Scientific World

Scientific World Cassava – how to explore the “all-sufficient” Making better and more diversified use of plants in order to benefit from existing resources is one of the targets that the bioeconomy has set itself. As a rule, however, this means that first of all, a lot of research has to be carried out, as the following example of Cassava shows. Cassava is widely grown in nearly prepared from cassava starch can be cus more on the cassava leaves as an 105 tropical and subtropical coun- used in food industry and for produc- economical and sustainable source of tries with an estimated production of ing synthetic resins, plastics and rubber protein and nutrients. 263 million tonnes in 2012. The plant products. Cassava leaves are used as is considered as a 21st century crop food, feed and to raise silkworms, while The global demand for protein is as it responds to the global economy mushrooms can be grown with the increasing tremendously. According to trends and climate change challenges. ground stems. Finally, the waste from the UN Food and Agriculture Organi- Cassava is a staple food for one billion the cassava field and processing indus- zation (FAO), world-wide meat con- people, but it is equally important as try can be used to produce biogas. sumption is estimated to reach 463 mil- a source of feed and industrial appli- lion tonnes by 2050, requiring a huge cations, and is also an energy source, amount of feed protein which will be making it ideally suitable for cascade From waste to food: making use hard to produce in an eco-sustainable use (see article on pages 28–29). of the leaves way. On the other hand, plant protein (mainly of legumes, grains, nuts and After processing, cassava roots pro- There is still a big potential to ex- seeds) evidently contributes to meet- vide flour for human consumption. plore cascade uses of cassava. Post- ing the demand for food protein world- Bread, crackers, cakes and ice cream harvest loss is a serious concern which wide. In order to cover increasing pro- cones are produced from cassava flour. needs to be addressed while intro- tein demand, it is necessary to explore Cassava root starch is a high value com- ducing innovative processes. A huge new protein sources. Cassava leaves are modity in brewing, textile, pharmaceu- amount of waste generated in the form one of these interesting sources. How- tical, paper and oil industries. Cassava of peel, pulp, wastewater and leaves ever, they are generally considered as starch can also be a source for platform during post-harvest processing of cas- waste or as an inferior by-product and chemicals and ethanol production. sava causes severe environmental prob- are only used for human consumption Native starch is modified by physical, lems which need to be converted into in small quantities. chemical or enzymatic processes to ob- valuable products and energy in an en- tain different modified starch having vironmentally friendly manner. One of Cassava leaves contain high amounts numerous applications, e.g. preparing the plant’s most valuable wastes is cas- of protein (17.7–38.1 % on dry weight different types of foods, textile sizing, sava leaves. They are rich in protein and basis). In addition they are a rich source high-quality paper and animal feed. By nutrients and should using starch and modified starch, bio-/ be utilised properly photo-degradable plastics can also be in order to tackle produced. Various sweeteners can be food insecurity and prepared from cassava starch by hy- undernutrition pre- drolysis with acidic and enzymatic sub- vailing in developing stances or a combination of both. Ace- countries. Therefore, tic acid, citric acid and itaconic acids we are going to fo- Sajid Latif Cassava leaves could [email protected] play a key role in food Joachim Müller security. Research at Hohenheim University Institute of Agricultural Engineering is examining the University of Hohenheim optimal way to treat Stuttgart, Germany the leaves. Wojciechowski Photo: T. 30 Rural 21 – 03/2014 Scientific World of vitamins, B1, B2 and C, as well as ca- Cassava leaf protein utilisation is also recovery and valuable by-products. In rotenoids and minerals. The total essen- limited by the presence of high levels another approach, cassava leaf meal tial amino acid amount in cassava leaf of chlorophyll, xanthophylls and fibre, (CLM) or cassava pellets can be pre- protein is similar to that of a hen’s egg which can be overcome by extracting pared by pressing cake or whole leaves and greater than that of spinach leaf, juice from the leaves, followed by coag- and stems by reducing the moisture soybean, oat or rice. The Congolese call ulation to get leaf protein concentrate content (15–20 %) either with sun dry- cassava ‘all-sufficient’ as they can get (LPC). Chopped, ground cassava leaves ing or mechanical pressing. bread from the roots and ‘meat’ from are pressed and coagulated with steam the leaves. Cassava leaves are available injection. Several studies have been car- Food insecurity prevails not only throughout the year and should be giv- ried out on the preparation of LPC, but among the 842 million people of the en as much attention as the roots. a wide variation has been observed in world who are hungry but also among terms of extraction efficiency, nutrition- the three billion people who can cover al value, methionine and lysine, which their minimum dietary energy require- Identifying the right procession may be due to the extraction methods ment but suffer from various diseases method and tannin contents in different cassava caused by undernutrition (or malnutri- varieties and cultivars. Ultimately, the tion). After the successful development Cassava leaves are consumed in vari- attempts to prepare LPC on an indus- of suitable processing methods, cassava ous cassava-growing countries when trial scale failed because of low protein leaves have the potential to provide people don’t have alternatives. Toxicity recovery with high contents of tannins an enormous protein and nutritional and antinutrients limit the consumption and the low digestibility of the residue source to the vast majority of the popu- of cassava leaves as food. Cyanogenic fibre. Further work is needed to develop lation and hence can increase food and glucosides (linamarin and lotaustralin) novel technologies with high protein nutritional security. are responsible for the toxicity of cassava leaves, which is 5–20 times higher than that of the roots. Hence the consumption of cassava leaves may cause cyanide poisoning having symptoms like headache, dizziness, nausea, diar- rhoea and vomiting, sometimes leading to death. These toxic and antinutritional aspects must be addressed properly during processing before consumption. Various cassava leaf processing methods have been developed. Drying, pounding and long periods of boiling are the traditional methods for preparing cassava leaves, while pounding cassava leaves in a wooden pestle and mortar for 15 minutes followed by boiling in water for 10–120 minutes is the most common method. According to the literature, even ten minutes of boiling may reduce Photos: S. Latif and J. Freihart Two ways to unlock the nutrients of cassava leaves: Cassava leaf juice and press cake. 60 per cent of vitamin C content, and considerable losses may occur regard- ing vitamin A and the vitamin B group. Cassava protein for nutritious diets Boiling may also denature the native enzymes (linamarase and hydroxy ni- Based on consumer preferences, nutritionally balanced foods (snacks) or modi- trile lyase), which are responsible for fied traditional foods can be prepared with cassava leaves to provide the required the breakdown of toxic compounds amount of protein, minerals and vitamins. Similar efforts have already been made (linamarin and acetone cyanohydrin, in Brazil to combat malnutrition especially for pregnant women and children. respectively). Most of the processing A food supplement called ‘multimistura’ has been prepared by using cassava methods are not able to completely leaf powder as one of the ingredients. A typical cassava leaf dish including fish, detoxify the cassava leaves to the safe capsicums, groundnuts and onions is prepared in Sierra Leone. Such food prod- consumption level; there is still a need ucts need to be promoted in order to encourage cassava leaf consumption as a to develop efficient, simple, and low- valuable component of the diet instead of associating them with poverty. Fortifica- cost processing methods to deal with tion of common food items with protein and nutrient-rich cassava leaves can be a not only toxic but also antinutritional sustainable and cost-effective approach to dealing with protein and micronutrients aspects, low digestibility and bad taste deficiencies in millions of people. while retaining all the key nutrients. Rural 21 – 03/2014 31.

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