Fibre is found in many fruits and vegetables such as banana, avocado and onion, and the fibre from it helps improve the digestion when the food is processed in our stomach and intestines. In ice cream production, fibre can be applied to improve the texture by its water-binding capacity as well as bringing nutrients for our daily need. In this article, we will discuss about how chicory root fibre, a popular plant-extracted fibre, is applied in reduced-fat and Philadelphia style ice cream and its role in improving the overall quality of the products as well as milk fat substitute.
What is chicory root fibre?
Chicory (Cichorium intybus L.; 菊苣 ) is a major crop in northwestern Europe, and its roots are a rich source of the dietary fiber inulin. Chicory roots are used in the preparation of a bitter drink as a substitute for coffee in France and Japan(1), for example. People of all ages can drink the extract from chicory root, because it has noncaffeine ingredients. Chicory inulin also has the potential to replace dietary fat, resulting in decreased calorie intake. When inulin is mixed with water or any other aqueous liquid, it forms a colloidal suspension providing a white, creamy emulsion(2). Inulin is a type of oligosaccharide called a fructan. Fructans are a chain of fructose (sugar) molecules strung together. Inulin is found naturally in the roots of many foods, such as garlic, onion, asparagus and chicory.
Application in gelato & phyladelphia style ice cream
1. Gelato, Italian language as ice cream, is a variety of ice creams originated from Italy, known as having a reduced-fat but relatively sugary profile. Since total solids in gelato are lower (35-38%) compared to conventional fat-rich ice cream(38-42%), fibre is used to compensate the fat reduction, and chicory root fibre has been popularised in the industry for its versatile profile: odourlessness, strong water-binding capability and viscosity enhancement power. Also, inulin's freezing power is weaker than water at index 0.65, so it is a great solid to compensate the extra application of sweeteners in gelato making that accelerate the freezing point depression.
2. Phyladelphia style is an approach to make ice cream that excludes any egg ingredients. Customers may rule out ice cream with eggs for different reason such as allergens, vegans, religion or even the eggy off-flavour sometimes. Chicory root fibre perfectly compensates the solids loss from egg yolks; the latter of which is originally an natural emulsifier to enhance the homogeneity of serum (the milk fat, protein, melted sugar, sodium, lactose and other milk-solid-non-fat such as enzymes, calcium and vitamins of the pasteurised mix). Advantages of using chicory root fibre will also include convenience of storage and faster formulation of ingredients as the fibre has been extracted from plants into powder form already.
Texture improvement
1. Ice Crystals
Viscosity, also known as thickness, of a pasteurised ice cream mix may be one of many factors that affects the texture of the final products. An high quality ice cream requires balance between flavour, sweetness and texture; the second latter of which requires an average ice crystal size under within 40-50 μm, any more than that will be seen as coarse and be perceived by our tongue. As a pasteurised mix is divided by 2 parts: total solids and water (water = 100-total solid%), a certain viscosity has to be obtained by formulation in order to produce smooth texture - there should not be too much free water in the composition. The mechanism behind obtaining the smoothness is through friction and limitation of water diffusion. When fibre is evenly distributed in the composition, the enhanced viscosity promotes a frictional surface and thereby melts the ice crystals by heat. Besides, free water in serum is harder to diffuse to some of the small ice crystals during churning process in the ice cream maker that have been formed in earlier stage, which also restricts the growth of size.
2. Melting Rate
During consumption, a decent melting rate is required or it would be as if eating the serum itself without the airy chewiness. When the serum phase (fat globules, ice crystals, proteins, air cells, sugar and the concentrated unfrozen water), also known as the pasteurised ice cream mix, is viscous enough but not overly viscous, this viscosity helps slow down the melting rate during consumption. Nevertheless, Chircory root fibre does increase the viscosity in serum phase, final melting rate of the product is not exclusively dependent on viscosity itself, nor only on the portion of planted fibre being used.
3. Changing freezing point depression
Water is the neutral liquid that freezes at 0°C but it changes with substance dissolved in - either go up or down, for example dextrose sugar has 1.9 times of sucrose in terms of freezing point depressing power. The measurement is then defined as the difference between the temperatures from 0°C and the temperature at which the water starts to freeze. Chicory root fibre, surprisingly, increases the freezing point, which means more frozen water is formed in the ice phase at a higher termperature, and since more frozen water (nucleation) is formed, less re-crystalisation is likely to happen during static storage in freezer. However, as ice cream is a complicated structure, overall texture is not exclusively decided by freezing point depression itself, but rather other components that contributes every little function do.
The figure (3) shows that fructose and sucrose in serum phase reach 40% sugar concentration in frozen state at different temperature i.e the freezing point depression power of fructose is strongly greater than that of sucrose and it's likely that re-cystalisation will demonstrate much more than that of sucrose; and the texture will then become coarser. Apply the same concept, since chicory root fibre increases the freezing point, given that an identical composition where all other ingredients remain equal, the texture using chicory root fibre will be smoother because more frozen water was formed in ice phase and less likely to develop re-cystalisation.
Milk Fat Reduction
Chicory root fibre is odourless, sufficient in terms of solid counts, an almost favourless and contains very little natural sweetness and few calories. As its main function water-binding capability is assured, it has become one of the ideal options to replace milk fat in ice cream products. A moderate amount, depending on the flavour, applying in composition may cut down 25% milk fat so that the calories intake from ice cream will be lowered as well. In my experiences, some of the flavours do benefit from using chicory root fibre because a high fat profile ice cream tends to coat and delays the delivery of perception of the flavour, especially fruity flavour that is supposed to be the fresher and more straight-forward.
Summary
Fibre is commonly found in many plants and vegetables; it is a nutrient that we need on daily basis. Fibre can also be applied on ice cream manufacture to cut down calories from milk fat as a fat replacer due to its effective water-binding capability to enhance viscosity of the mix, which is one of the independent factors to produce ice cream with smooth texture. Chicory root fibre is a fibre extracted from our daily common plants like onion, garlic, asparagus and chicory, from which inulin, a chain of fructose is found naturally in the root.
Reference
1. Roberfroid M.B. Inulin-type fructans: functional food ingredients. J Nutr. 2007;137:2493S–2502S. 2. Franck A. Technological functionality of inulin and oligofructose. Br J Nutr. 2002;87:S287–S291.
3. https://www.dairyscience.info/index.php/ice-cream/228-ice-cream-hardness.html?jjj=1666811075973
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