By Eben van Tonder | EarthwormExpress | 9 July 2025
Introduction: The African Mystery
In our meat processing operations in Africa, we’ve observed a consistent problem: our minced meat refuses to produce the characteristic “spaghetti look”, those long, clean, defined strands that roll out of the mincer like perfect threads. Instead, what we get is soft, wet, short-fibre mince that sticks to the mincer head, clumps on the table, and resists any attempt at clean structure. For months, we suspected mincer faults, temperature issues, or even poor blade alignment. But the answer, as it turns out, lies much deeper—in the muscle biology of the animals we work with.
The culprit? DFD meat, Dark, Firm, Dry. What follows is the most comprehensive explanation of why DFD meat behaves this way and what can be done about it.
What is DFD MeWhat is DFD?
DFD stands for Dark Firm Dry, a condition in meat that results from physiological stress before slaughter. Though the meat appears visually dry and dark in colour, it is in fact excessively hydrated at a microscopic level. Understanding the biochemical and hormonal processes behind this condition reveals why it presents such serious challenges for meat processors, shelf life, and sensory quality.
The Biochemical Origin of DFD Meat
DFD meat arises when animals experience chronic stress before slaughter. This could be due to prolonged transport, overcrowding, inadequate lairage conditions, or repeated handling. This stress leads to a depletion of muscle glycogen reserves, which in turn means that lactic acid cannot accumulate post-mortem. Without enough lactic acid, the ultimate pH remains high, typically above 6.0.
Let us revisit this process for context. When an animal is slaughtered, the supply of oxygen to its muscle cells stops. Without oxygen, the muscle can no longer rely on aerobic respiration to produce energy and instead shifts to anaerobic glycolysis.
How Aerobic Respiration Works
Under normal conditions, when oxygen is available, muscle cells produce energy through aerobic respiration. This process begins with glycolysis, where glucose derived from muscle glycogen is converted into pyruvate. In the presence of oxygen, pyruvate enters the mitochondria where it is further processed through the Krebs cycle and the electron transport chain. Oxygen serves as the final electron acceptor, enabling the complete oxidation of glucose into carbon dioxide, ATP, and water.
This pathway is highly efficient and generates approximately 36 to 38 molecules of ATP per molecule of glucose. The water produced in this process, known as metabolic water, is not lost as vapour in the living animal. Instead, it contributes to intracellular hydration. Some of this water enters the capillary network and interstitial space, helping to maintain tissue turgor and cell volume. It also stabilises the microenvironment between muscle fibres and muscle cells, influencing osmotic balance and mechanical integrity. In life, the capillary system regulates this water flux. After death, when circulation ceases, this regulatory mechanism collapses, and the movement and retention of water in these spaces becomes subject to osmotic gradients, protein denaturation, and the structural integrity of the capillary network.
Anaerobic Glycolysis After Slaughter
When oxygen is no longer available, such as after slaughter, aerobic metabolism is interrupted. The electron transport chain halts, and the muscle must shift to anaerobic glycolysis to continue producing ATP. In this process, glycogen stored in the muscle is broken down into glucose, which is then converted into pyruvate. Because pyruvate cannot enter the mitochondria without oxygen, it is instead converted to lactic acid. This reaction regenerates NAD⁺, allowing glycolysis to proceed. The accumulation of lactic acid lowers the muscle pH from around 7.0 in the living animal to an ultimate pH of approximately 5.4 to 5.8. This acidification is essential for proper meat quality, affecting colour, tenderness, water-holding capacity, and microbial stability.
Lactic Acid Fermentation in Muscle and Microbes
The conversion of pyruvate to lactic acid in muscle cells during anaerobic metabolism closely mirrors a well-known microbial process: lactic acid fermentation. The biochemical pathway used by muscle tissue post-mortem is essentially the same as that employed by lactic acid bacteria such as Lactobacillus and Streptococcus, which are prominent in food fermentation.
In both systems, glucose is converted into pyruvate through glycolysis, producing a small amount of ATP and reducing NAD⁺ to NADH. Under aerobic conditions, NADH is oxidised via the electron transport chain, with oxygen as the final electron acceptor. However, in anaerobic environments—whether in muscle tissue after slaughter or in bacteria—this oxidative pathway is blocked. To sustain ATP production, the cell must regenerate NAD⁺. This is achieved by converting pyruvate into lactic acid through the action of lactate dehydrogenase, which oxidises NADH back to NAD⁺.
In lactic acid bacteria, this pathway is the primary method of energy production. In muscle tissue, it is a temporary adaptation to oxygen deprivation during intense activity or following death. While the biological context differs, the underlying metabolic logic is the same. Lactic acid fermentation is a universal biochemical strategy for maintaining glycolytic energy production in the absence of oxygen.
Recognising this shared mechanism reinforces the idea that lactic acid is not merely a waste product, but a vital metabolic tool that supports survival under anaerobic conditions. In meat science, it plays a transitional role that determines whether a carcass will produce high-quality meat or exhibit severe functional defects.
Glycogen Depletion and the Stress Response
If an animal experiences chronic stress before slaughter, the situation changes dramatically. The muscle’s glycogen stores may be severely depleted by the time of death. Glycogen, a highly branched polymer of glucose, serves as a readily mobilised energy reserve in muscle. It differs from glucose, which is a single sugar molecule and the basic energy substrate for cellular metabolism. Glycogen’s advantage lies in its dense energy storage and rapid availability when energy demand increases.
When glycogen reserves are exhausted, there is insufficient substrate for anaerobic glycolysis. As a result, little lactic acid is produced, and the muscle pH remains elevated. This leads to the development of DFD meat, which is characterised by a high ultimate pH, dark colour, firm texture, and shortened shelf life. Such meat is less desirable for both fresh consumption and further processing.
Cortisol and the Catabolic Cascade
At the heart of this glycogen depletion is the hormone cortisol. Released from the adrenal cortex under the influence of the hypothalamic pituitary adrenal axis, cortisol orchestrates the body’s response to long-term stress. It promotes gluconeogenesis in the liver, where glucose is synthesised from non-carbohydrate sources, particularly amino acids derived from muscle protein. This catabolic process maintains blood glucose levels but drains the muscle of energy reserves.
Cortisol also suppresses insulin sensitivity, preventing glucose uptake by muscle cells and hindering glycogen synthesis. Cortisol suppresses insulin sensitivity as part of the body’s broader metabolic response to stress. During periods of prolonged stress, such as transport, fasting, or fear, the animal’s physiological priority shifts from building energy stores to mobilising available resources for survival. Cortisol plays a central role in this shift by ensuring that glucose remains available in the bloodstream for vital organs, especially the brain, which depends almost entirely on glucose and cannot use fat for energy.
To preserve circulating glucose, cortisol interferes with the action of insulin. Under normal conditions, insulin promotes glucose uptake into muscle and fat cells, where it is either used for energy or stored as glycogen and fat. Cortisol counters this by reducing the sensitivity of insulin receptors, thereby preventing glucose from entering cells. This mechanism, often referred to as cortisol-induced insulin resistance, helps maintain blood glucose levels during extended stress but comes at the cost of depleting glycogen stores in muscle tissue.
In addition to blocking glucose uptake, cortisol directly inhibits glycogen synthesis. It suppresses the activity of enzymes responsible for converting glucose into glycogen in muscle cells. At the same time, it promotes gluconeogenesis in the liver, the process of generating new glucose from non-carbohydrate sources such as amino acids derived from muscle protein. This dual action ensures a steady supply of glucose for essential systems but leaves the muscle depleted of its primary energy reserve.
The result is a shift from an anabolic to a catabolic metabolic state. While insulin favours storage and repair, cortisol drives tissue breakdown to supply energy. This hormonal environment prevents the muscle from rebuilding its glycogen reserves, making it physiologically unprepared for post-mortem glycolysis. Consequently, animals that remain in this cortisol-dominant state until slaughter often produce meat that lacks adequate lactic acid development, resulting in the high pH and poor quality associated with DFD. In combination, these effects lead to a net breakdown of muscle proteins and exhaustion of glycogen stores. In the hours leading up to slaughter, a stressed animal may be unable to restore its depleted glycogen pool, leaving its muscle physiologically unprepared for post-mortem acidification.
Entrenchment of the Stress State
Animals subjected to prolonged stressors, such as transport without rest, food deprivation, social disruption, or handling, remain in a cortisol-driven catabolic state. As the muscle is broken down and glycogen is diverted to maintain blood glucose, very little remains available by the time of slaughter. Without this glycogen, lactic acid production post-mortem is negligible, and the muscle pH remains high.
The resulting meat is dark in appearance, firm in structure, and visually dry. Paradoxically, DFD meat is not dry at all. It retains a great deal of water tightly bound within the muscle fibres. What appears dry is overhydrated at the microscopic level, with water held so strongly that it cannot easily be expressed or lost. This water-binding capacity arises because the pH remains above the isoelectric point of key muscle proteins, where their net charge repels water rather than allowing it to drain.
Final Considerations
Thus, the chain of events from pre-slaughter stress to compromised meat quality is traceable with precision. Glycogen serves as the essential fuel for post-mortem acidification through lactic acid formation. Chronic stress, through the prolonged action of cortisol, disrupts this process. As a result, the muscle fails to acidify properly, leading to DFD meat, a condition with major consequences for processing, shelf life, and consumer acceptance.
“The absence of sufficient glycolysis post-mortem keeps the muscle pH above the isoelectric point of most muscle proteins, resulting in enhanced water-holding capacity” (Honikel, 1998).
DFD meat is not dry. It is hydrated to an extreme degree. What looks like dry, firm muscle on the outside is a sponge on the inside, holding water tightly inside the myofibrillar network. And this has massive consequences for processing.
Capillary Collapse and Water-Holding
All meat undergoes vascular collapse post-mortem. Capillaries drain during exsanguination and then collapse structurally. But in DFD meat, the capillary collapse does not lead to visible purge or drip loss, as it does in PSE meat.
The high pH prevents protein denaturation, the microstructure remains intact, and water is trapped inside the myofibrils rather than squeezed into the extracellular space.
“Capillaries collapse in all post-mortem meat, but drip only occurs when sarcomeric and myofibrillar structures contract and squeeze out fluid. In DFD meat, these spaces remain hydrated and expanded” (Huff-Lonergan & Lonergan, 2005). Lactic acid is essential in this process because it lowers the muscle pH toward the isoelectric point of myofibrillar proteins, particularly myosin and actin. At this point, the proteins have no net electrical charge, causing them to pack more tightly. This tightening, coupled with rigor mortis-induced contraction of sarcomeres, leads to a mechanical compression of the water-holding matrix. As a result, water that was previously bound or loosely associated within the muscle fibre network is forced into extracellular spaces and may appear as surface drip.
Why We Can’t Get the Spaghetti Look
We now get to the heart of the matter. In parts of Africa, many of our animals are nomadic, subjected to long treks, and often arrive stressed. The result is DFD meat. Here’s why it fails to give us clean, fibrous mince:
- Muscle Swelling: Water is held tightly inside the muscle. When ground, the internal pressure forces water out, resulting in a mushy consistency.
- Low Protein Denaturation: Since the proteins remain intact, they do not shear cleanly through the grinder. Instead of clean strands, we get compression, smearing, and clumping.
- Overhydrated Texture: The meat holds too much water. During mincing, the fibres break down easily, producing a product that behaves more like a paste.
- Visual Deception: DFD meat appears dark and dry. But this dryness is external. Once you cut or grind, fluid seeps out—not as drip, but as tightly held moisture breaking loose from disrupted cells.
“DFD meat fools the eye: its surface is dry, but its interior is saturated. Moisture is invisible until the structure is disturbed” (Lawrie & Ledward, 2006).
Hydration Comparison: DFD vs Normal vs PSE
Let’s compare what we can expect from DFD meat. PSE meat and normal meat.
| Trait | DFD Meat | Normal Meat | PSE Meat |
|---|---|---|---|
| Ultimate pH | >6.0 | ~5.5 | ~5.4 |
| WHC | Very High | Moderate | Very Low |
| Drip Loss (2448h) | 0.5–1.5% | 2–4% | 5–10% |
| Appearance | Dark, tacky | Bright, firm | Pale, soft |
| Cutting/Grinding | Sticky, mushy | Structured | Wet, pasty |
| Internal Hydration | Excessive | Balanced | Dehydrated |
| Capillary Support | Intact but collapsed | Supportive | Collapsed, denatured |
Additional Water Loss: DFD vs Normal Beef
In terms of beef, what can we expect in terms of water loss from DFD meat and normal meat?
Water Loss Comparison: DFD Meat vs. Normal Beef
| Source of Water Loss | DFD Meat | Normal Beef |
|---|---|---|
| Drip Loss (24–48h) | 0.5–1.5% | 2–4% |
| Deboning Loss (visible during cutting) | 2.0–3.0% | 1.0–1.5% |
| Curing Loss (non-tumbled, static brine) | 1–2% | 1.5–2.5% |
| Total Expected Loss (before cooking) | 4–6.5% | 5–8% |
While DFD meat retains water more effectively during storage and packaging, it can release significantly more moisture during cutting, trimming, or grinding. This is due to its higher total water content and the structural collapse that occurs during mechanical processing.
“Even DFD meat, with low drip, suffers evaporative losses when exposed to air or during brine equilibration” (Tornberg, 1996).
Is DFD Meat Good for Sausage Processing?
Emulsified Sausages
DFD meat performs very well in emulsified products (e.g., frankfurters, mortadella) due to its:
- High pH, which increases protein extraction and solubility
- Excellent water-holding capacity, leading to higher yields
- Strong emulsifying properties, especially when kept cold
However, temperature control is crucial. DFD meat becomes sticky quickly and can overbind or smear if overmixed.
“High pH meat is ideal for emulsified systems if temperature is tightly managed during chopping” (Huff-Lonergan & Lonergan, 2005).
Coarse Sausages
For coarse or textured sausages (e.g., boerewors, bratwurst, krainerwurst), DFD meat is more problematic:
- The lack of muscle firmness and elasticity prevents clean particle definition
- It can make the product look and feel pasty or soft, especially if not well-chilled
Some batch-to-batch variation can be corrected by blending DFD meat with firmer normal meat or stiffening with rusk, TVP, or starch.
Conclusion for Sausage Use
We can summarise the use of DFD meat in sausages as follows.
| Sausage Type | Suitability of DFD Meat |
|---|---|
| Emulsified | Excellent (with temp control) |
| Coarse/Textured | Limited (unless blended or corrected) |
| Semi-coarse (e.g., cooked sausages with binders) | Acceptable |
“DFD beef, if used smartly, can outperform normal meat in yield and emulsification. The key lies in the processing technique” (Joo et al., 2013).
Freezing of DFD Meat
In South Africa, it is customary to freeze meat after slaughter and then thaw it for retail display. This is typically done in two ways:
- Thawing the meat directly in modified atmosphere packaging (MAP) trays and displaying them in cabinets
- Or, removing frozen meat from bulk boxes, packing it in foam trays, over-wrapping it with plastic film, and placing it in the display fridge
This system works relatively well in South Africa where most red meat has a balanced pH and develops a firm structure post-rigor. However, in some parts of Africa, such as Nigeria, we’ve observed a very different consumer response. Thawed meat often appears “saggy,” soft, and dull. It lacks the bloom and structure of fresh meat, and there is a well-established perception that previously frozen meat can never look like fresh meat.
In many cases, the answer lies in the unique structural and biochemical properties of DFD meat. Unlike normal meat, DFD muscle retains large amounts of water within the myofibrillar network. This is due to its elevated pH, which prevents protein denaturation and reduces post-mortem contraction. The muscle fibres remain open and hydrated, maintaining a sponge-like matrix that holds water tightly. Because of this, DFD meat freezes with more intracellular water than normal meat, setting the stage for greater damage during freezing and thawing.
When DFD meat is frozen, the high water content inside cells makes it especially susceptible to ice crystal formation. These crystals physically rupture the cell membranes, damaging the muscle structure. Upon thawing, the already weakened tissue cannot reabsorb the released fluid, leading to a visible collapse of the muscle. The result is a soft, waterlogged appearance, a surface that remains dull and tacky, and a greyish discolouration that fails to bloom into the bright red colour consumers associate with freshness.
As Lawrie and Ledward (2006) note, “DFD meat’s high pH and hydration cause it to suffer disproportionately during freezing and thawing, especially under retail conditions without temperature staging.” This observation helps explain a widespread consumer resistance to frozen meat in parts of Africa. It is not freezing itself that causes the perceived quality defect, but rather the freezing of already overhydrated, high-pH DFD meat without proper control over freezing rate, staging, or packaging. In such cases, the collapse of structure and visual quality upon thawing reinforces the belief that frozen meat is inferior, even though well-handled normal meat may perform perfectly well under identical freezing conditions.
Strategies for Freezing DFD Meat So It Looks Fresh
While challenging, there are several strategies available to improve the visual and structural quality of DFD meat following thawing. One of the most effective is rapid freezing at ultra-low temperatures, typically at or below -40°C. This approach results in the formation of smaller ice crystals, which reduces the extent of intracellular damage. By minimising ice crystal size, structural integrity is better preserved, and the risk of visible collapse or excessive purge upon thawing is significantly reduced.
Vacuum packaging prior to freezing is another valuable technique. By removing oxygen from the environment around the meat, vacuum packaging helps reduce oxidative discolouration during frozen storage and thawing. It also supports structural cohesion by maintaining surface tension and limiting the formation of large air pockets that might otherwise disrupt tissue during freezing.
The method of thawing is equally important. Controlled thawing in refrigeration, typically at 0 to 2°C over a period of 24 to 48 hours, prevents water from rapidly migrating to the surface. This slower process allows for the partial reabsorption of intracellular fluid, reducing surface wetness and improving the overall appearance of the meat after thawing. Rapid or ambient thawing, by contrast, tends to flood the surface with fluid and amplify structural collapse.
Post-thaw interventions can also make a difference. Modified atmosphere packaging (MAP), if applied after thawing, can promote oxygenation of myoglobin, resulting in improved blooming of surface colour, particularly if residual deoxygenated myoglobin remains present in the muscle. This technique can help DFD meat regain some of its visual appeal, although its success depends on the degree of protein damage and pigment retention.
Another key consideration is the timing and method of mechanical handling. To reduce post-thaw collapse, meat should ideally be cut and packaged either before the onset of rigour mortis or after full rigour resolution. Handling meat during the intermediate stages can increase susceptibility to structural breakdown during thawing.
One experimental intervention that has drawn interest is surface pH adjustment through a mild acid dip. Limited studies suggest that immersing DFD meat for one to two minutes in a diluted acetic acid solution (approximately 1 to 2 percent) can slightly reduce surface pH. This may encourage light protein contraction and improve surface firmness and colour development. However, this method is not standard industry practice and must be validated with respect to flavour alteration, microbial safety, and labelling requirements. As Tornberg (1996) notes, “Acid dipping is not standard industry practice, but surface pH manipulation could be a novel tool in restoring appearance to DFD meat if applied judiciously and scientifically.”
While none of these strategies can fully transform DFD meat to resemble fresh, low-pH muscle, they can collectively reduce the visual and structural defects that lead to consumer rejection. The issue lies not in the act of freezing itself, but in the freezing of already overhydrated, high-pH DFD meat without proper preparation or control. Addressing this point with the right techniques can significantly improve acceptance of frozen-thawed beef at the retail level.
Solutions: Getting the Spaghetti Look Back
After a brief detour into the challenges of freezing and the structural collapse of DFD meat, we return to the original, practical question: Is it possible to restore the spaghetti-like texture in minced beef when working with high-pH DFD meat? This texture, defined by distinct, resilient strands of meat exiting the mincer cleanly without smearing or slumping, is critical not just for appearance but for water control, fat distribution, and processing performance.
DFD meat presents a unique challenge in this regard. Its high water content and lack of post-mortem contraction leave the fibres soft, open, and highly hydrated. When minced under the wrong conditions, the result is often a smeared, pasty texture that resists structure and appears unappealing. Fortunately, there are several techniques that can help bring back that desirable spaghetti-like structure.
First, temperature control is essential. Lowering the temperature of the meat to below two degrees Celsius prior to mincing is one of the most effective interventions. Cold meat is firmer and less prone to smearing, especially in high-pH muscle where the absence of protein contraction already compromises texture. This firmness helps the meat shear cleanly through the mincer rather than deform under pressure.
The order and size of the mincer plates also influence the result. Using a coarse plate first, such as eight millimetres, before switching to a finer plate like four point five millimetres, reduces mechanical stress on the fibres. This two-step reduction process protects the structural integrity of the muscle, avoiding the squashing effect that a single fine plate can have on soft, high-pH meat.
Another simple but effective tactic is to allow surface drying of the meat for one to two hours before mincing. When the surface moisture is slightly reduced, more water is drawn back into the proteins rather than forming a film that causes slippage through the mincer. This improves traction against the blades and helps preserve the visual separation of fibres.
Blending DFD meat with a portion of normal-pH lean meat can also help stabilise the texture. Normal meat, having undergone full pH decline and protein contraction, contributes firmness to the mixture. Even a modest percentage of low-pH material can act as a structural stabiliser within the protein network, improving both bite and visual grain.
Mixing must also be handled with care. DFD meat becomes sticky very quickly when mixed, and overmixing can easily destroy the structure you are trying to maintain. The ideal approach is to mix only until the ingredients are just combined. This ensures even distribution without turning the muscle into a paste.
An additional method involves the use of slight vacuum during grinding. Applying gentle vacuum pressure helps pull water back into the protein matrix, improving internal binding and reducing free surface moisture that contributes to smearing. This approach is common in the production of high-end emulsified products and is increasingly applied to minced meat for water-sensitive raw materials.
Finally, the condition of your mincer blades and plates is critical. Equipment that is dull or pitted increases smearing, particularly with high-hydration DFD muscle. Regular sharpening and cleanliness are essential not only for texture but also for preventing protein buildup and microbial contamination.
These methods do not eliminate the fundamental challenges of working with DFD meat. However, when applied carefully and systematically, they can restore much of the structure, functionality, and visual appeal that is often compromised. The spaghetti look is not out of reach. It simply requires thoughtful adjustments at each stage of the process.
Conclusion
DFD meat, common in tropical and nomadic systems found in some parts of Africa, behaves very differently from standard meat. Though its water-holding capacity is high and visually it appears dry, it is anything but. The internal hydration and lack of protein denaturation make it difficult to process—especially for producing structured products like fibrous minced meat. By understanding these mechanisms and applying the right corrective steps, we can partially reclaim the performance of DFD meat and deliver better structure, texture, and yield in our products.
References
- Honikel, K.O. (1998). Reference methods for the assessment of physical characteristics of meat. Meat Science, 49(Suppl. 1), S447–S457.
- Joo, S.T. et al. (2013). Control of fresh meat quality through manipulation of muscle metabolism. Animal Frontiers, 3(4), 45–52.
- Hambrecht, E. et al. (2005). Effect of feeding intensity and slaughter weight on pork quality. Meat Science, 72(4), 795–806.
- Lawrie, R.A. & Ledward, D.A. (2006). Lawrie’s Meat Science (7th ed.). Woodhead Publishing.
- Tornberg, E. (1996). Biophysical aspects of meat tenderness. Meat Science, 43(Suppl. 1), S175–S191.
- Huff-Lonergan, E. & Lonergan, S.M. (2005). Mechanisms of water-holding capacity of meat: The role of postmortem biochemical and structural changes. Meat Science, 71(1), 194–204.