The Variable pH of Raw vs. Processed Cassava
Unlike fruits and vegetables with a more consistent pH, cassava's acidity is not a fixed value. Its pH changes dramatically depending on whether it is raw, cooked, or fermented. The natural state of fresh cassava roots is surprisingly close to neutral. However, the methods used to make it safe for consumption, particularly fermentation, introduce a new level of acidity.
Raw Cassava and Its Inherent pH
Fresh, unprocessed cassava root typically has a pH of around 6.5, placing it on the slightly acidic side of neutral. This slight acidity is not the main concern, however. The real issue with raw cassava is its high concentration of cyanogenic glucosides, which are toxic compounds that can release hydrogen cyanide when consumed. This toxicity necessitates thorough processing before the root can be eaten.
Fermentation and the Rise of Acidity
One of the most common processing methods, especially in West Africa, is fermentation. This process is used to create staples like fufu and lafun. During fermentation, microorganisms such as lactic acid bacteria break down starches and produce organic acids, including lactic, acetic, and propanoic acids. As a result, the pH of the cassava drops significantly, sometimes reaching a pH of 4.0 or lower. This is what gives fermented cassava products their characteristic sour flavor and also serves to detoxify the root by degrading the cyanogenic glucosides.
Cassava Flour: A Different pH Profile
Cassava flour also demonstrates a variable pH depending on its processing. One study found the pH of raw cassava flour to be 6.75, which is slightly higher and more alkaline than the raw root. Another source even cited a significantly alkaline pH for certain types of processed cassava flour. This variability highlights that the final product's pH is highly dependent on the specific processing techniques involved, such as soaking, drying, or the addition of other ingredients. Tapioca maltodextrin, derived from cassava starch, is also known to have a more alkaline pH compared to its corn-derived counterpart.
Cassava's Role in Acid-Alkaline Diets
For those following an alkaline diet, the food's pH before digestion is less important than its Potential Renal Acid Load (PRAL). PRAL measures the acid or alkaline load a food imposes on the body after being metabolized. While many grains and processed starches are acid-forming, cassava flour is often classified as an alkaline-forming food. This is due to its relatively low mineral content, particularly the alkaline minerals like potassium, which contribute to a neutralizing effect after digestion. This is distinct from the food's actual pH, which can still be acidic, especially in fermented products.
Potential Impact on Acid Reflux
For individuals with acid reflux or GERD, the slow digestion of certain foods can be a concern. Some health professionals note that starchy foods like cassava and potatoes can be slow to digest, potentially triggering reflux symptoms by requiring more stomach acid and sitting in the stomach longer. However, many people with GERD find plain-cooked tubers like cassava to be well-tolerated. The key is proper preparation—cooked plain, without heavy spices or fats that can worsen symptoms.
Comparing Acidity in Different Cassava Preparations
| Preparation | Processing Method | Typical pH Range | Acidity Profile |
|---|---|---|---|
| Raw Root | None (Toxic) | ~6.5 | Near-neutral, but toxic |
| Cooked Root | Boiling, Baking, Frying | ~6.5-7.0 | Near-neutral (safe after cooking) |
| Fermented Products (fufu, lafun) | Soaking, Fermenting | ~3.5-4.5 | Highly Acidic |
| Sour Cassava Starch | Fermentation, Processing | ~3.0-4.0 | Highly Acidic |
| Cassava Flour | Varied (drying, sifting) | ~6.7-9.4 | Varies from slightly acidic to alkaline |
Cassava Processing Methods Affecting Acidity and Safety
Proper processing is essential not only to detoxify cassava but also to control its final acidity and safety. Here are some key methods:
- Boiling and Steaming: Cooking raw cassava by boiling or steaming effectively breaks down the cyanogenic glucosides, making the root safe to eat. This process also tends to keep the pH near neutral. The cooking water, which contains leached toxins, must be discarded.
- Soaking and Fermenting: Submerging cassava roots in water for several days allows for natural fermentation by lactic acid bacteria. This process drastically lowers the pH, increases acidity, and detoxifies the root. The fermented pulp is then processed into food products.
- Drying: Sun-drying or oven-drying cassava chips or flour helps reduce hydrocyanic acid levels. Dried cassava can be stored for months and later processed into flour or other products.
- Grating and Pressing: In methods used to make products like gari, the grated cassava is pressed to remove moisture and toxins, followed by further heating.
For more detailed information on traditional processing, see this FAO Publication on Cassava Processing.
Conclusion
Ultimately, whether cassava is acidic depends on its form. Raw cassava is near-neutral but toxic and must never be eaten. Fermentation transforms cassava into an acidic product, which is a key part of its traditional preparation. Cooked cassava, on the other hand, maintains a neutral or near-neutral pH and is safe for consumption. Furthermore, in the context of the body's metabolic function, cassava flour is often considered an alkaline-forming food, regardless of its initial pH. Therefore, the acidity of cassava is not a simple yes-or-no question but is instead defined by its preparation and its eventual effect on the body's biochemistry.
