A good cook knows well how to thicken a sauce and make fluffy mashed potatoes – food that’s delicious to consume. The cook is using rheology to create food that looks good to our eyes and feels good in our mouths. Food scientists and manufacturers need to take that cook’s expertise and reproduce it on a larger scale – that’s what fills grocery store shelves.
An individual cook may come up with a new dish using instinct, trial and error, and good friends to sample and give feedback. The end goal is a food that people perceive to be delicious and really want to eat. It may take quite a few steps and a lot of time to create just the right new food combination. This may work in an individual restaurant setting, but it needs to be faster and easier when developing processed foods. That’s where rheology plays a role.
Most people know that foods and drinks must be prepared at certain temperature for health safety reasons. However, temperature also affects the food’s proper composition. For instance, one flour company noted that “butter’s melting point is lower than that of vegetable shortening, so a 100% butter crust will neither hold a crimp as well nor stand as tall in the pan as an all-shortening (or partial shortening) crust.” In addition, chilling the crust before baking will help solidify the fat, which helps prevent shrinkage. One pie company can produce tens of millions of pies per year; if the normal pie product doesn’t meet brand and quality standards, a significant amount of revenue can be lost.
Another example of how fat content can affect the physical properties of a food can be found in chocolate. Chocolate is supposed to be smooth and creamy to the palate, not rough or grainy. (Read How Does that Chocolate Feel?) The chocolate can contain all the right, fresh, ingredients, but if the properties aren’t quite right, it will be perceived as having gone bad or is of poor quality. If it doesn’t feel right to the customer when they take that first bite, or if they don’t hear that snap when they break off a piece of the chocolate bar, your brand and your bottom line suffer.
Rheology involves the study of the mechanical properties of foods and how they flow and deform under different conditions – pouring, cold storage, over time, etc. Rheometers measure those properties so food scientists can more quickly develop new foods that fall into the desirable range for various properties. Of course, there’s still likely to be a panel of people who taste test a new food before it goes into full production, but rheometers expedite a manufacturer’s ability to get food to that point in the first place. They also help the manufacturer design a food processing plant and workflow that will pump, stir, coat, fill, spray and handle food mixes effectively until the final food product is ready for sale.
How do they work? Rheometers measure viscosity, elasticity, yield stress, extensional flow, tack and other structural and mechanical properties of food that can be numerically associated with consumers’ sensory perception, ie how is that ‘mouthfeel’ when one is tasting and chewing? It’s not an easy task as foods are often structurally complex, incorporating emulsions and mixing solids, liquids and gels into a single food product. Food scientists and manufacturers need to know what to measure in their food development and processing workflows, and which tools are best to measure it. They evaluate and formulate products based on the rheological data so the results really matter.
There are also different types of rheometers depending on the application. We’ll discuss those in future articles.
If you’re in Europe, take advantage of our complimentary seminars to help figure out the right instrument for your applications.
Thermo Fisher Scientific will host application-oriented seminars on food rheology with a practical demonstration of rotational, oscillatory and extensional rheological tests at the locations below. There is no charge for the seminar. For more information, visit www.thermofisher.com/mc-seminars.
- May 4, 2017 in Germany (language: German)
- May 17, 2017 in Germany (language: German)
- May 17, 2017 in Denmark (language: English)
- May 18, 2017 in Switzerland (language: English)
If you’re interested, but not able to attend the seminar, visit our web page or contact us to discuss your food rheology applications. Discover how your recipe should not only include precise measurements of your ingredients, but also rheological measurements for quality control.