All About Kombucha & Sugar

Kombucha is a fermented tea drink that is made by adding a culture of bacteria and yeast, known as a scoby (symbiotic culture of bacteria and yeast), to sweetened tea. The scoby feeds on the sugar in the tea, producing beneficial acids, enzymes, and other compounds that give kombucha its characteristic flavor and health benefits.  If you were to compare kombucha to the human body, the sugar is like the calories your body needs to function -- and the tea is like vitamins and nutrients. That means a sugar source of some kind is an essential ingredient in kombucha, as it is the primary source of food for the bacteria and yeast in your brew -- "the bugs". Without a sugar source, the bugs can't ferment the tea and produce the acids and other compounds that give kombucha its flavor and health benefits.  While normal table sugar or organic sugar are the most common sugar sources for kombucha, kombucha can also be made with other sugar sources, such as brown sugar, dextrose, honey, agave nectar, and fruit juice.  These alternative sources can provide unique flavors and mouth feels to the brew -- and can even effect health benefits to kombucha, as some likely encourage the production of desired acids and compounds more than others. But before we talk about them, first we need to understand the difference between sucrose, fructose, and glucose -- which are the types of sugar the bugs can eat.

What's the difference between sucrose, fructose, and glucose?

Sucrose, fructose, and glucose are all types of simple sugars that are commonly found in sweeteners and foods. These sugars are the primary source of energy for the body, and are also the primary source of food (and fermentation) for the bugs in kombucha. Sucrose is a disaccharide, or a double sugar, composed of two monosaccharides -- glucose and fructose -- that are bonded together.  Sucrose is commonly found in white sugar, which is made from sugar cane or sugar beet juice.  Sucrose is fermented by the bacteria and yeast in the scoby, and can provide a consistent and slightly sweet flavor to kombucha.  So when you're feeding your brew white or organic sugar, you're feeding it both sucrose and glucose. Fructose is a monosaccharide that is commonly found in fruits, honey, and agave nectar.  Fructose is slightly sweeter than sucrose, and can be easily fermented by the bacteria and yeast in the scoby.  Pure fructose can add a mild and slightly sweet flavor to kombucha, and can also provide additional aromas and flavors vs white sugar. Glucose is a monosaccharide that is commonly found in starchy foods, such as bread, pasta, and rice. Glucose is less sweet than sucrose or fructose, and is more easily used by the body (and the bugs) for energy.  Glucose can be easily and cleanly fermented by the bacteria and yeast in the scoby -- and while less commonly used, in our opinion produces outstanding kombucha -- significantly faster than sugar.

What's the difference in the way bacteria and yeast consume disaccharides vs monosaccharaides?

Bacteria and yeast in the booch consume sugar in different ways, depending on the type of sugar present. In order to consume disaccharides, the bugs must first break down the disaccharide into its individual monosaccharides using enzymes. The bacteria and yeast can then consume the individual monosaccharides for energy and fermentation. Monosaccharides, such as glucose and fructose, do not need to be broken down to be consumed by bacteria and yeast -- meaning the bacteria and yeast can directly consume monosaccharides for energy and fermentation. Bottom line: disaccharides must be broken down into monosaccharides by enzymes in order to be consumed by bugs.  Monosaccharides, such as glucose and fructose, can be directly consumed by them.

What does this mean for kombucha brewing?

This means that the type of sugar used in kombucha brewing can affect the fermentation process and the flavor of the kombucha. Disaccharides must be broken down into monosaccharides to be consumed by the bugs -- this process can take a little longer and may result in a slower fermentation rate and a slightly different flavor compared to using monosaccharides.  Monosaccharides can be directly, so this can result in a faster fermentation rate and a more consistent flavor compared to using disaccharides. Monosaccharides can also provide unique flavors and aromas to kombucha, depending on the type of sugar used.

What sugar sources can be used for kombucha brewing?

In short, anything that contains a high percentage sucrose, glucose, fructose, or a combination of them, you can give a try.  But here's some of the most common options:

• White sugar:  White sugar is the most commonly used type of sugar in kombucha, as it is readily available and provides a consistent source of food for the culture.  White sugar is highly refined and consists mostly of sucrose.
• Raw organic sugar (organic evaporated cane):  Raw sugar is a type of sugar that is made by refining sugar cane or sugar beet juice.  Raw sugar is less refined than white sugar, and contains more nutrients and minerals, as well as a slightly more complex flavor.
• Honey:  Honey is a sweetener that is made by bees from the nectar of flowers.  Honey contains a variety of sugars, including glucose and fructose, as well as other compounds that add unique flavors and aromas to kombucha. Honey can also provide additional health benefits to kombucha, such as antioxidants and anti-inflammatory compounds.
• Agave nectar:  Agave nectar is a sweetener that is made from the juice of the agave plant.  Agave nectar contains mostly fructose, which can be easily fermented by the bacteria and yeast in the scoby.  Agave nectar can add a mild and slightly sweet flavor to kombucha, and may provide additional health benefits.
• Brown sugar:  Brown sugar is a type of sugar that is made by mixing white sugar with molasses. Brown sugar contains slightly more nutrients and minerals than white sugar, and can add a slightly sweet and slightly caramel-like flavor to kombucha -- it also increases the funk.
• Fruit juice:  Fruit juice contains a variety of sugars, including fructose and sucrose, as well as other compounds that can add unique flavors and aromas to kombucha.  Fruit juice can also provide additional nutrients and antioxidants to kombucha.
• Dextrose:  A monosaccharide commonly used in food and beverage production.  Most dextrose is made from corn and is chemically identical to glucose.  Dextrose (in our experience) is the most easily fermented by the bugs and produces outstanding kombucha.  In addition to its fermentability and finished product, dextrose also has several other benefits for kombucha brewing.  Dextrose is a readily available and inexpensive sugar source with no additional flavors or aromas, which can make it a good choice for kombucha brewers who want the most control over their flavor profile.

Can you tell which one most of us here at the brewery think is best?  Hint: it may be listed last, but it's certainly not least!

Do I need to use an organic sugar source for my kombucha?

Kombucha does not require the use of an organic sugar source specifically.  Any type of sugar containing a high percentage of sucrose, fructose, glucose, or a combination of the three can be used in the brewing process.  Whether or not to use organic sugar is a personal choice that depends on your preferences and priorities. Using organic sugar may be important to some, but other people may not be as concerned about this and may choose to use a different type of sugar instead.  We use organic products here at the brewery, but the most important thing is to use a pure, unadulterated sugar source that will provide the necessary food for the bacteria and yeast in the brew.

How does adding more or less sugar affect the taste of kombucha?

The amount of sugar added to kombucha can affect the taste of the finished product in several ways, and like with most things kombucha, the answer isn't exactly clear cut. Generally speaking, increasing the amount of sugar in the kombucha will make it sweeter -- but there's a caveat.  Remember that because the sugar is fermented by the yeast and bacteria in the kombucha, and the more sugar that is present, the more that can be fermented and converted into alcohol, acids, and other compounds.  So increasing the amount of sugar in the kombucha can also result in a more intense fermentation process. This means that often times using less sugar can actually produce a sweeter kombucha -- or at least one that is perceived sweeter by the taste buds.  The key is trying different amounts of sugar and fermentation times to figure out what you like the best.  Remember that keeping good records in a log is essential for brewing consistent pro-quality kombucha.

Why should I always dissolve my sugar, heat it, and cool it before adding it to my brew?

It is important to dissolve sugar in water, heat the mixture, and cool it before adding it to kombucha for several reasons:

1. Dissolving sugar in water ensures that the sugar is fully incorporated into the liquid and evenly distributed throughout the kombucha. This allows the yeast and bacteria in the kombucha to access and ferment the sugar evenly, leading to a more consistent and predictable fermentation process.
2. Heating the sugar and water mixture to a minimum of 180°F/80C can help to kill any unwanted microorganisms that may be present on the sugar or in the water. This can help to prevent contamination of the kombucha and ensure that the fermentation process is not disrupted.
3. Cooling the sugar and water mixture before adding it to the kombucha is important because kombucha is a living culture of yeast and bacteria, and exposing it to excessive heat can kill or damage these microorganisms. This can affect the health and viability of the culture and ultimately the quality of the kombucha.

Dissolving sugar in water, heating the mixture, and cooling it before adding it to kombucha is important for ensuring a consistent and predictable fermentation process, preventing contamination, and protecting the health and viability of the kombucha culture.

Should I add my sugar before steeping? What are the benefits?

Because sugar is acidic, adding sugar before steeping the tea leaves can allow the sugar to extract more nutrients from the tea leaves during the steeping process.  This is why we suggest adding your sugar to the hot water prior to adding your tea.

How much sugar remains after fermentation?

The amount of sugar remaining in kombucha after fermentation can vary depending on several factors, including the type and amount of sugar used, the duration and intensity of the fermentation process, and the specific strains of yeast and bacteria present in the kombucha.  Generally, kombucha fermentation is an incomplete fermentation process, meaning that not all of the sugar is converted into alcohol and other compounds.  As a result, some sugar will typically remain in the kombucha after fermentation.  The percentage of sugar consumed during kombucha fermentation can range from 30-80%, with an average of around 50-60%. The exact percentage of sugar consumed during kombucha fermentation can be determined by measuring the specific gravity or brix of the kombucha before and after fermentation and calculating the difference. This can provide a quantitative measure of the amount of sugar consumed during fermentation.

How can I test how much sugar is left in my kombucha after fermentation?

There are several methods that can be used to test the sugar content of kombucha after fermentation. One common method is to use a refractometer.  A refractometer is a tool that measures the refractive index of a liquid, which is a measure of the bending of light as it passes through the liquid.  The refractive index of a liquid is directly related to its sugar content, so a refractometer can be used to determine the sugar content of a liquid, such as kombucha. To use a refractometer, a small sample of kombucha is placed on the refractometer's prism, which is a clear glass or plastic surface.  The refractometer is then held up to a light source, and the light passing through the kombucha sample is observed through the refractometer's eyepiece. The refractive index of the kombucha is determined by the bending of the light as it passes through the sample.  Once the refractive index of the kombucha is determined, a conversion chart can be used to convert the refractive index to a sugar content.  Different refractometers may have different conversion charts, so it is important to use the correct chart for the specific refractometer being used. Another method for testing the sugar content of kombucha is to use a hydrometer.  A hydrometer is a tool that measures the density of a liquid, which is a measure of the amount of matter in a given volume of the liquid.  The density of a liquid is directly related to its sugar content, so a hydrometer can be used to determine the sugar.  To use a hydrometer, a sample of kombucha is placed in a test jar.  The hydrometer is then carefully floated in the liquid, and the level at which the hydrometer floats is observed and measured.  The specific gravity, or density, of the kombucha is determined by the hydrometer's reading. These tools can provide a reliable and accurate measure of the sugar content, which can be used to determine the level of fermentation and the sweetness of the kombucha.  But remember you've got to measure both before and after fermentation.