Heat has applications:

• Flavor formation from precursors & homogeneous mixtures of water soluble & fat soluble compounds

• Releases flavor (precursor) from fatty structures

• Enable mixing of fat soluble & water soluble compounds ( fat melts & becomes part of meat juices)

• Favors browning reactions through evaporative & exudative dehydration & through protein degradation

Effect of cooking on flavor

• Amino acids and reducing sugars react when heated MAILLARD REACTION

• Fatty acids get oxidized and degraded to create volatile flavor compounds

• Thiamine is a source of meat flavor generated on heating THIAMIN DEGRADATION

• INTERACTION BETWEEN LIPID OXIDIZED PRODUCTS WITH MAILLARD PRODUCTS

• Vitamin gets degraded during cooking VITAMIN DEGRADATION

LIPID DEGRADATION

Meat Flavor Aroma• Meat flavour comprises mainly the two sensations of taste and smell • Other sensations such as astringency, mouthfeel and juiciness may also play

a part. Receptors in the mouth can recognize four main taste sensations (sweet, salt, sour and bitter)

• In contrast, many hundreds or even thousands of different odours can be distinguished by the human nose

• The sensation of odour is produced by volatile chemical substances which stimulate the receptors in the nasal epithelium

Aroma Flavor PrecursorsFlavor precursors Names in detail

Free amino acids Cystine; cysteine; glycine; lysine; alanine; valine; isoleucine; leucine; threonine; serine; proline; asparagines; aspartic acid; methionine; glutamic acid; phenylalanine; glutamine; ornithine; histidine; tyrosine; tryptophan; arginine.

Reducing sugars Ribose; glucose; xylose; starch; mannose; fructose; maltose; mannose 6-phosphate, glucose 6-phosphate; fructose 6-phosphate; ribose 6-phosphate.

Fats/ lipids Triglycerides and phospholipids, Oleic acid (C18:1n-9), Linoleic acid (C18:2n-6), Linolenic acid (C18:3n-3) and etc.

Vitamin Thiamine

Nucleotides and peptides

Glutathione; carnosine inosine; inosine monophosphate; inosine 5’-monophosphate; guanosine 5- monophosphate; creatinine; Hypoxanthine and etc.

The low molecular weight, water soluble compounds and fats in meat constituents are the most important precursor of aroma flavor characteristics of cooked meat.

Flavor Active VolatilesCompound name: ALDEHYDES

Aroma flavor characteristics

Methional caramel, sweet, alcoholic, “cooked”, broth, spicy Propanal Cooked potato, meatyButanal smoky, fish, amylic, aldehyde-enal or dienalHexanal Sweet, fatty, green, fruityHeptanal Sweet, fatty, fruity, oil Octanal Green, lemon, citrus, aldehyde Nonenal Sweet,fatty,greenDecanal Sweet, fruity, like aldehydes, roasty Undecanal, E,2-undecenal Sweet, pungent, greenE,2-nonenal, E,2-hexenal Fatty, GreenBenzenacetaldehyde Sweet, honey 2-methylbutanal Pungent, sweet, roasty

acetaldehyde-like 3-methylbutanal

Meaty, fish, rotten, aldehyde,valeric acid, fatty

Flavor Active VolatilesCompound name: KETONES

Aroma flavor characteristics

2-octanone, decanone, decanone

Fruity, musty

1-octen-3-one Fresh, mushrooms, pungent, rubbery3-octanone Fruity, nutty, moldy, fatty, earthy 2,5-dimethyl-4-hydroxy-3(2H)- furanone

Roasted almonds, sweet

4,5-dihydro-5-propyl-2(3H)-furanone

Fruity, fatty, sweet, pungent, roasty

2,3-butanedione Sweet, buttery 2-heptanone Citrus grapefruit, limonene, floral, cheese2-nonanone Hot milk, soap, green, fruity, floral 6-Methyl 2-heptanone Cloves, menthol2,2,6-Trimethylcyclohexanone

Mint, acetone

Flavor Active VolatilesCompound name:ALCOHOLS

Aroma flavour characteristics

1-octen-3-ol Mushroom

Cyclobutanol Roasted

1-heptanol Fragrant, woody, oily, green, fatty, winey, sap

2-Ethyl-1-hexanol Resin, flower, green 1-octanol Penetrating aromatic odor, fatty, waxy, citrus, oily

Compound name: HYDROCARBONS


Ethenylbenzene Pungent, aromatic, fragrant, roasty

1-undecen Fatty, burnt, nutty, rubbery

Hexane Faint peculiar odor

(Z)-3-Octene Fruity, old apples Pentane Very slight warmed-over flavor, oxidized

Flavor Active Volatiles

Compound name: PYRAZINES


2-ethyl-3,5-dimethylpyrazine

Burnt, fragrant, meaty, green

2-ethenyl-3,6(5)-dimethylpyrazine

Sweet, cooked rice, fatty

2,3-diethyl-5-methylpyrazine

meaty, roasty, fragrant, sweet

2,5-dimethylpyrazine Fried rice, popcorn, pungent, green

2-ethenyl-5(6)-methylpyrazine

Roasty break-like, cooked rice, coffee-like

2-ethenyl-5(6)-methylpyrazine

Smoky, roasty, break-like, cooked rice, popcorn

2-isopentyl-3,6-dimethylpyrazine

Sweet, fragrant, fatty, fruity, pungent

2,3-diethyl-5-methylpyrazine

Meaty, roasty, fragrant, sweet


Compound name: S and N CONTAINING COMPOUNDS


2-fufurylthiol, 2-acetylthiazole Roasty2-acetyl-1-pyrroline Roasted, sweet2-formyl-5-methylthiophene, Benzylthiol

Sulfurous

2-methyl-3-furanthiol Meaty, sweet, sulfurous2,4-dimethylthiazole Rubbery, moldy, fruity, pungent, onion-likeDimethyltrisulfide Fragrant, musty, roasty, rubberyBis(2-methyl-3-furyl)disulfide Meaty-likeBenzothiazole Metallic4,5-dimethylthiazole Smoky, roasty, fragrant, nutty2-methylchinoxaline Aromatic, roasted, nutty, sweet, fruity, fatty3-mercapto-2-butanone Fried onion, sulfury, cooked meat2-mercapto-3-pentanone Brothy, mashed potatoes meaty, roast meat3-[(2-furanylmethyl)dithio]-2- butanone

onion, burnt rubber, burnt wood


Maillard Reaction STEP A

STEP B

STEP C

STEP D

STEP E

STEP F

STEP G

STEP H

Condensation of CO group of a reducing sugar (aldose) with a free amino group of an amino acid, which loses a molecule of water to form N-substituted glycosylamine Undergoes the "Amadori rearrangement" to form "1-amino-1-deoxy-2-ketoses"

Dehydration (loss of 2 water molecules) into reductones & dehydro reductones (caramel products)Production of short chain hydrolytic fission products such as diacetyl, acetol, pyruvaldehyde, etc

"Strecker degradation" with amino acids to aldehydes

or they may react in the absence of amino compounds, to give aldols and high molecular weight, nitrogen-free polymersFormation of brown nitrogenous polymers and copolymers called melanoidins Direct route to fission products from N-substituted glycosylamines, without the formation of an ARP

Strecker Degradation

1. Amino acids undergo oxidative deamination & decarboxylation in the presence of dicarbonyls

2. Lead to formation of aldehyde (e.g.furfural)and amino ketone

Strecker Degradation

3. Sulphur containing amino acids such as Cysteine or cystine form H2S , NH3 etc by Strecker Degradation

Flavor Compounds formed from the Maillard Reaction

Flavor class Characterized Flavor/aroma

Remark

Pyrazines Cooked, roasted, toasted, baked cereals

Alkylpyrazines Nutty, roastedAlkylpyridines Green, bitter, astringent, burnt Unpleasant flavorAcetylpyridines Caracker-likePyrroles Cereal–like Furan, furanones, pyranone

Sweet, burnt, pungent, caramel-like

Oxazoles Green, nutty, sweet Thiophenes Meaty Formed from heated meat by the reaction of

cystein and ribose6-Methyl 2-heptanone

Cloves, menthol

2,2,6-Trimethylcyclohexanone

Mint, acetone

Lipid Oxidation• The oxidation of unsaturated acyl chains of the lipids accompanied with thermal

conditions. • Auto-oxidation of these unsaturated fatty acids associated with phospholipids is

responsible for the undesirable flavors associated with rancidity. • Hundreds of volatile flavor compounds derived from lipid degradation have been

found in cooked meat including aliphatic hydrocarbons, aldehydes, ketones, alcohols, carboxylic acids and esters. The degradation of lipid is catalyzed by Iron.

The oxidative breakdown of unsaturated alkyl chains of lipids involves a free radical mechanism to form hydroperoxides. The reaction is initiated when a labile hydrogen atom is abstracted from a site on the lipid with the production of lipid radicals.

RH R· + H· Reaction with oxygen yields peroxy radicals which is followed by abstraction of

another hydrogen from lipid molecule R·+ O2 ROO· ROO·+ RH ROOH + R·

• The resulting radical can undergo rearrangement prior to reaction with oxygen, giving rise to a number of hydroperoxides. The degradation of hydroperoxides formed leads to the formation of various volatile components.

• The degradation of hydroperoxides initially involves homolysis to give an alkoxy radical (RO·) and a hydroxy radical (OH·).

• The nature of the volatile product for a particular hydroperoxide depends on composition of alkyl chain and the position where the cleavage of the chain takes.

Hydroperoxides containing a diene system will give a complex mixture of volatiles such as dienals and alkylfurans

The other classes of volatiles including long chain alkylthiophenes and alkylpyridines are produced from the interaction of lipid degradation products with ammonia and hydrogen sulphide.

Thiamin Degradation• Primary product: 4-methyl-5-(2-hydroxyethyl)thiazole & other flavor compounds like 5-hydroxy-3-mercaptopentan-2-one which then gives some sulfur-containing compounds such as thiophenes and furans as well. • Some of those compounds at low concentrations in themselves smell like cooked meat and some of them contribute significantly to thearoma of cooked meat

Interaction of Maillard browning and Lipid oxidation products

Effect of cooking temperatureCooking

Dry Cooking

Aqueous Cooking

Roasting, Broiling, Pan frying: 150°C-160°CSubjecting aroma precursors to heating

Boiling, Stewing, Braising : 100°C

Dry Cooking• Due to low Aw, high temperatures & dried surfaces, there is an increased

production of flavor compounds which give roasted odor notes & flavor• Amounts of most volatile flavor compounds increase with cooking temperatures

• Amino acids & reducing sugars react when heated above 110°C MAILLARD REACTION

• Sugar melts & decomposes at temp above 170°C and produce “burnt sugar” flavor

• Fatty acids get oxidized and degraded to create volatile flavor compounds

CARAMELIZATION

LIPID DEGRADATION

Changes in flavor compounds on dry cooking

• LIPID OXIDATION: High temp increase oxidation processes in meat.

Volatile compounds generated by lipid oxidation: Pentanal, hexanal, 2-hexanal, heptanal, benzaldehyde, octanal, nonanalTrend for hexanal : Roasted > Microwaved > Fried > GrilledHexanal is dominant in the flavor profile as it can be generated from oleic acid, linoleic acid & arachidonic acid, and through degradation of other unsaturated aldehydes such as 2,4-decadienal.Lipid oxidation increase the number of free radicals which attack other less susceptible fatty acids, favoring synthesis of heptanal, octanal & nonanal.

Roasting at 200°C for 12 min > Frying at 140-180°C for 4 min


• ESTERS: Generated from esterification of alcohols & carboxylic acids, their content decrease on cooking. This is because thermal treatment degrades the esters & this decrease is higher in roasted treatments as compared to grilled and fried treatments.

• ALKANES: Alkane content was found to be higher after microwaving than after grilling.

The most abundant alkanes: Undecane, nonane, 2,2,4,4,6,8,8-heptamethyl and octane• AROMATIC HYDROCARBONS: Highest increase in roasted meats when treated for

long time.The most abundant aromatic hydrocarbons: Toluene and p-xylene• FURANS: Highest increase in furans after microwaving.Furans in microwaving: Furan, 2-ethyl, furan, 2-n-butyl and furan, 2-pentyl; roasting: furan, 2-ethyl and furan, 2-pentyl; frying & grilling: furan, 2-pentyl


• KETONES: Aroma imparted by methylketones, which are products of β keto acid and are derived from triglycerides on heat treatment. There is an increase in the ketone level with an increase with the lipid oxidation.

• ALCOHOLS: 1-hexanol,2-ethyl is found in raw samples, while only one alcohol (1-pentanol) is present in roasted steaks.

• PYRAZINES & THIAZOLES: Production increases with increased roasting

Correlation Hexanal Aldehydes

Furans Esters Total volatile compounds

Lipid oxidation

+ + + - +

Comparison of flavor compounds in different methods of cooking

Flavor Compounds (%)

Fresh Fried Roasted Grilled Microwave

Alcohols 0.56 - 0.71 - -Furans - 0.29 0.49 0.64 0.83Lineal Alkenes - 0.32 0.33 - 0.21Aldehydes 3.2 53.21 65.19 54.31 59.99Cyclic Hydrocarbons 2.33 1.37 0.52 0.48 0.34Other compounds 3.01 1.15 0.97 1.01 0.71Aromatic Hydrocarbons

15.83 6.96 9.89 10.17 8.00

Ketones 6.63 1.47 0.85 1.32 0.43Esters 39.86 7.59 2.59 8.90 3.82Lineal Alkanes 28.58 27.64 18.46 23.18 25.66

Wet Cooking• While collagen softens in moist heat, muscle fibers firm as their proteins unfold and

form new linkages during cooking. Various proteins in meat fibers coagulate over a range of temperatures from 40°C-90° C, temperatures that are far below boiling point 100 °C

• Wet cooking prevents Maillard Reaction• As lipid degradation can take place at lower temperatures, therefore flavor

compounds can be produced on the surface and throughout the meat• No caramelization takes place as temperatures do not reach greater than 100°C• Except pressure cooking, interior of the pieces of meat cannot rise above 100°C until all

water has been driven off, thus it will have little flavor in comparison with exterior where high temperature and less moisture produces various substances

• Unless cooking is pressurized, browning doesn’t take place; no roasting flavor & appearance

• Low heating yields homogeneous appearance but less distinct layers of doneness

Wet Cooking• Well cooked boiled beef has major amounts of Benzenoids

Well cooked, boiled Underdone, boiledHIGH MW HYDROCARBONSTetra-, penta-, hexa- and hepta- decanes

LOW MW HYDROCARBONSHeptane, octane, decane, undecane, hept-1-ene, undec-1-ene

BENZENOIDSBenzene, n-propylbenzene, toluene, o and p-xylenes, ethylbenzaldehyde

PYRAZINESDimethyl-, ethyl- and dimethylethyl pyrazines

FURANS2-ethyl and 5-n-pentyl furansMISC3-methylbutanol, pyridine, 2-metylthiophen

MISCAcetone, methylbutanol

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