Kombucha and fructose（果糖）

Kombucha and fructose (果糖)

Sucrose (table sugar蔗糖) consists of a glucose and a fructose (葡萄糖與果糖) molecule linked together.

The bacteria and yeasts in kombucha prefer to feed on glucose rather than fructose.
They convert the glucose into glucuronic acid (葡萄糖醛酸) and a variety of other acids, all with anti-bacterial and other beneficial properties.

They convert fructose into acetic acid (vinegar,醋酸).

Ps：glucuronic acid 葡萄糖醛酸參與肝臟生化作用

Because of this preference for glucose, most of the glucose is used up quickly. The sugar that remains in your kombucha is mostly fructose. In a strong and vinegary kombucha most of the fructose is also consumed.

Unlike most other sugars, fructose can only be metabolised (新陳代謝) in your body through your liver. You should limit the amount of fructose that you consume, especially if your liver is not as healthy as it could be. This means avoiding fruit juice, large quantities of sweet fruit, and of course most processed and restaurant foods which all have large quantities of sugar / HFCS(高果糖漿) added.

(只有肝臟能夠消化代謝果糖。所以肝臟功能低落，少吃果汁、甜水果、甜食。)

(Kombucha 可以將 fructose 轉成醋酸)

Small quantities of tart kombucha are of course still highly beneficial. But I suggest that you should not normally drink more than one glass of kombucha every day(每日不要超過一杯的量), especially sweet short-fermented brews.

This suggests that you can substitute glucose powder for sucrose (蔗糖) in the kombucha recipe. I made a brew in which a quarter of the sugar was substituted with glucose, and it seemed to work OK. It is important that the pH of your brew is strongly acidic or moulds will take hold, so you do need some fructose in the brew to produce the vinegar. It seems that nobody has yet tested this important question. If anyone has further information or laboratory results, I would be most grateful if you would contact me.

Kombucha and caffeine

The kombucha culture does not break down the caffeine in the tea. If you want a low-caffeine kombucha, then make it with decaffeinated tea, green tea or other low-caffeine teas like oolong (烏龍茶) or kukicha (twig tea,莖茶). They all work well - I make mine with Gunpowder green tea.

Similarly, kombucha does not break down the oxalic acid (草酸) in the tea. This is yet another reason to use green tea, which has only 10-20% as much oxalic acid as black tea.

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