Freeze-dry technology can slow ice cream melting rate, research finds

03 Apr 2020 --- Researchers have found freeze-drying technology could result in tastier ice cream that melts at a slower rate – offering food processors new opportunities, according to European Freeze Dry, a freeze-dried ingredients manufacturer. The research, published in the Journal of Food Processing and Preservation, was carried out by the Agricultural Research Service (ASR) in the US, found freeze-dried fruit powders including strawberries, blackberries and raspberries improved the taste and structure of ice cream and other frozen desserts.

Freeze-dried strawberry powder is such an effective stabilizer that including frozen dairy desserts with it will maintain their shape even after reaching room temperature. That is according to ASR research food technologist Cristina Bilbao-Sainz with the Healthy Processed Foods Research Unit in Albany, California, US.

Standard stabilizers, such as sodium alginate, guar gum, iota carrageenan, xanthan gum and carboxymethyl cellulose, are commonplace. However, people tend to react negatively to these unfamiliar, chemical sounding names when they appear on an ice cream label. With a rise in consumer demand for natural ingredients driving new food markets, food processors can benefit from using raw ingredients in sweet products, according to Diana Morris, Country Manager (UK) at European Freeze Dry.

“The addition of strawberry or raspberry powder completely prevented the melt‐down of the frozen desserts. These samples retained their original shapes once the ice crystals melted. Blackberry powder prevented the melting of the frozen desserts, but the foam structure collapsed and lost its original shape. The incorporation of blueberry powder did not prevent the melting of the frozen desserts,” Morris tells FoodIngredientsFirst. 

The research added 3.5 percent of freeze-dried strawberry, raspberry, blackberry and blueberry powder to ice cream. This equated to roughly 20 grams of powder per liter of ice cream. Strawberry powder was found to act as the most effective stabilizer, completely preventing melt-down, followed by raspberry and blackberry. Blueberry powder was found to have a minimal effect. 

“This research allows ice-cream producers and makers to revisit the stabilizers that they use in their products and move to a raw fruit alternative that is more attractive to consumers,” she continues. “While different varieties of fruit powders were tested as part of the research, strawberry powder was found to be the most effective as a stabilizer, with raspberry powder also having a positive effect.”

The powders, which are created by a gentle freeze-drying process which removes all water content, absorb the liquid from the ice cream as it rises in temperature, which rehydrates the powder rather than causing the product to melt. The powders also reduce the formation of ice-crystals during the ice-cream making process, while giving the product a creamier taste.

Without a stabilizer, ice cream – home-made or commercial – can become unpleasantly crunchy with the growth of large ice crystals. When temperatures change, iIt can happen in either or both the ice cream maker or the freezer, when temperatures change. Stabilizers also slow down melting, prevent wheying off (the leaking of a clear, watery serum), which helps avoid shrinking during storage and increases the mouth’s perception of creaminess.

Freeze-dried technology 
During the freeze drying process, a deep vacuum is applied and under these conditions neither ice or water can exist. The pressure from the vacuum, with a controlled amount of heat applied, causes the ice to leave the product as a vapor trail which is then captured on an ice condenser within the freeze drier, upon which the vapor forms again as ice. 

The process takes on average a day to complete, carried out in a set of ‘chambers’ which can be controlled at various temperatures and time schedules depending on specific product requirements.

The reduction in water in the final freeze dried product means there is a much reduced potential for microorganisms existing in such low amounts of water, leading to a shelf life of up to two years at room temperature. 

Morris further highlights the potential of this same technology working in plant-based ice cream. “The science of freeze dried powder absorbing the water could be similar whether in dairy or dairy-free ice-cream. This particular research only looked at dairy ice cream, however,’ she notes. 

As the world’s global supply chains and business are affected by the COVID-19 pandemic, Morris says. European Freeze Dry is continuing business as usual to meet the demand for food production across the world. “Freeze dried food lends itself to extreme situations in all kinds of circumstances, from sustaining nutrition in remote locations to preparing for an extended period indoors,” she comments. 

“We are responding to different demands and we are resourcing our operations ready for our existing and new customers in the public and private sectors. Individual consumers are also asking about which supplies we can provide. Freeze dried food is an alternative in different forms including ready-made meals and ingredients such as fruit, meat and vegetables,” Morris concludes. 

By Elizabeth Green