I often see recipes (usually for fruit mead or beer) warning against boiling fruit for fear that it will release pectin. I know that this is important for making jam, and bad for home brewing. What I don't quite know is why it's a bad thing. Does pectin have a negative impact on the fermentation process? Is it bad for yeast? Does it negatively affect flavour? Does it affect aging? Why is it so important to avoid pectin?
Pectin causes a really strong haze. Of course if you have a lot of pectin you can get some gummy residues or globs, but these settle out. Pectin haze tends to be tough to get rid of even with cold temps and aging.
All in all, if you are making a cloudy-style wheat beer that you want to add fruit to, worrying about the pectin haze is a but overkill.
There are mainly two issues when dealing with pectins:
- The haze it can cause, and this is just cosmetics
- Pectins being very large molecules make filtration very difficult
A rule of tumb is to use low to medium pectin content fruits:
- High pectin content: tart apples, citrus fruits, cranberries, currants, gooseberries and sour plums.
- Medium pectin content: Cherries, blueberries, blackberries and raspberries.
- Low pectin content: Strawberries, peaches, pear, pineapple, apricots and rhubarb.
Pectin can make a major contribute to the methanol levels in cider(hard cider).
Methanol results from the decomposition of pectin into Galactose. If you do not add pectinase and/or pasturise your apple juice before fermentation you can significantly reduce the levels of methanol in the final product. Although it is rarely above 0.2%.
Here is an interesting article on the subject: https://www.sciencedirect.com/science/article/pii/S0960852409013194
It can also cause haze as others have suggested.