Différents essais de laboratoire sont utilisés depuis longtemps pour évaluer le risque d'apparition d'un trouble protéique. Les auteurs comparent ces différents tests en utilisant les méthodes récentes de mesure de la limpidité (néphelométrie) et de dosage des protéines (CLHP).
Les résultats obtenus montrent que le test à la chaleur (80° C-30 mn) reste l'essai de laboratoire le plus fiable, car il est simple à mettre en oeuvre et il se rapproche le plus des conditions d'apparition des troubles protéiques dans la pratique.
Various laboratory stability tests have been used for a long time to check the risks of protein turbidity. The authors have been comparing those different tests with the help of more modern methods of measuring out cloudiness (nephelometry) and protein (HPLC).
Six tests were examined :
- The test consisting in heating for 5 minutes at 80° C in a double-boiler.
- The test consisting in heating for 30 minutes at 80° C in a double-boiler.
- The test consisting in heating for 10 days at 35° C in an oven.
- The adding of 0.5 9 of tannin per litre.
- The adding of a reagent to phosphomolybdic acid (bentotest).
- The adding of trichloracetic acid.
The results are as follows :
- For the tests involving heat, the longer the heating at 80° C, the higher the measures of the turbidity are; the cloudiness observed for the test consisting in heating at 35° C for 10 days is quite important. If the results obtained with these heating tests are to be compared to the real protein values, the most efficient test consists in heating 30 minutes at 80° C.
- For the tests consisting in adding tannins, a high variation of turbidity values must be related to the results obtained through high performance liquid chromatography. Moreover, the important cloudiness observed when the tannins were added does not correspond to the small difference observed between the chromatograms of the wine streated with the tanins and those of the original samples.
- The reagent to phosphomolybdic acid (bentotest) and the trichloracetice acid test create an important turbidity. After chromatographic examination, the use of these reagents proved to be acting more thoroughly on every sort of protein than the use of heat in the heating tests. For two out of the four wine-samples examined, the bentotest was more drastic than the addition of trichloracetic acid.
As a conclusion the heating test (80° C for 30 minutes) remains the most reliable laboratory test, because it is sample and easy to make; it is also very close to the conditions in which protein turbidity may appear in reality.
AttachmentsNo supporting information for this article