For this article, I skimmed through the available scientific information to find out if pasteurization kills the good bacteria in milk and other probiotic foods and if these products still remain as beneficial for consumption as they were before this food disinfection process.
Raw milk has a great nutritional profile which is why it may support a wide range of good bacteria such as Lactococcus, Lactobacillus, Streptococcus, and Bifidobacterium species, but many pathogens may co-occur with them.
Although pasteurization does modify the diversity of the viable bacteria in the milk, its less extreme methods may not eliminate the resistant probiotics.
Hence, in this article, I’ve discussed what population of bacteria is lost due to pasteurization and the kind of probiotics that can bear this stress.
Also, to find out if pasteurization affects yogurt, sauerkraut, and kefir in the same way as milk, keep reading till the end.
Does Pasteurization Kill All Bacteria? (Probiotics)
No, pasteurization may kill most heat-sensitive bacteria, but certain thermophilic, endospore-forming, lactic acid bacteria and thermoduric species are able to survive the high temperatures.
Here, thermoduric bacteria refer to those species that can withstand high temperatures but may proliferate under refrigeration temperatures. Whereas for the thermophilic bacteria, temperatures ranging between 50-110°C allow their optimal growth.
Before I explain further on this, please keep in mind that there are three pasteurization methods, namely, Low-temperature long time (LTST), High-temperature short time (HTST), and Ultra-high temperature (UHT).
Now, here is how the milk’s microbial profile may change when it is heated at these different pasteurization conditions, as reported in various studies.
The Microbial Profile Of Post-LTST Milk
For LTST pasteurization, the milk is held at 63°C for 30 minutes. This may not kill some endospore-forming and lactic acid bacteria such as Bacillus, Streptococcus, and Lactobacillus species.
Correspondingly, a study examined the survival potential of selected microbial species in LTST pasteurization. It reported that the probiotic Bacillus cereus lived through these conditions as it forms endospores that get killed at temperatures above 100°C.
Furthermore, in 2010 researchers checked the effect of LTST pasteurization on the bacterial flora of milk and found that under these conditions, the acid-producing group of bacteria may overgrow all other bacterial species.
Gladly, this acid-producing group includes the probiotic lactic acid bacteria such as Lactobacillus and Streptococcus species.
The Microbial Profile Of Post-HTST Milk
In HTST pasteurization, the milk is held at 72°C for 15s. This may reduce the abundance of endospore-forming bacteria, while some lactic acid bacteria may resist effectively.
A 2021 study assessed and compared the microbiota present in pre and post-High-Temperature Short Time (HTST) pasteurization.
The scientists reported that the pre-HTST milk was abundant in Staphylococcus, Pseudomonas, Lactococcus, Enterobacteriaceae, and Bacillaceae species.
In contrast, the endospore formers in the post-HTST milk were predominated by the Clostridiales and Turicibacter species rather than the probiotic Bacillus species.
The post-HTST milk also had a higher proportion of the Acinetobacter, Streptococcus, and Thermus species than the pre-HTST milk. But on the bright side, The HTST pasteurization killed the opportunistic pathogens like yeast, mold, Escherichia, Brevibacillus, and Enterobacteriaceae bacteria decreased in the milk.
To sum it up, the probiotic bacteria in the post-HTST milk included some spore-forming Bacillus species and some Lactic acid bacteria like L. plantarum, L. fermentum, and S. thermophilus (it is also considered a thermophile).
Still yet, although these probiotics might be beneficial for your gut when milk is stored for long durations, they ferment its sugar to produce lactic acid and cause spoilage.
In addition to these bacteria, other thermoduric bacteria that may survive the pasteurization process and are involved in milk spoilage are the Micrococcus and some Enterococcus and spores of Clostridium species.
Similarly, in a 2015 article, scientists identified that the Lactic Acid Bacteria (LAB), especially the L. brevis and L. fermentum species in raw and pasteurized milk is similar, but their concentration is greatly reduced in the latter (9.27×103 CFU vs. 0-76 CFU m/L).
The Microbial Profile Of Post-UHT Milk
In UHT pasteurization, the milk is treated at 140°C for 4-6 seconds which gets rid of most probiotics and microbes.
Since the conditions in UHT pasteurization target both the heat-resistant endospores and the thermoduric Lactic acid bacteria, so it has the least probiotic goodness.
Apart from this, a 2012 study revealed that UHT wipes out pathogenic organisms like E. coli, Salmonella, Shigella, Staphylococcus aureus, coliform, yeast, and molds in milk.
So, Is Pasteurization Bad? (Since It Kills Probiotics)
No, pasteurization is not bad because it kills many disease-causing and food-spoilage microorganisms. Besides, some pasteurization methods may spare some heat-resistant probiotics as well.
But it must be considered that research has proved that raw milk of both cows and goats has a high LAB concentration than pasteurized milk.
However, if you are looking for good probiotic sources, then opt for fermented foods rather than milk. The reason is that the raw milk will simultaneously harbor pathogens while the pasteurized milk has sub-optimal to none good bacteria.
Now, you might be wondering if pasteurization affects other probiotic foods as well, so here is the answer.
Does pasteurization kill probiotics in sauerkraut?
Yes, but it does not wipe out all probiotics from sauerkraut.
To understand this, you need to know that it mainly has three lactic acid bacterial species, namely Leuconostoc mesenteroides, L. brevis, and L. plantarum.
And according to the conclusion of a 2019 Pakistani study, the resistance of Ln. mesenteroides is strain dependent, but it is generally more susceptible to LTLT pasteurization (63°C for 30 min) instead of HTST pasteurization (72°C for 20 sec).
Apart from this, the Lactobacillus species may survive HTST or LTST pasteurization but may get killed from UHT pasteurization.
Does pasteurization kill bacteria in yogurt?
Yes, most probiotics in yogurt are lost due to pasteurization. But then again, lactic acid bacteria like Lactobacillus bulgaricus or Streptococcus thermophilus may survive unless it is UHT sterilization.
What Bacteria Can Survive Pasteurization?
In most cases, thermoduric, thermophilic, and endospore-forming bacteria can survive pasteurization. This is because these bacteria are adapted to tolerate, protect, or thrive at high temperatures.
These bacteria may include Streptococcus, Bacillus, Micrococcus, Clostridium, Enterococcus, or Lactobacillus species.
Does Pasteurization Kill Lactobacillus?
Yes, but not all of them. Lactobacillus species are thermoduric bacteria, so some of them may survive pasteurization temperatures.
Nonetheless, their abundance and concentration may get affected. And if you think about it, pasteurized milk may also go bad or taste sour eventually because even when some LAB bacteria like Lactobacillus remain behind, they’ll produce acid in it.
Does Pasteurized Kefir Have Probiotics?
Yes, pasteurization does kill probiotics in kefir, but some of them may still be left behind in minimal quantities.
The reason is that kefir has a diverse range of probiotic bacteria, such as the thermoduric Lactobacillus species or the heat-sensitive yeast species. Hence, the LAB bacteria such as L.plantarum may survive the heat, whereas probiotic yeast species such as Saccharomyces cerevisiae may get killed as the most they can take is 52°C.
Does Pasual Yogurt Have Probiotics?
No, according to the official website, Pascual Yogurt does not have live probiotics because it undergoes pasteurization.
Does Pasteurization Kill Nutrients In Juice?
Yes, pasteurization alters the nutritional profile of juices. It may reduce the bioavailability of minerals like calcium or phosphorous, cause loss of some vitamins like vitamin A or C and reduce phytonutrients such as flavonoids.
Final Thoughts – Pasteurization Doesn’t Kill All Probiotics
Different pasteurization methods may kill certain proportions of probiotic bacteria, but all of them may not be lost during this process.
The reason is that most probiotic species are endospore-forming (e.g., Bacillus spp.) or thermoduric (e.g., Lactobacillus spp.)
Such bacteria may be able to endure the LTST and HTST pasteurization conditions. Nonetheless, the UHT may be too much for them to handle.
In the end, it is not a preferable deal to drink pasteurized or unpasteurized milk to meet your probiotic requirements, and you should always look for fermented foods or supplements like Yourbiology’s Gut+ for this purpose.