**2. Cassava**

Cassava (*Manihot esculenta* Crantz), also known as mandioca, is a starchy root belonging to the Euphorbiaceae family and is one of the most important energy sources for tropical areas

Thermoplastic Cassava Flour 25

After harvest, fresh cassava roots can deteriorate very quickly, since they have a 65% water content (Ceballos, 2002). In order to preserve the fresh cassava, an alternative is by drying to obtain dried pieces, which can be obtained flour, whether for food, feed or industrial use. The cassava flour for human consumption can be classified as fermented (gari) or not fermented. Unfermented flours are made by grinding the roots peeled or cut into small pieces, then the resulting material is dried and milled (Ceballos, 2002). According to the Codex standard for edible cassava flour (*Manihot esculenta* Crantz), it is the product obtained from cassava chips or pasta with a grinding process, followed by screening to separate the fiber from flour. In the case of edible meal prepared with the bitter cassava (*Manihot utilissima* Pohl) it shall be made by soaking the tubers detoxification in water for several days prior to drying in the form of milled whole tuber

Cassava flour is obtained by grinding dried cassava chips, as explained in detail below

Receiving. A visual inspection of the raw material is performed. The performance

Peeling. When the process is done on a small scale, cassava peel is removed by abrasive

Crushed. The roots will dry quickly, so, is necessary to increase the surface exposed to

Milling. Once dried cassava chips, reducing the particle size using a hammer mill

 Sieving. The ground flour is passed through a series of mesh to determine particle size. According to the CODEX STAND 176-1989, cassava flour is fine when at least 90% passes through a 0.6mm mesh sieve and it is thick when 90% passing through a 1.20mm

Cassava flour consists mainly of starch (80 - 90%) and fiber (1.5-3%) depending on the variety of cassava from which one obtains (Charles, Sriroth, & Huang, 2005). It is considered a potential raw material in the field of developing new materials, including biocomposites,

Cassava flour should have a moisture content no greater than 13% for easy storage and transport conditions (Codex Stand 176, 1989). Cassava flour can also be classified as integral or bakery. The integral flours are the result of grinding the dried cassava chips with bark, which is used as a substitute for carbohydrates in cereals (maize, wheat, sorghum) and it is usually used in food formulations for animals. The bakery is obtained by grinding the dried pieces of peeling cassava, passing the product through a fine sieve. If the product of grinding through a sieve less dense, it is obtained granulated or cassava semolina

Washing. It removes dirt and other debris present in cassava roots with water.

equipment or knives. When the shell is not removed you get cassava meal.

Drying. It can be accomplished by hot air dryers or in yards by sunlight.

because of its high concentration of starch, (Martínez et al, 2007).

**2.1 Cassava flour** 

(pasta) or small pieces.

generally.

mesh sieve.

(Montaldo, 1985).

(Alvarado & Cornejo, 2009):

process is determined by the cassava weight.

Cutting. Cassava is cut into small pieces.

hot air grinding cassava chips until slurry.

of the world. Although cassava thrives in fertile soil, its comparative advantage to other more profitable crops is their ability to grow in acidic soils of low fertility, with sporadic rainfall or long periods of drought. The crop is widely adapted as it is planted from sea level up to 1800 meters, at temperatures between 20 and 30C with an optimum of 24C, relative humidity between 50 and 90% with an optimum of 72% and an annual rainfall between 600 and 3000mm with an optimum of 1500mm (Casaca, 2005). It is widely cultivated in tropical Africa, Asia and Latin America, and it is the fourth most important global crop in developing countries, with an estimated production in 2006 of 226 million tonnes. It is characterized by great diversity of uses both roots and leaves can be eaten by humans and animals. Cassava products can be used in industry mainly from the starch (Ceballos, 2002).

The bulk of cassava produced in farms of small farmers and marginal areas, so that a significant proportion of production is not recorded in the statistics accurately, in addition, these farmers are generally isolated from the distribution channels and the product processing industries, mainly in areas that have little or no access to improved varieties, fertilizers and other production inputs. Governments have not yet made the necessary investments to boost its value added, that would make cassava starch products uncompetitive internationally (FAO, 2007).

This root is composed of three tissues: the periderm (husk), the cortical parenchyma (cortex) and inner parenchyma, where approximately 80% of fresh weight of the root, corresponds to the parenchyma or pulp, which is the tissue that plant stores starch. The dry matter content of cassava root fluctuates between 30% and 40%, dry matter is composed of parenchyma, mostly (90% to 95%), the nitrogen fraction, ie, carbohydrates (starch and sugars), the rest of this dry matter corresponds to fiber (1% to 2%), fats (0.5% to 1.0%), ash and minerals (1.5% to 2.5%) and protein (2.0%); starch also represents most of the carbohydrates (96%) and it is, therefore, the main component of root dry matter (FAO, 2007).

Moreover, cassava varieties can be classified as bitter, which contain a cyanogenic glycoside called linamarin, which are hidrolized in the presence of enzymes and acids linamaraza, resulting in the formation of hydrocyanic acid. This acid is under the skin of the roots, inside a layer of viscous-looking latex, white and with characteristic odor, usually this variety is used for industrial processes.

Sweet varieties have low or no presence of hydrocyanic acid, therefore its use is safe after cooking (Aristizabal & Sanchez, 2007). If cassava use is for human consumption, it will be called culinary quality, but it used for the manufacture of products such as flour, starch or dry pieces it be called industrial cassava, and finally it can be called dual purpose if it is intended to human consumption or industrial use (Aristizabal & Sanchez, 2007). In Colombia, CIAT, Corpoica and CLAYUCA have developed improved varieties of cassava for growth in certain areas of the country, taking into account biological and climatic factors. The Cauca region is located within zone which it can grow varieties such as HMC-1, MPER 183, MBRA 383, among others (Cadavid, 2005).

Cassava roots are rich in calories but deficient in protein, fats, minerals and vitamins. It also presents several secondary compounds in the root tissues as polyphenols, tannins, carbohydrates and cyanogenic compounds (Sanchez & Alonso, 2002).

#### **2.1 Cassava flour**

24 Thermoplastic Elastomers

of the world. Although cassava thrives in fertile soil, its comparative advantage to other more profitable crops is their ability to grow in acidic soils of low fertility, with sporadic rainfall or long periods of drought. The crop is widely adapted as it is planted from sea level up to 1800 meters, at temperatures between 20 and 30C with an optimum of 24C, relative humidity between 50 and 90% with an optimum of 72% and an annual rainfall between 600 and 3000mm with an optimum of 1500mm (Casaca, 2005). It is widely cultivated in tropical Africa, Asia and Latin America, and it is the fourth most important global crop in developing countries, with an estimated production in 2006 of 226 million tonnes. It is characterized by great diversity of uses both roots and leaves can be eaten by humans and animals. Cassava products can be used in industry mainly from the starch

The bulk of cassava produced in farms of small farmers and marginal areas, so that a significant proportion of production is not recorded in the statistics accurately, in addition, these farmers are generally isolated from the distribution channels and the product processing industries, mainly in areas that have little or no access to improved varieties, fertilizers and other production inputs. Governments have not yet made the necessary investments to boost its value added, that would make cassava starch products

This root is composed of three tissues: the periderm (husk), the cortical parenchyma (cortex) and inner parenchyma, where approximately 80% of fresh weight of the root, corresponds to the parenchyma or pulp, which is the tissue that plant stores starch. The dry matter content of cassava root fluctuates between 30% and 40%, dry matter is composed of parenchyma, mostly (90% to 95%), the nitrogen fraction, ie, carbohydrates (starch and sugars), the rest of this dry matter corresponds to fiber (1% to 2%), fats (0.5% to 1.0%), ash and minerals (1.5% to 2.5%) and protein (2.0%); starch also represents most of the carbohydrates (96%) and it is,

Moreover, cassava varieties can be classified as bitter, which contain a cyanogenic glycoside called linamarin, which are hidrolized in the presence of enzymes and acids linamaraza, resulting in the formation of hydrocyanic acid. This acid is under the skin of the roots, inside a layer of viscous-looking latex, white and with characteristic odor, usually this variety is

Sweet varieties have low or no presence of hydrocyanic acid, therefore its use is safe after cooking (Aristizabal & Sanchez, 2007). If cassava use is for human consumption, it will be called culinary quality, but it used for the manufacture of products such as flour, starch or dry pieces it be called industrial cassava, and finally it can be called dual purpose if it is intended to human consumption or industrial use (Aristizabal & Sanchez, 2007). In Colombia, CIAT, Corpoica and CLAYUCA have developed improved varieties of cassava for growth in certain areas of the country, taking into account biological and climatic factors. The Cauca region is located within zone which it can grow varieties such as HMC-1, MPER

Cassava roots are rich in calories but deficient in protein, fats, minerals and vitamins. It also presents several secondary compounds in the root tissues as polyphenols, tannins,

carbohydrates and cyanogenic compounds (Sanchez & Alonso, 2002).

(Ceballos, 2002).

uncompetitive internationally (FAO, 2007).

used for industrial processes.

183, MBRA 383, among others (Cadavid, 2005).

therefore, the main component of root dry matter (FAO, 2007).

After harvest, fresh cassava roots can deteriorate very quickly, since they have a 65% water content (Ceballos, 2002). In order to preserve the fresh cassava, an alternative is by drying to obtain dried pieces, which can be obtained flour, whether for food, feed or industrial use. The cassava flour for human consumption can be classified as fermented (gari) or not fermented. Unfermented flours are made by grinding the roots peeled or cut into small pieces, then the resulting material is dried and milled (Ceballos, 2002). According to the Codex standard for edible cassava flour (*Manihot esculenta* Crantz), it is the product obtained from cassava chips or pasta with a grinding process, followed by screening to separate the fiber from flour. In the case of edible meal prepared with the bitter cassava (*Manihot utilissima* Pohl) it shall be made by soaking the tubers detoxification in water for several days prior to drying in the form of milled whole tuber (pasta) or small pieces.

Cassava flour is obtained by grinding dried cassava chips, as explained in detail below (Alvarado & Cornejo, 2009):


Cassava flour consists mainly of starch (80 - 90%) and fiber (1.5-3%) depending on the variety of cassava from which one obtains (Charles, Sriroth, & Huang, 2005). It is considered a potential raw material in the field of developing new materials, including biocomposites, because of its high concentration of starch, (Martínez et al, 2007).

Cassava flour should have a moisture content no greater than 13% for easy storage and transport conditions (Codex Stand 176, 1989). Cassava flour can also be classified as integral or bakery. The integral flours are the result of grinding the dried cassava chips with bark, which is used as a substitute for carbohydrates in cereals (maize, wheat, sorghum) and it is usually used in food formulations for animals. The bakery is obtained by grinding the dried pieces of peeling cassava, passing the product through a fine sieve. If the product of grinding through a sieve less dense, it is obtained granulated or cassava semolina (Montaldo, 1985).

Thermoplastic Cassava Flour 27

plasticizer (glycerol) and fiber (cellulose) in TCF, finding that the use of plasticizer, significantly reduced the degradation of starch, while that the increase in fiber content,

There are few investigations made in TCF biodegradable packaging. At the international level have been evaluated physical and chemical properties of varieties of cassava flour for different applications, however, in the field of biocomposites studies are scarce. Researchers in Ghana, concluded that 31 varieties of cassava studied should not be wasted by their low quality cooking or high cyanogenic, however recommend its use in industrial applications such as extraction of starch and/or flour, sugar production, adhesives, among others (Aryee et al, 2006). In Nigeria, a study on the effect of type of material (pellets and cassava flour) and drying method (solar-oven) of material on the yield and physicochemical properties of starch in these materials and found that drying oven yielded the most appropriate results (Olomo & Ajibola, 2003). Venezuelan authors studied the effects of heat treatments on cassava meal, finding that pre-gelatinized flour decreased the tendency to retrogradation, consistency and rate of absorption and suggested the use of these conventional products

As part of the implementation of the program "Use By-Products of Cassava", cofinanced by the Agriculture and Rural Development Ministry, the Cauca University and the Cauca Productivity and Innovation Regional Center (Popayán, Cauca, Colombia),we have carried out some important technical developments for the use of cassava flour thermoplastic in the biodegradable materials manufacture. Next, we present some results of these studies of both

Samples were spread on glass sheets to be observed with optical microscope (Nikon Eclipse 80i, Japan) coupled to digital camera (Nikon DS-2MV 2Mp, Japan), through the bright field

Photomicrographs of cassava flour in Figure 1 were captured with 10x (down) and 40x (up) objectives; in them may be observed longitudinal and amorphous fibers, and round

Fibers, stained blue-violet because dye used (toluidine blue), it were longitudinally elongated and not elongated amorphous. As shown in Figure 1, there is a greater number of starch granules by number of fiber (s) found in each catch, this is because the fiber content in the flours studied is very low, between 1.7 and 2.7% in wet basis, compared with the starch content, between 75 and 85% wet basis, according to proximate analysis

increased it.

and new product development (Pérez et al, 2007).

**3. Related research** 

technique.

/truncated starch granules.

results (not shown).

raw materials and product obtained.

**3.1 Characterization of cassava flour** 

In this regard, we have used the following techniques of analysis:

**3.1.1 High Resolution Optical Microscopy- HROM** 
