Integrierte Vermeidung und Verminderung der Umweltverschmutzung

Chapter 2
2.2.12.2 Sugar cane
Raw cane sugar is usually separated, purified and crystallised in the country of origin. The cane
sugar, which is in a crudely refined state, undergoes final processing when transferred to the
country of use.
2.2.12.3 Sugar refining
Raw sugar is typically a minimum of 96 % sucrose. The impure crystals, with adhering
molasses, are blended in a saturated sugar solution to soften the surface molasses film which
can then be removed by centrifugation. The partly processed sugar is dissolved in reclaimed
liquors, i.e. light waters from the refining process. Carbonation, which is treatment with milk of
lime and carbon dioxide, then follows. This produces a precipitate which contains impurities
such as pectins and proteins and removes suspended impurities such as waxes, gums and
starches. The sugar syrup is filtered and decolourised using ion exchange resins and activated
carbon to produce a fine liquor, which may be sold as a finished product or passed on for
crystallisation.
The fine liquor is concentrated by evaporation to produce a syrup of around 60 – 70 % solids,
known as thick juice. The juice is filtered and transferred to vacuum pans. When the liquor is
slightly supersaturated, the pan is seeded with fine icing sugar to initiate crystallisation. The
mixture is centrifugally separated to extract crystalline sugar, which is dried, conditioned for
packaging or bulk loaded. Each pan boiling yields around 50 % of the available sugar.
The liquor separated during centrifugation, also called jet, is re-boiled for further extraction.
Three boilings yield white sugar. A fourth boiling yields off white industrial sugar. Jet four,
together with liquor from blending, goes to a recovery house for three further boilings to
produce brown sugars which go back to the start of the refining process and are treated as raw
sugar. Various intermediary products from jets one to four and the corresponding syrups from
recovery and boiling are sold as the starting materials for syrups such as molasses and treacle.
Molasses are sometimes used in animal feed, alcoholic fermentation and a number of non-food
products.
2.2.13 Coffee
Commercial coffees are grown in tropical and subtropical climates at altitudes of up to
around 1800 metres. Coffees from different producing regions possess different characteristic
flavours. The main processing steps in the manufacture of roasted coffee are blending, roasting,
grinding and packing. Instant coffee is produced from a water extract of roasted ground coffee.
Roasting coffee beans and the production of instant coffee are energy intensive processes.
2.2.13.1 Roasting coffee
Green coffee is received and sorted to remove extraneous matter. Coffees from different
varieties or sources are blended before or after roasting. Roasting is usually carried out by hot
combustion gases in rotating cylinders. The final bean temperature is around 200 to 220 °C. A
water or air quench terminates the roast. Most of any added water is evaporated from the heat of
the beans. Fluidised bed systems may greatly reduce roasting times from around
8 to 15 minutes to 1 to 3 minutes. Finished coffee is transferred to storage bins. Any residual
foreign bodies are removed before grinding, usually by air classification methods. Most coffees
are ground in steel cutting rollers which are scored, once longitudinally and once across the
circumference. Cracking rolls break the beans before they are fed into a further series of rollers.
For fine grinds, the coffee may pass into further sets of rollers, being scored on each subsequent
pair of rollers and becoming progressively finer as the coffee travels through the system.
Roasted and ground coffee in Europe is typically vacuum packed in flexible pouches of plasticlaminated
foil.
102 January 2006 RHC/EIPPCB/FDM_BREF_FINAL