Viscosity characterization of melted chocolate

Chocolate is a food
with a comprehensive nutritional content and a relatively high calorific value.

Chocolate contains a variety of vitamins and minerals, especially more abundant flavonoids and a certain amount of alkaloids, theobromine and caffeine, etc.
, which have the functions of dilating blood vessels, promoting blood circulation, relieving depression, and enhancing the
spirit.

On Romantic Valentine's Day, sticky and silky chocolate is the choice to
express love.

Processed chocolate From the perspective of production and processing, chocolate refers to a cocoa product (cocoa butter, cocoa or cocoa mass, cocoa cake, cocoa powder) as the main raw material, with or without the addition of non-cocoa plant fat, sugar, dairy products, food additives and food nutrition enhancers, made by a specific process to maintain a solid or semi-solid state at room temperature
.

Chocolate products are made by chocolate and other foods in a certain proportion, through a specific process to maintain a solid or semi-solid state at room temperature
.

In terms of dispersion system, chocolate is a complex multiphase dispersion system with fat as the dispersion medium and sugar, cocoa, solid and a small amount of water and air as the dispersion phase
.

The rheological properties of melted chocolate and its measurement have important significance and role
in the production and processing of chocolate, especially in the process of refining, pouring, coating, and conveying chocolate.

In the production and processing process, if the viscosity of raw materials is too large, it will lead to mixing difficulties, increased resistance of the conveying pipeline, increased load of the pump, poor material filling and molding performance, thick coating or coating amount in the coating molding process, and plugging of the nozzle supplying raw materials; Too low viscosity will lead to insufficient coating amount during the coating molding process, and the core body will be partially exposed, increasing the proportion of cocoa butter consumption, and it is also not conducive to the storage and transportation
of materials.

The apparent viscosity of chocolate The apparent viscosity of chocolate is related to the type and ratio of raw materials, and the factors that cause the apparent viscosity change of liquid chocolate include: grease content, particle size of solid particles, moisture content of raw materials, amount and type of emulsifier, crystallization of oil, etc
.

Therefore, in the processing process of chocolate, the apparent viscosity and rheological characteristics of chocolate slurry must be characterized and determined, so as to control product quality, identify product advantages and disadvantages, and provide a basis
for process and formula improvement.

The general configuration is recommended as follows: DVNext rheometer / DV2T viscometer + SSA small sample adapter
.

In this paper, the apparent viscosity of the two chocolates was measured using the HADV2T viscometer with the SSA Small Sample Adapter (shown in Figure 1) and the rheological properties of the two chocolates
were analyzed.

Figure 1 SSA+TC Series Water Bath Circulation System TC Series Water Bath Circulation System is used to control the sample temperature (test temperature is 40°C), Rheocalc T software connects to the host computer, program editing and data acquisition, draws rheological curves, and fits
the mathematical model according to its viscosity change characteristics.

Melt the sample at 50 °C before transferring a certain amount of sample to the sample cup of the small sample adapter, wait for the sample temperature to drop to 40 °C and stabilize after starting the viscosity measurement
by shear rate scanning.

The test data is shown in Figure 2
.

According to the test results of Figure 2, the viscosity of Sample 1 decreases from 15400 cP to 6500 cP and the viscosity of Sample 2 decreases from 11000 cP to 4310 cP when the rotor speed is increased from 5 rpm (shear rate of 1.
7 1/S) to 100 rpm
(shear rate of 34 1/S).

Both samples have the characteristics of shear thinning and belong to typical non-Newtonian fluids
.

A large number of studies and practices of the Casson equation have shown that the flow law of the melted chocolate slurry is in line with the Casson equation
.

In the viscosity measurement of chocolate, Casson models are often used to describe its flow behavior, determining plastic viscosity and yield stress
.

Through the viscosity measurement data, the flow curve of the two chocolates is plotted, and the plastic viscosity, yield stress and linear fitting correlation coefficient are calculated, and the analysis results are as follows: The flow law of the two chocolate samples conforms to the Casson equation, and the linear fitting correlation coefficient is greater than 95%.


The yield stress was 4.
37 Pa and 3.
73 Pa, respectively; The plastic viscosity was 4679 cP and 2966 cP
, respectively.

Yield stress is an important rheological parameter that determines the storage and application performance of chocolate products, and plastic viscosity reflects the flow properties
of chocolate slurries.

And this is precisely the meaning of chocolate viscosity characterization
.