Subreddit: r/ExplainLikeImFive
User: u/XinGst
Original Post:
Are bacteria that survived heated drinks always the same one?
I'm new to pasteurizing, I like making herbal drinks. From what I understand I should kill them with heat and then knock them with cold water before keeping them in fridge. I also clean bottles, all items with hot bottles first.
The point is to kill bacteria and then kill the rest with cold temperature before they have time to adapt,
What I don't understand is how can they survived the heat? Are they the same one? And then since I kill them with cold temperature too how come my drinks still go bad eventually?
Thank you in advance 🙏🏼
My Response:
So this is a common issue in the food industry. And the truth is that most pathogens and spoilage microorganisms of concern aren’t going to adapt to higher temperatures beyond a certain point. Otherwise we would have to be constantly changing our pasteurization methodologies to account for this. Our assumption, and it’s a very good one, is that the vast majority of species won’t survive or even adapt to above 50 to 55 degrees Celsius for an indefinite amount of time. That is why you can do things like sous vide.
The real issue is that some species, such as Bacillus cereus and Clostridium botulinum (responsible for botulism), produce highly heat tolerant spores. So most generic pasteurization protocols aren’t going to destroy them. They usually require a combination of heat at the right temperature and time to ensure complete destruction, acidic conditions below a certain pH, or full on retort, which is essentially like pressure cooking the beverage so that all of the spores are destroyed.
There’s also a good number of molds and yeast that have varying resistances to different temperatures. It also depends on the conditions; foods with more sugars, salts, or protein can protect or be more detrimental to certain species at specific temperatures. Time at certain temperatures also plays a role.
So for the most part, yes these are likely to be the same. But there’s also other species of microorganisms that can come from different sources - some microbes are more prevalent from drains (Listeria), others are more prevalent in cold temperatures (Pseudomonas), and others are only sourced from soil or manure (Bacillus, Escherichia).
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