Frequently Asked Questions
- Simple subtraction. Take a hydrometer reading right before you pitch the yeast into your must (see “How do I take a hydrometer reading?” in FAQs).
- Make a note of this reading, which should be in the range between 1.060 and 1.120, depending on the recipe and style you are making.
- After the fermentation is complete, take another hydrometer reading right before you bottle. This reading will usually fall between 0.090 and 1.010, again depending on the style of wine made.
- Then you simply subtract the second reading from the first, and consult a conversion chart (such as the one found in “First Steps in Winemaking”, or many other winemaking books) to determine the alcohol content. Let’s say that your starting gravity was 1.085, and your terminal gravity was 1.010. This makes a difference of 0.75. Looking this up in the conversion chart will tell you that your wine is 10.4% A.B.V. (alcohol by volume).
You’ve given the yeast a chance to start, but yet you still see nothing. At this point, this isn’t a cause for concern because there are many things that can help get the fermentation process started. Some options are very simple, while others can take some time.
It is best to follow these ideas in the order that they are written here so that you do not cause your wine problems by skipping steps.
- Move the wine to a warmer area to see if the yeast doesn’t kick in. Give it 24 hours before you move on to the next step.
- Create a yeast starter. To do this you need a packet of yeast, some juice from the fermenter, table sugar, and a glass. Make sure that the glass is sanitized. Add 16 oz. of the juice (2 cups), 1 tablespoon of table sugar, and the yeast to your glass. In roughly 15 minutes to an hour you should notice foam forming on top of the glass. This lets you know that the yeast is active and ready to go. Just pour the active yeast into your fermenter. DO NOT stir the yeast in.
Note: If you added your yeast and metabisulphite into your fermenter at the same time that is the cause of your problem. Metabisulphite needs to be added 24 hours prior to the yeast addition. Then add your yeast to the fermenter, but do not stir it in. Metabisulphite kills bacteria, but it also kills yeast.
- If all else fails you can do what we refer to as a reverse starter. How this works is that you start with a normal yeast starter, like the directions above. But instead of pouring the yeast starter into the fermenter, you add a little bit of the juice, or must, to the starter instead. So, you essentially need another fermenter to be able to do this. Start by making the yeast starter. Once that gets going, pour that and another 16 oz. of juice into a fermenter. Let that start fermenting. Then continue to add a ½ gallon to a gallon of juice at a time until the whole batch is fermenting. Be careful to pay attention to the amount of juice added at one time, because you are trying to overpower whatever is causing the yeast not to start. By adding a little juice at a time and letting that start to ferment, you are overcoming the issue.
Note: The reverse starter is a last effort to get the wine to ferment. Ninety-nine percent of the time, the wine will start to ferment before having to move on to this step. If you try this and nothing happens there is nothing else that can be done. Something major is causing the yeast to not start. This is usually due to large amounts of metabisulphite being in the juice.
Keep in mind that most issues are either due to too much acidity, or too much metabisulphite in the juice. Most times these issues can be overcome, but on very rare occasions you cannot get the yeast to start. When buying juice from the store, make sure the packaging doesn’t say that it contains anything along the lines of metabisulphite, benzoate, or sorbate. All three of these ingredients will cause you fermentation issues.
Why do I need to stabilize my wine before bottling? Can I bottle it immediately after it is stabilized, or should I wait seven days?
- Wine is stabilized to stop fermentation so that remaining yeast do not ferment added or residual sugar after bottling and cause the bottles to explode.
- After stabilizing, suspended yeast die off and lay down a thin layer of lees. If the wine has been bottled, the lees are trapped and are not only unsightly, but can impart off flavors.
- Our experience is that the dead yeast cells will precipitate out in 3-7 days. Allowing 7 days offers a 3-day margin of error, ensuring that all the dead yeast precipitates out.
- The wine is then racked off the lees, sweetened to taste and bottled.
Hydrogen sulfide (H2S) is the rotten egg odor you smell, and it usually forms at the end of fermentation. Most home winemakers won’t notice a smelly problem until the first racking. If you do smell rotten eggs, the quicker you can act, the better your chances of saving the wine. If your wine is not treated promptly, hydrogen sulfide will react with other carbon compounds in the wine to create mercaptans, and later into disulfides. These are extremely difficult to remove from your wine once they are present, so the faster you can detect and treat your wine for hydrogen sulfide, the better.
Many sources suggest that you add copper sulfate to your wine, but BREWERS DIRECT advises against this. While a very, very, VERY small amount of copper sulfate will take care of your H2S problem, it is poisonous. Big wineries use copper sulfate, BREWERS DIRECT suggests a kinder, gentler approach, using chemicals that most winemakers already have on hand.
- First, measure the level of sulfites in your wine using the SO2 Test Kit. If the wine is deficient, treat the wine to 50 p.p.m. sulfites.
- Next, rack the wine two or three times, making sure to splash it around a lot as the wine is transferred between vessels. This aeration introduces oxygen to the wine, and will help counteract the hydrogen sulfide.
- Replace the airlock, and let it sit overnight. This should take care of the problem in most cases, but if it still stinks, perform these extra steps:
- Buy a piece of copper flashing from a home supply store.
- Hold the piece of copper in the neck of the carboy while the wine is being racked, so that the wine runs over the copper surface and into the carboy. Fine and/or filter the wine.
- By now, that stinkiness should be greatly reduced. If you STILL detect a smell, try SUPER KLEER finings in the amount stated on the package.
- After fining, we suggest running the wine through a filter. The Vinbrite Filter, Buon Vino Minijet or Pressure Filter is fairly inexpensive, and works pretty well.
- If you’ve taken all of these steps to no avail, you could try using copper sulfate. But BE CAREFUL! Add NO MORE than 0.5 ml per gallon. Afterward, be sure to fine the wine with bentonite or Sparkalloid according to package instructions. Either of these will remove the copper sulfate. Then filter to remove the fining agent.
- Tannin is usually added to the must before fermentation begins, but this is not absolutely necessary. We add it to most non-grape wines before fermenting, but often adjust it upward by taste, just before bottling. This can be a delicate process.
- When the wine has cleared and is no longer forming sediments, sample it. The tannic bite is on the tip of the tongue and easily identified. If not adequate to your taste, add just a bit (1/16 of a tsp per gal) and gently stir with a glass rod or wooden dowel. Refit the airlock and let set about an hour and taste again. If still not adequate, add another 1/16 tsp per gal, stir, and let set another hour before tasting. If you think you’re almost but not quite there, add even less next time. By adding just a bit at a time, you’ll soon be able to taste the threshold you seek without a high risk of overdoing it. With most grape wines, it shouldn’t take too much to boost the tannin to your taste.
The amount of sulfite in a homemade wine is roughly 1/6 to 1/8 of the amount compared to a store bought bottle of wine. Some people believe that they are allergic to sulfites, and want to leave them out of their kits. While this is their option, it’s a bad idea. True sulfite allergies are extremely rare, and if someone has a reaction to drinking wine, it’s almost always due to some other cause. Besides… yeast produce sulfites themselves during fermentation, so no wine can ever be sulfite-free, no matter what.
Without the added sulfites, the kit will oxidize and can spoil very rapidly. It will probably start to go bad in less than 4 weeks, and be undrinkable in less than three months. Also, if the sulfite is left out, but the sorbate is added, the wine could be attacked by malolactic bacteria, which will convert the sorbate into the compound hexadienol, which smells like rotting geraniums and dead fish.
The bottom line is this: if you do not add the sulfite to the kit, BREWERS DIRECT can NOT guarantee the wine, so think carefully before you choose not to add it.
There are many things that can cause hydrogen sulfide contamination; all are preventable:
1. Too much sulfite, usually the result of grapes being dusted with too much sulfur during the growing season.
2. Lack of proper nutrients (nitrogen, yeast hulls) during fermentation.
3. Yeast combining with various forms of sulfur.
4. Bacterial contamination due to poor sanitation techniques.
That being said, here are the things you can do to prevent H2S contamination:
5. Add proper amounts of sulfites to wine.
6. If making wine from scratch (not from a kit), add a proper amount of yeast nutrient prior to pitching yeast.
7. Use proper yeast for the wine you’re making, and make sure it has not passed the expiration date or gotten too hot in storage.
8. Maintain sanitary conditions for your equipment and must (especially prior to pitching yeast).
By definition, a stuck fermentation is a fermentation that has stopped before all the available sugar in the wine has been converted to alcohol and CO2. If the bubbles in your airlock slow down before your wine has reached terminal gravity (usually 1.000 or lower), you may have a stuck fermentation. Were you to give up on the wine at this point, it would taste semi-sweet and pretty bad. Not to worry, there are ways to fix this. Before we get into how to fix it, let’s make sure that you have a stuck fermentation.
Here are a couple of ways to check:
Is the specific gravity of your wine no longer falling, or tremendously sluggish? If you take hydrometer readings for three consecutive days, and the reading remains the same and is higher than 1.000, it’s probably stuck. Make sure you have a good airtight seal at your airlock. Ensure that the airlock is firmly seated in the bung, and the bung is securely seated in the mouth of the carboy. If there was not an airtight seal, you would not see bubbles out of your airlock. Is the temperature of your fermentation area between 65 and 75 °F? If it is too cold, the yeast can’t do its job (or does it very slowly). Fortunately, stuck fermentations are pretty rare. But when they do happen, it’s important to make corrections right away and get the fermentation going again for optimum results.
Try the following tips to get that airlock bubbling again:
1. Simply move the fermenter to an area that is room temperature, or 68-70 °F. In most cases, too low a temperature is the cause of a stuck fermentation, and bringing the temp up is enough to get it going again.
2. Open up the fermenter, and rouse the yeast by stirring it with a sanitized spoon. Sometimes putting the yeast back in suspension will get it going again.
3. Add some yeast energizer to the wine. Add 1/2 teaspoon per gallon of wine, and stir well. NOTE: While it may seem like a good idea, Brewers Direct does NOT recommend adding yeast nutrient at this point. This may result in leftover vitamins that can stimulate spoilage microbes.
4. Rack the wine off of the old yeast, and pitch some fresh yeast in, preferably a highly active strain such as Lavlin EC-1118
5. If none of these tips get the fermentation going again, as a last resort, you can pitch a yeast starter. Do this by pulling a half gallon of must out of your fermenter. Add 1.5 to 2 teaspoons yeast energizer and a packet of yeast (Lavlin EC-1118). Stir this mixture up well, and place in a warm area. Once you see a vigorous fermentation, add it back to the original must.
- Wine kits are ready to bottle in 28 or 45 days. This does NOT mean that they are ready to drink. If you really, really can’t wait, the minimum time before a kit tastes good is about one month after bottling. This is long enough for the wine to get over the shock of bottling, and begin opening up to release its aromas and flavors.
- Three months is much better, and the wine will show most of its character at this point.
- For most whites, however, and virtually all reds, at least six months is needed to smooth out the wine and allow it to express mature character. Heavy reds will continue to improve for at least a year, rewarding your patience with a delicious bouquet.
- If you can have some patience, you will be rewarded. Time is definitely the “magic ingredient” in wine. Many home winemakers will add a couple of glass carboys and an additional primary fermenter to their home winery, enabling them to have several batches fermenting at once.
- Since wine takes a while to be ready to drink, having multiple batches going all the time will help fill your wine cellar in no time.
- You can accomplish this by making 2 to 3 batches per month. Each batch will take three to six months or more before it is ready to drink. If you start with a wine that does not require extended aging, and you made two batches every month, you would have about 60 bottles of wine ready to drink, every month, starting three to six months after you made your first batch!
It isn’t unusual for a homemade wine to be a little dry because we simply add the yeast and let it ferment. A winery will take measurements throughout the fermentation process and will stop the fermentation when they believe the wine is at the correct sweetness level. If your wine is a bit dry for your liking, then we’ll show you how to sweeten it up.
Wine conditioner is a product that is very easy for wine makers to use because you don’t have to worry about any sugars. Wine conditioner is simply a non-fermentable sugar, water, and sorbate. Look at it as an all-in-one solution for your wine. You want to use this product just prior to bottling for best results. We do not recommend adding any sweeteners until you are almost ready to bottle. The reason is because wine will change dramatically from month to month when it is very young. The alcohol bite that some people believe is making the wine dry will mellow out, and the wine might be just fine for you. Adding the sweetener in too early could leave you with a very sweet wine later on. Hint: Re-rack your wine before adding the wine conditioner so you don’t need to worry about stirring up sediment. All you do is add a little wine conditioner at a time, stir, and taste the wine. When it tastes good to you, go ahead and bottle. There is no set amount to add as every person has a different idea on what a wine should taste like.
Brewers Direct carries a red or white wine concentrate that you can use to sweeten your wine as well. There is one major difference when using these versus the wine conditioner: grape concentrate still has fermentable sugars in it. You want to make sure that you use metabisulphite before using this product as the sugar can activate the yeast, which will ferment the sugars and remove the sweetness to your wine. Some wine makers will add a second dose of metabisulphite to try and kill all of the active yeast cells in their wine. Both of these concentrates can be added just before bottling time. They are already filtered, and will not leave sediment in your wine. Just add a little at a time, stir, and taste. Just like wine conditioner, each person’s taste will vary, so add as much as you like.
**Brewers Direct recommends filtering your wine after sweetening with wine conditioner to avoid cloudiness developing in the wine. Cloudiness often happens after using conditioner, but can be avoided by filtering immediately after sweetening. (If cloudiness does develop, and you haven’t filtered, it is almost impossible to get rid of later, even with multiple filtering)
If your wine is clear, stable, and free of CO2, it’s ready. Clear means free of particles that could later fall out of suspension and leave a deposit in the bottles. Stable means finished fermenting and with enough sulfites (SO2) present to prevent oxidation and spoiling. Free of CO2 means that although the fermentation may be finished, a wine can still be saturated with carbon dioxide. If it is, it will go into the bottles with the carbonation intact, and depending on the conditions, could expand and push the corks out (or worse, break the bottles), or provide you with the dubious pleasure of drinking a sparkling wine that’s supposed to be still (sparkling Merlot, anyone?). To get rid of CO2, stir your wine.
The Fizzex (or Wine Whip) is an excellent tool for this purpose. When the fermentation is finished, most people add fining agents, and this is when vigorous stirring is called for. Like shaking up a soft drink, vigorous stirring chases the bubbles out and not only prevents the wine from being fizzy in the bottle, but also helps the fining agents to work better. If you’re not using fining agents, make sure your wine is free of CO2 before bottling.
Back in December I made some ice wine. It turned out great – beautiful color and had a great taste. About a week or so after I bottled it, sugar crystals settled in the bottle on the side. What’s wrong?
The crystals are potassium bitartrate. This is excess tartaric acid that is precipitating out. Potassium in the grape combines with tartaric acid to form a soluble potassium bitartrate. The solubility is reduced further by increased alcohol and the result is precipitation of crystals. If you chill the wine for a week or so, even more crystals will form.
These will not actually hurt the wine, but are unsightly and a nuisance to get out of the bottles once emptied. You have two choices. One, you can open the bottles and very gently transfer the wine to new bottles, or two, you can leave the wine alone and decant it before drinking. A chilled wine will take up less oxygen than a room temperature wine.
To prevent this from happening next year, cold stabilize the wine for two weeks or so before bottling it.
We always rack after five weeks of fermentation. The S.G. is generally between .992 and .995. What are the down sides of leaving it longer than five weeks? What are the benefits?
The indicator for the preferred dryness is the hydrometer. Each juice (properly termed must) is always a different entity. Five weeks is definitely too long to leave the fermentation. After 8-10 days of fermentation at room temperature 21C (72 F), your SG will be very close to 1.000, if not already below this. Now is the time to rack off the wine from the sediments. The prompt removal of yeast cells from new wine is desirable; this protects the wine from nitrogenous substances released both by excretions of the living yeast cells and the autolysis of dead cells. Nitrogenous excretions increase after the death of the yeast when autolysis (self-digestion of cellular constituents) occurs. Autolysis liberates strong reducing enzymes and produces compounds unpleasant to the taste and smell, but also favour the growth of lactic acid bacteria and so render the wine more susceptible to bacterial spoilage.
Filter pads should be soaked in cold water for 10 – 15 minutes before fitting them into your filter. It is also important to filter 1 – 2 gallons of cool water before beginning to filter your wine. This helps to remove any paper taste that you may get from the filter pads and allows you to check for proper assembly and leakage BEFORE you begin to filter your wine.
No matter how much I stir, I still have foam on my wine. How can I tell if my wine is really degassed?
If you follow the wine kit directions faithfully, which generally say to stir vigorously three times a day for three days with the handle of your spoon, you should have no gas left in your wine after three days. Other effective methods include transferring your wine into a primary fermentor and then pouring it quickly back and forth into another primary several times; siphoning your wine into the primary and stirring vigorously with your spoon as it fills the pail; using a Fizzex tool on your electric drill, and so on. To be sure that your wine is properly degassed, taste the wine – it should not be “prickly” like flat pop. Another way to tell if your wine is properly degassed is to take about a half bottle of the wine you are degassing, seal the bottle with your thumb or a removable cork and shake vigorously. If there is gas it will hiss out when you release the seal. If it is still gassy, continue to degas until you are satisfied that there is no gas left
Banana powder or flakes added to your wine in the primary fermentor will increase the body of a wine without conferring an obvious banana flavour.
Consumers think they need to be concerned about the water they use in winemaking. TRUE. Local municipal water is not suitable, mostly because of the high levels of chlorine. For the best results, you should use filtered, or REVERSE OSMOSIS water. If you have to use tap water, fill your primary fermentor and leave it out for 24 hours to allow the chlorine to evaporate.
The reason for adding the oak to boiling water is to be sure that there are no bacteria present before adding it to your wine. You wait 15 minutes to allow it to cool and then add the entire mixture.
Many people think that if they do not see any bubbles in the airlock that this means the wine is not fermenting. This is not true. Bubbles in the airlock are just CO2 escaping from the wine. If there are no bubbles in the airlock it could mean that your wine is not fermenting but it could also mean that the CO2 is just leaking out from another spot.
The ONLY TRUE way to know whether your wine is fermenting is by using the hydrometer. By taking an initial reading and then taking more readings on a regular basis throughout the fermentation, you will be able to see if the Specific Gravity is moving and this will tell you if your wine is fermenting or not.
In the instructions you are told that your wine is finished when the SG has reached .996 – .990. This is a range and you will know when it is actually finished when you have a reading in this range that remains constant for 2 – 3 days.
Filtering is not mandatory. We do however recommend it. By filtering your wine, you give it an extra polish and more professional finish. You will be sure to have a brilliantly clear wine with a crisp clean taste. If you do not filter, you should be aware that it is possible to have a fall out in your bottles at a later date.
IMPORTANT! Please ensure that the yeast is added properly. More experienced wine makers refer to adding the yeast as, “PITCHING” the yeast. Winemakers should follow the instructions found in all the winemaking kits to get the best fermentation results. For a quicker start to the fermentation, you can opt to follow the instructions on the back of the yeast pack.
During the fermentation, your wine will become gassy. Every wine kit will be a little different in regards to the amount of gas (CO2) that will develop. A very gassy wine will of course take longer to degas than one with less CO2 in it. CO2 will come out of your wine much more easily at warmer temperatures. Therefore, it is a good idea to keep the wine at a higher temperature during this step. Usually a wine will degas within one day but sometimes it can take as long as three days. The important thing is to continue the stirring process periodically until you see no more visible signs of gas or gas bubbles. Now you can lower the temperature for the clearing process.
In our wine kits the #4 Sorbate pack should ONLY be added to the wine if you are adding a sweetener before bottling time. If you will not be sweetening your wine, DO NOT add the Sorbate pack.
Specific gravity or density is actually just a measurement of how dense (or thick) a liquid is. The density of water is 1.000. When you start your wine it is full of unfermented sugars that are quite dense so your specific gravity is high (between 1.075- 1.090). As the wine ferments and the sugars are changed into alcohol, the density of the wine drops steadily. A finished wine should be between .996 -.990.
The best way to accomplish this task is as follows: Boil water in a small pot. Put the capsule on the top of the bottle and hold it in place with a wooden spoon. Turn the bottle upside down and immerse the top of the bottle into the boiling water. Within a fraction of a second, the capsule will shrink to form a tight fit on the bottle.
Some big full bodied red wines need to be opened an hour or so before drinking and poured into a decanter or jug. Taking the cork out and leaving the wine in the bottle does not do much as there is very little air contact in the neck of the bottle. Generally speaking though, most wines can be drunk immediately on opening. If you have run out of time and you feel your wine needs air contact (breathing) then pour the bottle (from a height) into a large jug and back into the bottle again – good aeration happens here.
The perceived wisdom is that red wines are enjoyed more when un-chilled. Chilling a wine does tend to kill the delicious flavours. You should never chill any of the more full bodied reds (e.g. those made from Cabernet Sauvignon or Pinot Noir), but a slightly chilled Beaujolais or Valpolicella can be delicious on a warm summer afternoon!
It is recommended that you chill white wines before drinking. Make sure that you don’t over-chill because, again, some of the important flavours will be hidden by the cold. In the end it’s your choice, but the important thing is to ENJOY IT!
Once grapes have been crushed and the ‘free run’ juice has been taken off for fermentation, the grape skins and pips remain as surplus to requirements. There are two main ‘outlets’ for this waste which is known as pomace. You can imagine that it is rich in protein and other nutrients . . . ideal, in fact for animal feeds. The pomace is packed into ‘cakes’ and sold off for this purpose.
Alternatively, mixed with a little wine the pomace can be distilled. The resulting brandy is a little fiery in character, and certainly an acquired taste! The Germans call it Trester, the Italians—Grappa—and the French—Marc.
Can old bottles of wine present a health risk? Also, how can I distinguish if a bottle of wine is tainted?
It is highly unlikely that any wine can present a health risk. The enjoyment of wine is a very subjective choice. Some wines were made to mature into their best, and others should be at their most delicious when young. But this decision is down to you.
If uncertain on a suspect wine, open the bottle in the right conditions, pour a little into a glass, and have a big old sniff! If the wine smells good then it will taste wonderful, but if the smell is horrible then the wine is probably past its best or has a taint of some kind. Visit Tainted-Wine.com to pick up some guidance on what to look for in unhealthy wines.
Red wines and some white wines need to age in order to reduce harsh acidity or tannins, and develop smoother, more drinkable characteristics.
There are two separate ways that wine can age: Barrel and bottle aging. Barrel aging is called “oxidative,” and uses contact with oxygen to encourage reactions between the acids, sugars, tannins and other complex chemicals in the wine. Bottle-aging is “reductive,” slowly using up the available oxygen between the wine and the cork to develop more complex, subtle flavors. Both processes are needed to achieve the ultimate quality of a fine wine.
It could be one of two things;
B. Tartaric acid crystals: a harmless malady that forms after the bottle has not been properly stored. or, C. Black tannic deposits: a deposit of tannin and other colored materials that form after years of aging. Affects mostly red wines, and is not a sign of bad wine.
There are other maladies that can affect wine’s quality, but they are very rare.
Wine has numerous vitamins: Vitamin C, Vitamin B2, Vitamin B3 and Vitamin P. On November 17, 1991, the TV show 60 Minutes aired a segment called “The French Paradox”. The show talked about how the French eat lots of fat, smoke unfiltered cigarettes and rarely exercise, yet they have one of the lowest heart attack rates in the world. Their consumption of red wine was given as the main reason for this phenomenon. This 60 Minutes segment virtually turned around the wine industry in the United States, and prompted hundreds of studies looking into the actual cause of this. Thus, numerous articles have emerged with proof revealing that people who consume moderate amounts of alcohol (no more than 2 drinks a day) have fewer heart problems than either alcohol abusers or non-drinkers.
The positive effect of alcohol appears to be “related to an increase in serum HDL (the “good” cholesterol), a decrease in serum LDL (the “bad” cholesterol) and inhibition of arterial blood clot formation.” But some studies have singled out wine as the best alcohol to drink, because of something called flavonoids, which are present in fruits, vegetables and red wine. A French research team wrote: “Wine, as compared to spirits, seems to supply natural antioxidants that inhibit the rebound effect, preventing the clumping of blood platelets in the arteries that can cause heart attacks.” Recent findings are stating that alcohol may even help prevent osteoporosis by increasing bone density.
Wine starts to deteriorate when oxygen hits it. Generally, a wine will last about a day if left opened in a kitchen, and up to three days in the refrigerator.
There are some inexpensive gadgets you can buy to preserve wine for longer periods of time. For instance, the Vacu -Vin system uses rubber stoppers and a pump-suction system to remove the oxygen from the bottle. The system will keep a bottle fresh for a couple of weeks and because of its new-found popularity, you can find it lots of places.
There are systems a little more expensive such as Private Preserve that involve inert gases and others that are geared more towards the professional or serious wine drinker, so ask your local wine merchant for advice about these.
Wine juice is sterilized at high temperatures for a short contact time (meaning seconds – for this reason it is referred to as “flash”). Sterilization kills any micro-organisms present (including cells and spores) – and the product, once sterile will be sterile forever up to the point of the opening of the juice package.
Flash sterilization preserves the flavour, taste and aroma of grape juice.
Furthermore sterilization brings to zero any risk of fermentations in the bag, and allows a better and safer fermentation, when needed, because any eventual wild yeast has been killed. This means it improves indefinitely the shelf life.
Pasteurisation is a process where the temperatures are usually lower but the product is under heating for a long time (not seconds like the flash sterilization). Pasteurisation REDUCES THE MICRO-ORGANISM BUT DOESN’T KILL ALL OF THEM. So a product that is pasteurised in not sterile at all and can have micro-organisms that can develop a second time.
Further to this, the long contact time burns the aromas and gives the taste of a typical “cooked aftertaste”. In the case of a wine kit another negative effect is on the colour – the colour will change very quickly with age giving to the white the typical gold/brownish tone and in the red the flat/brownish tone that has nothing to do with a real wine.
This means in short terms that whatever raw material you use – juice or concentrate or both – the pasteurisation process would have a heavy and negative impact on it. This would also become worse and worse with the passing of time.
Shorter contact time + aseptic filling
Low impact on the product
Longer shelf life
Sterilization kills ALL micro-organisms
Longer contact time
Deterioration of the product
Shorter shelf life
This is a question which we get from time to time, and we can say with the utmost confidence that it is virtually impossible for your wine juice to become mouldy in such a short period of time. What you are in fact seeing is the beginning of the normal fermentation process of wine. At the start of the fermentation process the yeast becomes very active and the wine may even have the appearance of boiling.
Sometimes however it is not that active and the surface of the wine must looks all greyish-brown and bubbly; in fact it looks like a swamp or a bog. In red wines you may not see the colour, but the appearance is the same – just like a bog. There is also a sharp, almost disagreeable odour which is produced by the fermenting yeast. It is, in fact, carbon dioxide which is a natural by-product of fermentation.
The grayish colour is due to the bentonite which you may have put into your must to help fermentation and clearing, and the yeast which is beginning to die off as the alcohol level begins to rise. There is nothing wrong with wine which has this appearance. Often you don’t see this because you are not looking at the right time. By the time most of us look at the wine juice, this stage has passed and what we may see is a ring of grayish muddy looking stuff around the pail and on the underside of the lid or plastic sheet that you have used to cover the pail.