Sweeteners is one of the 7 categories in ice cream production. The role of it is to provide sweetness, enhance flavour; to provide scoopability because of the mechanism behind which it softens the texture by changing the freezing temperature; and to provide the most economical total solids. The word ART on this theme is to deliver an idea that playing sugar right is one of the crucial elements in deciding whether the end product is qualified.
1. Which sweeteners are mostly used in ice cream production?
Sweeteners used in the production include sucrose (table sugar made with beet or cane), dextrose, honey, agave syrup, lactose, brown sugar, with some synthetic ones such as maltodextrin and fructose corn syrup. There are many sweeteners that are technically available to manufacture ice cream, the key is the consideration of which one to use as well as its portion becomes very vital.
2. Why do we need sweeteners in ice cream production?
The fundamental purpose of adding sweeteners is, of course, to make the ice cream sweeter and thus become more pleasing to consume. However, the role of sweetners is not just about providing sweetness, but also improving the texture, scoopability when served, and being the total solid enhancer.
2A Flavour improvement
It's so wonderful to eat a sweet ice cream rather than a plain, pure milky-like ice cream with no obvious flavour. An appropriate amount of sweetners can improve and strengthen the creamy flavour from dairy ingredients; but too much of it will also mask the flavour and become very heavy in taste. This applies on the seasoning of food in our daily diets: putting salt or peppers to fry a steak strengthens the meaty flavour.
2B Relative sweetness of different sweeteners
Relative sweetness is about a classification of relative sweetness of each sweeteners and sucrose is classified as the standard one with a given index 100 or 1.0 as being the neutral one. Any sweetener's relative sweetness higher or lower than this index is classified as ''relatively sweeter'' or ''relatively plainer'', respectively. Dextrose, for example, has a relative sweetness index 74, which means it is relatively plainer than sucrose; lactose (natural sugar from milk) is another example like dextrose with relative plainer sweetness but is even more extreme, with only the index 16, which means it's only 16% of sweetness of the neutral sweetener sucrose. One more example as fructose (natural sugar from fruit), whose relative sweetness is 173, which means its relative sweetness is much greater than sucrose.
2B.1 The perception of sweetness in our tongue
Different types of sweeteners also have different ways of perception delivery in our tongue - from speed - sharpness to fading. Since sucrose has a relative sweetness of index 100, which is neutral, it delivers intermediate sweetness in a slow way and also fade slowly in our tongue. Fructose has a sweeter profile compared to sucrose, so the way it delivers sweetness is rapid but also fades very rapidly. Dextrose has a plainer profile compared to sucrose and fructose, it delivers sweetness slower than fructose but faster than sucrose; it fades faster than sucrose but slower than fructose.
The picture shows how different sweeteners deliver sweetness in terms of intensity and time.
2B.2 Ice crytalisation
Ice crystal size is one of the very important standards to judge whether the ice cream is of high quality, with around 20µm is within the acceptable range. Any ice cream with ice crystal enlarged after recrystalisation to 50µm is considered too large and that is the margin that our tongue will start perceiving its existence that the shelf life is then ended. At this point, let's talk about how sweeteners will directly influence the ice crystal of the product.
-Freezing point depression & Ice Recystalisation
A pure water solution freezes at 0°C if there's nothing added. Bu when a substance such as salt and sugar is added, this will drop the freezing temperature of the solution. This phenomenon is called ''Freezing point depression'' and is defined as the difference between the temperature at which the solution begins to freeze and 0°C. Hence, The more substance added, the lower the temperature at which it freezes, the more ice cream solution is not frozen and thus the higher possibility of ice fusing together during recrystalisation and affects the quality of the ice cream. Besides, the molecules weight of the sweetener also affects the freezing point. With lighter molecules weight, the mix will start freezing at a lower freezing point whilst the one with heavier molecules weight does the opposite. In my experiments, there was a sample where I added bigger portion of sucrose with smaller portion of dextrose, the ice cream texture ended up being more firm with smaller ice crytal size; whilst another one with more dextrose and less sucrose became way too soft and melted very quickly.
The picture shows that freezing point depression and ice recystalisaion is inversely related.
According to the logic, when freezing point is dropped, the portion of ice recrystalisation is higher, and thus the melting speed is also faster because the "Air-Fat-Ice" structure is collapsed and become fragile.
Picture from above shows how different sweeteners has its own freezing point depression. So it is very important to consider the amount and types of sweeteners added into the ice cream mix, depending on the freezing point depression expectation, scoopability (how soft it is), which types of ice cream is manufactured (conventional, gelato or boozy etc.).
3. Provide total solids
Total solid is a range that ice cream mix has to fall onto, depending on the type of ice cream that you want to specifically make - 40-42% for ice cream with 14% fat rate; 35% for gelato ice cream with 8 % fat rate. In general, higher total solids supplied from protein, fat and carbohydrates from raw materials enable a more viscous mix after pasteurisation and aging, and thus more likely to have a firmer body and creamier mouthfeel in the end product. Sucrose is the most common sweeteners in ice cream production amongst sweeteners and it is economical, natural, easy to get and store.
Relative Sweetness (RS )or Podere Dolcificante (POD)
To make an ice cream that is not too sweet nor plain, calculating RS or POD is a must - it's never ''A cup of this or that'' because that is just not precise and we can't be bothered to taste the ice cream's sweetness every time using our sensual perception. Building up different ice cream compositions, there are always some limitation to get sorted - it may be total solids being in the margin ready to fall out of the upper limit but is still not sweet enough or total solids being in the margin ready to fall out of the lower limit but it is sweet enough reflected in the maths, or the ice cream flavour has a natural high fibre and fat content that some hardness needs to be cut, hence, applying sweeteners needs to be careful.
Besides, not only do sweeteners change the freezing point depression power, but also the sweetness itself. To deliver a stable sweetness on ice cream, calculating RS or POD is a necessity. In ice cream industry, the most common sweeteners are sucrose, dextrose and fructose, of which all have a different sweetness profile in terms of intensity and the delivery approach where sucrose is the neutral one of index 100 with an intermediate delivery nature; dextrose being 74 being faster in delivery than sucrose but slower than fructose; faster than sucrose and slower than fructose when fading; and fructose being 173 being very punchy as the fastest in delivery but also the fastest in fading; Lactose being too weak in sweetness, so some ice cream makers ignore it. Ice cream pursues flavour lingering after melting in mouth, so sucrose is always the major choice as it helps the flavour stay longer after melting in mouth.
Picture shows how relative sweetness is calculated from ingredients needed - RS 14.51% or POD 145.
Given :
Lactose: 0.423+2.368+1.586
Sucrose: 95.67+0.045+0.18
Dextrose: 21.629
Reduction weight after pasteurisation: 840
(Lactose+Sucrose+Dextrose)/Reduction weight after pasteurisation
= 121.901/840
= 14.51 or 145
Pic shows how relative sweetness is calculated from ingredients needed as RS 14.51% or POD 145.
Summary
Sweetener is the ingredients that make ice cream sweet, but sweetener itself is a substance that drops the freezing temperature. Each sweetener has its own relative sweetness, perception nature and freezing power, depending on its globule weight.
Reference
Hartel & Goff Ice Cream 7th Edition
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