Meat Color Measurement

Three approaches --- all very different in what they measure

1. Light absorbance methods

2. Light reflectance measurements

3. Human panel assessments

Light absorbance methods for meat color

Pigment quantitation --- how much?

a. extract the pigments from the meat sample

-fresh meat, use water or weak salt

solution

-this is for for heme AND globin

(intact myoglobin)

- cured meat- acetone for heme alone-the pigment is not water soluble

b. measure light absorbed at a wavelength appropriate for the pigment being measured

maximum absorbance:oxymyoglobin 580 nm

myoglobin 550 nm

metmyoglobin 505 nm

nitrosylhemochrome 545nm

c. Can determine total amount of pigment

i.e. 250 ppm of oxymyoglobin:

but………………?

color is not obvious – usually from a mixture of pigments

Amount of pigment is used for color values in calculating formulas ---

because it shows the potential intensity of color

– works well for cured meat pigment but difficult to do with fresh meat pigment because of rapid changes while handling

– also valuable in cured meat because it is related to effectiveness of curing reactionMore complete conversion for NO2

- NO gives greater amounts of nitrosylhemochrome

Light reflectance measurements

– Truly objective quantitation of color– widely used– measures light reflected from surfaces ---

– consequently measures what we see

– objective values (color numbers) allow communication of color and exact reproduction of color– i.e. paint industry

All reflectance systems are based on the original 1931 CIE system (International

Commission on Illumination)- established use of standardized light sources

i.e. Source A - incandescent lamp

B - noon sunlight

C - average daylight

– more recently these have become defined by lamp temperature

i.e. lamp at 6500 Ko is D65

– also may include flourescent lamps, etc.– must also consider aperture size and sample locations,

multiple measurements, i.e., 460 lab

Human vision is sensitive to light in the range of ~380 nm (blue) to 700+ nm (red)

– Lighter color reflect more total light over all wavelengths

– darker colors reflect less total light

There are three characteristics of any color that can be measured and reproduced

1. color perceived i.e. red, green, blue– due to dominant wavelength reflected usually called “hue”

2. lightness/darkness of the color– due to total amount of light reflected over the range of

380 - 700 nm

– called lightness or “value”

3. intensity of the color– due to the proportion of the total light reflected that occurs

at the dominant wave length

– called chroma or “purity”, “strength”, “intensity”, vividness”

All color reflectance measurement systems use 3 numbers and most can be converted

to others

CIE uses X,Y, Z

Hunter L, a, b

Minolta can be set to any of several systems

Hunter has been largely adopted for meat color measurement because

L = lightness

a = redness (+) green (-)

b = yellow (+) blue (-)

L measures Lightness 100 - perfect whiteness 0 - Black

a Redness + Gray 0 Greeness -

b Yellowness + Gray 0 Blueness -

Example of pigments in solution for reflectance values

myoglobin 8.0 13.7 7.6

metmyoglobin 8.7 4.1 10.6

nitrosylhemochrome 26.0 19.5 15.1

meat samples typically will give L values of 35-60 and a values of 2 -30.

L a boxymyoglobin 8.0 28.6 13.6

Human panels --- visual appraisal

– much more difficult than it seems due to individual perceptions and biases

– try to remove “human” factor as much as possible

– can include “liking” or “preference” for a specific color which the absorbance or reflectance values cannot do