Fundamentals of Water Holding Capacity (WHC) of Meat

Table of Contents

1. Introduction
   1. Objectives
   2. Learning goals
   3. Teacher page
2. List of Abbreviations used in this Learning Resource
3. Section I: Introduction and Significance of WHC
   1. What is WHC?
   2. Overview of Proteins, Fat, pH and Water and WHC
   3. Compartments for Holding Water in Meat
   4. Activity - Section I
4. Section II: Major Factors Affecting WHC
   1. Role of Animal Genetics and WHC
   2. Role of Pre-harvest Handling of Pigs on WHC
   3. Conversion of Muscle-to-Meat Issues and WHC
   4. Muscle Extensibility and Rigor Mortis
   5. Activity - Section II
5. Section III: Mechanism for Holding of Water in Pork
   1. Concepts for holding of Water in Meat
   2. How is Water Held in Meat?
   3. Graphic Representation of WHC and Important Concepts
   4. Examples of Extrinsic Factors Affecting WHC of Processed Meats
   5. Activity - Section III
6. Section IV: Fundamental Science of Water Holding Capacity
   1. Expanding the Knowledge of WHC
   2. The Assignment
   3. Activity - Section IV
7. Section V: Methods for Determining WHC
   1. Complexity of Measuring WHC
   2. What Moisture Categories of Water need to be Measured?
   3. Video: Great Visualization of four WHC Methods
   4. Methods for Measuring WHC of Meat
   5. Activity - Section V
8. Section VI: Recent Advances in Measuring & Monitoring WHC
   1. Need for Fast, Real-time, Non-destructive WHC Methods
   2. Potential Fast and Non-destructive Methods
   3. Activity - Section VI
9. Selected References related to WHC
10. References: Q-Pork Chain & Other Instrumental Methodology for WHC
11. Completion
    1. Comments
    2. Self assessment
    3. Evaluation
12. Acknowledgement

Role of Animal Genetics and WHC

The meat industry has known for years that some animals are more susceptible to a variety of production stressors than others. Pigs that are homozygous or heterozygous for the halothane (Ryanodine) gene are very susceptible to stress, which causes changes in the meat that predispose it to abnormal meat qualities ranging from pale, soft, and exudative (PSE) to dark, firm, and dry (DFD) pork. Carcasses with PSE meat have a faster than normal decline in pH post-mortem while the carcass temperatures are relatively high. These conditions lead to excessive protein denaturation, early cellular membrane disruption (that is, increased conductivity in PSE meat), and a lower than normal WHC. Rapid chilling will help minimize the severity this condition. At the other extreme, carcasses that are DFD have meat that is abnormally high in pH 24 hr post-mortem because the live animal metabolizes most of stored muscle glycogen before slaughter. This results in lower amounts of lactic acid accumulation during the conversion of muscle to meat. Chilling rate does not affect this condition because DFD meat is caused by ante-mortem stress.

Animals with the stress genotypes are often fast growing and heavy muscled, but because of the lower quality, breeding companies and pork industry organizations recommend eliminating this gene from breeding herds. WHC varies more between genetic lines of pigs than within genetic lines, so selecting breeding stock for higher WHC is possible.

Pigs with the RN gene (also known as the Napole gene; Lundström and Malmfors, 1985) have normal color and firmness, but have lower WHC because these animals characteristically have a higher than normal amount of glycogen in the muscle at slaughter. Hence, these carcasses develop a lower than normal pH (often near 5.2 to 5.4 (see Fig. II.4). Because their pH is closer to the isoelectric pH_I (5.1), the lower WHC is mostly due to protein insufficiently charged to bind water and to higher than normal protein denaturation. However, pigs with the Napole gene may be slightly more heavily muscled and have more tender meat than pigs without this gene. Thus, while WHC and processing yields decline, some measures of quality improve.