Why are my hazelnuts/filberts bitter?

Question

I live in the Mid-Atlantic area and have terrible luck buying raw hazelnuts/filberts in the store. They are often bitter and/or old-tasting, very expensive, and you'd never want to eat them raw.

Last fall, my dad shared some hazelnuts a West Virginia woman gave him straight from her trees as a thank you. It was like eating a completely different nut: chewy, sweet, no aftertaste. These weren't the wild variety, sometimes called "beaked"; they looked exactly like what I buy in the store, just a little smaller. I've read that commercial "raw" hazelnuts may have to be pasteurized before sale. Could this be affecting the flavor of the store-bought nuts? Anyone got a better source than roaming the West Virginia hills (as lovely as that sounds)? My chocolate hazelnut biscotti and I thank you :)

CLARIFICATION (based on the kind and thorough replies to date): The store-bought hazelnuts are often bitter even after I remove the skins, and I'd like to avoid roasting and/or peeling. (I want to make some raw hazelnut flour for a pastry crust, for example.) I will look for the DuChilly variety, however, and welcome thoughts on other varietals. Thank you!

Answer 1

Diarylheptanoids were recently identified as responsible for bitter off-flavor in hazelnuts. This correlates with

• infection with bugs (of the bush, not in storage) and
• starting germination

according to: Singldinger: Molecular-sensory studies on the development of a bitter off-taste in hazelnuts, PhD thesis, 2019, Munich Technical University.

Here's also a paper: Singldinger et al.: The Cyclic Diarylheptanoid Asadanin as the Main Contributor to the Bitter Off-Taste in Hazelnuts (Corylus avellana L.), J Agric Food Chem. 2017

Answer 2

As a horticulturalist, I can tell you there are many varieties of hazelnut (also called cob or filbert). We eat ours in England without ever removing the skins, because they're mostly kentish cob nuts - these are sometimes sold 'in the green' but more usually as a mature nut. The skin may be slightly bitter, but it is not noticeable and it is not necessary to remove the skin. Other varieties have thicker skins and are more noticeably bitter, and will need the skins removed. So, in other words, when you buy your hazelnuts, it's likely you're buying a variety which has a thicker, bitter skin, whereas the ones collected from the tree in West Virginia were a different variety. One available and widely grown in parts of America which is not bitter is 'DuChilly' - it has a more elongated shape than most hazelnuts and is usually called a filbert.

Answer 3

I have fresh hazelnuts that I harvested myself a month ago and I think they are starting to turn bitter. So it might have to do with age. I'd better dehydrate these! They were all so sweet when we first picked them!