Moldy ferment? Too sour? Is it safe?


Are fermented foods safe to eat?

Fermented foods use acidification to crowd out and kill harmful bacteria. Fermentation creates lactic acid, acetic acid, and carbon dioxide that make it difficult for food-borne or contaminating pathogens to survive. This is why fermentation as a food processing technique has survived over the centuries, and it is considered one of the safest foods that humans can eat. 

Of course, ferments are not completely without risk, especially if there are errors in the fermentation process. Here’s how to ensure safety in your ferments!  

How long do ferments last?

This is the most common question we get. As a food preservation technique, ferments should last months, even years. Having said that, remember that there are still a lot of factors that affect its shelf life, from the salt content to how it is stored to the temperature and humidity of its environment. 

Ferments are also living foods bustling with ongoing microbial and enzymatic processes, and they can also get progressively sour or intense in flavor. We like to refrigerate our ferments as soon as we like the level of sourness.

Do I have to sterilize everything?

Let us differentiate between clean and sanitary and sterile.

Clean means your ingredients, tools, and surfaces are free of visible dirt. You can achieve this simply by washing with soap and water. 

Sanitary means you reduce microorganisms to a safe level, and your ingredients, tools, and surfaces are free from potential pathogens. You can achieve this by using a sanitizing or disinfecting solution. We prefer to use natural/plant-based solutions like baking soda and white vinegar or vodka. 

Sterile means all your ingredients, tools, and surfaces are completely free of all microorganisms. Sterilization of surfaces is usually done in hospitals.

Whether you are fermenting or not, cleanliness is important. 

For purposes of home-based fermentation, we recommend keeping everything sanitary. 

Can we cook fermented foods?

If you are eating ferments for their live bacterial communities, then you have to make sure to eat them uncooked. If you do cook them, make sure that they are not subjected to heat above 115oF/45oC. (Any fermented food sold in supermarkets that are shelf stable and unrefrigerated are pasteurized or subjected to high heat, therefore they no longer contain live cultures.)

Remember though that there are also other benefits to be had from fermentation such as improving the nutritional availability of food, detoxification of food, and additional nutrients These generally do not disappear with cooking. 

Are ferments high in sodium? Will it cause/aggravate hypertension?

Salt is essential in fermentation. Salt keeps the vegetables crunchy and crisp. A sufficient amount of salt is needed to kill the pathogens and allow the good bacteria to thrive. This is why some people avoid fermented foods. 

However, there are studies that show that the fermented foods are not associated with increased risk of hypertension or that the high potassium in fermented food such as kimchi “neutralized the effect of elevated sodium intake on blood pressure levels”, and Chinese traditionally fermented soy sauce was found to have “no harmful effects on hypertension” (emphasis on traditionally fermented). 

Nonetheless this should not take the place of professional medical advice, and those watching their sodium intake should consult with their doctor when consuming fermented foods.   


Help! There’s mold in my ferment! 

Oxygen promotes the growth of fungi, such as molds and yeasts, so it’s typical to have these on the surface, which comes into contact with air. This is why it is essential to keep ferments packed and submerged in their brine, using fermentation weights or covering the surface layer with cabbage leaves. 

While dramatic-looking yeasts like Kahm yeast are generally not cause for alarm for some, those with gut sensitivities should be extra careful with any indication of mold growth. Throw out or compost ferments with colored molds.

My ferment is too salty. 

Just add a little water, mix, and taste. You can also mix in more vegetables, wait for the moisture to be drawn out, and taste again. If it is still too salty and you may need to add a lot of water, drain the mature brine and set it aside for use in future starters. You can also rinse the fermented food, but that also means rinsing away the live cultures. 

To prevent over-salting, invest in a kitchen scale so you can weigh your salt. You can also taste your vegetables as you go to check for saltiness.

My ferment stinks. 

Ferments typically have strong odors so it may help to ferment in a well-ventilated area, especially when it’s time to burp the ferments. If it smells putrid, try to remove the offensive layers and see if the deeper layers have been affected. If the entire batch smells really bad (e.g., rotten food), compost it. 

Why is my ferment mushy? 

Salt seizes the pectins in the vegetables to make them crunchy and crisp. Mushy vegetables may be due to low salt content. 

Enzymes that digest the pectins, resulting in mushiness, also thrive in high temperatures, which is why fermentation is usually done in the colder months. 

You can also add tannins to the ferment, e.g., black tea leaves. 

Why is there foam in my ferment?

Some foaming (bubbling) is quite common especially during the first few days of fermentation. Don’t worry about it. It means your ferment is alive.

Why is there slime?

In the early days of the ferment, the concentration of slime-forming bacteria Leuconostoc may be a bit high. Don’t worry, it dissipates, so you can let it ferment for a longer period, like a week or two, then check it again. 

Another cause may be the overproduction of two kinds of lactobacilli, L. cucumeris and L. plantarum, due to less-than-ideal fermentation temperatures. This is why some prefer to wait for colder weather when fermenting. 

Either way, it eventually disappears. 

Got any more questions–or even answers? Drop it in the comment section below to share with our community. You can also follow us on Instagram and Facebook to receive updates on recipes and tips, and grow our fermentation community!

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