Sugar is a generic name given to a variety of monosaccharides that includes compounds like fructose, galactose, and glucose. The sugar that we normally see in our kitchens and put in our food are usually disaccharides made with bonded monosaccharides in different combinations. Long chains of monosaccharides for starch which is mainly found in plants and is a part of the human diet as well. The white sugar that sugar factories produce are a refined form of sucrose that gets hydrolysed in the body to form simple sugars. The commercial extraction of sucrose usually happens from sugarcane or sugar beet.
A brief history of sugar
Sugar is one of the oldest items that was used for trade across the globe. The first references of a sugar exporter can be found around 8000 BC in New Guinea islands. In the old days, sugar was kept under lock and key as it was a costly commodity and mostly the rich could afford it. Nowadays over 120 countries across the globe produce sugar and almost 80% of it comes from sugarcane. The global sugar production is around 188 million metric tonnes and India is the second largest producer of sugar in the world after Brazil.
Forms of sugar
Sugar factories produce a variety of forms of sugar with the normal granulated sugar being the most common form. The larger crystals of granulated sugar are called coarse sugar while the superfine sugar has smaller crystals. Pearl sugar has a conglomerate of sugar particles, while brown sugar has different amounts of molasses present that provides it the distinctive brown color. Special types like powdered sugar contain cornstarch while the demerara sugar has large crystals coated with molasses. The turbinado sugar is partially purified and is also called raw sugar, while muscovado is a coarse brown sugar that is stickier.
Manufacturing sugar: Harvesting
Sugarcane is the most important cash crop that presents less risk to the farmers even in adverse climatic conditions in India. The process to make sugar that is finally used by any sugar exporter starts with harvesting the raw material from the fields. It is estimated that around 50 million farmers in India engage in its cultivation. Around half a million unskilled workers are engaged during the harvesting season to cut the sugarcane plants and transport them to the factories. The harvested plants are sieved to remove any clinging rocks and dirt before loading to the trucks or trains.
Washing and preparations
When the sugar factories receive the sugarcane from the fields they are washed extensively. Huge conveyor belts take these sugarcanes repeatedly under flues that are full of water and further water is sprayed to them to make them completely spotless of any dirt or dust. Rotating drums are also engaged at the washing stations to ensure all foreign materials are removed completely before sending the sugarcane ahead in the production chain. Then these sugarcanes are crushed using grooved crushers or swing hammer shredders. The sugar beets on the other hand are cut into small pieces and soaked in hot water.
Extraction of the juice
The sugarcane is then milled to extract the juice completely while the extracted material is then further used to make various textiles. These milling plants have a series of five mills that first compress the sugarcane fibers and then separate the bagasse from the juice. The bagasse thus removed is also used as a source of fuel. The juice thus extracted is dark green and it is highly turbid and acidic. The juice is collected in huge vats and checked thoroughly for its quality. The sugar factories have to further process the juice once optimal sugar concentration is attained.
Purification of the juice
The juice is transferred to tall towers that are around 20 meters high. These towers lighten the color of the extracted juice and purify it with the help of chemicals. Sulfur dioxide is passed through these towers of juices in the process of sulfitation. The sugar factories then further use alkalization and carbonation processes to separate the soluble materials that are non-sugars from the sugarcane juice. The process of carbonation uses calcium carbonate and then calcium hydroxide and carbon dioxide is added to lower its alkalinity. This allows the juice to become purified and the rest goes out as sludge.
This process takes several hours and the purified juice is taken out from the top of the towers. A secondary or even tertiary filtration is often used to extract any remaining sugar from the sludge as per the needs of the population which the sugar exporter defines. The final byproduct is known as mud and is often used to fertilize the fields later. The purified juice is next boiled in a series of evaporators till each batch hits a 65% concentration of sugar. Each evaporator also produces vacuum pressure progressively that finally produces a sugar syrup.
Crystallization
The sugar factories now use a vacuum pan to evaporate the syrup. This process allows the syrup to saturate into crystals of sugar that start to look like the sugar we know. This process is known as seeding. Next a milky solution of pure sucrose is added with glycerin and alcohol to make the crystals join further and take their most recognized cube shape. The small grains or seedings act as the nuclei around which other sugar particles join into crystals. The boiling also helps the water to evaporate and produces dense sugar crystals and syrup.
Centrifugation
The mixture is then transferred to a large container where it is slowly stirred and cooled before adding it to a high speed centrifuge machine. The centrifuge revolves the mixture at around two thousand revolutions per minute and has perforated metal baskets. This removes any molasses that may have traveled along the line and is then sent to storage tanks. These huge centrifuge machines at the sugar factories then use spring water to wash the crystals while they are spinning.
Drying and packaging
Large air dryers at the sugar factories bring down the moisture content of these damp sugar crystals to less than 0.02%. The final product is then tumbled through this heated air and separated into different sizes on vibrating screens. These are then stored into separate bins and packaged as per the needs of the consumer.