Welcome to Science Facts Sundays.

This is part of the notes I took about fermentation from Fermented Fruits and Vegetables. A Global Perspective. (Chapter 2). It was one of the sources I used when writing The Science Behind Sauerkraut Fermentation a couple of months ago (my ebook version is here).

You may find this geeky - so be forewarned! If fermentation doesn’t appeal to you, check back in a few weeks and I’ll have moved on to something else that you may be interested in.

Here are some morsels for you to chew on (written in my own words):

Bacteria initiates growth, followed by yeasts, and then molds (if it comes to that).

“Initiating” bacteria: L. mesenteroides is part of the Streptococcaceae family. L. mesenteroides is heterofermentative, small bacteria which produces lactic acid, acetic acid (vinegar), ethanol and CO2 from glucose.

“Gaseous stage” bacteria: L. plantarum is part of the Lactobacillaceae family, which can tolerate high salt concentrations. L. plantarum is the more important bacteria involved in fruit and vegetable fermentation, and produces only lactic acid.

Helpful anaerobic yeasts: S. cerevisiae is an anaerobic yeast that is helpful for healing candida. When oxygen is available, however, it will shift from fermentative to oxidative. [This is that white sediment you see on the bottom of your water kefir or sauerkraut.]

“Ferment” is when a food spoils naturally; “Spoiling” is an undesirable ferment.

Most spoilage organisms can not survive in alcoholic or acidic environments. [This is why you want the pH to drop.]

Major factors that influence growth and activity of micro-organisms in your ferments are: moisture, oxygen concentration, temperature, nutrients and pH. Of course spoilage organisms are on this list as well. [Let's take a closer look at moisture - we will look at the others next week.]

Moisture: water is essential for the growth and metabolism of cells. Less water makes for decreased cellular activity. There is free water, and there is bound water - and there is a difference.

Free water exists in and around tissues. Free water can be removed from the cells, and by doing so you can control microbial activity. Salt and sugar both bind free water, encouraging water activity to decrease. Water activity (aw) refers to the amount of water available for micro-organisms. Pure water has a water activity as 1.0.

Bound water is present within the tissue and is essential to the cell’s physiologial processes.

Bacteria require more water than yeast, which requires more water than mold. Below a water activity of 0.7, most molds are prevented from growth; a water activity below 0.8 will prevent most yeasts from growing; and bacteria won’t grow well under a water activity below 0.9.

That’s it for today! I hope you learned something. If you did, feel free to leave me a note in the comments If you didn’t, then you are definitely a geek!

• Notes on Fermenting Pickles
• Stages of Fermentation, and Moisture
• Fermentation and Oxidation, Temperature, Nutritional Requirements, and pH
• More Notes on Fermenting Pickles
• And More Notes on Fermenting Pickles

Similar Posts:

Science Facts Sundays: Notes on Sauerkraut Fermentation, Part 4
The Science Behind Sauerkraut Fermentation

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