AMSA Meat Color Measurement Guidelines Revised December 2012 American Meat Science Association http://www.m eatscience.org AMSA Meat Color Measurement Guidelines Revised December 2012 American Meat Science Association 201 West Springfi eld Avenue, Suite 1202 Champaign, Illinois USA 61820 800-517-2672 [email protected] http://www.m eatscience.org iii CONTENTS Technical Writing Committee .................................................................................................................... v Preface ..............................................................................................................................................................vi Section I: Introduction ................................................................................................................................. 1 Section II: Myoglobin Chemistry ............................................................................................................... 3 A. Fundamental Myoglobin Chemistry ................................................................................................................ 3 B. Dynamics of Myoglobin Redox Form Interconversions ........................................................................... 3 C. Visual, Practical Meat Color Versus Actual Pigment Chemistry ........................................................... 5 D. Factors Affecting Meat Color ............................................................................................................................... 6 E. Muscle Metabolism and Meat Color ................................................................................................................. 7 F. Cooked Meat Color ................................................................................................................................................... 8 G. Cured Meat Color ..................................................................................................................................................... 8 H. Iridescence ...............................................................................................................................................................10 Section III: Physics of Color and Light ...................................................................................................11 A. Introduction .............................................................................................................................................................11 B. Color Perception of Meat ....................................................................................................................................15 C. The Physics of Light and Instrumental Color Measurements .............................................................17 Section IV: Visual Appraisal Principles ................................................................................................19 A. Introduction .............................................................................................................................................................19 B. Types of Visual Panels ..........................................................................................................................................19 C. Conducting Research Using Human Panelists ...........................................................................................19 D. Summary ...................................................................................................................................................................23 Section V: Display Guidelines for Meat Color Research ..................................................................25 A. Purpose of Display Studies ................................................................................................................................25 B. Packaging Materials Affect Meat Appearance ............................................................................................25 C. Product Handling and Storage Should Mimic Real World Parameters ...........................................26 D. Lighting Types and Intensity Affect Meat Appearance ..........................................................................26 E. Display Temperature Affects Color Life ........................................................................................................28 F. Meat Color Evaluated Against Time to Determine Meat Color Stability .........................................29 .....................................................................................................................29 SectionG. Configuring VI: Guidelines, a Meat VisualDisplay Meat Case Color Measurement ................................................................31 A. Selecting Panel Type .............................................................................................................................................31 B. Screening and Training of Panelists ...............................................................................................................31 ..........................................................................................................31 D. Conducting a Pretrial ...........................................................................................................................................31 C. Standardization of Significant Factors iii E. Selecting Appropriate Scoring Scales ............................................................................................................31 F. Using Reference Aids and Pictures ..................................................................................................................31 G. Sample Thickness ..................................................................................................................................................33 H. Packaging Format ..................................................................................................................................................33 I. Panelist Viewing Angle..........................................................................................................................................33 J. Rotating of Packages During Display ..............................................................................................................33 K. Objective Measures of Surface and Subsurface Pigments ....................................................................33 L. Display Case Temperatures and Defrost Cycles ........................................................................................33 M. Lighting Type and Intensity ..............................................................................................................................34 N. Visual Parameters to Report .............................................................................................................................34 Section VII: Visual-Color Scoring Scales ...............................................................................................35 A. Hedonic Scales for Consumer Panels ............................................................................................................36 B. Descriptive (Psychometric) Scales for Trained Panels ..........................................................................36 C. Meat Display Color Stability (Whole Muscle, Not Ground) ..................................................................38 D. Ground Meat Color ................................................................................................................................................41 E. Cooked Meat Color .................................................................................................................................................42 F. Cured Meat Color ....................................................................................................................................................43 G. Other Scales Associated with Meat Color Evaluation .............................................................................44 Section VIII: Guidelines, Instrumental Meat Color Measurement ...............................................45 A. Instrument Selection ............................................................................................................................................45 B. Illuminant Selection ..............................................................................................................................................45 C. Degree of Observer Selection ............................................................................................................................46 D. Aperture Size Selection .......................................................................................................................................46 E. Instrument Standardization ..............................................................................................................................46 F. Sample Thickness and Uniformity ..................................................................................................................47 G. Protecting the Aperture Port ............................................................................................................................47 H. Two-Toned Versus Discoloration Pattern ....................................................................................................47