Chestnut Flour.

There is a chestnut grove near us, apparently in all the years it has been producing it has never been harvested apart from some locals filling their buckets. Probably partly because of the time-consuming harvesting and their limited shelf-life, which is due to their high water content. This makes them more prone to growing mould or rotting that most other nuts, which have a higher fat content and are more likely to go rancid when old. Chestnuts in their shell will be good for up to a week and if stored in the fridge this can be extended up to a month. Chestnut flour should be used within a day or so or stored in the freezer for up to a year. Apparently chestnuts should be eaten cooked due to their high tannin content when raw. 

Most chestnut peeling methods we investigated called for the nut shell to be scored either across the base or around the side before heating it to release the shell. Methods included microwaving (we haven’t owned one for at least 20 years) roasting or boiling. Roasting sounded good but I found that while the outer shell came away easy the inner skin dried out and was very hard to remove. Immersing them in boiling water for a couple of minutes helped some of the nuts inner skins peeled well, but for most it was a time-consuming tedious task. For this lot I started with 300g of fresh chestnuts roasted 15min, yielded 200g peeled nuts, then dehydrated ground flour 94g. I used the woodstove to dry them and may have over dried them a little. 

These same methods all said that the inner skin was bitter if left on and this seemed to be the only reason for removing it. Further research showed the skin would be non-digestible fibre, which is helpful in the intestines to keep things moving so not an issue there. Another method I saw from a local lady kept the skin on and blended the dried nut with skin into chestnut flour. This would save a lot of time and a few taste tests showed no noticeable bitterness in the skin. We chose to boil the next lot of chestnuts for about a recommended eight minutes to make peeling easier and tried different scoring methods. The nuts with the cross cut across the base, right through the shell and skin were the easiest to peel, a single cut on the base or side did not seem to let enough boiling water in to soften the shell enough. It is best to leave the chestnuts in the water, removing just a few at a time to peel as they are harder to peel if they dry out. We did find after peeling about 4kg of chestnuts that it was rather drying on your hands and when scoring them you need a sharp and comfortable knife if doing a lot. 

The nuts were then sliced and spread on dehydrator trays in a single layer and dried for a few hours, I decided not to fully dehydrate as the edges were getting hard and I did not want hard bits in the flour. Since the flour was to be frozen for storage the slight moisture content should be fine. 

For this lot we started with 1 kg fresh chestnuts, deshelled but still with skin we had 903g, these were partially dehydrated which gave us 648g to be ground into flour. One cup of chestnut flour equaled 120g. I used this flour in our Keto bread recipe and found it worked well, producing a slightly moister loaf than other nut flours. In the bikkie recipe I did notice that if the chestnut was not ground up well you did end up with some firmer lumps of the skin which were slightly bitter, but if ground finely this was not an issue.  The removal of thicker pieces of skin while peeling would mitigate this issue also.

Chestnuts are higher in carbohydrates than most other nuts, for each 100g of boiled chestnut they contain approximately 28g of carbohydrates, 1.4g of fat and 2g of protein. Hazelnuts, in comparison, are approximately 17g carbohydrates, 61g fat and 14g protein. Apparently, chestnuts retain more carbohydrates if roasted at about 50g per 100g serving. So, boiling must remove a large portion of the carbohydrates and is therefore a better method if you are low-carb. 

Over all I found chestnuts be rather labour intensive and have to be dealt with quite promptly after harvest unlike other nuts. But the flour is quite good with a mild flavour and can easily be frozen and used from the container for bread and baking.  

Here’s some more information on chestnut trees…

Sweet Chestnut – Castanea sativa 

An attractive deciduous tree reaching approx. 30 metres in height. Preferring slightly acidic free draining soils and dislikes waterlogged, alkaline soils and exposed sites. Both male and female flowers appear in summer on the same stalk, these are wind and insect pollenated. The edible nuts develop in a prickly case that splits open in autumn when they are ripe. The nuts and leaves etc. can be used as stock fodder and all parts of the tree, except the actual nut, are said to have anthelmintic (anti worming) properties.  

Sweet Chestnut is a durable wood which coppices very well and can be coppiced at various ages for different purposes. At 5 years timber is used for walking sticks, yurt poles, garden stakes, woven panels, balustrades and rustic furniture.  At 7-12 years, rustic furniture, laths, pales, garden arches, gate hurdles, trellis panels and trug handles. 20 years, rustic furniture, laths, pales, charcoal, firewood, barrels, fencing posts. 30 + years, roundwood timber framing, post-and-rail fencing, fencing posts, decking, cladding, arbours, gates, shingles, window frames, charcoal and firewood.