Refractive Index Determination of Soluble Solids 1 Scope This method uses refractometry to determine the content of soluble solids in beverages. This method is applicable to the determination of the content of soluble solids in liquid soft drink products. The results are reported in % content, and the measured value is retained at one decimal place. 2 Principle The refractive index of the sample solution to be tested is measured with a refractometer at 20°C, and the soluble solid content is read directly from the refractometer using the conversion table of the refractive index and the soluble solid content. 3 Instruments 3.1 Refractometer: Measuring range 0 to 80%, accuracy ± 0.1%. 4 Operation steps 4.1 Sample Processing 4.1.1 Transparent Liquid Beverage Mix the sample thoroughly and measure directly. 4.1.2 Semi-viscous products (fruit and vegetable pulp) Mix the sample thoroughly, extruding the filtrate with four layers of gauze, discarding the first few drops, and collecting the filtrate for testing. 4.1.3 Suspended Substances (Including Fruit Beverages) The sample to be tested is placed in a tissue masher and crushed. Four layers of gauze are used to extrude the filtrate. The first few drops are discarded and the filtrate is collected for testing. 4.2 Sample determination 4.2.1 Correct the refractometer according to the instructions before measurement. 4.2.2 Separate the two prisms of the refractometer and clean them with absorbent cotton. 4.2.3 Use a glass rod with a rounded end to draw 2-3 drops of the treated sample and place it in the center of the prism face of the refractometer (be careful not to touch the mirror with a glass rod). 4.2.4 Rapidly close the prism and let it rest for about 1 minute to make the sample uniform and free of bubbles and full of field of vision. 4.2.5 Align the light source and observe the contact lens through the eyepiece. Adjust the indication gauge to divide the visual field into two parts, light and dark, and rotate the fine-tuning spiral so that the light and dark boundaries are clear and the boundary line is exactly at the intersection of the objective lens. Read the percentage or refractive index in the field of view of the eyepiece and record the prism temperature. 4.2.6 If the scale of the eyepiece reading scale is a percentage, it is the percentage of soluble solids; if the scale of the eyepiece reading is the refractive index, it can be converted into soluble solids percentage according to Appendix A. The above percentage content is converted into the percentage of soluble solids at 20°C according to Appendix B. 5 Precision The difference between the two measured values ​​of the same sample shall not exceed 0.5%. 6 References GB12143.1-89 "Method for determination of soluble solids in soft drinks by refractometry" Hot Forging Parts,Closed Die Forging ,Cold Forging Machine ,Types Of Forging Metal Processing Machinery Parts Co., Ltd. , http://www.nbprecisionparts.com
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