Direct Vat Set Starter Culture
A direct vat set starter culture is a concentrated preparation of food fermentation bacteria sold at a potency high enough to be added straight to the production vessel, without the intermediate bulk starter propagation that dairies once carried out on site. The term describes the delivery model rather than the organisms, and the same species are sold in both direct vat and bulk propagation formats.
The change the format brought about is significant in practice. A traditional dairy maintained a mother culture and propagated it daily in pasteurised milk, which introduced two persistent problems: strain balance drifted from day to day as the faster organisms outgrew the slower ones, and the propagation vessel was the point at which bacteriophage entered and destroyed the culture. A direct vat culture is manufactured, standardised and tested under industrial conditions, arrives as a sealed unit sized to a defined volume of milk, and is used once, which removes the drift entirely and confines phage risk to the production plant itself.
Cultures come as deep frozen pellets, stored at around minus forty five degrees Celsius and added directly to the vat as pellets, or as freeze dried powders, stored frozen or refrigerated and either sprinkled in or rehydrated first. Frozen pellets give faster and more predictable activity, while freeze dried powder is easier to ship and store. Potency is expressed in activity units sized to a stated volume of milk rather than in colony forming units, since what a dairy is buying is a rate of acidification rather than a cell count.
We source bulk Direct Vat Set Starter Culture from top China manufacturers for our partners. The manufacturer is in Jiangsu. A smaller requirement can ship in a combined container with other ingredients.
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- Function
- Probiotic
Specifications
| Item | Specification |
|---|---|
| Appearance | Free flowing frozen pellets or off white lyophilised powder |
| Odour | Characteristic cultured dairy, free from foreign odour |
| Activity | Not less than declared units per unit of substrate volume |
| Viable Count | Not less than declared potency in cfu/g |
| Identification | Declared species and strains confirmed by sequencing |
| Strain Ratio in Blend | Within declared range on differential plating |
| Phage Sensitivity | Conforms to declared rotation set profile |
| Loss on Drying (freeze dried) | Not more than 5.0 percent |
| Water Activity (freeze dried) | Not more than 0.25 |
| Coliforms | Not more than 10 cfu/g |
| Yeast and Mould | Not more than 100 cfu/g |
| Escherichia coli | Absent in 10 g |
| Staphylococcus aureus | Absent in 10 g |
| Listeria monocytogenes | Absent in 25 g |
| Salmonella | Absent in 25 g |
Common Markets Grades
Cultures are graded first by the fermentation they are intended for, and this determines the species mixture. Thermophilic cultures for yoghurt and for Italian and Swiss type cheese pair Streptococcus thermophilus with Lactobacillus delbrueckii subspecies bulgaricus or with Lactobacillus helveticus. Mesophilic cultures for Cheddar, Gouda and cultured butter are built on Lactococcus lactis subspecies lactis and cremoris, with Leuconostoc or the diacetyl producing biovariant added where buttery aroma and eye formation are wanted. Propionibacterium freudenreichii serves as a secondary culture for Swiss types, and surface ripening cultures of moulds, yeasts and coryneform bacteria are traded alongside for soft and washed rind cheeses.
The second axis is phage robustness. Defined strain cultures arrive as rotation sets, several sets of compatible strains with different phage sensitivities that a plant cycles through so that a phage population never has time to build against one composition. Undefined mixed strain cultures take the opposite approach and rely on internal diversity to survive attack. Beyond dairy, meat starter cultures combining Pediococcus or Lactobacillus with Staphylococcus carnosus and nitrate reducing organisms take the same format for fermented sausage, and cultures for vegetable, plant based and sourdough fermentation follow the same pattern. Buyers specify the species and strain composition, the activity per unit, the format, and the storage temperature at which the declared activity is guaranteed.
Applications
- Yoghurt and drinking yoghurt, where the thermophilic pair sets the acidification rate and the texture
- Hard and semi hard cheese, where mesophilic lactococci acidify the curd and contribute to ripening
- Mozzarella and pasta filata cheese, where rapid acidification by thermophilic strains controls stretch
- Swiss and Alpine cheese, where a propionibacterium secondary culture produces the eyes and the sweet flavour
- Cultured butter, buttermilk and sour cream, where diacetyl forming strains give the buttery aroma
- Fresh cheese, quark and cream cheese, where acidification alone sets the curd
- Fermented sausage, where lactic acid bacteria acidify and staphylococci develop colour and flavour
- Fermented vegetables, where a defined culture replaces spontaneous fermentation for consistency
- Plant based fermented products, where dairy cultures are adapted to soy, oat and coconut bases
- Sourdough and fermented bakery products, where the culture sets acidity and aroma in the dough
China Manufacturers of Direct Vat Set Starter Culture
Top Direct Vat Set Starter Culture manufacturers in China.
Company names and logos are the property of the manufacturers themselves. They are listed here because our own directory records them as producing this ingredient. A listing is not an endorsement by them, and we do not represent them or speak on their behalf.
Regulatory Status
Food fermentation cultures are foods rather than food additives, and are handled as ingredients in every major jurisdiction. In the United States dairy starter cultures are established substances whose use is generally recognised as safe, and cultures for other applications are used as food ingredients on the same basis, with novel organisms proceeding by a generally recognised as safe determination supported by a notification to the Food and Drug Administration. Standards of identity for cheese and for cultured dairy products specify that the product be made with a lactic acid producing culture, and the culture is declared in the ingredient list.
In the European Union cultures are not food additives and carry no E number. Safety of the organism is assessed against the qualified presumption of safety list that the European Food Safety Authority maintains, which covers the lactic acid bacteria and related species with a long history of use, and an organism outside that history would fall under the novel food regulation. Cultures used in animal feed and silage require authorisation under the feed additives regulation. The Codex standard for fermented milks requires that the product be made with the specified starter organisms and that they be viable and abundant in the finished product, and the Codex general standard for cheese similarly recognises starter cultures as a permitted ingredient, so in these categories the culture is written into the compositional standard rather than merely permitted.
Manufacturing Process
Each strain is grown separately, because strains in a mixed culture would otherwise compete during propagation and the finished blend would not match its specification. A vial from the master cell bank is expanded through seed stages into a production fermenter charged with a medium based on milk solids or a protein hydrolysate with added carbohydrate, yeast extract and mineral salts. Growth is under pH control with continuous alkali addition, since lactic acid bacteria would otherwise stop their own growth. Fermentation is stopped at the point that gives the best combination of cell density and subsequent robustness, which is generally not the point of maximum yield.
The broth is concentrated by centrifugation or microfiltration to remove spent medium, and the concentrate is blended with a cryoprotectant, typically sucrose, trehalose, glycerol or skim milk solids. For the frozen format the concentrate is dripped into liquid nitrogen, which freezes it into free flowing pellets that are collected, sized, filled into cans or sachets and held at deep frozen temperature. For the freeze dried format the concentrate is frozen and lyophilised, then milled and filled under nitrogen. Blending to the finished multi strain composition is carried out on the concentrated or dried single strain materials, in a low temperature environment, and each lot is released against an activity test in the substrate itself, milk for a dairy culture, in which acidification rate is measured over time instead of a cell count. Phage resistance testing against a bank of phage isolates is part of release for rotation sets.
