meat chemistry - importance of compositional components and chemistry of each in processed meats 1....

Meat Chemistry - Importance of Compositional Components and

Chemistry of Each in Processed Meats

1. Water

– present in greatest quantity in meat and most products

– important to: 1) eating quality, and 2) economics

– remember: water is both a meat component and a non-meat (added) ingredient

Functions of water

a. palatability

– juiciness

– initial juiciness impression

– contributes to tenderness

b. yields / economics

– must provide for the water expected to be lost in cooking

– binding mechanisms for water become important to yields

c. universal solvent

– dispersion and distribution of ingredients i.e. nitrite

– 3% added water allowed in fresh sausage “to facilitate mixing”

– also critical as a protein solvent

d. temperature control

– improved protein solubility

– bacterial control

– thermal capacity, especially ice, is very large

Thermal capacity

Specific heat of water - 1 BTU/lb/oF

ice - 0.5 BTU / lb/oF

latent heat of crystallization - 144 BTU/lb

(energy required to melt ice (or freeze water)

without a temperature change)

Example of effects:

10 lbs of cold (32oF) water added to frankfurter emulsion

chopped from 32oF to 55oF

= 10 lbs x 23oF x 1 BTU/lb/oF = 230 BTU

Thermal capacity (continued)

Specific heat of water - 1 BTU/lb/oF ice - 0.5 BTU/lb/oF

latent heat of crystallization - 144 BTU/lb

Example of effects:

10 lbs of ice (32oF) added to emulsion at 32oF & chopped to 55oF

= 10 lbs x 144 BTU/lb = 1440 BTU (conversion to water)

plus 10 lbs x 23oF x 1 BTU/lboF = 230 BTU

1670 BTU

(over 7 x that of cold water alone)

Temperature control is a major advantage to using frozen meat but frozen meat has

less functional protein and thermal capacity is less than ice

Thermal capacity of meat 0.8 BTU/lb/oF (fresh)

0.4 BTU/lb/oF (frozen)

Water in meat systems

– Bound by proteins

– In order to understand water in meat systems it is necessary to understand:

water : protein interactions

- and-

water : water interactions

Water is a unique compound with a unique structure:

two positive poles

and

two negative poles

(think 3-dimensional tetrahedron)

+H H+

O

- -

H2O

Structure and charged poles create intermolecular “H bonding”

– Each molecule binds 4 others --- one at each pole

therefore water attracts water

= water : water interaction

Meat also has a variety of polar groups --- due to proteins

– this is a critical property of proteins and is a unique “fingerprint” for each protein.

– Why?

Proteins are composed of amino acids

– amino acids each have polar / non-polar properties and charges

– combination of amino acids determines protein properties such as protein : water interaction

R C COOH

H

NH2

Meat proteins first bind water directly to the charged amino acid groups

– This is a small amount of water 5 - 10 g/100 g protein

– very tightly bound “Bound water”

Bound water attracts other water molecules

– Another 2 - 3 molecule layer around protein groups (50 - 60 g/100 g protein)

= “Immobilized water”

Bound water and immobilized water are considered as one in terms of

water movement and changes in meat products.

Which leaves water attracted weakly to the bound and immobilized water.

= “Free water” (~ 300 g/100 g protein)

“Free” water is loosely held and very dependent upon capillary space between and within proteins.

Muscle structure therefore becomes a determinant of water binding ability

Anything which will alter protein structure and spacing will affect water retention

Remember that this is 3-dimensional…

Thus, it is myofibrillar proteins that are most important ----- have most

polar and charged amino acids.

70 -75% - myofibrillar

~ 20% - sarcoplasmic

< 10% - stromal (connective tissue)

This is why lean muscle is most desirable for processed meats.

- and -

we need to know how to manipulate proteins to change water binding

Three fundamental ways to manipulate water binding ability of meat

1. pH - concentration of H+

2. Salt Na+ Cl–

3. Phosphates PO4

(– = )

Effects of pH on water binding

– water binding is minimal at about pH 5.0 - 5.2

– water binding increases above or below this pH

protein – – – + – + – + –

pH 6.0 net charge = –3

protein – H+ – – + – +H + – + H+–

pH 5.1 net charge = 0

Isoelectric PointIsoelectric Point

+3H +

protein H+ – H+ – – + – H+ + H+ – + H+–

pH 4.5 net charge = +2

+2H +

+ +

+ +

H2O H2O H2O

pH 6.0pH 6.0 pH 5.1pH 5.1 pH 4.5pH 4.5

Note: Isoelectric Point [Know this!]

– pH at which charge on protein = 0

– minimum water binding

– dependent on amino acid composition

i.e. will be different for different proteins

Effects of salt on water binding

– Shifts isoelectric point curve to the left

– raises water binding at all typical meat pH’s

protein – – – + – + – + –

pH 6.0 net charge = 3

protein – – – + Cl ¯ –

+ – Cl ¯ + –pH 6.0 net charge = –5

+ Na Cl

Na+ Cl ¯

Note:

– salt increases the net negative charge on meat proteins which increases protein repulsion and water binding

– because more H+ are needed to completely neutralize the negative charges, the pH must be lower to reach the isoelectric point

Effects of phosphates on water binding

– phosphates are basic and raise the pH of meat

– phosphates are anions (-) and may create a chloride effect on charges

– solubilize structural proteins to “loosen” myosin and actin

Effects of Phosphates(cont’d)

– chelate cations such as Ca++ that can crossbridge proteins

protein + – – – – +

+ – – – – +

+Ca +

After pH, salt and phosphate effects are maximized, then other ingredients can be considered for further increases in water binding

i.e. proteins: soywheycaseinatecollagen

carbohydrates: corn syrupmaltodextrinsstarch

hydrocolloids: carrageenanxanthan gum

Measurement of water holding capacity (WHC)

1. Drip loss

– suspend intact muscle sample inside bag or container

– measure drip weight/drip loss after fixed time period

2. Press method

– sample placed on dried filter paper and submitted to pressure between two plates

– separated “water ring” measured with planimeter.

– Ratio of water ring area to meat ring area is a relative measure of WHC

Measurement of water holding capacity (WHC) (continued)

3. Centrifuge method

– muscle sample or blended sample (with water, salt, etc.) centrifuged and separated water measured.

4. Yields after heating

– samples heated at fixed time/temperature

– weight loss/water loss measured

5. Nuclear magnetic resonance (NMR)

– measures relative “freedom” of water molecules to move in magnetic field

Increasing WHC is not always desirable i.e. dry sausage, jerky, etc.

Concerns for water

1. Hard water

– decreases WHC due to minerals Mg++, Fe++, etc.

– may reduce effectiveness of phosphates - reaction with mineral cations

– may cause product discoloration Fe++, Cu+, NO3-

– may induce rancidity developments from metals like Fe++ or Cu+

– can induce “scum” when making injection “pickle” and make other ingredients such as phosphates hard to dissolve

Hard water = 10 grains/gal or more (175 pmm)

Ames ground water = 24 grains/gal

2. Nitrate can be a health risk at 10 ppm or more especially for babies

– methemoglobinemia

3. Water cleanliness (bacteria, etc.)

-cross-contamination of lines

-backflow from outlets

-ice machines

-dead-end lines