An Origins Global Meat Special by Eben and Kristi van Tonder, 13 October 2015
Introduction: The Colour That Tells a Story
In the trade of goat meat, one of the most striking observations is this: some carcasses present white and clean, staying fresh for days, while others are red from the start, turning purple by the third day and black with a sour odour by the fifth.
How the surface of the carcass is treated immediately after slaughter. Those first few hours determine whether the meat stabilises or deteriorates.
While carcass handling after slaughter is the primary factor determining surface appearance and stability, several biological and environmental variables also contribute within certain bounds. Goats with naturally higher myoglobin concentrations, typically older or more active animals, produce slightly darker meat even under ideal processing conditions.
Dietary influences such as pastures rich in iron or specific minerals can also deepen pigmentation modestly. Similarly, environmental temperature, pre-slaughter stress, and genetic differences affect how rapidly muscle pH declines, subtly shifting surface colour between lighter or redder tones. These variations, however, are minor when compared with the effects of hygiene, moisture, and cooling rate.
Importantly, not every instance of darkening over several days signals poor practice; a small degree of colour change can result from normal oxidation if storage humidity or temperature fluctuates. In contrast, when the surface turns black with a sour odour, it indicates microbial spoilage, a clear sign that bacterial contamination, rather than natural pigment chemistry, has taken over.
The Purpose of This Review
This article outlines the key interventions that lead to a stable, white, and clean surface that resists bacterial growth while limiting weight loss to under 0.5%.
Each step is given an order-of-magnitude value to show its relative impact on final quality.
Understanding the Order-of-Magnitude Scale
To make this practical, we use a 1–10 scale:
| Value | Meaning | Expected Contribution |
|---|---|---|
| 10 | Absolutely essential | Directly determines success or failure |
| 8–9 | Highly influential | Strongly affects colour, stability, and hygiene |
| 6–7 | Moderately important | Contributes to overall control, supports main factors |
| 4–5 | Helpful in some environments | Useful fine-tuning where infrastructure allows |
| 1–3 | Minimal effect | Marginal improvements, mostly optional |
A rating of 10 means the process cannot succeed without it. A 5 indicates something valuable but not essential, and a 1 suggests minimal impact on the outcome.
1. Preventing Surface Contamination During Skinning (10/10)
This is the single most critical step in determining whether a carcass remains white and stable or turns dark and unstable within days. The moment knives, gloves, or the inner side of the hide make contact with the freshly exposed meat, bacteria begin to colonise the surface. These microorganisms trigger pigment oxidation and set in motion the chain of reactions that lead to the purple or black discolouration seen in unstable carcasses.
Although the principle is simple, it is one of the most difficult to control in practice. Skinning is often performed under pressure, with limited working space, inconsistent water supply, and tools that may not be sanitised between carcasses. Under such conditions, even a single lapse in attention can undo every other good measure applied elsewhere in the process.
Eben and Kristi have made this a central focus of their work, shaping it into a simple yet powerful system of management for meat plants. Their framework not only addresses hygiene at the skinning stage but also integrates yield tracking, batch control, and meat flow management into one coherent discipline. The result is a replicable model tailored to African processing environments, where stability and order must be created from variable conditions.
Their approach is rooted in workflow design, disciplined hygiene, and operator training. Workers are taught to regard the carcass surface as a living boundary that must never be touched, re-wetted, or exposed to unsterilised contact. This single discipline becomes the anchor point around which the rest of the plant’s system of order is built.
This is where the greatest transformation occurs. With the right producer and mindset, controlling contamination during skinning produces the most dramatic improvement in carcass colour, odour, and shelf stability, enhancing both the product and the reputation of the plant.
Their work can be explored further in the following publications:
- Van Tonder, E. and Van Tonder, K. (2025). Order Out of Chaos: Japan’s System of Organised Work and the Creation Story. Earthworm Express.
- Van Tonder, E. and Van Tonder, K. (2025). From Iteration to Entropy: Why 5S Works and How to Upgrade It for the AI Era. Earthworm Express.
- Van Tonder, E. and Van Tonder, K. (2025). From Ritual to Reality: Japan’s Path to Industrial Order and Africa’s Future Renaissance. Earthworm Express.
- Van Tonder, E. and Van Tonder, K. (2025). From Sacred Home to Sacred Factory: Rethinking Industrialisation in Africa. Earthworm Express.
Impact: Absolute
Typical weight loss: 0.0%
Result: Bright, clean surface with long colour stability.
2. No Washing or Dipping After Slaughter (9/10)
Water washing appears hygienic, but in fact increases surface moisture, spreads bacteria, and delays the natural sealing of the muscle surface. Moisture is the bridge between cleanliness and decay.
In many parts of Africa, including Nigeria, this practice has become widespread not for hygiene, but as a way to artificially increase carcass weight. Carcasses are often rinsed or even dipped in water immediately after slaughter so they appear cleaner and heavier on the scale. The gain, however, is deceptive and short-lived. The added water quickly evaporates or drips away, leaving behind a wet, contaminated surface that deteriorates much faster.
Warm meat proteins, still open and highly reactive immediately after slaughter, absorb water easily. At this point, the muscle fibres act like sponges, their structure loose and uncontracted. If a little salt is added to the wash water, the effect intensifies. The sodium ions dissolve surface proteins and increase the meat’s ability to bind water, creating a visible weight increase. The carcass swells slightly and looks glossy, but this gain is entirely superficial.
As soon as cooling begins and the proteins tighten during rigor mortis, much of the absorbed water seeps out again, carrying bacteria deeper into the surface layer. The result is a darker, wetter surface that spoils faster. What appears as a clever weight trick in the short term quickly turns into financial loss, odour, and reputation damage.
Proper dry handling, combined with the sorbate–acid cloth wipe, achieves the opposite result: a firm, pale surface that resists bacteria and retains its true weight through stability, not moisture.
Impact: Very high
Typical weight loss: 0.0%
Result: Drier feel, better odour, longer shelf life and honest yield.
3. Sorbate–Acid Cloth Wipe (8/10)
When handling has been less than ideal, for example, if there was contact between hide and meat or uncertainty about knife or glove hygiene, this step becomes essential. The sorbate–acid wipe compensates for early contamination by immediately lowering the bacterial load on the carcass surface and creating a mildly acidic environment that prevents further growth. It also assists in surface drying, helping the natural protective film to form more quickly.
It is inexpensive, safe, compatible with Halal requirements, and can be prepared directly on site.
Solution preparation
1 L clean water
1% acetic acid (10 ml per litre)
0.2% potassium sorbate (2 g per litre)
0.05% salt (0.5 g per litre)
Wring out the cloth well before use so that it is damp but not dripping.
Water temperature: The water should be lukewarm, around 25 to 35 °C, not hot. Warm water dissolves potassium sorbate and salt more evenly and enhances the wetting and antimicrobial effect. Cold water can be used if ambient conditions are hot, but the solution should not exceed 40 °C, as this may drive off acetic acid and reduce its acidity.
Water source and hardness: Borehole water is acceptable provided it is microbiologically clean and free of heavy metal contamination. Water hardness has only a minor influence on this application. High hardness, meaning very high calcium or magnesium, may slightly reduce the surface-wetting and antimicrobial action, but will not negate it. If water is extremely hard, above 300 ppm as CaCO₃, it is advisable to add 0.1% sodium citrate to improve solubility, although this is rarely necessary.
Why not sodium benzoate? The pair of Sodium Benzoate with Potassium Sorbate is a powerful and well-known combination (see my work on this at Potassium Sorbate & Sodium Benzoate). Why only Potassium Sorbate is important? This is because it remains active at a slightly higher pH, up to 6.5, while sodium benzoate is effective only below pH 4.5. Meat surfaces usually have a pH between 5.4 and 6.0, so sorbate provides stronger and more consistent inhibition. Sorbate also has a cleaner odour and does not leave a perceptible residue.
How many carcasses per cloth: A single cloth can effectively wipe three to five carcasses if contamination is light and the cloth remains visibly clean. However, once the cloth shows soil, hair, or visible residue, it should be rinsed or replaced immediately.
Cloth decontamination: Between carcasses, simply rinse the cloth in the same sorbate–acid solution. The acidity and preservative content are sufficient to prevent microbial growth in the cloth during use. However, to maintain consistency and hygiene, it is best to use one cloth per carcass for high-value or export meat.
At the end of the shift or after approximately 50 carcasses, all used cloths should be boiled in clean water for 10 minutes, air-dried, and reused the following day. This eliminates biofilms that could survive low-acid conditions.
Expected outcome: The wipe will noticeably lighten the colour of the surface, remove blood film, and produce a clean, slightly dry feel within minutes. It typically causes no measurable weight loss and helps restore confidence in carcass stability even where initial handling was imperfect.
The timing of the wipe down is critical: The ideal timing is immediately after the skin has been removed and before the carcass enters the cooling area. That short window, within the first 5 to 10 minutes after dehiding, is critical for stabilising the surface and preventing bacteria from establishing themselves.
Here is how to apply it correctly in sequence:
- Right after dehiding
As soon as the skin is completely off and before any visible drying begins, wipe down the carcass while it is still warm (around 30–35 °C surface temperature). This ensures that the solution spreads evenly and penetrates the thin surface film of moisture where bacteria would otherwise grow. - Before evisceration (if the system allows). In some plants, it can be done just after dehiding but before the carcass is opened, which helps reduce contamination from tools and hands during evisceration.
- Immediately after evisceration (if wiping before is not possible) If carcasses are moved along quickly, do it straight after evisceration, once all visible contamination has been removed and the surface is free from blood and debris.
- Never wait until after chilling. Once the carcass surface cools and begins to dry, the solution is far less effective. At that stage, bacteria may already have attached and formed microfilms that the acid cannot reach.
In short, the sooner the wipe is applied after dehiding, the better.
Impact: High
Typical weight loss: 0.0%
Result: Lighter colour, clean odour, smooth and stable surface.
4. Rapid Surface Cooling (Pre-Chill) (9/10)
A brief exposure to –1 to 0 °C air at 65–75% relative humidity for 30–45 minutes forms a thin protein film that locks in moisture and repels bacteria. This “surface sealing” is fundamental to quality preservation.
-> Likely Natural Relative Humidity Conditions (Country Ranking)
When considering how easily each country can meet the target relative humidity of 65 to 75 % during the rapid pre-chill, both ambient humidity and the type of cooling systems used must be taken into account. Many chillers in these regions draw in outside air, so the climate plays a major role.
Here is a ranking from highest to lowest likelihood of naturally achieving the target range.
| Rank | Country | Typical Ambient RH | Comment |
|---|---|---|---|
| 1 | Ethiopia | 60–85% | Cool, humid highland air often close to ideal conditions |
| 2 | South Sudan | 55–80% | Warm and humid near Juba; may even exceed the target |
| 3 | Pakistan | 45–75% | Coastal and plains regions moderately humid; drier inland |
| 4 | India | 40–70% | Variable, humid in the east and south, drier inland |
| 5 | Tanzania | 45–65% | Coastal zones adequate, highlands drier |
| 6 | Kenya | 35–60% | Often too dry, especially inland; humidifiers usually required |
In summary, Ethiopia and South Sudan are best suited, Pakistan and India are variable but manageable, Tanzania is moderately suited, and Kenya will normally need humidity control.
-> Why Relative Humidity Matters
If relative humidity drops below 60 %, the carcass surface dries too quickly, causing unnecessary weight loss and cracking of the natural protein film. If it rises above 80 %, condensation forms, and bacteria can multiply more easily. The ideal range of 65 to 75 %allows a thin surface film to develop without drawing excessive moisture from within the muscle.
-> How to Adjust Humidity Economically
To increase relative humidity, water vapour must be added to the air.
Low-cost methods include:
- Water trays or shallow tanks placed inside the chiller beneath the airflow path. As the cool air moves over the surface, it absorbs moisture and raises humidity by about five to ten %. Suitable for small rooms up to fifty cubic metres.
- A simple misting line or fog nozzle using low-pressure water near the air intake. The mist evaporates into the chilled air, increasing humidity by ten to twenty %without wetting the carcasses. Effective in rooms up to two hundred cubic metres.
- Wet cloth or hessian pads in front of a fan. The air passing through the damp material gains moisture, functioning like an evaporative cooler. The pads must be rinsed daily to prevent bacterial build-up.
- Slightly wetting the concrete floor before chilling begins. As the air circulates, it absorbs moisture from the surface. Puddles should be avoided as they increase bacterial risk.
To reduce relative humidity, moisture must be removed from the air or its evaporation slowed.
- Use increased airflow combined with mild heating. A small heater raising temperature by only one or two degrees Celsius is sufficient. Warmer air carries more vapour, so measured relative humidity falls.
- Increase the intake of outside air when it is drier than the internal air. This dilutes the moisture content.
- Use a simple dehumidifier, ice condenser, or chilled metal coil to trap condensation. This can lower humidity by about ten to fifteen %.
- Keep floors and drains dry at all times. Standing water is a major source of excess humidity.
- Combining a Fan, Heater and Water Source
The three elements can work together to give practical control in facilities of any size.
The fan keeps air moving evenly around the room. The water source, whether trays or misting nozzles, increases humidity. A small electric heater, around one to two kilowatts, placed near the air intake can gently reduce humidity if it rises above the target.
At larger scale, for rooms between one hundred and five hundred cubic metres, a simple timer system can alternate these functions.
> The misting line runs for five minutes every half hour if humidity falls below sixty-five %.
> The heater operates for five minutes every half hour if humidity rises above seventy-five %.
> The fan remains on continuously at low speed to keep conditions even.
A digital hygrometer placed at carcass height allows staff to monitor and adjust easily.
-> Summary Table
| Goal | Practical Method | Expected RH Shift | Cost Level | Notes |
|---|---|---|---|---|
| Increase RH | Water trays under airflow | +5–10% | Very low | Simple and effective for small rooms |
| Increase RH | Mist line or fog nozzle | +10–20% | Moderate | Best control, avoid wetting carcasses |
| Increase RH | Wet hessian pads and fan | +10% | Low | Requires cleaning daily |
| Reduce RH | Use heater and fan | –5 to –15% | Low | Gentle warming removes vapour |
| Reduce RH | Dry air intake | –10% | Low | Needs filtered outside air |
| Reduce RH | Dry floors and drains | –5% | No cost | Critical daily step |
Among these regions, only a few naturally offer humidity close to the ideal range for controlled pre-chilling. Most plants will need to adjust the air conditions deliberately. A fan, a small heater, and a simple water source are sufficient to balance the environment.
The goal is not technology for its own sake, but steady control of a microclimate: cool air that carries just enough moisture to let the surface dry slightly without losing weight or allowing bacterial growth. In this controlled balance, quality preservation becomes predictable rather than accidental.
Impact: Very high
Typical weight loss: 0.3%
Result: Whitish surface, smooth touch, extended freshness.
5. Controlled Main Chilling (8/10)
After pre-chill, carcasses enter a main chilling phase at 0–2 °C and 88–92% relative humidity.
Gentle airflow maintains the seal while avoiding further dehydration.
The same environmental principles apply in the main chilling phase as in the pre-chill—the only difference is that the process continues for many hours rather than 30–45 minutes.
In countries such as Kenya, where the ambient air is relatively dry, the relative humidity inside the chill room will naturally fall below the target (88–92%) unless moisture is actively added. Without control, the surface will dry too fast, resulting in excess weight loss and a dull, leathery film rather than the fine protein glaze that preserves colour.
Keeping the floor slightly wet is indeed a simple and effective way to help maintain humidity under Kenyan conditions. Here is how to manage it safely and effectively:
- Lightly sprinkle or mop the floor with clean water before starting the chill cycle. The surface should look damp, not flooded. A thin film of water evaporates slowly and raises the room humidity by several percentage points.
- Avoid standing pools of water. These can encourage bacterial growth and may create condensation on carcasses if airflow is too low. The floor should remain damp but not slippery.
- Combine with gentle airflow. A low, steady air speed of about 0.2 to 0.5 metres per second keeps moisture evenly distributed and prevents condensation pockets.
- If available, use a simple mist nozzle for brief bursts during long chilling periods, especially if humidity drops below 85 percent.
Impact: High
Typical weight loss: 0.2%
Result: Surface firmness, colour stability up to seven days.
6. Air Hygiene: Filtered or UV-Treated Inlet Air (6/10)
Clean air reduces recontamination during both pre-chill and main chilling. Air filtration or mild ultraviolet treatment at the air inlet lowers airborne bacterial counts and prevents dust or spores from settling on carcass surfaces. These units have become relatively inexpensive, but in many facilities, the real challenge lies in consistent maintenance rather than cost. Filters must be cleaned or replaced regularly, and UV lamps need periodic inspection to ensure they still emit effective radiation levels. Without this upkeep, their benefit drops sharply.
Impact: Moderate
Typical weight loss: 0.0%
Result: Reduced airborne spoilage risk and greater microbiological stability throughout the chilling process.
7. Humidity Control (7/10)
Relative humidity between 88 and 92 %is the fine balance point that determines whether the surface seals properly or begins to deteriorate. This range allows a thin protein film to form while still retaining internal moisture. Once humidity falls below about 85 %, the surface dries too quickly, producing a tough outer layer and unnecessary weight loss. When it rises above 95 %, moisture condenses on the meat, leading to a tacky surface and darker colour as bacterial activity and pigment oxidation increase.
Wind speed interacts closely with humidity. Even small changes in airflow can shift the outcome. A light movement of air, around 0.2 to 0.5 metres per second, supports even drying and colour stability, but higher speeds intensify water loss and may push the surface below the target humidity.
In short, the tipping point is a moving balance between moisture and air velocity. Maintaining both within these narrow limits determines whether the carcass remains supple and bright or begins to dehydrate and darken.
In Kenya, humidity control is generally the least critical factor among the top interventions, because the natural climate already tends to be on the dry side, and most small or medium-scale chillers operate at modest air speeds where the risk of over-humidification or condensation is low.
Impact: Moderate to high
Typical weight loss: 0.1%
Result: Balanced dryness with minimal mass loss.
8. Short Rest Before Freezing (4/10)
Resting carcasses for 4–6 hours at 0 °C before freezing equalises temperature and prevents surface cracks during blast freezing.
In a fresh-meat system, the previous steps, such as hygiene, the sorbate wipe, pre-chill sealing, gentle airflow, and humidity control, become even more critical because there is no freeze step to stop bacterial growth. Once the carcasses have reached full internal equilibrium, the same chill conditions should be maintained rather than resting for freezing. The process then moves directly to storage or dispatch, with no temperature change.
Impact: Moderate-low
Typical weight loss: 0.0%
Result: Improved surface integrity.
9. Floor Drainage and Hygiene (10/10)
Standing water below carcasses reintroduces bacteria and destabilises humidity.
Clean, fast-drying floors are as important as knife hygiene.
It is indeed striking that something as ordinary as floor drainage and cleanliness scores as high as knife hygiene. Yet in every meat plant, the condition of the floor determines the microbial load of the air, the humidity balance, and the rate at which surfaces re-contaminate. The floor becomes the silent generator of either clean or dirty air.
Inexpensive chemical cleaning options work well as long as they are used systematically.
- Hydrogen peroxide or peracetic acid blends
These are the most effective broad-spectrum sanitisers. They kill bacteria, yeasts, moulds, and spores and penetrate small cracks and biofilms. They work well even in the presence of organic matter. However, they are more expensive and require trained handling. Best suited for periodic deep cleaning in plants with established safety practices. - Chlorine-based cleaners
Sodium hypochlorite, ordinary household bleach, is highly effective, quick acting, and inexpensive. A working solution of 100 to 200 parts per million available chlorine is sufficient for daily use. This means about 10 to 20 millilitres of standard bleach, containing 5 percent available chlorine, per litre of water. Floors should be rinsed clean of visible dirt first, then mopped with the solution and left to dry. Chlorine solutions should always be prepared fresh, as they lose strength rapidly in light or heat. - Quaternary ammonium compounds (quats)
These disinfectants are gentle on concrete and leave a residual antimicrobial film that continues to suppress bacterial growth after cleaning. They are more expensive and slightly less effective against spores and resistant bacteria but provide an excellent complement to chlorine when used once or twice a week in rotation. - Simple acid rinse for scale control
A weak acid rinse, such as 1 percent citric or lactic acid, is not a disinfectant on its own but helps to dissolve mineral deposits, maintain floor integrity, and keep the surface slightly acidic, which discourages bacterial growth. It is useful once or twice per week as part of a regular cleaning programme.
In most small to medium abattoirs, the combination of good drainage, physical cleaning with detergent, followed by a dilute chlorine rinse gives the best balance of cost, effectiveness, and safety. Consistency is more important than product strength; cleaning properly every day achieves more than deep cleaning once in a while.
It is simple, but it earns a score of ten because nothing else maintains air hygiene, humidity stability, and surface cleanliness so directly at so little cost.
Impact: Absolute
Typical weight loss: 0.0%
Result: Sanitary environment and stable air quality.
Summary Table
| Step | Description | Impact (1–10) | Typical Weight Loss (%) |
|---|---|---|---|
| 1 | Prevent contamination during skinning | 10 | 0.0 |
| 2 | No washing or dipping | 9 | 0.0 |
| 3 | Sorbate–acid cloth wipe | 8 | 0.0 |
| 4 | Rapid pre-chill sealing | 9 | 0.3 |
| 5 | Controlled main chilling | 8 | 0.2 |
| 6 | Air hygiene (filtered or UV) | 6 | 0.0 |
| 7 | Humidity control (88–92%) | 7 | 0.1 |
| 8 | Rest before freezing | 4 | 0.0 |
| 9 | Floor drainage and hygiene | 10 | 0.0 |
Total expected weight loss: ≤ 0.5%
Shelf life: Up to seven days with maintained whiteness and neutral odour.
Conclusion: Precision, Not Luck
The whiteness of a carcass is not luck, breed, or weather. It is the product of controlled exposure, disciplined handling, and respect for the material. Each step adds or subtracts stability in measurable degrees.
By understanding their order of magnitude, producers can focus energy and investment on the interventions that truly matter, those rated eight and above, while refining the rest according to resources and climate.
A white carcass is not simply cleaner; it is a signal of mastery. It shows that the surface has reached equilibrium, dry enough to resist life yet moist enough to preserve it. That balance marks the meeting point of science and craft—the art of meat handling expressed through precision rather than chance.
References
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- Belk, K.E., Scanga, J.A., and Tatum, J.D. (2003). “Meat colour and the importance of surface oxygenation.” Colorado State University Meat Laboratory Bulletin.
- Nychas, G.J.E. et al. (2008). “Meat spoilage during distribution.” Meat Science, 78(1–2), 77–89.
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- Sofos, J.N. (2005). Improving the Safety of Fresh Meat. Woodhead Publishing.
- Mancini, R.A. and Hunt, M.C. (2005). “Current research in meat colour.” Meat Science, 71(1), 100–121.