When we think about walnuts, we somewhat imagine a unique taste that can be described as earthy and tangy—with hints of astringency—due to some components, particularly the highly polyunsaturated fat profile of the meat and the mild tannins on the skin.
This combination makes the walnut interesting to combine for contrasting or accentuating certain flavors in other food products but challenging for formulation and shelf life.
Unlike most nuts, walnuts are mainly composed of polyunsaturated fatty acids (76% of total fats) and exceptionally rich in the omega-3 alpha-linolenic acid (14%). Although this specific composition is favorably regarded for the high nutritional value, it also makes walnuts more susceptible to oxidative damage from light and heat.
For this characteristic, chocolate-covered and candied walnuts will have a longer shelf life than shelled walnuts for being protected from light and air by a fat or sugar exterior. Furthermore, roasting walnuts may mellow the tannins and make the overall flavor rounder, but eventually, walnuts may go rancid if time/temperature treatments are not gentle.
The mild tannins in air-dried in-shell walnuts are great for balancing out sweet flavors, such as banana, caramel, and maple syrup. Because tannins dry out the mouth and feel astringent on the palate, they balance the effects of high-fat ingredients like blue cheese, ricotta, butter, white, and milk chocolate.
Ingredient applications with a smoother finish that won’t overcharge the tannins of dark chocolate could find a match in blanched walnuts or blanched walnut meal. Removal of the skin through a blanching process with water would extract 96% of the tannins, thus significantly reducing the astringent taste experience.
Unfortunately, walnut skin removal is still complicated and inefficient at an industrial level due to the irregular borders of the edible portion.
What’s sure is that capitalizing on the walnut flavor dimension is a fascinating process that hugely appeals to savvy food developers for its versatility.