How to Ferment Vegetables, Fruits, and Grain | FREE MASTERCLASS #11
The Fundamentals of Lacto Fermentation
Hi,
In this newsletter I thought I’d take you on a journey into the microcosmos and share with you more than a recipe teaching you how, but deep-dive into why certain practices are followed in the world of fermentation, and how an understanding of these simple rules will give you free range to be creative in the kitchen. I’ll cover the basic range of techniques, address the health claims surrounding it, give you my honest thoughts on what I’ve noticed in my life over the last 12 years of fermenting, and share with you my approach to recipe development and getting creative within these techniques.
Topics in this newsletter
Introducing lacto fermentation (and bacteria)
Why making your own is better than buying it
Health claims of lacto fermentation
Salt, the great purifier
Fermenting by formula (a recipe for all vegetables, fruit, and grain)
Additional infusions, get creative with fermentation
Selecting suitable ingredients to ferment
Cleaning and safety
Curious for more?
For the following technique, all you need is a glass jar of any kind, sea salt, and vegetables, fruit, or grains.
Video footage of yeast and bacteria by James Weiss from Jam and Germs
Shot 1+3: yeast and bacteria flowing in liquid
Shot 2: microorganisms feeding on sugar grains
What is ‘Lacto Fermentation’?
For most people, lacto means something to do with milk. The word crops up with others such as lactic, lactate, and lactose after all. But lacto is the label fermenters give to foods made with lactic acid bacteria, known and celebrated for its ability to convert sugars into lactic acid. The production of which is what makes the foods safe and preserves them, as acidic environments are hostile places for a lot of the harmful pathogens that could cause trouble for us. This is why vinegar will last forever in a cupboard, because it’s high in another form of acid (acetic).
Lactic acid bacteria (LAB) is responsible for that delicious sour tang in yoghurt, kimchi, sauerkraut, honey fermented garlic, sourdough, miso, buttermilk, creme fraiche, labneh, cheese, kvass, pickles (not to be confused with vinegar based pickling), and plays a role in kombucha and kefir. Lactic acid also happens to be what your cells produce when your muscles burn after strenuous exercise, for the very same reason, a lack of sufficient oxygen supply forces them into anaerobic respiration.
As a bacteria, it is one of the smallest, most simple living organisms. Therefore, it can reproduce at a far quicker rate than yeasts and moulds, which are larger and more complex. This makes it ideal for fermentation, especially for beginners, as it rapidly outcompetes its competition, becoming the dominant microorganism and creating a safe and healthy ecosystem within our fermented food.
Why make your own fermented foods?
There are some great producers of fermented foods, such as kimchi from Kimchi&Radish (owned by my friend Kimmy), that are alive, unpasteurised, and full of flavour. But for the most part, a lot of fermented products in shops are either pasteurised or so acidic they’re past the point of peak flavour. This is partly thanks to food safety standards and their lack of understanding in such matters (certainly those I’ve spoken to), as well as the issue of packaging a living food (which continues producing carbon dioxide, blowing jar lids and packets). Homemade ferments can be eaten when they’re at their best, full of thriving microbial communities that benefit us, and full of balanced, delicious flavour. Imagine if all meat in shops was sold pre-cooked and the only option was very well done. If you wanted something else, you’d have to make it yourself. This is somewhat similar to most fermented foods on the market.
You may think I’m biassed, but it also couldn’t be easier. If you want to preserve food in an easy, safe, and cheap way, lacto fermentation is my go-to method. You want an incredible powerhouse of flavour in your kitchen? Something bioavailable and nutritious? Gut healthy? You know my answer by now.
But why are fermented ingredients so damn tasty?
Broadly speaking, raw ingredients are packed full of delicate compounds that become denatured by cooking, but a lot of their molecules (chains of atoms strung together) are long and complex, which we can’t really taste (or digest). Cooking them breaks these molecules down into shorter molecule chains, which taste great because they’re more digestible. Evolution rewards us for seeking them out. For example, we are unable to taste starches, however we can taste maltrose, glucose, and sucrose, which are molecules made when starches are broken down. But the process of cooking irreversibly damages the delicate compounds. Through fermentation we get the best of both worlds. By subjecting ingredients to the enzymes and acids of bacteria, we can cleave the molecules into shorter forms, making them more digestible and broadening their profile. Sweet elements get sweeter, umami elements get umami(er?). But we also preserve the delicate compounds. It’s a win win.
Something interesting happens during this process. By the nature of bacteria and enzymes floating around in undirected chaos, molecules are broken down into random lengths. Unlike the uniformity of industrially produced goods, fermented foods have a plethora of molecules, even with one type, such as sugars. And wouldn’t you know it, we can taste them all. This gives fermented foods a rounded depth, a dimensional flavour, that other foods lack by comparison. Pretty cool, right?
Health Claims
I’ve seen some pretty extensive health claims surrounding fermented foods, some of which I think have evidential support, others perhaps less so. Lacto ferments have gained attention for the potential benefits due to the presence of probiotics (bacteria that benefit us as a living component within our bodies), enzymes, and bioactive compounds. I’ve included links to the studies that support these claims, for those who might want to find out more.
I will say, I read into one of these studies quite extensively and found that they achieved their results by using pig stomachs and manual pumps to ‘recreate’ the digestive conditions in humans, with stomach acid and bile. This particular study was testing how well beneficial bacteria adhere to the wall of the intestines after passage through the digestive system. Whilst I’m sure measures were taken to make it as accurate as possible, pig stomachs and manual pumps are indicative of the caveats these studies should all come with, and why it’s important to read more than the title alone.
Gut Health and Digestion.
LAB from fermented foods can improve gut health, everyone’s favourite kind of health these days, by balancing the intestinal microbiota. Within your intestinal tract, there are billions of symbiotic microorganisms that digest elements of the food we ingest that our bodies cannot, turning them into available nutrients for us. If we were to take every living individual within us that doesn’t share our genetic code and compare it to our own cells, we are actually more ‘them’ than we are ‘us’. So it’s quite important we understand how to look after them, after all, they have a larger impact on our everyday lives than many of us realise. Directly relating to gut health, they can help alleviate conditions like irritable bowel syndrome and improve digestion. (Stanford School of Medicine)
Immune System Support.
Fermented foods can enhance immune function by promoting the production of immunoglobulin A (IgA) and influencing immune cells. LAB can also help produce antimicrobial compounds that protect against pathogens, notably in reducing the severity of respiratory infections. (Macro Lab UC Davis)
Anti-Inflammatory Properties.
LAB in foods has shown potential in reducing inflammation, which is linked to many chronic diseases such as obesity, diabetes, and heart disease. This is believed to occur through the regulation of gut microbiota and immune response, by strengthening gut barrier function, producing anti-inflammatory compounds like short-chain fatty acids, like butyrate, and through the influence and modulation of immune cells such as T-cells (Tregs), which help suppress excessive inflammation and contribute to lower C-reactive protein, a substance produced by the liver in response to inflammation in the body. Which is all a bit scientific.
In a real life example, I suffer from eczema, and as a purely anecdotal story, I’ve noticed my condition seems more manageable since eating more fermented foods. Of course, there are numerous factors at play here, I no longer chef, so my stress levels are lower. I no doubt eat a more overall varied diet, I drink more water, and I spend time outside at the farm.
Nutrient Absorption and Bioavailability.
LAB fermented foods break down anti-nutrients like phytic acid, enhancing the bioavailability of important minerals like iron, zinc, and magnesium. It also produced additional vitamins, such as B12 and K2. A study published in the Journal of Applied Microbiology also suggested that fermentation increases the bioavailability of certain nutrients by breaking down complex molecules into simpler, more digestible forms. From a chef perspective this makes intuitive sense, as fermented foods often taste incredible, and our sense of smell and taste are our window into the world of nutrition, our sense of smell alone is able to detect the bonds between every molecule we’ve ever tested. Put simply, without artificially enhancing flavour with sugar, MSG, and other enhancements, good taste = more good stuff.
Mental Health and Brain Function.
There is emerging evidence of the gut-brain axis, and as someone who has always looked after my gut (way before it was cool, simply because I love food and a wide range of vegetables, pulses, and legumes), I can personally attest to having a happy, content brain that seems to work in every way I need it to.
The balance of gut microbiota influences the production of neurotransmitters like serotonin and gamma-aminobutyric acid (a catchy name), which affect mood and cognitive function. A systematic review in Frontiers in Psychiatry suggests that probiotics, including those found in fermented foods, may play a role in reducing symptoms of anxiety and depression by interacting with the gut-brain axis.
Weight Management and Metabolic Health.
Research published in BMC Gastroenterology suggests that fermented foods can improve metabolic markers, such as blood glucose levels and insulin sensitivity, potentially aiding in weight management and reducing the risk of type 2 diabetes.
Conclusion.
Would you look at that? The adages “you are what you eat” and “food is medicine” couldn’t be more accurate. Although, as I’ve said a thousand times, I am not a health specialist, so the best I can provide is what others publish in research studies. Whilst I’m careful to also check who funded each study, sometimes these important details slip through the cracks. But I do my best not to allow my curiosity on the subject cloud my critique and healthy level of scepticism over such matters. I also wouldn’t trust anyone who speaks on such matters in terms of absolutes.
What I do know is flavour. So let’s get stuck in.
Salt, the great purifier.
You may have noticed that I often stick with the golden rule of 2% salt. But what does this mean? Whatever I’m fermenting, I prepare the ingredients by cleaning and chopping them, then weigh them all together. If working in grams, I multiply this number by x0.02 to find out how many grams of salt is required to make this recipe safe. If working in pounds and ounces, you need to convert the weight into just ounces, then multiply this by x0.02 to know how many ounces of salt to add. As there are 16 ounces to a pound, multiply the number of pounds by 16, then add any extra ounces of weight to this total before multiplying it by x0.02. For example:
4 pounds = 4 × 16 = 64 ounces
64 × 0.02 = 1.28 ounces of salt
The amount of salt added is very important for safety. Salt is what slows the unwanted microbes down long enough to let our favoured bacteria (LAB) take over. The lowest percentage this should be is 2%, meaning that 2% of everything in a jar should be salt. This includes adding water, which would otherwise dilute the salt to dangerously low levels. If you’re making a ferment that involves adding water, you must factor the weight of it into your calculation. And for the sake of accuracy, I always weigh ingredients over using volumetric measurements. It’s a habit I picked up working at a bakery that I’ve kept to this day.
But not all salt is suitable for fermentation. Table salt, which should be banished to the hell it came from, is full of anticaking agents that have a negative impact on beneficial microbes. Salts that are fortified with iodine are also unsuitable for the same reasons. The best salt to use are natural (sea salt or rock salt). And for my US readers, this includes kosher salt, which is just rock salt used in the Jewish culinary tradition of koshering (salting meat before cooking to remove the blood).
For LAB, our bacteria of choice for this newsletter, you want to stick to between 2% and 6% salinity. Much higher than that, and you’ll start to impact how effectively LAB can ferment. There are a number of reasons for using more than 2% salt, and a range of flavours and textures it promotes in the final product. It also helps preserve the food for longer. However, high salt levels within food can also cause damage to our bodies, often for the same reasons harmful pathogens can’t tolerate it, so use these foods sparingly.
Fermenting by Formula
The following recipe is a template you can use to lacto ferment all sorts of plant ingredients, from vegetables, fruits, and berries, to grain. Within these simple rules, the scope for creativity is vast. At the end of this recipe, I’ll include some of my favourite, most effective ways to enhance and customise this formula for endless culinary fun.
Ingredients:
1kg (2.2lbs) of vegetables
Enough water to cover them
2% the total combined weight of water and vegetables
Equipment:
2kg (4.4lbs) jar
A smaller jar, glass, or ceramic weight
Clean and chop up the vegetables. All vegetables are suitable to ferment, but not all react in the same way. Some, such as cabbage, retain a satisfying texture. Whilst others, like tomatoes, soften. The most important thing at this stage is to wash well and remove signs of damage, spoilage, or pests. The LAB needed for this ferment is already on the ingredients and you, waiting for you to provide the ideal conditions for it.
LAB (and it’s beneficial friends) live on ingredients and us Weigh the prepared ingredients and pack them into a clean, sanitised jar.
Place the whole lot on a set of scales, tare the scales to the weight of the jar and ingredients, then top up the jar with enough water to cover all the ingredients. Make note of how much water you added (in grams or ounces), then add that to the weight of the ingredients (also in grams or ounces).
Multiply this number by x0.02 to calculate how much salt to add. Example:
1,000g of vegetables + 1,800g water = 2,800g × 0.02 = 56g of salt.
2.2lbs of vegetables + 3.9lbs water = 6.17lbs × 16 = 98.7oz × 0.02 = 1.97oz of salt (which I’d round up to 2oz for ease).
Now we know how much salt to add, weigh it in a mixing bowl, then tip some of the water back out from the jar into the bowl and stir until the salt is fully dissolved.
Tip the salty brine back into the jar, making sure no salt is left behind in the bowl, then place a weight inside to hold the ingredients from floating above the surface. This weight can be a small glass jar (such as a jam jar, or something you’ve reused from the shop, once you’ve completely removed the label and residue glue). It could also be a glass or ceramic fermentation weight, or a smooth, cleaned, and sanitised stone from the beach. If using a stone, make sure it’s non-porous and shows no sign of heavy metals.
Once the weight is in place, secure the lid of the jar or fit it with an airlock if you have one. Lacto fermentation is always anaerobic, which helps prevent other microbes from introducing unwanted flavours and effects.
Leave the jar somewhere between 18-29°C (64-84.2°F). This range is ideal for lactic acid bacteria. Any higher, and it will suffer. Any lower and it will slow right down.
Keep an eye on it over the following 2 weeks, opening the jar daily to release carbon dioxide.
Microbial activity is an ark, starting slowly, then exploding into life, then slowly tapering off again as food runs out and acidity grows. I find that most foods taste at their best between 2-4 weeks, but if you want to let a ferment run for a longer period you can, as the acid production will slowly level off and preserve the food. To capture it at just the right stage for your taste, try some at the 2 weeks mark and move the jar into a fridge when it reaches your ideal acidity. The colder temperatures will slow activity and hold your favoured flavours for longer.
Lacto fermented ingredients, if held beneath the brine, will last for several months if not years. The most important factor for safety and preservation is acidity, which should reach pH 4.5 or lower (4.6 being the threshold for botulinum).
Additional Infusions
Besides the mixing of different ingredients and the incredible effects of infusion, you can also customise your ferments by adding any combination of the following ingredients. But remember, if any are in addition to the default recipe, you need to take note of their weight and factor this into your salt calculation.
Smoked salt - A great way to introduce smokiness to a ferment for both savoury and sweet.
Aromatics - Ferments infuse aromatic ingredients like allium beautifully.
Herbs - Pick your favourite and add them in. If including woody parts, the tannins help preserve crunch.
Spices - Dried, fresh, seeds, leaves. Go wild.
Chilli peppers - For my fellow spice lovers, heat from chillies does amazing things when fermented.
Flowers - Edible petals will deteriorate quickly in acidic environments, but a 2-3 day infusion will impart incredible floral notes to a ferment.
Teas - Teas of all kinds can be infused in the brine prior to fermentation for additional layers of aroma and infusion.
Soy sauce - Also salty, so take care if you’re making a ferment that’s at the higher salt threshold already. Soy sauce, shoyu, or tamari will impart incredible umami and depth to a ferment.
Honey - A little sugar and a lot of flavour really boosts a ferment with a supercharged shot of nectar.
Whey - Collect leftover whey from butter or yoghurt making and replace some of the water in your ferment with it for a yoghurty cheesy tang.
Wine - Much like adding wine to your sauces or stews, a small amount in a ferment goes a long way.
Raw Vinegar - Introducing a different kind of acid making bacteria called acetic acid bacteria (AAB) will give your ferment a lively, lip smacking tang.
Picking Ingredients
I tend to use our homegrown ingredients for the best results and as a means to preserve them, but you can also use lacto fermentation to give new life to ingredients that would otherwise go to waste, turning the practice into an amazing zero waste product. Following this line of thought, I sometimes visit expensive organic farm shops and see what they have on discount. If you’re feeling brave, you can even haggle with them, as they often hate waste as much as we do. It’s a cheap way to get your hands on high quality ingredients that would otherwise end up as compost, and in my experience, organic, in season produce makes the best ferments.
Seasonality is important. Whilst we can sometimes be fooled by the look of an ingredient that is grown outside of season using modern farming methods, the lack of microbes won’t lie. In the same way that certain pests appear in the garden in Spring, following the cold absence of Winter, the microbial world also follows the seasons. A lot of modern farming practices also use chemical fertilisers that have been proven to hamper or destroy microbial life throughout the soil, severing a plant's very connection to the extended living world through its rhizosphere. The knock on effects can detrimentally impact our food, ferments, and health.
But fear not, for you yourself are a walking, talking inoculant. LAB also thrives within and all over you. So, getting stuck in and mixing vegetables by hand is a great way to introduce that tasty spark of life.
Cleaning and Safety
One of the most important things to get right in fermentation is cleaning and safety. If you handle raw animal products in the same kitchen as you plan to ferment, it's important to make sure you clean every surface and piece of equipment well, with hot soapy water. The goal here is sanitisation, which is to reduce the microbial population on the surface of objects to a safe level prior to fermentation. The word sterilisation is often used interchangeably with sanitisation, but to sterilise is to wipe out all microorganisms completely. This is important if you plan to use the same chopping board for raw meat and fermentation, and you can get products that make this process as simple as washing up. For the most part, I sanitise my equipment, such as glass jars and knives with hot soapy water, and scald fabrics with boiling water. I’m sometimes sceptical of over using sterilising products as there is always that 0.01% they claim not to kill. The same 0.01% that is so tough it can resist death now has no competition from the microbes we wiped out with the spray, and is free to multiply. So pick and choose what you want to use and when. For all the recipes I share around fermentation, I am very particular whether I use the word sanitise or sterilise, but you do whatever you’re more comfortable with. As long as you’re taking measures to make sure equipment is clean and dry, you should be fine.
I’m also obligated to write that fermentation is a living process. Despite doing everything right, sometimes, unexpected things can happen. In the case where a ferment grows mould, smells bad, or acts in a manner you don’t expect, don’t take chances with it. Throw it out and start again. If you’re nervous about this, let me reassure you. In my 12 or so years of fermenting, I’ve never had something go bad in a way that was damaging to health or led to food poisoning. The worst I’ve ever had was kahm yeast, a harmless but foul tasting yeast that forms a biofilm over the surface of some ferments.
Curious for MORE?
If you’re busy reading this newsletter thinking, “Man, it sounds like you should write a book on this stuff!” you’re in luck. I have. And it’s coming out in November (7th for the UK, 12th for the US and worldwide). Join me on a delicious journey through the microcosmos and learn how to wield other bacteria, a range of yeasts, and the national fungus of Japan. Experience the world of food like never before, with no need for expensive lab equipment.
If you’d be so kind as to preorder a copy using the link below, it really helps show booksellers around the world that there is a demand for this book and those like it. A rising tide lifts all boats.
And, if you’re new here and want to learn more about growing food, fermenting, recipes in general, and seasonal eating, consider subscribing to my newsletter.
Thank you for joining me,
I hope you have a great week.
Hi. I've ordered your book , but before it arrives I'd be interested to know if you know about and if you've compared the 2% salt with what we do here in eastern europe which is add 1 TBSP of salt which is 25
g to 1 litre of water. That's how we've done it for hundreds of years but we always use water to cover.
To keep the veggies under we cris cross dried sticks of dill and to preserve the crunch we use big amounts of horseradish and sour cherry leaves 🙂
Since following you I've also tried the no water variation and I liked it but I also been throwing away stuff as I didn't mange to use the weight and the parchment paper properly 🙄
Thank you
You inspired me this morning to start a jar of fermented salsa - I had all the ingredients just needing to be used up. I’ve always been a bit leery about the idea - something to do with salsa and tomatoes in the past that started to ferment on their own in an less-than-delicious way. But you’ve given me the confidence to try it, so thank you. I added whole coriander seed and minced preserved lemon, which as well as adding a lemony note I think should kick-start the fermentation. Do you agree?