FAQ: “I have to measure the gloss of the surface of chocolate bars and have used your color measurement units in the past. Do you have such equipment? Here are my questions:
- Do you have a unit that can measure very small changes in gloss that cannot be differentiated with the naked eye?
- Can you unit measure a product with a curved surface?”
Chocolate is one of the few food products (cheese is another) where gloss and finish characteristics of the surface, usually related to fat content or the molding process, can be an appearance concern.
At one time HunterLab manufactured gloss and appearance instruments but no longer does so. There are several companies worldwide who manufacture and sell gloss meters.
- If properly applied, an ASTM D523 60-degree gloss meter will differentiate surface micro-roughness directly related to gloss better than the human eye, and with higher precision. In measuring the gloss of chocolate, a flat representative surface should be read, averaging several readings (suggest 4) with a 90 degree rotation between each reading. Avoid all embossed areas. Averaging multiple readings will help ensure a repeatable measurement. The user is left to define the relationship between the gloss measurement and the quality of the product.
- There are gloss meters specifically designed to measure curved surfaces but the applications are typically high gloss mirror or coating surfaces.
If the product is something like a chocolate ball with an approximate diameter of 25 mm, you should be able measure this with a standard 60 degree gloss meter. Typically an ASTM D523 gloss meter has a port opening of approximately 15 mm with a viewed sample area of 10 mm (verify this with manufacturer’s spec sheet). The viewed area of the gloss meter is sufficiently small as to effectively flatten the curvature of the chocolate ball when it is brought in solid contact at the port. Again, averaging 4 - 6 readings (one or multiple chocolate balls) is recommended to yield a repeatable measurement.
In your communications with the gloss meter supplier, send pictures of your products (good and bad quality is helpful) for their opinion on the application.