Mead too sour/acidic

Did my first batch of mead, using natural yeast, and it taste ok except that it's too sour... I stirred it every day, following the instructions of Zimmerman's video, "Make mead like a viking", haven't got his book yet, but planning to buy it.
Maybe also one reason to the problem is that in the same room I have a Kombucha brewing, so maybe some of the yeasts from it might have influenced the mead? Been doing Kombucha for 20 years, never had a bad batch, and so thought it would be the same with mead, but this it different, and need to learn more about it. Any suggestions? The taste in not bad, and not bitter nor tart, just too sour.

When you say "using natural yeast" did you leave the mead uncovered for a period of time for native airborne yeast to fall in and inoculate your mead? How old is your mead? I've made meads before, and when they are young they will have a certain astringency that could be interpreted as sour, but this astringency will fade with time. I used to brew a lot, and it was generally understood that young meads may not be very palatable, and they need to age a year or more to mellow out. I once made a Cyser that was pretty harsh at the beginning but mellowed quite a bit after a year, and after two years was pretty nice. I managed to save a few and they made it five years, and they turned out quite pleasant.

Stirring eh? Seems like that would introduce oxygen, which is just the thing that vinegar or kombucha mother needs for growth. Which would lead to creation of acids in the mead.  Alcoholic fermentation is typically done anaerobically.

OK, so I used yeast naturally occurring from air and a few pieces of apples and raisins (wild fruits/berries are the best, but there aren't any this time of the year around here).  I used a thin piece of cotton on top of the jar, and stirred once a day. I didn't know that one was supposed to be ageing mead. I've just bottled it some days ago. I followed the instructions of Zimmerman, and he says that one has to stir... But I am open to different ways: Joseph, you say I should do it anaerobically, does it mean I need to make sure no air comes in? So I need some special equipment...

Wine is typically made in the absence of oxygen, because oxygen feeds vinegar bacteria. Oxygen is kept out of the ferment using bubblers, or balloons, so that the gasses can escape without pressurizing the vessel and leading to an explosion.

Wine is turned into vinegar by exposing it to oxygen. Some vinegar recipes expose the ferment to air all along, so that alcohol and vinegar are made simultaneously. Other recipes separate it into a two step process: Alcohol first, and then vinegar.

A bit of oxygen is useful early on to get the yeasts growing well, but later in the process that can encourage the growth of acid-producing bacteria.
https://www.northernbrewer.com/connect/2011/09/stirring-aeration-and-mead/

Natural yeast inoculation can result in quite unique ferments, sometimes tasty, sometimes downright unpalatable, but often unpredictable and some breweries prefer to use the wild yeasts native to their region. Some Trappist breweries in belgium, like Westmalle, use wild yeast which create all sorts of unique phenolic compounds, which we taste and make the resulting beer as unique as those particular wild yeasts that occur only in that region of the globe. Doing open ferments, allowing wild yeasts to populate a wort or mead, often results in a more sour beer. Belgian lambics are sour due to open fermentation by native wild yeasts. And open ferments mean that not only are wild yeasts inoculating and populating a wort or mead, bacteria are as well, and they can throw some pretty sour notes. Some craft breweries intentionally make sour beer using brettanomyces, which is one of the yeasts that give lambics their unique sour notes.

As far as stirring goes, gentle stirring post fermentation is largely for degassing. Often degassing is adequately achieved in racking beer/wine/mead a few times, or transferring by siphon from one container to the next. Racking is a good practice, as it removes the fermented beverage from the trub that’s settled on the bottom of the vessel, which is largely dead yeast and a little other particulate matter which can impart funky flavors if left in contact with the fermented drink too long.

Oxygen at the beginning, before yeast is introduced, is very important for yeast cells to populate and create healthy daughter cells. Once fermentation begins, which can happen in as little as a few hours after introducing yeast, oxygen becomes the enemy and introducing more oxygen will often ruin alcoholic beverages. Like Joseph mentioned, one-way airlocks are often used as an assurance to prevent not only oxygen from entering the top of fermentation vessels, but it also prevents other undesirable microbes from entering and ruining a controlled fermentation.

Ok, thanks Joseph and James for the useful info... I don't mind that much that sour taste, but as I already have my kombucha, I'd like something else that is not that acidic. I could try the open air fermentation for a short time, and then seal it from oxygen with the one-way airlock.
Or, a commercial yeast could be one other option. What type should I use? Are commercial yeasts natural products, or do they have some nasty hidden ingredients?

Lana Weldon wrote:Ok, thanks Joseph and James for the useful info... I don't mind that much that sour taste, but as I already have my kombucha, I'd like something else that is not that acidic. I could try the open air fermentation for a short time, and then seal it from oxygen with the one-way airlock.
Or, a commercial yeast could be one other option. What type should I use? Are commercial yeasts natural products, or do they have some nasty hidden ingredients?

When I made meads and wine and brewed beer, I always chose to use commercial yeasts, and they are a natural product. The liquid live yeast cultures don't contain anything nasty. I've used Wyeast and White Labs. I used "commercial" yeasts because they are isolated strains with known flavor profiles and are guaranteed pure. They're a great way to get a quality ferment.

Based on your methods, you most likely have inoculated the mead with lactic acid bacteria. Every time you stir the mead, you introduce more oxygen which benefits the propagation of the bacterial colony.

BTW, yeast will only produce alcohol in an anaerobic environment. When you stir the mead and introduce air, the yeast will consume the sugars and simply reproduce and multiply. You will end up with lots of yeast and very little alcohol, which also reduces the preservative qualities of the finished mead.

Nick Kitchener wrote: When you stir the mead and introduce air, the yeast will consume the sugars and simply reproduce and multiply. You will end up with lots of yeast and very little alcohol, which also reduces the preservative qualities of the finished mead.

Sorry, but this is not really true. Yeast multiply and create daughter cells using nitrogen and amino acids and oxygen, along with other simple peptides. Once a yeast has populated and consumed the available oxygen, healthy yeast cells take in sugar, such as glucose for example, and produce ethanol and CO2. It’s called the Embden-Meyerhoff-Parnes pathway or EMP in brewing studies. Using glucose, it looks like this: C6H12O6 (glucose) --> 2(C2H5OH) (ethanol) + 2(CO2). In no way do brewing yeasts consume sugars only to reproduce. There is one exception, which is not limited to cell reproduction, and that’s with Saccharomyces ludwigii, which can metabolize sugars but will not produce ethanol.

Introducing oxygen post fermentation makes beer stale, can feed undesirable bacteria, and can oxidize compounds. For example, ethanol can become acetaldehyde with oxygen: 2 CH3CH2OH + O2 --> 2CH3CHO + 2H2O