Most of the domestic cane sugar mills use the sulfite method, with sulfur dioxide as the main clarifying agent. White sugar residual trace sulfur dioxide is difficult to avoid. However, as long as it does not exceed the national standard, it is not a problem. Just some sugar mills in the process, equipment or management are not proper, so that the white sugar residual sulfur dioxide amount exceeds the standard.

Sulfur dioxide added to the cane juice sulfur fumigation most of the clarification process in the formation of calcium sulfite precipitation and discharge from the mud, but there is a small amount of retention in the clear juice, the proportion and clarification of the technical conditions of the process and operational management. Sulfur dioxide in the clear juice in the evaporation process, part of the juice vapor volatilization, another part of the oxidation (to become sulfur trioxide), but most of them are left in the crude syrup. The syrup is again sulphured and the amount of sulphur dioxide in it increases. They partly overflow with the juice vapor during boiling and refining, and partly are oxidized, but most of them are left in the syrup by the formation of a precipitate of calcium sulphite, or dissolved calcium bisulphite, and compounds of sulphurous acid and organic matter. When cooking sugar crystallization, they are able to enter the white sugar product in several different forms, such as crystal growth will be a small amount of mother liquor wrapped in crystals, precipitate particles mixed in the product and so on.

(1) sensory identification of white sugar

White sugar is also divided into white sugar, white sugar. White sugar is processed from sugar cane as raw material granular sugar. Mian white sugar is processed from sugar beet as a raw material of fine granular sugar. In addition, there are square sugar, rock sugar are sugar as the main material processed from the hexahedral or multi-faceted crystal sugar reproductions. These four kinds of sugar and its properties are basically similar, so they are discussed together.

①Color identification

When observing the color of white sugar, the sample should be spread into a thin layer on white paper, and then observed.

Good quality white sugar - white and bright color, shiny.

Second-quality white sugar - white with a slight light yellow color.

Inferior white sugar - yellowish, dark luminosity, no luster.

②Tissue state identification

Sensory identification of the state of the organization of sugar, the sample should be spread on a thin layer of white paper, the first to observe the shape of its grains, the presence of agglomerates, moisture absorption and impurities, and then formulated into a 20% aqueous solution of sugar, to observe the presence of precipitation and impurities.

Good quality white sugar - white sugar: particles as large as sand grains, grain uniformity and neatness, crystal surface is obvious, no fragments, sugar hard. Mian white sugar: small and uniform particles, soft texture, moist. Rock sugar: complete block shape, uniform grains, tight crystalline organization, transparent or translucent, no broken. Sugar: hexahedral, flat surface, no cracks, iron edge, broken corners, no prominent grains of sand, no mold. All white sugar should be dry, loose grains, non-sticky, no lumps, no impurities visible to the naked eye. Aqueous solution of white sugar should be clear and transparent without impurities.

Sub-quality white sugar - uneven grain size, broken and powdered, moist, poor looseness, sticky hands.

Inferior quality white sugar - moisture-absorbing lumps or dissolved. There are impurities, sugar water solution can be seen with precipitation.

3 odor identification

Can take a sample of sugar directly smell its odor, or take a small amount in the mortar, crushed and smell its odor.

Good white sugar - with the normal odor of sugar.

Second-quality white sugar - a slight molasses flavor.

Inferior quality white sugar - has a sour, alcoholic or other foreign odor.

④Taste identification

Check the taste of white sugar, take a small sample of direct taste, and then prepare a 10% sugar solution to try.

Good quality white sugar - with pure sweetness.

Second-quality white sugar - the taste is basically normal.

Inferior white sugar - impure taste or foreign odor.