Glass jars of soft homemade yogurt on a linen cloth

Bifidobacterium infantis: How to Culture It at Home (100-105°F / 24h)

ByCraig Brockie Last updated

What Bifidobacterium infantis is

Bifidobacterium infantis is the bifidobacterium most closely tied to breastfed babies. A review from researchers at the University of California, Davis calls it unique among gut bacteria in its ability to digest any of the complex sugars found in human milk, known as human milk oligosaccharides, thanks to a large set of genes for breaking down and importing them (Underwood et al., 2015). Its genome includes a 43,000-base cluster of genes that appear to target those milk sugars (Sela et al., 2008).

The reference strain held by the German culture collection DSMZ was isolated from the intestine of an infant and is grown without oxygen at 37°C, or 98.6°F (DSMZ). So making bifidobacterium infantis yogurt means asking a baby-gut specialist to live in cow’s milk, which is not what it evolved for. The home protocol below uses 100 to 105°F (38 to 41°C) for about 24 hours, with steps that limit air and add food it can use.

Ordinary homemade yogurt, by comparison, incubates at 108 to 115°F for 6 to 10 hours (University of Illinois Extension). Expect a slower, milder and softer result.

Taxonomy at a glance

DomainPhylumGenusSpeciesStrain
BacteriaActinomycetota (formerly Actinobacteria)BifidobacteriumB. longum subsp. infantisVaries by product, for example 35624, EVC001 or the type strain ATCC 15697

B. infantis is no longer a species of its own. In 2008 it was reclassified as a subspecies, Bifidobacterium longum subsp. infantis, alongside subsp. longum and subsp. suis (Mattarelli et al., 2008). The List of Prokaryotic names with Standing in Nomenclature (LPSN) lists it as a correct, validly published name in risk group 1, the lowest-risk category. The phylum name Actinomycetota replaced Actinobacteria in 2021 (Oren and Garrity, 2021).

Labels still use both names, so “B. infantis” and “B. longum subsp. infantis” mean the same thing. A label that says only “B. longum” usually means the other subspecies, covered in our Bifidobacterium longum guide. The strain code is what links a product to a study.

What the research shows

Most human research on B. infantis used one strain in capsules or infant powders, often with industry involvement. No study tested homemade yogurt.

IBS symptoms in adults (strain 35624): mixed results

In a 4-week trial of 362 women with irritable bowel syndrome, only the middle dose of 35624 (100 million CFU) beat placebo for abdominal pain, bloating and other symptoms; the lower and higher doses did not, and the high dose had formulation problems (Whorwell et al., 2006). A later 4-week trial in 302 adults with bloating and abdominal discomfort who had not seen a doctor for it found no difference in symptom severity versus placebo, though the probiotic group had more bloating-free days (Ringel-Kulka et al., 2017).

A 2017 meta-analysis concluded that the effect of B. infantis on its own in IBS “has not been confirmed yet,” while blends containing it showed small benefits (Yuan et al., 2017). That is a fair summary: some signal, not settled, and not evidence that the strain treats IBS.

Colonizing breastfed babies (strain EVC001)

In a study of 66 breastfed infants, 34 were given EVC001 from day 7 to day 28 of life. Their stools held far more B. infantis and fewer leftover milk sugars, and the higher levels lasted more than 30 days after the supplement stopped (Frese et al., 2017). Several authors worked for the company developing the strain, and the study measured gut bacteria and stool chemistry, not illness. It also depended on breast milk: the point was pairing the bacterium with the sugars it is built to eat.

Premature infants: a hospital matter only

B. infantis has been given to premature babies in hospital research. In October 2023, the FDA warned that probiotics given to preterm infants in hospitals can cause invasive, potentially fatal infections, reported one infant death, and stated that it has not approved any probiotic as a drug or biological product for infants of any age (FDA). Never give homemade probiotic ferments to a premature baby, and ask a pediatrician before giving any to an infant.

Why B. infantis fades fast in milk, and what helps

Yogurt jars chilling on a refrigerator shelf

Researchers at a Japanese dairy company described growing bifidobacteria in milk as “a difficult and industrially valuable task.” They found that breaking milk casein into small pieces, and two amino acids in particular, boosted growth across many bifidobacteria (Yonezawa et al., 2010). Adding peptides and amino acids, and using oxygen-tight containers, are among the ways a dairy science review lists to keep probiotic bacteria alive in dairy foods (Shah, 2000).

B. infantis seems to be among the harder cases. In lab yogurts stored at 39°F (4°C), the type strain stayed above one million live cells per gram for only 7 days, while a B. longum subsp. longum strain lasted 28 days (Xie et al., 2024). Adding a human milk sugar, 2′-fucosyllactose, did not help it survive.

Some strains do better. Two riboflavin-producing B. infantis strains were used to make fermented dairy drinks, which had the highest riboflavin levels after a month in the fridge, and fermenting with B. infantis alone gave more of the vitamin than co-fermenting with yogurt starters (Tamés et al., 2025). The practical lesson is to give it milk solids, keep air out, and eat the batch early.

Before you start: who should skip this

In healthy people, probiotics may cause gas but rarely cause infections, while people who are seriously ill or have weak immune systems can develop bacterial infections from them (NIH Office of Dietary Supplements). The risk of harmful effects is greater in people with severe illnesses or compromised immune systems (NCCIH). If that applies to you, or you are pregnant, talk with your health care provider first. Do not feed this yogurt to babies; it is a ferment for adults, made in cow’s milk.

Probiotic capsules are usually dietary supplements, and their makers, not the FDA, are responsible for checking safety and labeling before sale (FDA). This article is general information, not medical advice.

Home protocol: B. infantis yogurt at 100-105°F for 24 hours

This makes 1 quart. Plan on about 30 minutes of hands-on time, 24 hours of incubation and at least 6 hours of chilling.

Equipment

  • An incubator that holds 100 to 105°F for 24 hours: an adjustable yogurt maker, a multicooker on a low yogurt setting or a proofing box. See How to Incubate Yogurt.
  • A probe thermometer to check the real temperature with a jar of water first.
  • Small glass jars with tight lids, filled to the rim to leave little air.

Ingredients

  • 1 quart (946 mL) whole milk for body and a better set.
  • 1/4 cup nonfat dry milk for extra milk protein and thickness.
  • 1 teaspoon inulin powder, a fiber bifidobacteria can use.
  • B. infantis starter: a capsule or powder that lists B. infantis or B. longum subsp. infantis, ideally with a strain code. Use the label’s serving as a starting dose; see how much starter to use.
  • Optional helper: a pinch of a mild Streptococcus thermophilus starter for a firmer set. It will do much of the souring.

Steps

  1. Whisk the dry milk into the cold milk and heat it slowly to 180 to 185°F (82 to 85°C), stirring gently (University of Illinois Extension). Heating to 180°F kills competing bacteria and changes the whey proteins so the milk sets (University of Missouri Extension).
  2. Cool to 102°F (39°C). Do not add the culture above 105°F.
  3. Stir the starter and inulin into a few spoonfuls of warm milk until smooth, then fold it into the rest without whisking in air.
  4. Fill the jars to the brim and close them tightly.
  5. Incubate at 100 to 105°F for 24 hours, undisturbed. Check one jar at 16 hours, and stop early if it has set and smells clean and tangy.
  6. Refrigerate at 40°F or below right away, for at least 6 hours.
  7. For food safety, eat within 14 days (University of Illinois Extension). For live B. infantis, aim to finish it within about a week, given how quickly the type strain declined in cold yogurt.

The same method, with small changes, is used in our guide to Bifidobacterium breve. Yogurt Temperature explains why a few degrees matter.

How to tell it worked

  • Texture: a soft set or a thick, pourable yogurt. Do not expect a firm gel from bifidobacteria alone.
  • Smell and taste: mild and tangy, sometimes with a slight vinegar edge, because bifidobacteria make acetic acid along with lactic acid (Salazar et al., 2009).
  • Acidity (optional): pH strips should show a drop from fresh milk’s 6.7. Faster probiotic strains in a lab study reached 3.9 to 4.4 after 24 hours at 37°C (Østlie et al., 2003); a B. infantis batch may stop higher.
  • No thickening and no tang after 24 hours means the culture did not grow.

There is no way to confirm at home that B. infantis grew or survived. Counting it takes selective lab media (Shah, 2000). With a helper culture in the jar, assume the helper made most of the texture.

Failure modes and fixes

ProblemLikely causeFix
Still liquid, smells like milkDead or weak starter, or milk too hotUse a fresh starter, add it at 102°F, and check the incubator
Slightly thick, barely sourSlow growth in cow’s milkKeep the dry milk and inulin, fill jars to the rim, or add a mild helper
Very sour and separatedToo long or too warmStop at 16 to 20 hours and hold closer to 100°F
Fizzy, yeasty or cheesy smellContaminationDiscard, wash everything in hot soapy water, start again
Fuzzy spots, or pink, orange or dark patchesMold or spoilageThrow out the whole batch

The USDA says to discard yogurt with mold, because moist foods can be contaminated below the surface and bacteria may grow with the mold (USDA FSIS). A little clear whey on top of a clean-smelling batch is normal; see Whey from Yogurt.

Can you reuse a batch as starter?

Not reliably. Given how fast B. infantis declined in cold yogurt in the lab, a spoonful from last week’s jar may carry few of them, and any helper bacteria will take over. Start each batch from a fresh capsule. Heirloom Starter Weakened Over Time explains why reused starters drift.

Is B. infantis the same as B. longum?

It is now a subspecies of B. longum, called B. longum subsp. infantis, but it differs from subsp. longum in how it uses sugars (Mattarelli et al., 2008).

Can I give B. infantis yogurt to my baby?

No. Homemade probiotic ferments are not for infants, and the FDA has warned that probiotics can cause serious infections in preterm babies; ask a pediatrician about any probiotic for a child.

Why does my B. infantis yogurt taste mild?

Bifidobacteria grow slowly in cow’s milk and make less acid than yogurt bacteria, so a mild, soft result is normal.

Sources

Craig Brockie is the founder of Ultimate Health Solutions, the company behind Ultimate Gut, and the author of Ultimate Health, The Ultimate Gut Health Guide and The Unlimited Probiotics Guide. After injuries and chronic health problems in his twenties that conventional care didn’t resolve, he began researching health on his own and has studied natural health for 30 years. He is not a medical professional, and his articles are general information, not medical advice.

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