Sugar, Starch and Cellulose (BIOL 1300 Unit 8) PDF

**BIOL 1300 UNIT 8** **SUGAR, STARCH AND CELLULOSE** - **Sugar:** Refers to monosaccharides (e.g., glucose, fructose) and disaccharides (e.g., sucrose, maltose) with a sweet taste. Table sugar is specifically sucrose (glucose + fructose) from sugar cane or beets. - Mono=the mo...

**BIOL 1300 UNIT 8** **SUGAR, STARCH AND CELLULOSE** - **Sugar:** Refers to monosaccharides (e.g., glucose, fructose) and disaccharides (e.g., sucrose, maltose) with a sweet taste. Table sugar is specifically sucrose (glucose + fructose) from sugar cane or beets. - Mono=the most basic singular structure for sugar - Di=two monosaccharides linked by a glycosidic bond - Easily digestible - **Starch:** A polysaccharide made of glucose units linked by alpha (α) 1-4 glycosidic bonds. Amylase (or diastase) breaks these bonds, converting starch into digestible maltose and glucose. It's a common component of plant seeds and a main food source for germinated seedlings. - Polysaccharides consist of \>1000 glucose units - Very common in seed plants, especially seeds and storage organs like the endosperm, recall that it has mostly starch - Unlike cellulose, starch is digestible - **Cellulose:** Like starch but with glucose units linked by beta (ß) 1-4 glycosidic bonds, which are harder to break. Most organisms (including humans) can't digest cellulose, so it's termed "dietary fiber" or "roughage." Ruminants, cows, and termites rely on symbiotic microorganisms in their guts to digest cellulose. It's the main structural component of plant cell walls, making up a third of plant matter (e.g., wood is 50% cellulose, cotton fibers are 95% cellulose). - Has numerous (2000-3000) glucose units - Alpha and beta refer to the bond orientation **BIOETHANOL** - **Gasoline**: A refined petroleum product (petrol in the UK), a mixture of chemicals with 5 to 12 carbon atoms, including alkanes, alkenes, naphthalenes, and aromatic compounds like benzene, toluene, and octane. It is not a renewable energy source. - **Bioalcohols**: Typically, bioethanol (two carbon atoms) can be added to or substituted for gasoline with engine modifications. It is considered sustainable because it comes from plants in comparison to fossil fuels which is a limited resource. Photosynthesis makes it sustainable as plants generate energy constantly. - **Ethanol Production**: 2 carbon alcohol easily obtained from sugar (usually sucrose) breakdown via anaerobic fermentation by yeasts or other organisms (which obtain sugar units). Bioethanol can also be produced from cellulose, but efficient production requires advances in cellulosic technology (i.e. the development of efficient methods to convert cellulose into sugar). The efficiency of bioethanol production is measured by the **energy balance**, which is the ratio of bioethanol energy produced to the energy required for its manufacture. For instance, if two units of fossil fuel produce three units of ethanol, the energy balance is 1.5 (3/2=1.5). In the U.S., bioethanol facilities using corn starch have low energy balances of 1.3 or less. Lower values are considered inefficient, as the energy obtained is only slightly higher than the energy used. In contrast, Brazil achieves an energy balance of 8 or higher using sugar cane, with modern facilities burning bagasse (sugar cane residue) for electricity achieving even higher balances. Variations in energy balances may be due to variation in chemical structures. Brazilian sugar cane plantations produce 5,300-6,500 liters of bioethanol per hectare. Non-tropical species like switchgrass, micranthus, and hybrid poplar are potentially productive but impractical for bioethanol production due to their high cellulose content, which requires further innovation. **PLANT SUGAR SOURCES** **Sugar cane** is a tall perennial grass, growing up to 3.5 meters. Its origins are uncertain, but it has a long history of domestication. It was likely first selected as a sweet chewing cane in New Guinea. Over time, it hybridized with related species from Southeast Asia and India. This cultivated variety was then spread to the Pacific region, Southeast Asia, India, and later back to China and India. **Sugar cane** was first commercially grown in the Mediterranean. Europeans, especially the British, later established large plantations in the Caribbean, which led to the African slave trade, beginning around 1500, due to a lack of technology to handle labour intensive harvesting. African slaves were forced to work in harsh conditions in the cane fields and processing plants. This trade evolved into the "Sugar Triangle," where Caribbean sugar and molasses were shipped to Europe. This trade involved three main stages: 1\. **Europe to Africa**: European merchants shipped manufactured goods such as arms, textiles, and wine to Africa. These goods were traded for enslaved Africans. 2\. **Africa to the Americas**: Enslaved Africans were transported across the Atlantic Ocean to the Americas in a journey known as the Middle Passage. This leg of the trade was notorious for its brutal and inhumane conditions. 3\. **Americas to Europe**: In the Americas, enslaved people were forced to work on plantations, producing commodities like sugar, tobacco, and coffee. These products were then shipped back to Europe, completing the triangular trade. These slaves were transported under horrific conditions to work in the Caribbean and South American sugar fields. The middle passage involved many sugar plantations in South and Central America and the Southern U.S. The plants were harvested in fields or facilities, which also had awful conditions. To obtain sugar, lots of heat is needed so workers were exposed to high temperatures which often led to exhaustion and dehydration and ultimately death. The British slave trade ended with the Emancipation Act of 1834. Sugar cane is extensively cultivated in Brazil, India, and less so from the Caribbean, and Florida (where the industry is subsidized and not as profitable). It is the largest global source of commercial sugar (sucrose), with over 1 billion tons produced annually, primarily in India and Brazil. Additionally, a significant portion of Brazilian sugar cane is used to produce bioethanol fuel for the domestic market. Sugar cane thrives in a moist, frost-free climate with fertile soil. It is propagated using stem cuttings called setts. The harvested stems and leaves are crushed to extract sugary juice (about 15% sucrose). The juice is concentrated by boiling, then centrifuged to separate molasses from crude sugar. The dark crude sugar is purified through repeated crystallization to produce pure sucrose. **SUGAR BEET** (Beta vulgaris var. vulgaris) The sugar beet is a temperate, biennial crop harvested after 2 years. It is closely related to edible (var. esculenta) and fodder beets for livestock (var. rapacea), was developed in Europe in the late 1700s from a white fodder beet with about 8% sucrose to meet demand for sugar after cutoff of supplies due to Napoleonic Wars. Crystallized sugar was a luxury in Europe at the time, commanding a high price. The first sugar beet production facility opened in Silesia (now part of Poland) in 1802. By the mid-1900s, modern high-yielding cultivars with 18-20% sucrose were developed. Today, about 250 million tons of table sugar are produced annually from sugar beets, accounting for 20- 25% of the global supply. Major producers include Russia, Ukraine, France, Germany, and the United States. Manitoba had a sugar beet plant in the Fort Garry area from 1940-1997. **CORN SYRUP** (Zea mays) Corn syrup, primarily composed of glucose and fructose (not sucrose), is produced from cornstarch (obtained from corn kernels) through enzymatic fermentation. Glucose-fructose syrups can also be made from other high starch sources like wheat, rice, and potatoes. Fructose, which is sweeter and more water-soluble than glucose, is obtained by enzymatically converting glucose. **TROPICAL PALMS** Several tropical palm species are important local, not commercial sources of sugar. The sugary sap is tapped from these palms, concentrated into syrup, and dried. The sap can also be fermented to produce alcoholic palm wine. There is a small export market for sugar from tropical palms. **SUGAR PALM** (Arenga pinnata): The sugar palm, is large and native to tropical East Asia, produces separate male and female flower clusters. It has been used historically for sugar and palm wine production. The palm is tapped by cutting off male flower clusters to collect sap, which initially flows at a high rate (few days) but decreases over time. Brown palm sugar is made by boiling the sap to concentrate it. In general, boiling is central to sugar creation. Annually, a single palm yields about 1,800 liters of sap, producing around 150 kg of sugar. It can be used for candies and brown sugar. **PALMYRA PALM** (Borassus flabellifer): This palm is large and grows up to 30 meters. It is native to dry tropical regions of India and Southeast Asia and has separate male and female plants. Male plants are tapped for their sugary sap, while females are kept for their edible fruit. The male flower clusters are cut off to collect the sap, which is boiled to concentrate the raw sugar. A single palm can produce over 100,000 liters of sap over four years (up to 20 liters per day). The sugar from this palm is known as "jaggery," and the fermented sap is called "toddy wine." Several other palm species are tapped, including the fishtail palm (Caryota urens) from tropical Asia, and the mokola palm (Hyphaene petersiana) from South and North Africa. Both are used to produce sugar and fermented palm wine. **MAPLE SUGAR** The sugar maple (Acer saccharum) is a large deciduous tree native to eastern North America, particularly New England, southern Ontario, and Québec. In late winter and early spring (February-March), the phloem tissue is tapped to collect sugary sap (1-3% sucrose). The sap is boiled and concentrated into syrup, which can be granulated to produce maple sugar. Maple sugar is used in confections and as a flavoring. Québec is the largest global producer, with smaller amounts from northern New England states. **SWEETENERS FROM PLANT SOURCES** A sweetener is a *non-sugar* substance that produces a sweet taste when added to food and unlike sugars, is not absorbed into the body. Most sweeteners are artificial (e.g. aspartame, saccharin, the latter is banned in Canada) and were developed as low-calorie sugar substitutes. The following are natural sweeteners from plants: **STEVIA or SUGAR-LEAF (Stevia rebaudiana)** Stevia is a perennial herb from Paraguay, known as *caa*-*ehe*, and part of the Sunflower family (Asteraceae). Its leaves contain up to 20% of the active sweeteners called steviol glycosides. The most important glycosides are stevioside and rebaudioside, which are intensely sweet, non-caloric (not absorbed by the gut), and have a liquorice-like flavor. These compounds are 300 times sweeter than sucrose and half as sweet as saccharin. Stevioside breaks down in the gut to form aglycone Steviol, a diterpene which has been linked to cancer in some research. However, this needs further inquiry. Recent innovations include combining rebaudioside with erythritol, a naturally occurring sugar alcohol found in fruits. Stevia has recently been approved as a sweetener in the US and Canada, and is popular in Japan, where it dominates nearly half of the sweetener market. However, artificial sweeteners (e.g. saccharin, aspartame) are banned or strictly regulated. It is also grown and used in China, Malaysia, Thailand, and South Korea. **MIRACLE BERRY** (Synsepalum dulcificium or Sideroxylon dulcificum) The miracle berry, native to tropical West Africa, contains a glycoprotein called miraculin that binds to taste buds and makes salty and sour foods taste sweet. It is not a sweetener itself but alters the taste of food consumed afterwards, with the effect lasting for several hours. For example, a lemon eaten after consuming miracle berry tastes sweet, not sour. Fresh or dried miracle berries are available in North America and Europe but cannot be marketed as a food additive. Efforts were made to commercialize it as an additive but was stopped by the FDA. Efforts are ongoing to purify miraculin and obtain regulatory approval for the berry as a dietary supplement, as it could potentially be used to help people eat healthier and for people with medical conditions that affect their diet.