PRODUCING RECONSTITUTED SKYR: CHOOSING THE RIGHT CULTURE AND PROCESS
UNDERSTANDING THE DIFFERENT SKYR-TYPE PROCESSES
There are several possible approaches to producing a Skyr-type product:
1. Milk Fortified with Functional Milk Proteins
In this process, the milk base is fortified with functional milk proteins and / or other dairy solids before fermentation.
This approach is particularly relevant when producing a reconstituted Skyr, where the desired protein and total solids levels are created through formulation rather than by physically removing whey after fermentation.
For this application, Lyofast YCE 438 A is the recommended starter culture.
It is suitable for:
- Milk fortified with functional proteins before fermentation.
- Reconstituted Skyr-type formulations with elevated protein and total solids.
- Milk concentrated by ultrafiltration before fermentation.
2. Concentration Using a Centrifugal Separator
A Skyr-type product can also be produced by first fermenting the milk and then concentrating the fermented product using a centrifugal separator.
For this type of process, Lyofast YCE 128 A is suitable.
The concentration step takes place after fermentation, allowing whey to be removed to achieve the characteristic high-protein, thick Skyr-style consistency.
3. Concentration Using Ultrafiltration
When ultrafiltration (UF) is used, it is important to establish when the UF step occurs, as this influences culture selection.
· UF before fermentation: The milk is concentrated first and then fermented. Lyofast YCE 438 A is suitable for this application.
· UF after fermentation: The yoghurt or fermented milk is concentrated after fermentation. Lyofast YCE 128 A is suitable for this process.
This distinction is important when selecting the most appropriate starter culture.
WHY PROTEIN CONTENT AFFECTS CULTURE DOSAGE
Producing a high-protein cultured dairy product involves more than simply increasing the amount of protein in the formulation.
As the total protein and total solids increase, the buffering capacity of the milk system also increases. Higher protein levels are associated with increased concentrations of colloidal calcium phosphate, which can resist changes in pH during fermentation.
In practical terms, the starter bacteria continue producing lactic acid, but the pH may remain relatively stable for longer before beginning to decline at the desired rate.
For this reason, a standard culture inoculation rate designed for normal milk may not be sufficient for a highly fortified Skyr formulation.
ADJUSTING THE INOCULATION RATE
Consider the following example for a 10,000-litre production batch:
Parameter | Average Milk | Standard Guideline | Fortified Milk | Adjusted Guideline | Highly Fortified Milk | Adjusted Guideline |
Total Solids | 12.50 % | 100 UC | 14.00 % | 112 UC | 29.00 % | 232 UC |
Total Protein | 3.10 % | 100 UC | 3.76 % | 121 UC | 8.00 % | 258 UC |
When milk is fortified to approximately 8 % protein and 29 % total solids, the protein level becomes the primary consideration in this example.
The calculated inoculation requirement is approximately 2.6 times the standard inoculation rate.
Example Culture Guideline
For a highly fortified milk base:
· Culture: Lyofast YCE 438 A
· Inoculation: More than 2.5 UC per 100 litres of fortified milk
· Incubation temperature: 42 °C ± 1 °C
The precise inoculation rate should always be determined according to the final formulation, particularly the total protein and total solids content.
CULTURE SELECTION AT A GLANCE
Skyr-Type Process | Concentration Stage | Suggested Culture |
Functional milk protein fortification | Before fermentation | Lyofast YCE 438 A |
Reconstituted/high-solids Skyr | Before fermentation | Lyofast YCE 438 A |
UF of milk | Before fermentation | Lyofast YCE 438 A |
Centrifugal separation | After fermentation | Lyofast YCE 128 A |
UF of fermented yoghurt | After fermentation | Lyofast YCE 128 A |
DEVELOPING A RECONSTITUTED SKYR
For manufacturers looking specifically at a reconstituted Skyr, the first step is to establish the target formulation.
Important parameters include:
- Target protein percentage
- Target total solids
- Fat content
- Type and quantity of functional milk proteins used
- Desired final texture and viscosity
- Fermentation time and temperature
- Whether any additional concentration step will be used
Once these parameters are established, the starter culture and inoculation rate can be selected more accurately.
For a reconstituted Skyr produced by fortifying the milk base with functional proteins before fermentation, Lyofast YCE 438 A provides a suitable culture solution. As protein and total solids increase, however, the inoculation rate must be adjusted to compensate for the increased buffering capacity of the fortified milk system.
THE RIGHT CULTURE STARTS WITH THE RIGHT PROCESS
There is no single processing route for producing a Skyr-type product. Culture selection should therefore begin with one important question:
Is the protein concentration achieved before or after fermentation?
For protein-fortified or UF-concentrated milk before fermentation, Lyofast YCE 438 A is suitable. For products concentrated by centrifugal separation or ultrafiltration after fermentation, Lyofast YCE 128 A is suitable.
Understanding this distinction helps manufacturers achieve more predictable acidification, fermentation performance and final product characteristics.
Dynamiko Food Ingredients can assist dairy manufacturers with culture selection and technical guidance for the development of Skyr-type and other high-protein cultured dairy products.
