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Ice cream generally contains seven categories of ingredients: milk fat, milk solids-not-fat (the lactose, proteins, minerals, water-soluble vitamins, enzymes, and some minor constituents), sweeteners, stabilizers, emulsifiers, water, and flavours. In this post, we’ll be looking at why stabilizers are used in ice cream production.
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Table of Contents
- 1. Why are stabilizers used in ice cream?
- 1.1 Increase Mix Viscosity
- 1.2 To produce smooth and creamy texture
- 1.3 To provide resistance to melting
- 1.4 Retard or reduce ice and lactose crystal growth during storage
- 1.5 To prevent wheying off
- 1.6 To help prevent Shrinkage
- 2. How much stabilizer is used in ice cream?
- 3. Ice Cream Defects Caused by Stabilizers
- 4. Summary
- 5. References
1. Why are stabilizers used in ice cream?
The primary purposes for using stabilizers in ice cream are: to increase mix viscosity; to produce smooth and creamy texture; to provide resistance to melting; to retard or reduce ice and lactose crystal growth during storage; to prevent wheying off; and to help prevent shrinkage during storage (1 2). Many of these functions are attributed to enhanced viscosity of the ice cream mix.
1.1 Increase Mix Viscosity
The best ice creams in the world have a smooth and creamy texture. This texture, primarily associated with a high milk fat content and small ice crystal size, is also strongly influenced by the viscosity of the ice cream mix (3 4). Viscosity can be loosely defined as the thickness of a liquid, with thicker liquids having higher viscosities (honey has a higher viscosity than water for example). In general, as the viscosity of an ice cream mix increases, the smoothness of texture and resistance to melting increases, but the amount of air, or overrun, decreases (5).
1.2 To produce smooth and creamy texture
Creaminess perception is strongly influenced by mix viscosity, with higher ratings of creaminess attributed to samples of higher viscosity (4). Soukoulis et al.10 found that the use of stabilizers improved creaminess and reduced wateriness in ice cream, a sensory property that occurs when the sample melts unusually quickly into an uncharacteristically thin, water-like fluid. Carboxylmethylcellulose, guar gum, sodium alginate, and xanthan gum were used as the stabilising agents. The researchers found that samples containing 0.2% sodium alginate or xanthan gum, which had the highest viscosity, provided the best texture.
1.3 To provide resistance to melting
The slow meltdown, good shape retention, and slower foam collapse are some of the important quality parameters of ice cream (11). Stabilizers significantly affect the melting quality of ice cream through their viscosity-enhancing properties. As viscosity increases, the rate at which ice cream melts slows significantly (12 13 14 10).
1.4 Retard or reduce ice and lactose crystal growth during storage
Ice crystal size is a critical factor in the development of smooth and creamy ice cream (15). Smooth and creamy ice cream requires the majority of ice crystals to be small, around 10 to 20 µm in size. If many crystals are larger than this, ice cream will be perceived as being coarse or icy (16 2). During storage, ice and lactose crystals grow and undergo recrystallisation. Recrystallisation is defined as “any change in number, size, shape… of crystals [during storage]” (17) and basically involves small crystals disappearing, large crystals growing, and crystals fusing together. Ice crystal growth and recrystallisation during storage eventually lead to coarse or icey texture.
Stabilizers are added to ice cream mainly to retard or reduce ice and lactose crystal growth and recrystallisation during storage (or mask the effects of crystal growth), especially during periods of temperature fluctuation, known as heat shock (5 18). Heat shock occurs when ice cream is left at room temperature for extended periods of time and then re-frozen.
1.4.1 Which stabilizers are used to reduce ice crystal growth and recrystallisation?
The most widely used stabilizers to inhibit ice crystal growth and recrystallisation are guar and locust bean gum (19). Locust bean gum has been shown to reduce recrystallisation rates better than guar gum (20 21 22). Sutton & Wilcox22 showed that the inhibition of recrystallisation by these two stabilizers was concentration dependent up to a level of about 0.3%, after which further addition did not result in further inhibition. Other stabilizers that are commonly used to retard or reduce ice crystal growth and recrystallisation during storage include sodium carboxymethylcellulose, alginate, k-carrageenan, and xantahm gum (23 24 5 25).
1.5 To prevent wheying off
Most of the stabilizers used in ice cream production (locust bean gum, guar gum, carboxymethyl cellulose, and xanthan) are incompatible with milk proteins and will thus cause a phase separation known as ‘wheying off’. Wheying off refers to the leaking of a clear watery serum layer during the melting of ice cream, which has an undesirable appearance (2). Xanthan gum is the most incompatible with milk proteins, followed by guar gum, and locust bean gum (26).
1.5.1 Why is carrageenan added to ice cream?
Along with its ability to retard or reduce ice and lactose crystal growth and recrystallisation during storage, carrageenan can retard wheying off at very low concentration and is thus used extensively as a secondary stabilizer in most stabilizer blends: it is included in most blended stabilizer formulations at usage rates of 0.01-0.015% (2). At higher concentrations (0.05%), carrageenan begins to gel and fail to function well (26).
1.6 To help prevent Shrinkage
A potential problem that occurs during storage of ice cream is shrinkage. This defect, defined as the loss of volume in ice cream before any part of the product has been removed from the container (27), appears as the ice cream pulling away from the walls of the container, and occurs most often when ice cream is transported between regions of different pressure (as when ice cream is transported over mountains) or via air transport (27 2). The use of emulsifiers such as mono- and diglycerides with polysorbate 80, along with stabilizers such as a combination of locust bean gum, guar gum, and carrageenan, could be one of the solutions to shrinkage (27).
2. How much stabilizer is used in ice cream?
Goff and Hartel(2) note that individual stabilizers seldom perform all of the desired functions. Each has a particular effect on body, texture, meltdown, and stability in storage. Therefore, to gain synergism in function, individual substances are usually combined as mixtures of stabilizers and emulsifiers. Usually 0.2-0.5% of a stabilizer/emulsifier blend is used in the ice cream mix.
Table 2.4. Suggested mixes for hard-frozen ice cream. From Goff & Hartel (2).
3. Ice Cream Defects Caused by Stabilizers
Excessive use of stabilizer leads to an ice cream defect known as gumminess, in which the product does not melt sufficiently quickly in the mouth and retains excessive chewiness. Stabilizer/emulsifier components may also impart off-flavours because they are prone to oxidation if not kept in a dry and cool environment (5).
The primary purposes for using stabilizers in ice cream are to produce smooth and creamy texture; to retard or reduce ice and lactose crystal growth during storage; to slow the melting rate of ice cream; and to help prevent shrinkage during storage. Carrageenan is added as a secondary stabilizer to prevent a defect known as ‘wheying off’. Many of these beneficial functions are attributed to stabilizers’ ability to enhance mix viscosity (produce a thicker mix). Usually 0.2-0.5% of a stabilizer/emulsifier blend is used in an ice cream mix, which includes 0.01-0.015% of carrageenan. Excessive use of stabilizers leads to a defect known as gumminess, in which ice cream does not melt sufficiently quickly in the mouth and retains excessive chewiness.
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