Week 7 (Unit 13)
Sugarcane & Sugar Beets
In the mid-18th century, European explorers brought back clones of S. officinarum from the South Pacific which they referred to as "noble clones", due to their high sugar content. It was not until late in the 19th century that seed production was observed in Barbados, and efforts were initiated to develop varieties through seed propagation.
Early in the 20th century, sugarcane plantations in Java were ravaged by mosaic (a potyvirus) and sereh disease (which no longer exists). There were no resistant clones of S. officinarum available, so interspecific hybrids were developed with a resistant clone of S. barberi brought from India. Later, interspecific clones were developed from crosses with S. spontaneum, which were rapidly adopted in plantations around the world. These crosses were high in sugar content, and S. spontaneum provided resistance to several diseases, improved vigor, and better tolerance to drought and cold.
The inflorescence of sugarcane is a loose panicle. Each spikelet is bisexual and pollination occurs by wind. The seed is used only for breeding purposes. Short days are required for flowering to occur, and cultivated types are less likely to flower than wild types, because seed production has been bred out of cultivated sugar cane to some extent.
Sugar cane is grown in tropical and subtropical environments throughout the world. It is a perennial crop that is propagated vegetatively using cuttings. Stalks are cut into short 20 inch (50 cm) segments, laid in furrow rows, and then covered with soil. Within a few weeks, plants grow from the buds in the stalk segments.
Sugarcane can grow in a wide range of soil types, from heavy clay types to organic soils. In West Africa, sugarcane is grown in fadamas, which are wet areas along rivers that are seasonally flooded. Ideal soils for sugarcane are well-drained, sandy loams to clay loams with adequate organic matter.
Temperature is one of the key factors determining adaptation of sugarcane. Temperatures must be above 21° Celsius (C) for satisfactory growth. Optimum temperatures for germination, stalk length and diameter are 30-32 °C. For this reason, many of the world's sugarcane growing regions lie between 20 °N and 20 °S, where high temperatures with relatively minor seasonal fluctuations occur.
Sugarcane is grown in areas receiving 500-2500 mm rain annually.
Unlike the cereal crops, it is the sugarcane stem that is harvested as a source of food rather than the inflorescence. After a harvest, the time required for the crop to regrow and be harvested again varies from 10 to 24 months, depending on conditions. In general, yields of cane decrease with successive ratooning, and the crop must eventually be replanted. The frequency of replanting varies a great deal, but is typically 2-4 years in the US.
To see pictures of sugarcane harvest in Africa, go to http://www.africapictures.com/02culturepeople/sugarcane.shtml
About 19.5 million ha are planted to sugarcane in the world each year. This is similar to the area planted to potatoes and sunflower. However, sugarcane is the leading crop in the world in terms of dry matter production. About 1273 million metric tons are produced annually, which is more than twice the weight of wheat grain produced.
Sugarcane production in the USA
Before sugar became an important food crop in the world, honey was the universal sweetener. Today, sugar is our cheapest energy source. The sugar in sugarcane is sucrose. A sucrose molecule consists of one molecule of glucose and one of fructose. Sucrose is not an essential food in our diet, yet we consume enormous amounts of it.
Sugarcane stalks are 85% juice. An average stalk will yield about 1/3 of a pound of sugar. The composition of the cane is 10.5 - 14% sugar.
Uses of sugarcane:
Methods for processing sugarcane into sugar were developed in India around 400 BC. The stalks are cut at maturity and pressed to remove the juice. However, this juice does not store well. The juice must be boiled and allowed to thicken until the sugar crystallizes. Crystalline sugar stores well and can be readily transported.
Blackstrap molasses is the noncrystalline liquid that is left behind after as much of the sucrose as possible has been removed as crystals from the cane juice. Molasses consist mostly of glucose and is used primarily as animal feed, but it can also be fermented into rum. Bagasse is the cane refuse left over after sugar cane processing. It is used in the manufacture of paper, cardboard, and fuel.
Steps in the processing of sugarcane
See http://www.incauca.com/index.php?xlang=en&xskin=incauca&PHPSESSID=8092da3cf243e7e9632cf84f9doc3385 for more information and good photos of the steps in sugarcane processing.
Sugarcane as an energy source
Brazil is the leading producer of sugarcane in the world. In the late seventies, the Brazilian government introduced policies to promote production of alcohol from sugarcane for use as fuel. Sugarcane is processed in 128 ‘energy powerhouses'. These are mills and distilleries that process biomass from sugarcane: they produce sugar for use as a food, electric energy from bagasse burnt in their boilers, hydrated alcohol for use as a vehicle fuel and anhydrous alcohol to improve gasoline's energy and environmental performance. The program was quite successful, but has not received the same level of support from the government in recent years. To find out more about Brazil's alcohol program, read Sugarcane as an energy source in Brazil.
See http://www.apsnet.org/online/slideset/sugrcane/ for images and descriptions of major diseases, pests, and nonnutrient disorders of sugarcane.
gumming disease - Xanthomonas vasculorum (Cobb) Dows. - yellowish stripes occur at the leaf tips and the vascular bundles exude a yellowish gum when cut
leaf scald - Xanthomonas
albilineans (Ashby) Dows. - yellow stripes occur on the leaf blade,
many side-shoots are produced, and the vascular bundles of the stalk are
red rot - Colletotrichum falcatum Went - causes the setts to be seriously damaged at low temperatures.
root rot - Pythium graminicolum Subr. - responsible for the failure of "Otaheite" (a noble cane) in Mauritius in 1846
pineapple disease - Thielaviopsis parodoxa (de Seynes) C. Moreau - attacks the setts causing the center to turn black and smell like overripe pineapples
downy mildew - Sclerospora sacchari Miy
smut - Ustilago scitaminea Syd. - important in southeastern Asia and South Africa
Mosaic - vectors include Aphis maidis Fitch; first recognized in Java in 1892; causes severe stunting in some cases
stem-borers - the larvae burrow into the stem and cause loss of sucrose and weakened stems on emergence.
termites - India
white grubs - Queensland.
The production of sugarcane and manufacturing of sugar requires large tracts of good land and access to specialized equipment. It is a fairly profitable business for those who are able to do it. Prior to the modern era, producing cane was a labor intensive undertaking. Mechanized harvesters became available in the 1950's.
When sugar was first introduced into Europe it was a luxury item, and the canes were used for chewing and medicinal purposes. It was only after 1700 that sugar was transformed from a luxury product into one that was used everyday by people from all walks of life. This took place as Brazil and the new West Indies colonies began producing sugar in such large quantities that the price was significantly reduced. Lower prices led to increased consumption, which, in turn, fueled demand.
The development of efficient roller mills for extracting juice from sugarcane in the 17th century was an important technical innovation for the sugar industry. The rollers could be turned by animal, water, or wind power. With this mill, it was no longer necessary to chop the stalks into pieces before processing.
Sugarcane was introduced to Madeira in 1432 and the Canary Islands in 1480 and was transported to the Hispaniola (the Island now consisting of the Dominican Republic and Haiti) by Columbus in 1493. Sugar plantations began to develop in the colonies in the early 1500s. The economies of Brazil, Cuba, Jamaica, Barbados and other places in the Caribbean became dominated by the production of sugar products. Sugarcane plantations marked the shift from agriculture as a way of obtaining food to a process for accumulating capital. Plantations possessed certain features that are hallmarks of modern commercial farms:
Negative aspects of plantation culture:
The development of sugarcane plantations led to reinvigoration of the slave trade as a source of labor, especially black slaves from Africa, resulting in the mass importation of Africans against their will into the New World.
Being a highly profitable enterprise, sugarcane plantations often displaced other farming systems once they were introduced. In Madeira, the Canary Islands, and São Tomé, it was possible to grow sugarcane year-round without irrigation. Yields were very high, and sugarcane rapidly displaced traditional crops on those islands.
Slavery has been abolished, but controversy surrounding the sugar industry continues. In the US the Friends of the Everglades advocates removal of sugar subsidies. In particular, they are concerned that the government's sugar price supports have led to rapid expansion of sugar plantations in the Florida Everglades, which has resulted in degradation of this important ecosystem. Representatives of the sugar industry in Florida believe that science can address many of these environmental concerns.
Large-scale production and processing of sugar can have undesirable effects on the environment in several ways:
Considerations for human health
When we eat fruit containing about 10% fructose and 10% glucose, for example, the remaining dry matter must be digested before the sugars become available. When we consume pure white sucrose (table sugar), there is little digestion required, and energy is released in a sudden flood into our bloodstream, giving us a rapid, but short-lived burst of energy.
For people who consume large amounts of sugar, nearly the whole of the body's energy requirements are met by the sugar, and the rest of the food or drink consumed becomes merely a transport system for the sugar. Production of starch and fiber converting enzymes is inhibited once the body gets used to obtaining its sugar requirements directly from sucrose, so after a while the stomach finds it difficult to digest any accompanying starch or fiber. People will naturally avoid foods which they find hard to digest, so food manufacturers then reduce the fiber content in processed or packaged foods. A vicious cycle is created in which the victim becomes hooked on a constant flow of industrial sugar to the bloodstream while reducing intake of fiber. A diet high in fiber has many important health benefits.
The white sugar addict becomes prone to obesity, tooth decay, and malnutrition. Due to the speed with which white sugar becomes available for metabolism, the addict's blood sugar level rises and falls very rapidly and the pancreas works excessively hard to deal with high inputs of sucrose to the stomach. The body becomes used to a feast/famine syndrome in the blood sugar, and this produces an addiction which is chemical, not psychological. The bloodstream signals a deficiency, and the cycle is frequently repeated.
During the Renaissance, people consumed only about one teaspoon of sugar a day. Today, some people eat and/or drink over 4 pounds of sugar each week. Sugar is not necessary for any endeavor, but it is addictive. In effect, we have all become slaves to the sugar industry.
Sugar beet is cross pollinated by wind or insects and is strongly self-sterile through a self-incompatibility mechanism. The fruit is an aggregate that yields a seedball with two or more viable seeds. Fruits with one seed were discovered in 1948. This trait permits more precise planting and eliminates the need to thin stands after planting.
Use of beet sugar was initiated by the French when cane sugar was prevented from reaching Europe due to a British blockade during the Napoleonic wars of the 19th century. Beet sugar is produced in the United Sates and Europe but must be subsidized, as the plant is not as efficient as the tropical sugarcane.
For some nice images of sugar beet and a description of the sugar beet industry in Michigan, see http://www.michigan.gov/hal/0,1607,7-106-1751_18793-53367--,00.html.
The Ukraine, Russian Federation, and the USA grow the largest acreages of sugar beet. The leading producers of sugar beet are France, Germany, and the USA.
Disease, insect, and nematode pests can be very problematic for sugarbeet production. See http://www.beetseed.com/index.php for more information on these pests and available control strategies.
Uses of sugar beets
Sugar beets contain from 13 to 22% sucrose. The primary use of sugar beet is for sugar for human consumption.
High fiber dietary food additives are also manufactured from sugar beet pulp.
Molasses by-products from sugar beet processing are used widely in the
alcohol, pharmaceuticals, and bakers yeast industries.
Take the quiz on this Unit on the Blackboard.
Additional Study (recommended)
Review the basic steps in the manufacturing of sugar from sugarcane
as it is carried out at the INCAUCA sugar
mill in Colombia:
Read more about the history of the sugarcane industry and its cultural
significance, particularly its connection to the slave trade:
American Phytopathological Society. 1999. Diseases, pests, and nonnutrient
disorders of sugarcane.
Cattanach, A.W., A.G. Dexter, and E.S. Oplinger. 2000. Sugar beets. Alternative
Field Crops Manual, University of Wisconsin Cooperative Extension Service.
Duke, J.A. 1983. Saccharum officinarum L. In Handbook
of Energy Crops. unpublished.
Feldmann, P., A. D'Hont, E. Guiderdoni, L. Grivet, and J.-C. Glaszmann. 2001. Sugarcane. In A. Charrier, M. Jacquot, S. Hamon, and D. Nicolas (eds.) Tropical Plant Breeding. CIRAD, France.
Holly Hybrids. 2004. http://www.beetseed.com/index.php
Hunsigi, G. 1993. Production of sugarcane: theory and practice. Advanced Series in Agricultural Sciences. Springer-Verlag, Berlin, New York.
INCAUCA. 2003. Website for the INCAUCA sugar mills in Colombia.
Janick, J. 2002. History of Horticulture, Lecture 34: Horticulture, Politics,
and World Affairs: Sugarcane and Plantation Agriculture. Purdue University.
Kiple, K.F., and K.C. Ornelas. 2000. Sugar. In The Cambridge
World History of Food.
Sharp, P. 1998. Sugar Cane: Past and Present. Ethnobotanical Leaflets.
Solbrig, O.T. and D.J. Solbrig. 1994. So shall you reap: farming and crops in human affairs. Island Press, Washington, DC.
Sugar Knowledge International (SKIL). 2005. http://www.sucrose.com/home.html.
University of Florida Cooperative Extension Service. An overview of Florida