The effect of stabilisers in an ice cream with high overrun
Emulsifiers in ice cream are always used in combination with stabilisers, which are hydrated and dispersed in water, reducing the amount of free water in the ice cream mix. They bind the water by means of hydrogen bonds or trap it in a three-dimensional network, resulting in increased viscosity.
The main functions of stabilisers in high overrun ice cream are to:
- Increase mix viscosity
- Prevent whey separation (syneresis)
- Improve whipping properties
- Improve texture
- Prevent ice crystal growth during storage
- Improve melting resistance
- Regulate sensory properties
When it comes to choosing stabilisers, there’s far more choice than there is with emulsifiers, with most regions allowing a wide range of options. The most commonly used stabilizers in ice cream are:
- Guar gum (E412)
- Locust bean gum (E410)
- Cellulose gum (E466)
- Sodium alginate (E401)
- Carrageenan (E407)
Manufacturing ice cream with 150 - 180% overrun
Palsgaard recently set out to create a solution for the production of ice cream with overrun as high as 150 – 180%. Our key goal was to achieve a level of quality (in terms of sensory attributes, melting resistance and storage stability) that was comparable to standard ice cream.
Our trials included ice creams with fat levels from six to ten per cent. We used vegetable fat, and whey powder and/or skim milk powder as milk-solid non-fat. The use of whey powder also meant that the protein level was low in some of the trials.
The ice cream was produced in our pilot plant using an HTST unit and a continuous freezer. After hardening, the samples were transferred to a storage freezer at -18°C. To evaluate storage stability, heat-shock tests were carried out by increasing the temperature to -10°C for four days, after which the samples were returned to the storage freezer.
Sensory properties, as well as melt-down properties, were evaluated in both the samples that had been exposed to heat-shock and those that had not. Melt-down properties were analysed at a controlled temperature of 25°C over 90 minutes.
High shear benefits
In order to obtain an ice cream with high overrun and homogeneous air cell distribution, it was necessary to apply higher shear, so the dasher speed in the continuous freezer was increased. Additionally, the cylinder pressure was increased to facilitate finer air cell distribution. Higher shear meant a higher degree of churning out in the freezer, and therefore stronger air cell walls and higher stability, which was confirmed in the melt-down and heat-shock tests. Figure 3 shows the melting curves of 10% fat ice creams with 180% overrun. Results for ice cream stored at constant temperatures as well as heat-shocked ice cream are shown. For comparison, the melting properties of a 10% fat ice cream with 100% overrun are also shown. Both ice creams were stabilised with Palsgaard® ExtruIce 285.
