When you think about walnuts, you probably imagine a complex taste that's earthy, fruity, and tart — maybe with hints of astringency. That's why developers of walnut products must go beyond the surface to understand this nut's multidimensional flavor. Once they explore the components (polyunsaturated fat and mild tannins) found in the walnut's skin, they can easily match ingredients that complement the unique sensory attributes of walnuts.
Balancing the Tannins
Walnut flavor is, in general, fairly mild, but it has a complexity that includes some tangy and sharp notes. Researchers have identified three contributors to this bite: oil content, a tendency to become rancid if not stored properly, and the tannins in the walnut skin. Dr. George Ennis, flavor chemist at David Michael & Company, explains it in these terms: "The astringent taste is a result of the tannins and catechin from the paper-like skin (pellicle) surrounding the nut kernel."
Product developers take note: The tannins in walnuts are great for balancing out sweet dishes! According to David Rosengarten, wine editor at Saveur magazine, "The most important thing to keep in mind about walnut flavors is ‘sweet'! Sweet wines balance the tannins, and if it's the kind of sweet wine that has nutty flavors, even better." Rosengarten lists sherry, port, and Madeira as ideal wine-flavor pairings for walnuts because they are sweet and nutty. Other sweet ingredients that complement walnuts are bananas, caramel, and maple syrup. The goal is not to cover up the astringent notes but rather to balance them out to achieve a more uniform flavor in between the two extremes.
Of tannins' multiple dimensions, the most important is texture. Because tannins dry out the mouth and feel astringent on the palate, they balance out the effects of high-fat ingredients like blue cheese, ricotta, butter, and milk chocolate. The astringency from the walnut skin manages to lighten the rich intensity of the final dish. It's the type of pairing commonly used with wine and food — dry, highly tannic wines are paired with fatty meats such as preserved duck confit.
Balancing Out Fats
Despite their ability to balance out high-fat foods, walnuts themselves have a fair amount of polyunsaturated fat and have a rich, buttery texture. Bitter vegetables like cabbage and endive, as well as sour cherries and grapefruit, have the same effect on walnuts that walnuts have on the sweet ingredients. The bitter components found in green vegetables can actually lighten up the perceived flavor and texture of a finished recipe and can cleanse the palate in between bites, enabling the consumer to go back for more. Too much richness would result in an unbalanced dish, so walnuts too must have their flavor profile tempered.
Tannins are a crucial part of the walnut package, but at times a developer wants to create a finished product that includes only the mild nut flavors found beneath the skin. Dr. Ennis notes, "Removal of the skin through a blanching process with water would extract 92% to 98% of the tannins, thus greatly reducing the astringent taste experience." The process of walnut skin removal has been studied by various nut producers that are investigating methods for removing skin while leaving the nut intact. One method under evaluation is dry roasting followed by air blasting in a tumbler and then use of high-pressure water streams. Developers should consider using blanched walnuts or blanched walnut meal in recipes and formulas when the application calls for delicate flavor.
Walnuts are quite versatile and pair well with many ingredients, but some flavors can really help a developer achieve that "wow" factor. The dual nature of the walnut — its sharp flavored skins and a very rich interior — enable it to play two roles in the pairing game. The astringent notes allow it to combine with sweeter and higher fat foods but at the same time, its own richness can be lightened up with other astringent foods or with citrus fruits and vegetables. Recognizing — and capitalizing on — these flavor dimensions is the key to your walnut development success.
Charoset is a classic Passover dish that symbolizes the mortar used by Jewish slaves in ancient Egypt to make bricks for building the pyramids. Many variations of this dish exist, but the key elements are sweet red wine, chopped walnuts, cinnamon, and apples. These four ingredients combined together are a great example of how the sweet, rich, and tannic components can be unified in a perfectly balanced traditional spread. While this dish is traditionally only consumed during Passover, it can also be served as a Mediterranean tapas and goes well with lamb, pita bread or spicy chips.