The RVA is a rotational rheometer.
RVA stands for Rapid Visco Analyser which is an instrument for measuring viscosity in starch or other water-binding mixtures.
An RVA instrument can measure viscosity under variable cooking, cooling, and shear stress conditions which can mimic the manufacturing process enabling small batch analysis prior to production.
Common tests carried out with the RVA:
- Native starches
- Peas and beans
- Heat-treated flour
- Chemically modified starches
- Other gelling systems
The RVA is also used to measure the synergistic effect of combing two or more of the above gelling systems.
The Importance of Rheometry in Food Production
Measuring the flow properties of thickening agents such as starch and hydrocolloid-based systems allows the manufacturer to determine correct concentrations for use and flow rates for pumps within the plant.
Using an RVA can rapidly reduce product development time by using the equipment as a small batch cooking process. It can also be used to benchmark raw material quality.
Rheometry is the study of the flow of matter, and how it deforms. It is based on the science of rheology, which is the interrelation between force, deformation, and time.
Using rheometry, we can better understand how various products will behave and perform under different conditions of storage and use.
A rotational rheometer operates with continual rotation, exerting shear force on the substance it is testing. This will then measure the viscosity of the substance.
Viscosity is an important property in various foods. It is defined as the internal friction of a fluid or its ability to resist flow.
It is also a characteristic of the texture of food. Therefore, measuring and monitoring viscosity is important in food production to ensure batch consistency and quality control.
Uses of Rapid Visco Analysis (RVA)
In the food industry, RVA can assess:
- Pasting or gelatinisation characteristics of starchy ingredients
- Hydrocolloid thickening properties
- Stability of emulsions and foams
- Enzymic activity
- Stability under freezing and thawing conditions
- Quality of cereals or flours
- Sprout damage of wheat kernels, pre-harvest
As a method, RVA will measure the development of viscosity during heating and cooling of the material in water. It will also help determine the appropriate conditions for getting a desired consistency and thickening effect.
How an RVA Instrument Works
A heating block heats the sample until it reaches the starch gelatinization temperature. The electrical current required by the paddle to stir at a constant speed is converted to the apparent viscosity of the sample.
Apparent viscosity is the shear stress applied to the sample fluid divided by shear rate.
Using an RVA is simple. The instrument’s software will automatically calculate the precise amount of water you need to process a given sample.
The software will record the behavior of the sample and plot a curve as a function of temperature, analysis time, and apparent viscosity.
The Benefits of RVA techniques for Food Production
The RVA is an advanced rheometer used by the food and associated industries for:
- Checking the raw material quality
- process and quality control
- product development
There is a range of RVA models available for various applications, including:
- Milling and baking
- Starch manufacture
- Bakery ingredients
- Malting and brewing
- Extruded snack foods
- Pet foods
- Paper manufacture
You can create test programs from 3 minutes up to 15 hours depending on the application. Typically, a starch pasting profile is carried out in 13 minutes. You can tailor its test routines to emulate processing conditions that meet your specific requirements.
It is easy to use, with an automated function that minimizes the need for specialist training to operate it. This automation also ensures its consistency and reliability.