Ice cream is a food appreciated all over the world for its sweet and creamy structure which amplifies the taste of the ingredients of which it is composed, but one of the main problems to be addressed in its formulation is the phenomenon of “melting”, i.e. the dissolution which can severely limit its usability, especially in the “artisanal” version.
This phenomenon can also compromise the quality of the product (for example the formation of large crystals during storage), reducing its palatability and shelf life in optimal conditions.
In recent years, research has focused on the use of natural ingredients to improve the stability of ice cream alongside or replacing the now well-known and studied hydrocolloids (natural or not); quite well-known are also some ingredients derived from milk such as binding whey proteins and phospholipids, but also products of plant origin such as soluble citric fibres. In all these cases the operating principle is quite similar to that of hydrocolloids, i.e. the binding of more or less large quantities of free water transformed into the so-called bound or non-available water.
Strawberry polyphenols have emerged in the last decade as potential anti-melting agents and periodically return to the spotlight in the summer press when used by some industrial producers. The news of the production of slow-melting ice creams by the Japanese Kanazawa Ice dates back to this period and therefore in this article, we will explore the role of strawberry polyphenols as natural stabilizers in ice cream, analyzing their chemical properties and the mechanisms through which they can influence the structure and melting resistance of ice cream.
Strawberry Polyphenols: Chemical Properties
Polyphenols are a class of natural chemical compounds widely found in the plant kingdom, known for their antioxidant properties. In strawberries, the most abundant polyphenols include anthocyanins, flavonols, phenolic acids and tannins. These compounds are responsible not only for the bright red color of strawberries, but also for numerous benefits recognized by medicine thanks to the presence of multiple phenolic groups known for their powerful antioxidant properties, which derive from the ability to donate electrons and neutralize free radicals leading, for example, the reduction of inflammation and protection against cardiovascular diseases. However, polyphenols also have properties that make them interesting for the food industry, in particular for their ability to interact with proteins and sugars, ingredients of great importance in ice cream.
Mechanism of action in the ice cream matrix
Strawberry polyphenols can influence the structure of ice cream through various mechanisms. Their ability to bind to milk proteins is fundamental, forming stable complexes that can help maintain the integrity of the ice cream matrix even at high temperatures. This protein-polyphenol bond reduces the melting speed at positive temperatures without affecting the mouthfeel of the finished product as often happens in the case of hydrocolloids and fibers, improving the stability of the product during consumption.
Data in the literature also demonstrate how polyphenols interact with the sugars and fats present in ice cream, helping to stabilize the emulsions. This stabilization is essential to maintain a homogeneous structure, reducing the formation of ice crystals during the freezing process. Polyphenols, therefore, not only improve the consistency of the ice cream, allowing the production of a more appreciable finished product due to the reduction in the size of the ice crystals normally obtainable with the same process, but they also increase its resistance to melting, making it more stable during storage, transportation and distribution.
The main processes taken into consideration are therefore:
- Interaction with Milk Proteins: Strawberry polyphenols can form stable complexes with milk proteins, such as casein. This bond between polyphenols and casein increases the cohesion of the protein matrix in the ice cream, which becomes more resistant to breaking when subjected to high temperatures. This effect helps keep the structure of the ice cream intact even when exposed to conditions that would normally cause melting.
- Stabilization of Emulsions: The presence of polyphenols helps prevent the separation of the lipid and aqueous phases in ice cream, reducing the size of the fat globules and improving their distribution. This leads to a more uniform microstructure, which contributes to greater melting resistance.
- Reduction of Ice Crystal Formation: Another important characteristic of polyphenols is their ability to interfere with the nucleation and growth of ice crystals. During freezing, the presence of polyphenols reduces the size of ice crystals, which is directly related to the melting speed of ice cream. Smaller crystals tend to melt more slowly, contributing to greater thermal stability of the product.
There are therefore various studies that have explored the use of strawberry polyphenols in ice cream, as reported below in the bibliography and a Japanese study published in 2017, and recently examined in depth, studied the effect of adding strawberry extract rich in polyphenols in formulation of some types of ice cream. The results showed a significant reduction in melting rate compared to control samples, without compromising the flavor or texture of the final product.
Other studies have investigated the effect of different concentrations of strawberry polyphenols on the microstructure of milk ice creams. The results indicated that higher concentrations of polyphenols lead to a denser protein network and reduced ice crystal size. This results in a lower tendency to melt and a better sensory experience for the consumer.
Industrial applications
The use of strawberry polyphenols as natural stabilizers therefore offers several advantages for both the ice cream industry and artisanal ice cream and several applications have been made or are underway in both segments.
Firstly, being natural and safe ingredients, it responds to the growing consumer demand for “clean label” products, i.e. without artificial additives. A good formulation can in fact lead to ice creams completely free of additives with improved performance of products stabilized and emulsified with additives.
Secondly, the addition of polyphenols does not significantly alter the flavor of the ice cream and the structure, allowing the desired aromatic profile to be maintained without the need to work on the formulation, for example with masking agents.
From a production point of view, the use of strawberry polyphenols can not only reduce or eliminate the need to add stabilizers normally disliked by consumers, but also allow the formulation of products with a reduced percentage of total solids compared to the standards commonly accepted today while still obtaining finished products of comparable quality. This could translate not only into a more natural product but also into a reduction of formula cost, elements that are usually in strong conflict with each other.
However, the introduction of polyphenols in the production of ice cream on an industrial scale and, secondly, in the artisanal one, is not a particularly simple path to follow and presents some challenges, including the variability of the polyphenol content in strawberries depending on the variety and cultivation conditions. It is therefore essential to develop standardized protocols for extraction, normalization and standardization processes that only a few industries are able to do today with the necessary quality.
The Kanazawa Ice case
“Kanazawa Ice”, a particular type of ice cream developed in Kanazawa, Japan, has earned some articles in international magazines for its resistance to melting even at high temperatures. At the moment no comparison data have been provided with samples without the addition of polyphenols but it has come to the attention of the news that the addition of strawberry polyphenols, almost by mistake, in the standard recipes, has resulted in an innovative product which does not undergo the rapid melting which characterizes traditional ice creams even when faced with significant temperatures for several minutes.
The technology behind Kanazawa Ice was developed by the Biotherapy Development Research Center in Kanazawa, with the initial goal of using strawberry polyphenols to preserve fresh foods. During the research, scientists discovered that adding polyphenols to the ice cream mix not only improved its resistance to melting, but also had positive effects on the texture and shelf life of the product.
A specific study reported in the bibliography demonstrated that ice cream with the addition of strawberry polyphenol extract remained solid even at temperatures above 28°C. This effect has been attributed to what has been detailed above, i.e. the formation of a more stable protein network and a finer and more uniform distribution of fats and ice inside the ice cream.
Conclusions
Kanazawa Ice represents one real example of how strawberry polyphenols can be used to improve the stability of ice cream although this innovation was already available in terms of scientific data and is being studied in depth by industrial research centers and, last but not least, being applied in cases of “artisanal” ice cream. The writer believes that already during 2025 their application, in combination with gelling and emulsifying whey proteins, will begin to become more consistent precisely in the artisanal segment, where the operating temperatures are always very close to the melting temperature of the product and consumption is , especially in southern Europe, limited to the warmer seasons. The application in the industrial field could be less “under pressure” by producers, who experience a much more effective cold cycle and therefore a relatively more stable finished product.
Although further studies are needed to optimize industrial application, strawberry polyphenols offer an interesting opportunity for ice cream, responding to the growing demand for natural, high-quality products.
Bibliography
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