“Non-food Crops-to-Industry schemes in EU27”

WP1. Non-food crops

D1.3Carbohydrate crops that can be produced in EU27

Lead beneficiary: UNIBO – University of Bologna

Authors: Andrea Monti, Lorenso Nissen

Co-beneficiaries: CRES-Center for Renewable Energy Sources

Authors: Efthymia Alexopoulou, Myrsini Christou

May 2011

The project is a Coordinated Action supported by

Grant agreement no. 227299

Table of contents

INTRODUCTION

1.Cassava (Manihot spp L.) Fam: Euphorbiaceae

1.1.Plant anatomy

1.2.Domestication and area of origin

1.3.Growing conditions

1.4.Logistics: harvesting/handling

1.5.Production-Yields

1.6.Applications

1.7.Restricting factors

1.8.References

2.POTATO (Solanum tuberosum)Fam: Solanaceae

2.1.Plant anatomy

2.2.Domestication and area of origin

2.3.Growing conditions

2.4.Logistics: harvesting/handling

2.5.Production-Yields

2.6.Applications: current/potential

2.7.Restricting factors

2.8.References

3.SUGAR BEET (Beta vulgaris L.) Fam: Chenopodiaceae

3.1.Plant anatomy

3.2.Domestication and area of origin

3.3.Growing conditions

3.4.Logistics: harvesting/handling

3.5.Production-Yields

3.6.Restricting factors

3.7.References

4.SWEET SORGHUM (Sorghum bicolor L.)

4.1.Plant anatomy

4.2.Domestication and area of origin

4.3.Growing conditions

4.4.Logistics: harvesting/handling

4.5.Production-Yields

4.6.Applications: current/potential

4.7.Restricting factors and research gaps

4.8.References

D1.3 1/35

INTRODUCTION

Virtually all plants contain carbohydrate in one form or another, but it is primarily those which store carbohydrates that can latter be extracted that are of most interest here.

Worldwide, the main sources of starch for food and non-food industries are maize, wheat, potatoes and cassava (from which tapioca is derived). Potatoes contains the lowest recoverable starch content, about 17% of dry matter, maize has the highest content, about 60%, and wheat has approximately 50% of starch content in the seeds.

In Europe, the primarily starch crops are maize, wheat and potato, while sugar beet is the most important sucrose crop. Sugar beet has 15-18% of sugar content in fresh taproots that means about 5-7 tons of sugar yield per hectare.

There are many applications of starch in the non-food sector, each of which requires very particularly functional characteristics. The non-food applications accounted for 46% of all starch uses (29% in corrugating and papermaking, 13% in pharmaceuticals and chemicals, and 4% in “other” non food uses). The most important uses are paper and board, biodegradable plastics, adhesives and glues, agrochemicals, detergents, paints, cosmetics and toiletries, pharmaceutical, textiles, water purification, construction, super-absorption products.

In the present report only cassava, potato and sugar beet have been reviewed, while maize is being reviewed in the next report.

Task.1.3 – Carbohydrate crops (UNIBO, CRES)

Worldwide, the main sources of starch are maize, wheat, potatoes, cassava (from which tapioca is derived) and sugar beet mainly for the Southern countries.

Considerable European research efforts have focus on sweet sorghum (Sorghum bicolor) and Jerusalem artichoke (Solanum tuberosum), mainly for energy production purposes.

There are many applications of starch in the non-food sector, each of which requires very particularly functional characteristics. The most important uses are paper and board, biodegradable plastics, adhesives and glues, agrochemicals, detergents, paints, cosmetics and toiletries, pharmaceutical, textiles, water purification, construction, super-absorption products.

In this project the following crops are dealt:

  1. Cassava
  2. Jerusalem artichoke
  3. Potatoes
  4. Sugar beets
  5. Sweet sorghum

UNIBOstudiedpotatoes, cassava and sugar beets and CRES sweet sorghum and Jerusalem artichoke.

The information collected and evaluated by this task addresses the following topics:

  • Plants anatomy
  • Areas of origins and current cultivation
  • Growing conditions-input requirements
  • Logistics (harvesting-handling) until the industrial plant gate
  • Yields
  • Quality
  • Applications: current-potential
  • Research gaps

  1. Cassava (Manihot spp L.) Fam: Euphorbiaceae

1.1.Plant anatomy

Despite its economical importance, little information is available in literature about the anatomical study of cassava.

Cassava plant (FAO.org and Nasser, 2007)

Wild cassava derives from perennial species. It varies in growth pattern from nearly acaulescent sub-shrubs to small trees. Procumbent, semi-herbaceous subshrubs, shrubs, and trees are found in the genus. The branching pattern is typically dichotomous or trichotomous, having at the branching point a terminal inflorescence. Bark of the woody species is generally smooth. Many of the species are lacticiferous, and some species, particularly M. glaziovii (Ceará rubber), are cultivated in Brazil and in some African countries, such Nigeria for rubber production (Nasser, 2007)

1.2. Domestication and area of origin

All species of the genus Manihot have their origin in the central part of South America, in particular in Brazil and Paraguay. It was carried to Africa by Portuguese traders from the Americas. The only species found in other tropical regions of the world are those that have been introduced since Columbus’ voyages to the American continent. The species of Cassava are all rather sporadic in their distribution and rarely become dominant among the local vegetation. The majority of these species are found in relatively dry regions, and only a few are found in rainforest regions. It is a staple food in many parts for western and central Africa and is found throughout the humid tropics (Nasser, 2007).

1.3. Growing conditions

Cassava is a tropical root crop, requiring at least 8 months of warm weather to give products. It is traditionally grown in a bush climate, but can be grown in extremes of rainfall. In moist areas it does not tolerate flooding. In dry areas it looses its leaves to conserve moisture, producing new leaves when rains resume. It takes 18 or more months to produce a crop under adverse conditions such as cool or dry weather. Cassava does not tolerate freezing conditions. It tolerates a wide range of soil pH 4.0 to 8.0 and is most productive in full sun (O’Hair, 1995).

1.4.Logistics: harvesting/handling

The use of machinery for land preparation is preferable to manual labour to ensure the best possible seed bed for tuber development. Subsequent operations of planting, weeding, topping and harvesting can be done by hand as well as by machinery.

Cassava roots can be harvested at any time of the year. Some farmers harvest as early as six months after planting while others may leave the crop for 18 to 24 months. The food quality of roots, particularly the starch content, increases with time up to an optimal period of 12 to 15 months after planting, after which there is a loss of quality, mainly due to increased lignifications. During the dry season, cassava usually drops its leaves. At the onset of rains, a dramatic shift in root quality takes place, probably due to a remobilization of starch towards new leaf formation: the mealy texture of boiled cassava root is often lost, and roots can no longer be used for this purpose.

Harvesting cassava roots is usually made by hand; it is easy if the soil are sandy or during the rainy season. In heavier soils or during the dry season, harvesting usually requires digging around the roots to free them and lifting the plant. To facilitate lifting, the plant is usually cut down about 30 to 50 cm above ground. The protruding stem is used to lift the roots out of the ground. While lifting, care should be taken not to break the roots, as this will lead to losses if broken roots are not retrieved from the soil and to contamination that may evolve into spoilage.

After clearing the land, harvesting is the most labour-intensive operation, and agricultural engineers have sought to mechanise it. Mechanical harvesting of cassava is difficult because of the non-uniform geometry of the roots in the ground. Nevertheless, a few cassava harvesters have been designed and some are in operation, mostly by large-scale farmers. The cost of mechanical harvesting is too high for resource-pour farmers.

Young leaves and shoots of cassava are also harvested to be consumed as vegetables and may be as important as roots for generating cash income. Excessive harvesting of the leaves can have a negative effect on the yield of roots. However, it has been shown in D.R. Congo where cassava leaves are extensively commercialised, an optimal leaf harvesting schedule of once every one or two months will result in higher overall returns for the farmer (Bokanga, 1995).

Packing cassava roots in polyethylene bags was tried and shown to preserve the roots for about 2 months (Cock, 1985). However, complete loss of the stored roots occurred as a result of microbial deterioration. Treating the roots with fungicides retarded the onset of spoilage (Rickard and Coursey, 1981). The deterioration of cassava can be greatly reduced by cold storage. When kept below 4 °C, cassava roots do not show internal discoloration. They still, however, remain susceptible to spoilage by fungi (Rickard and Coursey, 1981). The same authors report that cassava roots could be kept satisfactorily under deep-freeze conditions but that changes in texture occurred in stored samples. Deep freezing of cassava has received little attention from researchers, probably due to the rationale that high-cost storage methods were not suitable for a low-cost commodity such as cassava.

1.5. Production-Yields

Cassava is not usually grown on soils where it would be most productive. When cassava is grown by traditional tropical methods, yields lie between 5 and 20 t/ha, varying with the region, the variety, the soil and other factors. However, when the crop is given more attention, yields of 30 to 40 t/ha are obtained. It has been reported that it is normal for some varieties, under appropriate cultivation methods, to yield over 60 t/ha. The high yields frequently achieved at agricultural experiment stations and occasionally by some active farmers show what might be accomplished with improved varieties and better cultural practices.

Production and yield of Cassava (FAOSTAT, 2000).

Production
(million tons) / Yield
(t/ha) / Area Harvested
(1000 ha)
World / 165.3 / 10.1 / 16240
Africa / 84.4 / 8.4 / 9880
Nigeria / 31.4 / 10.7 / 2940
Asia / 48.5 / 13.3 / 3634
Thailand / 18.2 / 14.0 / 1297
Indonesia / 15.4 / 12.2 / 1266
South America / 31.4 / 12.5 / 2512
Brazil / 25.5 / 12.9 / 1981
North and Central America / 1.0 / 5.1 / 198

Cassava is exported in three forms: as a human food, as a starch, and as an animal feed ingredient. Similar to the domestic markets, price and quality competition exists in the starch and animal feed export markets. There is less competition in the human food export market. The cassava export markets are primarily Europe and North America. There are a number of important but smaller markets in Asia, such as Japan, Korea and China. The export market for cassava chips and pellets and cassava starch is highly price competitive. Other cassava producing countries can enter these markets, but they need to realise that the export market is not for all cassava producing countries (FAO, 2004).

Quality

Fresh roots contain about 30% starch and very little protein. It is not recommended to eat cassava uncooked, because of potentially toxic concentrations of cyanogenic glucosides that are reduced to innocuous levels through cooking. In traditional settings of the Americas, roots are grated and the sap is extracted through squeezing or pressing.

Cassava Exports (FAO, 2004).

In Africa, roots are processed in several different ways. They may be first fermented in water. Then they are either sun-dried for storage or grated and made into a dough that is cooked. Alcoholic beverages can be made from the roots.

Cassava contains free and bound cyanogenic glucosides, linamarin and lotaustralin. They are converted to HCN in the presence of linamarase, a naturally occurring enzyme in cassava. All plant parts contain cyanogenic glucosides with the leaves having the highest concentrations. In the roots, the peel has a higher concentration than the interior. In the past, cassava was categorized as either sweet or bitter, signifying the absence or presence of toxic levels of cyanogenic glucosides. Sweet cultivars can produce as little as 20 mg of HCN per kg of fresh roots, while bitter ones may produce more than 50 times as much. This is not a totally valid system, since sweetness is not absolutely correlated with HCN producing ability. In cases of human malnutrition, where the diet lacks protein and iodine, under processed roots of high HCN cultivars may result in serious health problems.

Composition of Cassava leaves and roots

1.6. Applications

The flour produced from the cassava plant, which on account of its low content of non carbohydrate constituents might well be called a starch, is known in world trade as tapioca flour. It is used directly, made into a group of baked or gelatinized products or manufactured into glucose, dextrins and other products. Non-food use of starches - such as coating, sizings and adhesives - accounts for about 75 percent of the output of the commercial starch industry. In many industrial applications, there is competition not only among starches from various sources but also between starches and many other products. Resin glue has largely replaced starch in plywood because of its greater resistance to moisture; resin finishes are used in the textile industry and natural gums compete with starches in paper making. Nevertheless, the continuous development of new products has enabled the starch industry to continue its expansion. The growth of the starch industry in the future appears to be very promising, providing the quality of products and the development of new products permit them to compete with the various substitutes.

Main applications of Cassava varieties

Starch makes a good natural adhesive. There are two types of adhesives made of starches, modified starches and dextrins: roll-dried adhesives and liquid adhesives.

The application of cassava in adhesives continues to be one of the most important end uses of the product. In the manufacture of glue the starch is simply gelatinized in hot water or with the help of chemicals. For conversion into dextrin it is subjected separately or simultaneously to the disintegrative action of chemicals, heat and enzymes.

In gelatinized starch adhesives, quality requirements are such that the medium-quality flours can be used. In dextrin manufacture, the demands are much more exacting: only the purest flours with a low acid factor are acceptable. Cassava dextrin is preferred in remoistening gums for stamps, envelope flaps and so on because of its adhesive properties and its agreeable taste and odour.

Dextrins were accidentally discovered in 1821 when during a fire in a Dublin (Ireland) textile mill one of the workmen noticed that some of the starch had turned brown with the heat and dissolved easily in water to form a thick adhesive paste.

Three primary groups of dextrins are now known: British gums, white dextrins and yellow dextrins. British gums are formed by heating the starch alone or in the presence of small amounts of alkaline buffer salts to a temperature range of about 180–220 °C. The final products range in colour from light to very dark brown. They give aqueous solutions with lower viscosities than starch. White dextrins are prepared by mild heating of the starch with a relatively large amount of added catalyst, such as hydrochloric acid, at a low temperature of 80º-120°C for short periods of time. The final product is almost white, has very limited solubility in water and retains to varying degrees the set-back tendency of the original starch paste. Yellow dextrins are formed when lower acid or catalyst levels are used with higher temperatures of conversion (150-220 °C) for longer conversion times. They are soluble in water, form solutions of low viscosity and are light yellow to brown in colour. Particle boards could be made from cassava stalks by cutting them into small sections and mixing them with certain resins. The strength of the board can be varied by altering the resin content or the density (FAO, 1977).

1.7. Restricting factors

Cassava roots, when left attached to the main stem, can remain in the ground for several months without becoming inedible; farmers do often leave cassava plants in the field as a security against drought, famine or other unforeseen food shortage. It is from this property that cassava has earned its name as a 'famine reserve crop'. However, once the roots have been harvested, they start deteriorating within 2 to 3 days, and rapidly become of little value for consumption or industrial applications.

Two types of deterioration are known to occur. The first to appear consists of physiological changes characterised by an internal root discoloration called vascular streaking or vascular discoloration (Bokanga, 1995). It is displayed as blue-black or brownish occlusions and chemical deposits. The time to onset of primary deterioration and the rate at which it progresses, the intensity, pattern and distribution of the discoloration varies between cultivars and roots of the same plant. From a biochemical point of view, primary deterioration of cassava roots is associated with a conversion of some of the starch to sugars, an accumulation of cyanogenic glucosides, a decrease in linamarase activity (Kojima et al. 1983).

A second deterioration is induced by microbes that cause rotting. Two types of rot have been identified. Under aerobic conditions, fungi cause a dry rot which results in discoloration and a slight rise in acidity; under anaerobic conditions, bacterial activity (mainly due to Bacillus sp.) predominates, giving rise to rapid development of acidity Most of these organisms behave as wound pathogens and infect roots through the sites of injury, and this usually occurs after primary deterioration has set in, and the roots have already lost their appeal to consumers (Bokanga, 1995).

1.8. References

  • Bokanga, M. 1995. Biotechnology and cassava processing in Africa. Food Tech. 49(1), 86-90.
  • Cock, J.H. 1985. Cassava: New potential for a neglected crop. Boulder, Colorado, USA. Westview Press.
  • IITA. 1990. Cassava in Tropical Africa: A reference manual. International Institute of Tropical Agriculture. Ibadan, Nigeria.
  • FAO. 1977. Cassava processing: FAO Plant Production and Protection Series No. 3 by M.R. Grace.
  • FAO. 2004. Proceedings Of The Validation Forum On The Global Cassava Development Strategy. Volume 6: Global cassava market study Business opportunities for the use of cassava.
  • Nassar, N.M.A. 2007. Cassava genetic resources and their utilization for breeding of the crop. Genet. Mol. Res. 6(4),1151-1168
  • O'Hair, S.K. 1995. New Crop Fact Sheet: Cassava. Center for New Crops and Plant Products, PardueUniversity.
  • Rickard, J.E. and Coursey, D.G. 1981. Cassava storage. Storage of fresh cassava roots. Trop. Sci. 23(1), 1-32.
  1. POTATO (Solanum tuberosum)Fam: Solanaceae
  2. Plant anatomy

The genus Solanum comprises some 2000 species and is very variable in habit, about 170 species produce underground stem tubers. A few other species are horticultural crops, but many Solonaceous plants are poisonous.