Collagen, Myofibrillar Proteins and Gel Strength in Chicken-Based Krainer Sausages

By Eben van Tonder – 12 November 2025

Introduction

For years I have tried to firm up skins and tendons rich in collagen to enhance their inclusion in Krainer-style sausages such as the South African Russian and the Zambian Hungarian. I experimented with modified starches, methylcellulose, transglutaminase, carrageenan, sodium alginate, gums, fibres, and even by converting skins into micro-particles.

After five years of trials, I found that the answer lies not in exotic hydrocolloids but in the fundamentals of sausage making. The characteristic firmness of a Krainer arises from the natural network of myofibrillar proteins. Collagen alone cannot form a firm gel; it requires integration within the myofibrillar protein matrix to develop elasticity and structure.

This relationship mirrors biology. In the animal body, collagen and myofibrillar proteins form a cooperative structural network that resists tension and preserves tissue integrity. Recreating this system in sausage formulation reproduces the muscle’s natural architecture. The ideal Krainer recipe, therefore, is rooted in biology—it mirrors the way firmness and resilience occur in living muscle.

1. Collagen–Myofibrillar Interaction and Its Role in Krainer Firmness

When collagen is heated, it begins to shrink at about 60 °C due to triple-helix contraction. Without myofibrillar proteins, this contraction produces a soft, porous gel that cannot retain water. Salt-soluble myofibrillar proteins such as myosin and actin unfold and interact with collagen, forming a continuous elastic grid that resists shrinkage and holds moisture.

LaBudde’s polymer model (1995) describes this structure as a composite system: collagen acts as the filler phase, while myofibrillar proteins form the continuous polymer matrix. The result is a strong, elastic gel—achieved when both components are present in balanced proportions. Excess collagen, however, causes brittleness due to over-contraction during heating.

The best firmness occurs when collagen represents 20–25 % of the total protein, corresponding to roughly 5–8 % of the total batter in chicken MDM-based formulations.

2. Optimal Inclusion Levels

Firmness depends on both inclusion rate and collagen source. The following summary outlines the most effective ranges:

  • Pork skin (cooked and minced)
    Inclusion rate: 5–8 % of total batter
    Function: Reinforces the protein matrix, adds elasticity and cohesion
  • Beef skin (cooked and minced)
    Inclusion rate: 4–7 % of total batter
    Function: Produces a firmer, slightly chewier texture with a darker tone
  • Combined pork and beef skin
    Inclusion rate: 6–9 % total
    Function: Provides optimal structural balance and cost-efficiency

At less than 3 % inclusion, firmness improvement is minimal. Above 10 %, the collagen dominates, causing shrinkage and a rubbery bite on reheating.

3. Preparation of Pork Skin

To achieve maximum firmness, pork skin must be properly processed to preserve collagen integrity and allow even dispersion in the batter:

  • Use fresh or frozen pork skin with a thin layer of natural fat attached (improves mouthfeel and internal lubrication).
  • Simmer in water at 90 °C for 60–90 minutes until soft and translucent. Drain and cool to 40–50 °C.
  • Mince through a 3 mm plate while still warm; if finer texture is required, mince again after chilling to 4 °C.
  • Optional: chop briefly (10–15 seconds) in the cutter with 20–30 % of the total formulation water and 0.3 % salt to aid dispersion. Keep below 12 °C. Deduct this water from the total 30 % formulation allowance.
  • Spread on trays and chill to ≤ 4 °C before inclusion in the main batter.

4. Preparation of Beef Skin

Beef skin behaves differently due to thicker collagen fibres and higher crosslink density. Proper cleaning and cooking are essential:

  • Scald at 65–70 °C for 5–6 minutes and scrape manually, or lime-soak (2–3 % Ca(OH)₂ at 20–25 °C for 12–24 h) followed by rinsing until pH < 8.
  • Cook the cleaned hide in a 3:1 water-to-skin ratio at 95 °C for 3–4 hours until soft and translucent.
  • Mince first through a 6 mm plate, then through 3 mm while warm (45–55 °C). Avoid temperatures above 100 °C.
  • Optional: for coarse particles, chop briefly (10–15 seconds) using about 30 % of the formulation water, maintaining below 12 °C. Deduct this water from the 30 % total allowance.
  • Chill immediately to 4 °C before mixing.

5. Inclusion in the Main Batter

After salt and phosphate extraction of myofibrillar proteins from the MDM, add the prepared skin components.
Fold them in using a paddle mixer or slow-speed cutter rather than a high-speed bowl cutter to prevent collagen fibre breakage. Gentle incorporation maintains the structural integrity of the collagen network and improves binding.
Always add skins at or below 4 °C.

6. Process Flow Summary

To simplify production control, the key preparation and inclusion stages are summarised below:

  • Raw preparation
    • Pork: Rinse and retain thin fat layer
    • Beef: Dehair or delime thoroughly
  • Cooking
    • Pork: 90 °C for 60–90 minutes
    • Beef: 95 °C for 3–4 hours
  • Mincing
    • Pork: 3 mm warm mince
    • Beef: 6 mm + 3 mm warm mince
  • Optional fine-cut
    • Short chop (10–15 seconds) with 20–30 % formulation water
    • Deduct added water from total 30 % recipe water
  • Cooling
    • Chill to ≤ 4 °C before inclusion
  • Mixing inclusion
    • Add gently with paddle or slow-speed cutter
  • Inclusion rates
    • Pork skin: 5–8 %
    • Beef skin: 4–7 %
    • Combined: 6–9 % total

7. Practical Observations

When xₚₒᵣₖ ≈ 6 % or x_bₑₑf ≈ 5 %, firmness and water retention approach those of an all-meat Krainer. Pork skin enhances elasticity and bite smoothness, while beef skin gives strength and structure. A 1:1 blend (3 % pork + 3 % beef) delivers the best balance between mouthfeel and firmness.

During mixing, cold skins must be folded in slowly to allow full integration into the myofibrillar gel network. All water used for skin processing or fine-cutting must be deducted from the 30 % formulation limit.

8. Mechanical Principles

  • Collagen alone contracts on heating and releases water.
  • Myofibrillar proteins add structural support through covalent and hydrophobic bonds.
  • The mixture behaves like a filled polymer system: collagen fibres act as the filler, myofibrillar proteins form the continuous matrix.
  • Maximum firmness results when 75–80 % of the protein mass is myofibrillar and 20–25 % is collagen.
  • Excess collagen above 10 % softens the product and creates shrinkage artefacts.
  • Gentle mixing preserves collagen fibres and improves overall texture.

Conclusion

A firm Krainer made from chicken MDM and skin is not achieved through additives or emulsifying agents but through the controlled recreation of muscle structure itself. Collagen and myofibrillar proteins must work together, as they do in living tissue, to produce the balance of elasticity, cohesion, and bite that defines the true Krainer.

This biological principle is the foundation for both the science and art of sausage making: the optimal Krainer is not a product of chemistry but of biology—an edible reconstruction of muscle, firmed by nature’s own engineering.

References

LaBudde R. A. (1995). Review of Comminuted and Cooked Meat Product Properties from a Sol, Gel and Polymer Viewpoint.
Smith D. M. (1991). Factors Influencing Heat-Induced Gelation of Muscle Proteins. Interactions of Food Proteins, 454 243–256.
Hong G. P., Lee S., Min S. G. (2014). Effect of pork skin gelatin on the rheological properties of meat batters and thermal stability of emulsions. Food Science and Biotechnology, 23(4), 1075–1081. https://doi.org/10.1007/s10068-014-0148-1
Choe J., Kim H. Y., Kim Y. J. et al. (2017). Effects of porcine, chicken, and bovine gelatin on quality characteristics of low-fat frankfurters. Food Science of Animal Resources, 37(3), 388–397. https://doi.org/10.5851/kosfa.2017.37.3.388