SLNG in Gelato (Non-Fat Milk Solids)
This category contains all that is left of milk after removing fats and water, or proteins, lactose and mineral salts, and skimmed milk powder is its founding ingredient.
Deepening: how to calculate the percentage of SLNG?
The amount of SLNG in a mixture can vary depending on the type of ice cream you want to obtain.
Through a mathematical formula it is possible to calculate the percentage of SLNG in a mixture:
[100- (% Sugar +% Fat + Other Solids%)] x 0.15
In this formula, 0.15 must be considered a fixed number, and takes into consideration non-fat milk solids (expressed in lactose) contained in a mixture.
For a correct balance, we must consider that:
- The amount of skimmed milk powder should not exceed 11-12% of the total weight of the mixture
- 100 g of skimmed milk powder provide about 50 g of lactose: in addition to this value, you risk getting an excessively sandy ice cream due to the formation of lactose crystals.
In order to avoid problems of "sandiness", this formula was conceived, which originates from the following reasoning: " SLNGs are able to absorb water in a quantity equal to 6-7 times their weight ". In other words, 15 g of skimmed milk powder are able to absorb about 100 g of water: this ratio is expressed with the figure 0.15.
What is obtained from the formula is precisely the percentage of SLNG that can be used in the mixture.
Example. An ice cream brings:
- 15% of sugars
- 6% fat
- 3% of other solids
The SLNGs are calculated in this way: [100- (15 + 6 + 3)] x0.15 = 11.4
Considering that the general rule imposes a quantity of SLNG between 9 and 12%, the value 11.4 is ideal for a correct balancing of the mixture.
Dry Residue of Ice Cream (Other Solids)
It expresses everything that cannot be considered sugar, fat, SLNG or water. This category includes substances capable of acting as stabilizers, thickeners and emulsifiers, or all those ingredients capable of increasing the melting resistance of ice cream, of binding to water and of swelling.
The main substances that fall into this category are:
- carob seed flour
- sodium alginate
- guar gum
In this category you can also place lean solids present in flavoring pastes (eg in cocoa, hazelnut, etc.) and non-sugary fruit solids.
Deepening: carob flour in ice creams
Locust bean gum is a hydrocolloid polysaccharide extracted from the carob pod: probably, it is the most common ingredient as a component of thickeners and stabilizers for ice cream.
Carob seed flour disperses well both hot and cold, and its cold dispersion does not cause problems because it does not form lumps. However, to fully exercise their thickening capacities, carob seed flour requires high temperatures: in this regard, for excellent solubilization, it is advisable to bring the mixture to 80 ° C, and to maintain the temperature for at least 2 minutes .
Locust bean gum is used alone in concentrations of 0.5-1% or together with other thickeners, such as guar gum and mono / glycerides of fatty acids (eg Aglumix ®).
The amount of stabilizer contained in an ice cream mixture must not exceed 0.5-1%. However, emulsifiers and stabilizers are not so essential in "fruit base" ice creams (sorbets), or in all mixtures that do not include the addition of fats, formulated only with water, sugar and pulp / fruit juice.
Soy lecithin and mono / glycerides of fatty acids are also included in this category: these emulsifiers are mostly used in the preparation of industrial ice creams (which require long storage times). The function of the emulsifiers is to bind the fat particles to the water molecules contained in the mixture, increase the preservation of the ice cream, disadvantage the formation of ice crystals and optimize the structural characteristics (eg viscosity) of the finished product.
Even inulin can be used for the formulation of ice creams. It is a soluble fiber, indigestible from the human body, composed of long chains of fructose. In ice cream mixes, inulin shows a similar behavior, in some ways, to sugars: in fact it helps to lower the freezing point of the water contained in the mixture, enhancing the anti-freezing capacity of some sugars such as, for example, dextrose. Furthermore, since it consists of long chains of fructose, the inulin contributes - albeit very little - to softening the mixture: in fact, it has a sweetening power of about 10% compared to that of sucrose. Furthermore, in ice-creams, this soluble fiber is also used as a "body compensator" (ie to increase the fixed residue) in all mixtures lacking total solids (eg in fruit ice-creams and sorbets). Inulin is often used in fruit sorbets in a percentage of 1-2% of the weight of the mixture. When used in dosages higher than 2%, inulin appears to act as a sort of "fat substitute": in fact, it is able to give a pasty and creamy structure (just like a fatty substance does), but without negatively affecting total calories (inulin provides 1Kcal / g against 9Kcal / g of fats). Inulin therefore allows to limit the quantity of total fats in the mixture, guaranteeing a creamy and pasty consistency with ice cream, similar to that produced by fatty substances.
The presence of inulin in a mixture makes the ice cream "functional": in fact, this important fiber has positive effects in terms of intestinal transit, helps to lower levels of "bad" cholesterol and triglycerides in the blood and optimizes the composition of the flora intestinal.
In summary, the stabilizers are chosen for:
- To facilitate the absorption of air during the freezing of the mixture (to favor the overrun)
- Inhibit the formation of ice crystals in the finished product
- Improve the consistency of ice cream
- Stabilize the emulsions
- Enhance the aroma of ice cream
