Stabilising ice cream with freeze-dried strawberries
Researchers from the Agricultural Research Service (ARS) have found that some freeze-dried berry powders — particularly freeze-dried strawberry powder — can act as stabilisers in ice cream and other frozen dairy desserts. Including freeze-dried strawberry powder in frozen dairy desserts allows them to maintain their shape even after reaching room temperature.
Stabilisers prevent homemade and commercial ice cream from developing unpleasantly crunchy ice crystals. Stabilisers also slow down melting, prevent wheying off (the leaking of a clear watery serum), help avoid shrinking during storage and increase perception of creaminess.
Standard stabilisers such as sodium alginate, guar gum, iota carrageenan, xanthan gum and carboxymethyl cellulose can cause consumers to react negatively to the chemical-sounding names when they appear on an ice-cream label, assuming these must be artificial ingredients. However, many stabilisers come from natural sources; for example, sodium alginate is extracted from brown seaweed.
To be technically classified as ice cream, it must contain between 10 and 16% milkfat; everything else is called a frozen dairy dessert.
“We discovered that some of the freeze-dried fruit powders — especially strawberries — completely prevent the meltdown of dairy frozen desserts similar to ice cream made with whole milk, whole whipping cream, sugar and skim milk powder. Freeze-dried berry powder will absorb moisture from the premix base, improving its stability and texture to the point where the frozen dessert will keep its shape even after ‘melting’ to room temperature,” said Christina Bilbao-Sainz, a research food technologist at ARS, and the Healthy Processed Food Research Unit in Albany, California.
This can be attributed to the fibre in the berry powder becoming completely hydrated, which increases viscosity and resistance to meltdown. Researchers found that adding 3.5% of either strawberry, raspberry or blackberry freeze-dried powder reduced the water available for ice crystal formation during stirring and freezing, preventing crystal growth and slowly melting. This equates to adding approximately 19 grams for a 900 mL home ice-cream maker. Strawberry powder was found to be the best stabiliser, as it prevented meltdown, followed by raspberry. While blackberry powder prevented wheying off, the ice-cream’s structure still lost its original shape. Blueberry powder did not prevent meltdown or ice crystal formation during refreezing, and the frozen dessert showed a little wheying off.
It is important to note that using freeze-dried strawberry powder as a stabiliser in frozen dairy desserts also adds strawberry flavouring, which may not be suitable for all ice-cream flavours. The research was published in the Journal of Food Processing and Preservation.
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