Hi! I’m Elena, your nutrition expert from Castelló. Today we’re going to travel to the heart of our pantries to understand how the science of heat lets us enjoy food for months: heat preservation.
This morning, when I saw a few jars of preserved food in my kitchen in Novelda, I was reminded that, although it seems normal today, using heat to sanitize food was a revolution that began with Pasteur. Technically, what we do is raise the temperature to denature enzymes and destroy the microorganisms that spoil food. Let’s look at the differences between techniques!
1. Sterilization: The power of pressure
This is the most drastic method. Temperatures above 100 °C are applied, generally using an autoclave (a kind of industrial pressure cooker).
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The goal: To destroy absolutely all microorganisms and spores.
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Common use: Canned fish, vegetables, and legumes.
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Watch out for quality: Poor sterilization can cause the can to bulge or create bad odors. If, when opening a preserve, you hear a strange "hiss" or the liquid is cloudy, throw it away!
The modern variant: Uperization (U.H.T.)
You’re probably familiar with it from milk cartons. 140 °C for just 2 seconds are applied. It’s an ultra-fast process that sterilizes the food but, because it is so brief, preserves flavor, color, and vitamins much better than classic sterilization.
2. Pasteurization: Mildness and freshness
Here we do not go above 90 °C. It is a mild heat treatment that reduces the microbial load without noticeably altering flavor or texture.
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The downside: It does not destroy spores, so the food has a short shelf life and must always be kept in the refrigerator (like fresh milk or some juices).
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Blanching: This is the "pasteurization" we do to vegetables before freezing them to inactivate the enzymes that would make them go stale in the freezer.
3. Homemade preserves: The Water Bath
This is our grandmothers' technique. Temperatures between 70-90 °C are reached by submerging airtight jars in boiling water for 20-60 minutes.
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Safety first: At home, there is a risk of developing Clostridium botulinum. It is vital to maintain extreme hygiene and make sure the boiling time is sufficient for the food.
Elena’s "Life Tip"
Smart storage: Once you open a sterilized product (a can or an UHT carton), the heat "shield" disappears. From that moment on, you must treat it as a fresh product: keep it in the fridge and consume it within a few days. And remember to always store your jars in a cool, dark place; sunlight is the number one enemy of the nutrients in your preserves.
Are you one of those who get excited about making tomato or pepper preserves in a water bath at home, or do you prefer the convenience of supermarket cans? Tell me about your experiences!
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