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Sour cream is pasteurised cream soured by mesophilic lactococci at about 20 °C for most of a day. Aroma bacteria add flavour, and the cream thickens to a mild, slightly acid, fairly viscous body. The US standard asks for at least 18 % milkfat; Canada asks for 14 %.
Fully documentedFermented milk40 h – 44 h
Recipe
Amounts from a sourceBC food-service standard recipe for 10 L of cream; its sample batch filled nineteen 500-mL containers.
Pasteurised cream, 18 % fat10 L
10 % half-and-half also works but gives a thinner sour cream[bc-sourcream]
Sour cream culture (mesophilic)As the culture maker directs
The BC sample batch used 5 g; dairies add 0.01 % concentrated culture or 1–2 % bulk starter[bc-sourcream][tp]
Starter
defined-culture
Total time across the recorded steps: 40 h – 44 h
Start
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What changes:The cream's fat is broken into small globules for a smooth, thick body
Step 1 of 5
Standardise and homogenise the cream
Time
Not documented
Temperature
60–70 °C
Reported
Salt
None given
Acidity
Not documented
Which microbes the steps name, step by step
Lactococcus lactis
L. mesenteroides
Leuconostoc
Output: standardised, homogenised cream.
Flavour
Not documented
Texture
a warmer homogenising temperature gives a thicker final product
Colour
Not documented
Microbes at work in this step
Not documented for this step.
Method
Measured measured in a studySet fixed by a specification or tested recipeReported one source reports itTypical a general value, not sourced for this fermentUnconfirmed not yet checked against a source
At a glance
Sour cream is pasteurised cream soured by mesophilic lactococci at about 20 °C for most of a day. Aroma bacteria add flavour, and the cream thickens to a mild, slightly acid, fairly viscous body. The US standard asks for at least 18 % milkfat; Canada asks for 14 %. Made in 5 steps over 40 h – 44 h. The longest step, chill and mature, takes at least 24 h (Tetra Pak) and runs at 6 °C (Tetra Pak). Lactococcus lactis subsp. lactis and Lactococcus lactis subsp. cremoris do most of the fermenting.
In-pack fermented sour creamInoculated, filled and fermented in the retail pot at 20 °C to avoid stirring the set, common for high-fat cream.
Long-life fermented creamStabiliser is added and the product is heated, often at 85–90 °C for a few seconds, before packing.
Low-fat fermented creamMade from 10–12 % cream; thin enough to cool in a plate heat exchanger before packing.
Safety
Make it from pasteurised cream; the US standard also asks for a titratable acidity of at least 0.5 % (21 CFR 131.160). BC food-safety guidance sets pH 4.6 or lower as the critical limit, cools to 4 °C within 6 hours and keeps sour cream at 4 °C or colder.
Hazards the sources name: Spore-forming bacteria from the cream, if cooling to the culture temperature is slow.
Fermented cream has been used for decades in some countries, often in cooking. Factory sour cream uses defined mesophilic cultures, as the Tetra Pak handbook describes.