Garri is a dry crispy coarse flour obtained from raw cassava flesh. Cassava is a staple crop in Central and Southern America and also in the tropical regions of West Africa.
It is one of the many food crops that cannot be consumed raw due to the presence of toxins and anti-nutritional factors in their peels and flesh. It must be subjected to a form of detoxification by processing further into intermediate forms or peeled and cooked thoroughly to develop stability and edibility.
Garri, topiaco, cassava flour, and chips to mention a few, are the popular intermediate forms that cassava is commonly reduced into. The numerous operations involved in the conversion of raw cassava into these intermediate forms, significantly lowers the toxicity below a level acceptable for human consumption.
In this article, our focus will be mainly on garri; particularly how it is obtained from raw cassava flesh. We’ll uncover the entire process of extracting garri from raw cassava and show you how to properly preserve garri grain for longer duration.
In this article
- Toxicity of cassava.
- The garri making process.
- Improving the nutritional content of garri.
- Storage of garri.
Toxicity of cassava
Cassava, as mentioned earlier, is a poisonous root tuber in it’s raw form due to the presence of toxins in it’s peels and flesh. The main toxic principle is a chemical compound called linamarin which is converted into hydrogen cyanide once ingested into the body.
Cyanide exposure (from inhalation or ingestion) is associated with the development of goiter, and with neurological disorders like tropical ataxic neuropathy and epidemic spastic paraparesis. Chronic exposure in some cases, can also lead to death.
A great variation in toxicity exists between the sweet and bitter cultivars of cassava. Sweet cassava roots contain relatively low levels of cyanide; below 50mg per kilogram hydrogen cyanide on fresh weight basis, whereas the bitter cassava root may contain upto 400mg per kilogram hydrogen cyanide.
It is necessary to process cassava roots (using proven diminution techniques) in order to detoxify the cyanogenic glucosides present in them and reduce the risks of cyanide poisoning. Century-old methods have been developed for this purpose and one of the most popular across West Africa is the garri making process.
Garri Making Process
The seven arduous steps employed in the extraction of garri from cassava tubers significantly reduces the total cyanogenic contents by about 83-96%. At this level, the toxins exist at quantities far below the lethal dosage and are considered safe for human consumption. The operations must be observed conscientiously, otherwise, toxic levels of cyanide can still persist into the final product and if consumed, can present negative health effects to people. The steps involved in processing cassava into garri include:
- Peeling and Washing
- Grating and Bagging
- Fermenting and Dewatering
- Re-sieving (or Grading)
Peeling and Washing:
Peeling is the first and a very important step (if not the most important step) in the garri making process. Peeing, like other operations, contributes to the detoxification of cassava roots by eliminating the skin and cortex layer which contain the highest proportion of cyanide producing cyanogenic glucosides. By eliminating this parts, about 50% of the total toxins in cassava roots is reduced. Fresh and quality cassava roots should be used for making garri.
Method: Remove the skin and cortex layer (or the immediate inner cream layer) of the cassava root using a sharp knife or a peeling machine. Avoid shaving the roots with a knife or peeler in order to maximize the total garri yield. Any damaged or woody parts of the cassava roots should be trimmed off as well. After peeling, wash the naked cassava roots with clean water to remove dirt and stains which can mar the quality of the final product.
Grating and Bagging:
Grating disintegrates the micro-structure of cassava roots and liberates hydrogen cyanide which is the toxin produced in the digestive tract when cyanogens are ingested. Most of the liberated hydrogen cyanide (along with the other forms of cyanides) are eliminated during subsequent fermentation, dewatering, roasting and drying operations. Grating operation is efficient at removing linamarin (which is the predominant of the three cyanide forms that exist in cassava roots).
Method: After washing, let the cassava roots dry for about an hour, then reduce them into a wet mash. A power operated grater or a manually operated grater can be used for this purpose. The manually operated grater is commonly a piece of galvanized metal sheet punctured on one side to develop a jagged surface on the other. One form of manual grating involves scrubbing the cassava roots against the jagged surface of the metal until only about 3% of the original root of individual cassava is left. These remnants are ungratable due the proximity of fingers with the jagged metal surface. During grating, collect the wet cassava mash into a clean bowl and eventually transfer into a bag; a jute bag, a perforated plastic sack, or a clean woven polythene sack.
Fermenting and Dewatering:
Fermentation dissolves some of the liberated hydrogen cyanide in water by action of prolonged soaking. Dewatering removes most of the soluble cyanide along with the press liquor.
Method one (Fermentation before dewatering): Position the bag of mash on a fermentation rack and allow to ferment for 1-4 days depending on your taste preference. Fermentation for longer duration increases the sourness of the final product but reduces the total cyanogenic glucoside more compared to shorter duration. At least 72 hours of fermentation is recommended for effective removal of cyanogens. During fermentation, some of the milky water from the mash will drain freely from the sack. After fermentation, remove the bag of mash from the fermentation rack and press using a hydraulic press or a screw press. Remove bag from press when the moisture content of the mash is about 40-50%. You can intuit that manually by observing when the milky water stops dripping from the bag and the surface of the bag is still moist. Ensure not to remove too much water else the garri will not cook properly during roasting. Leaving too much water will also make the garri lumpy during roasting. Aim for 40-50% water content in the mash.
Method two (Simultaneous fermentation and dewatering): During fermentation, apply pressure on the bag of mash by piling heavy stones on it, or by twisting the neck of the sack and pressing water out from it. Pressing the bag between wooden poles tightened by ropes would also work. Re-tighten the sack everyday to facilitate the removal of more milky water as more and more gradually flow out.
Fermentation is a critical operation in terms of the taste, flavor, safety and texture of the final product.
Sieving is necessary to obtain a homogeneous granule which is essential for even and efficient roasting. During sieving, the cake formed from the dewatering operation is broken up into smaller bits (by hand or a manually operated sieving machine or a power operated sieving machine). Visible lumps and fibrous components of the granules are removed.
Method: Remove the dense cake from the bag and reduce it into smaller granules (or grits). Use hand, manual sieve or a mechanical sieve to perform the operation and ensure to remove fibrous and lumpy components.
Roasting eliminates some of the remaining cyanide from fermentation by means of evaporation. It is a crucial operation in terms of the development of flavor and edibility of garri. Roasting partially gelatinizes garri and dries it to a moisture content of 18%.
Method: Smear a thin layer of edible oil onto a large roasting pan, cast over fire. Traditional roasting methods employ shallow cast-iron pans or earthenware pans, over an open wood fire, whereas modern industrial methods employ a mechanized garri frying/drying machine. The use of red oil facilitates cyanide removal more compared to other fats and oils. Red oil produces a yellowish tinge on the final product and gives it a finer texture. Fats and oils with good nutritional value should be used to supplement the loss of nutrients of high value from the cassava roots during processing. Transfer the grits form the sieving operation (in batches) onto the surface of the frying pan and cook using a combination of stiring and quick pressing of the mash against the hot surface of the pan. Use a large wooden spatula or a calabash for the operation and allow intermittent breaks (while stiring) to allow proper gelatinization of the grits. When the temperature of the mash reaches 80 to 85 degrees (about 30-35 minutes), or the grits are cream white and crisp, the frying operation is completed. Leave a small amount of garri on the frying pan to facilitate the roasting of the next batch.
Drying eliminates the remaining cyanide from the roasting operation by means of evaporation. At the end of drying, about 83-96 % of the total cyanogenic content of cassava is reduced and the final product is edible and stable. The final moisture content of the cassava mash is also reduced to about 10%, so the product is more crisp.
Method: Transfer the roasted garri onto an elevated platform in the open air and spread thinly, allowing to cool completely in order to evaporate any remnant of cyanide from the preceding stages (about 4-5 hrs).
Re-sieving or Grading:
Re-sieving ensures a finer and more even granules of garri. Re-sieving improves the aesthetic value of garri, which is an important factor for sellers during marketing.
Method: After drying, grade the resulting granules by sieving (using a standard sieve size) to produce finer granules.
Improving the Nutritional Contents of Garri:
Garri produced from the method above has an unremarkable nutrient profile. The problem isn’t the unimpressive nutritional content of cassava roots, it’s the leaching of nutrients of higher value that occur during the progressive stages of making garri.
Some essential supplements like Vitamin C and protein, originally present in the cassava roots at detectable amounts are reduced to insignificant quantities in the garri form. The resulting garri grain is dominantly made up of carbohydrates (particularly resistant starch), and provides little amount of essential minerals, vitamins and other supplements. This can be changed however, by it’s fortification with nutrient rich foods during processing.
Fortification of garri:
Addition of palm oil:
Palm oil is a good source of Vitamin A and so adding it during the roasting or fermentation stages improves garri in this respect.
Use of yellow cassava cultivars:
Yellow varieties of cassava (with yellow flesh) are densely packed with vitamin A. Using them instead of the white variant would provide more nutrition, particularly vitamin A which is important for good vision and a healthy immune system.
Addition of protein rich foods:
Soybean and its derivatives such as (paste, milk residue or flour) can be added to garri to improve it’s protein value.
Storage of Garri:
Proper storage of garri is necessary to prevent mold growth and moisture accumulation which can affect the crispness and shell life. Garri should be stored in plastic bags or plastic-lined polyethene bags at air-tight conditions. The bags should be kept on pellets or elevated surface in a well ventilated room. Garri stored under these conditions can last up-to a year.