The term "acid proof" relates to the use of Caramel Colour in carbonated beverages. The term means the Caramel Colour is stable in a beverage concentrate where it is combined with phosphoric acid and must remain stable for several months. Many of the Caramel Colours manufactured by Sethness-Roquette are "acid proof", even those that may not be specifically formulated for soft drinks.
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Allows determining the alcohol concentration at which the Caramel Colour remains stable. This test is important to the distilleries and alcoholic beverage manufacturers. 
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The determination of the ash content of Caramel defines that portion of the product present as non-carbonizable materials usually consisting of metallic salts. The ash content of Caramel assists in identifying the Caramel’s raw materials and processing.
Incineration of a test portion, previously evaporated, at a temperature of 600°C until the carbonic residue has completely disappeared.
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The European Brewing Convention (EBC) colour method was developed from a visual comparison of a sample material to that of a standard. At the present time, there is no single acceptable method for determining this colour with a spectrophotometer. There are at least four different wavelengths used to determine EBC values. This is similar to Caramel Colour methods which require wavelengths of 560 nm for Tinctorial Power, K_0.56, require a 610 nm wavelength for Color Intensity and require a total dry solids basis for FCC colour.
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Caramel Colour molecules carry ionic (electrochemical) charges which may be either positive or negative - neutral depending upon the processing conditions of a particular product. Most of the Caramel Colour used today is negatively charged. However, there are specific applications where positively charged Caramel Colour is required, particularly in applications where it comes in contact with proteins as in beer and meat products. Often colour precipitation, flocculation, or migration problems can be eliminated with the use of an appropriate Caramel Colour.
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The net ionic charge can be changed with the addition of acid, or base, to a point where the net charge is neutral. The pH at this point is called the Isoelectric, or isoionic point. At the Isoelectric pH, a mixture of dilute caramel and gelatin, a soluble polypeptide, reacts to form a haze or tiny insoluble particles. The haze can be measured by absorbance using a spectrophotometer, or observed visually.

This method depends on the interaction of a dilute solution of gelatin and caramel around the Isoelectric Point. However, the turbidity is measured by absorbance with a spectrophotometer at 640 nm. The pH where the absorbance is the maximum is defined as the Isoelectric Point.
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This test determines the compatibility of Caramel Colour molecules with the negatively charged tannin radicals in solution. It relates to the compatibility of the Caramel Colour with the naturally occurring tannins in various flavour extracts. This test can also be used to determine whether a Caramel Colour is negative or positive in colloidal charge. Positive Caramel Colours precipitate in this test. It is possible that some negative Caramel Colours will also fail this test.
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Negative log of the hydrogen ion concentration.
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Accelerated stability test. The Caramel Colour is sealed in an airtight ampoule and heated at 100°C. The time in hours is measured until the material no longer flows. One hour represents approximately one month under normal storage conditions. The real importance of this test is to ensure the material being tested is the same as the previous lots.
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Colour strength of Caramel Colour. This is the absorbance of a 0.1% weight/volume solution measured through a 1 cm light path at a wavelength of 560 nanometers (nm) using a high quality spectrophotometer. The higher the value of the absorbance, the tinctorial power, K_O.56, the darker the Caramel Colour. A Caramel Colour with a TP of 0,400 is twice as strong as a Caramel Colour of 0,200, and you would only use half as much material to generate the same final colour.
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Caramel Colour is manufactured by heating food grade carbohydrate materials in combination with food grade acids, alkalies and/or salts. During the process organic acids are produced as the result of the degradation of the carbohydrate components. The acidity of the Caramel Colour is an estimate of the organic acid content resulting from the carbohydrate degradation and any residual acids from the process formula.

Titratable Acidity is a measure of the amount of base required to adjust the pH of a Caramel Colour to a defined pH value and is calculated as hydrochloric acid or citric acid.
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Viscosity is the measure of the internal friction of a liquid to resist flow resulting from the combined effects of cohesion and adhesion.  The viscosity of Caramel Colour is an important physical characteristic indicative of the manufacturing process as well as the type and age of the product. Viscosity of Caramel Colour can be also greatly affected by temperature.

This method employs a Brookfield Viscometer.  This is of the rotational variety. It measures the torque required to rotate an immersed cylindrical spindle in a fluid.
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