For most people, ice cream is a staple requirement of the summer days now upon us, even better when served in a cone on a sunny beach. Europeans have eaten ice cream out of paper cases, seashells, and the edible cones we are now so familiar with, for at least 150 years. However, in the US, the ice cream cone’s inception can probably be traced back to the 1904 World’s Fair in St Louis, Missouri. Popular belief has it that a stallholder selling waffles stepped in to help an ice cream vendor, who had run out of cardboard dishes, by folding waffles to produce cone shapes.
The rheological analysis of ice cream
In terms of rheology it’s not so much the cone but the ice cream placed in it that is of interest – specifically, how to get the perfect scoop without sacrificing taste. It may surprise you, but the rheology of ice cream is an established and well-investigated field, with research first appearing as far back as the 1930s.
By using a rotational rheometer, such as our Kinexus system, it is possible to analyze the ease with which ice cream scoops, the way it feels in the mouth and its creaminess. Ice cream product quality relies on the interplay between ice crystals, air bubbles, fat globules, and the viscous liquid matrix that makes up the final product.
Getting the best scoop, mouthfeel and creaminess
Good ‘scoopability’ ensures the person serving the ice cream can easily get that perfectly rounded dome to top the cone. Serving temperature is, of course, a crucial factor, consumers preferring a product that can be easily served direct from the freezer. The yield stress of the ice cream is a critical parameter here – this is the point at which the ice cream begins to flow. Rheometers can measure the yield stress of materials, by performing a shear stress ramp at a relevant temperature for example. Products with a lower yield stress will have better ‘scoopability’ so this test directly assists with the development of an ‘easy to serve’ product.
The creaminess and mouthfeel of ice cream is related to the speed with which it melts in the mouth; an ice cream that is slow to melt will take longer to taste, and won’t feel particularly soft on the tongue. Again, it is possible to use a test on a rheometer to analyze both factors – using a small strain oscillation test to monitor the ‘structure’ of the ice cream as temperature is steadily increased. Resolving the resultant oscillation stress and strain signals from the rheometer allows viscoelastic material parameters to be calculated – the complex modulus (which demonstrates hardness) and the phase angle (the tangent of which shows a peak as the components in the ice cream melt). Comparing the rheometer data with consumer assessments of mouthfeel and creaminess, reveals the formulation characteristics of an ice cream that provide the best taste experience when we finally get the product inside our mouths!
As can be seen for ice cream, the rheometer is a valuable tool in providing data that can be correlated to sensory characteristics – and it is this latter aspect that many food companies spend a great deal of time and effort in working with taste panels to gain proprietary knowledge. So, something to ponder as the ice-cream van beckons during the hot months – how do you get a job as an ice-cream tester……??