Gelatine Testings

GELATIN TESTING

Through the combined efforts of the technical staffs of the member companies, the Gelatin Manufactures Institute of America has published a detailed volume which describes the methods of sampling and testing of gelatins (8).  In addition, the analytical procedures are continually reviewed and updated via collaborative testing.  This cooperative testing has led to significant improvements in the testing precision and accuracy of gelatin results.

Gel strength and viscosity are the two most important measurements used to assess the grade and quality of a gelatin.  The gel strength is determined using a texture analyzer (52).  A pipet viscometer is used to determine viscosity.  Both tests are based on a standard 6.67%test solution.  Gelatin weights for standard tests are made as is, without moisture correction.

The procedure for gel strength determination is summarized as follows:

A water solution consisting of 6.67% gelatin (7.50 +/- 0.1g gelatin and 105.0 +/- 0.2g deionized water, melted at 60-65°C) is carefully prepared in a specified 150 ml, wide-mouth, glass bottle, which is then placed in a chilled water bath and held at 10+/- 0.1°C for 17 +/- 1 hours.  After chilling, the rigidity of the gel is measured as the force, in grams, required to mpress a standard 0.500 +/- 0.001 inch diameter plunger to a depth of 4 millimeters into the surface of the gel.  This weight is referred to as the gel strength, or Bloom rating, of the gelatin. The greater the force required, the higher the strength of the gel. Commercial gelatins range from 50 to 300 Bloom grams.

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In practice, the viscosity of gelatin is usually measured on the very same sample used for gel strength determination.  The 6.67% test solution is carefully brought to 60°C whereupon 100 ml is introduced into a calibrated capillary pipet.  The efflux time, in seconds, is recorded, and later converted to millipoise based on the relationship established at time of calibration.  Each individual gelatin viscosity pipet is calibrated with oils traceable to the National Institute for Standards and Technology. Other analytical procedures in the gelatin Standard Methods manual include the determination of:

TEST

METHODOLOGY

Identity

Hydroxyproline analysis and gel   reversibility testing.

Moisture

Loss in weight on drying

PH

Potentiometric

Granulation

Standard sieve analysis

Ash

Residue on ignition

Heavy Metals

Wet chemistry

Fluoride

Colorimetry

Arsenic

Colorimetry

Clarity

Light transmittance at 640nm

 


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