Viscosity of chocolate

Use

Chocolate is a tasty treat, frequently used in candies, icings, pastry fillings, and many other desserts.

Test equipment

Instrument: Viscometer or rheometer

Torque range: HA

Spindle: SC4-27 Spindle with SC4-13RPY

Sample chamber accessories: Small sample adapter,

TC-550SD Programmable temperature

Speed dubain: 5, 10, 20, 50 and 100 RPM

Temperature: 40 ° C Test Method

The Small Sample Adapter ™ can be used with various Brookfield viscometers or rheometers. In our example, we used a Brookfield HADV3T, with RheocalcT ™ software for automated instrument control and data acquisition. Our test temperature of 40 ° C was maintained by connecting the Small Sample Adapter ™ water jacket to a Brookfield TC-550SD programmable refrigerated bath. Representative data from the analyzes are shown in Figures 1 and 2. The

Figure 1 demonstrates that the viscosity of dark chocolate decreases as the shear rate increases. This behavior is known as "shearing".

Figure 1: Viscosity of dark chocolate at 40 ° C

Figure 2 illustrates a good fit of the Casson NCA / CMA model to the raw data. The “CoF”, the confidence of adjustment (%), from raw data to fitted curve, is close to 100 %, which means a great fit. As shown in Figure 2, generated in RheocalcT ™, the plastic viscosity is 1241 cP and the yield strength is 129 dyn / cm2. The chocolate has been tested to specifications provided by the National Confectioners Association and the Chocolate Manufacturers Association.

Figure 2: NCA / CMA Casson graph of chocolate rheology at 40 ° C

Some chocolates are tested at different shear rates, to ensure data to scale. 1, 2.5, 5, 10, 20 and 50 rpm are suitable in some cases, for example.

MacMichael Degrees values can be calculated from Brookfield data at 20 rpm. This is discussed in our AR-79 reprint article. The couple, %, read at 20 rpm, obtained by measuring chocolate with the HA spring torque range instrument using pin SC4-27 in chamber SC4-13R or SC4-13RP, is multiplied by 3.40. The above example has a torque of 31.4 % at 20 rpm - corresponding to a viscosity of 7850 cP at a shear rate of 6.8 s-1 or 6.8 1 / s. Therefore, (31.4 %) x (3.40) = 106.8 MacMichael degrees.