Why yeast

My father of italian origin has been making perfect wine for years and has not once used yeast. What is the purpose of adding yeast? What does it do?

Richard Sulfaro

Reply to
Richard Sydney
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It turns sugar into alcohol. And it's *impossible* to make wine without it.

Your father is getting yeast from somewhere. Not necessarily buying it from a winemaking supply outlet, mind you: he may be depending on wild yeast (which are literally everywhere), he may be starting fermentation of each batch with yeast from the lees of the previous batch, or even fermenting his wines in a wooden barrel that's become impregnated with yeast over the years -- but he's using some kind of yeast from somewhere.

Reply to
Doug Miller

There will always be some yeast spores...of some kind...on the grapes. Introducing a cultured wine yeast gives you a better chance of obtaining a pleasant and predictable wine....the wild spores may make great wine, but may just as often not make good wine.

Truenorth

Reply to
Truenorth

Hello, I am also Italian and most of my relatives still do NOT add any yeast to their crushed grapes. There will always be wild yeast present in all fruits. The crushed grapes always start fermenting on their own. The wine will be noticeably better with the addition of store bought yeast. I assume that the wild yeast will still grow and reproduce along with the cultured yeast. You may want to add campden tablets to the crushed grapes to kill off any wild yeast spores present before adding cultured yeast just to be sure. Most wine made by leaving the crushed grapes alone produce good results. However, most of the problems arise from improper cleanliness and oxidation, turning a good wine bad rather quickly. The old school vintners are hard to change in their methods :-) My father used to use an old oak barrel to ferment his grapes in. The old (15 years++) wood harbored many a bacteria and usually produced bad wine. It took years of convincing to switch to a plastic fermented that was sterilized!!

Reply to
Alfonse

Saying it that way seems to imply that wild spores will make great wine and a packet of yeast will make somewhat less great wine. In fact most of the purchased yeasts are cultured exactly because they create great wine. IMO, you probably have a chance at creating as great wine with wild spores as you do with cultured yeast but doubtfully better and almost assuredly worse. Unless the area the grapes came from is "ripe" with a great natural yeast and then it's still a crap shoot.

Don

Reply to
Don S

Reply to
donny

fermentation,,,,,com.

That's inaccurate. Grapes do not "make" yeast. The waxy white coating on the grape skin (called the bloom) causes airborne yeasts to adhere to the grapes. When the grapes are crushed the yeasts come in contact with the juice, which renders them active, resulting in fermentation.

If you're lucky, the fruit will have "caught" a friendly strain of yeast and the wine will turn out OK. If not there may be a serious problem with excess production of volatile acidity by competing spoilage organisms.

Sounds like grampa has been lucky.

Tom S

Reply to
Tom S

There is so much I disagree with in this, I don't know where to start.

1) Grapes do not "make" yeast. There may be wild yeasts present on the grapes, but it may not give the characteristics you're looking for. 2) Speed is not the only reason cultured yeast is used for fermentations. Certain yeast strains are used to promote specific characteristics in the finshed wine. It also reduces the chance of stuck fermentations. Some yeast strains consume more malic acid than others. The list goes on and on why cultered yeasts are used. 3) Cost. $1 for a packet of yeast is a small price to pay for piece of mind.

Yes, there are commercial wineries that do not add yeast. Most of these have been around for a long time and the vineyard and winery have a dominant strain all over the place. This strain works for them to create the style of wine the want.

There are also many commercial wineries, even in "the old world", that use cultured yeast to insure the strain they want is the dominant one in the fermentation.

In home wine making, relying on wild yeast is a crap shoot.

Andy

Reply to
JEP

A lot depends on where the grapes come from. If the grapes are from an area where grapes have been grown and wine has been made in the vineyard for many years, then probably a good wine quality yeast is the dominant yeast growing on the grapes. If the grapes are from an area new to growing grapes or where few grapes are grown the other wild yeasts are probably the dominant yeast growing on the grapes. Adding a good strain of yeast to the must is just insurance. Insurance is purchased, or not, at the discretion of the individual. Some people are luckier than others.

Ray

Reply to
Ray

One issue that has not been brought up is "YEAST FINNING" (All Reds). This is a technique used to increase the amount of phenolics donated to the wine fom yeast. Commercial yeast or wild yeast may be used for the primary fermentation, but active yeasts are added to the wine after dryness to increase mouthfeel and reduce bitter and astringent flavors. When the active and rehydrated yeasts are added they will produce polyphenols as the lyse and eventually fall out of the mixture to settle at the bottom of the tanks. The wine should be left on these dead yeasts until maturity is obtained. This "fining" should take place after an appropriate aging period. Note: Be careful to monitor any VA as the yeast will become a nutrient source for any opportunistic spoilage yeasts or bacteria. One of the most predominant American wild yeasts Kloeckera Apiculata also has high VA levels, so I also recoment that primary fermentations use comercial, low VA yeasts with proper nutrition. A good strain for yeast fining is Lalvin D254

Reply to
Zack S

I would have thought the the reason for using commercially produced yeast over naturally produced yeasts is that the results are more controlled and the alcohol produced of as know type (i.e. ethonol). Certain types of alcohol are toxic to humans and I believe these types can be produced by using wild yeasts (In some circumstances).

Allowing wild yeasts to be used in your ferments can produce unpredictable results leading to stuck ferments, off tastes and Volitile Acidity problems.

I know of many people who only rely on wild yeasts to ferment however I have never had the bottle to experiment and waste a once a year opportunity by taking a chance.

Lets face it, many older italian winemakers produce superb wine one year and average the next. Isnt it all about being consistent year after year...?

AB1

Reply to
ab

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