Wasabi, known for its vibrant green hue and pungent kick, is a popular accompaniment to many dishes, particularly sushi. Encountering brown wasabi can be confusing. This discoloration is common and stems from factors related to both authentic wasabi and its imitations.
Factors Influencing Wasabi Color
One primary reason wasabi might appear brown is natural oxidation. For genuine Wasabia japonica, the vibrant green color comes from chlorophyll in the plant’s rhizome. When fresh wasabi is grated, cell walls break, exposing compounds to air. This initiates an enzymatic reaction, causing green pigments to gradually break down and turn brownish.
Imitation wasabi can also appear brown or off-green due to its ingredients. Most “wasabi” pastes blend horseradish, mustard, and green food coloring. Horseradish is naturally off-white, and mustard powder has a yellowish tint. While green dyes are added to mimic authentic wasabi, these colorants can fade or change over time due to chemical reactions, contributing to a duller or brownish appearance.
Authentic vs. Imitation Wasabi and Their Hues
Genuine wasabi, derived from the Wasabia japonica plant, has a distinct appearance when freshly grated. It typically presents a natural, light green hue, often described as paler than mint, with a slightly coarse texture. Upon grating, its flavor peaks within minutes, and its color subtly shifts to a duller green, then brownish-green as it oxidizes. This rapid oxidation means much of its flavor and color diminish within 15-20 minutes.
In contrast, imitation wasabi, commonly found in tubes or at most restaurants, is typically a blend of horseradish, mustard, starch, and artificial green food coloring. These products often have a much brighter green color when fresh due to the dyes used. However, the inherent colors of horseradish and mustard, combined with the potential for artificial colors to degrade, mean imitation wasabi can often appear dull green, yellowish-brown, or distinctly brown, even when relatively fresh. The “brown” appearance can therefore frequently indicate that the product is an imitation or has simply aged.
Assessing Brown Wasabi for Quality and Safety
A slight brownish tint in genuine wasabi due to oxidation is generally harmless and does not indicate spoilage. However, distinct signs of spoilage mean any wasabi product should be discarded. These signs include a strong off-odor, such as a rancid or musty smell, mold growth, or a slimy and mushy texture. If the vibrant green color changes to blue or gray, it indicates the paste has gone bad.
For imitation wasabi, some browning can be normal due to its ingredients or age. However, similar to real wasabi, any signs of mold, a foul smell, a separation of ingredients, or an unusual texture indicate it is no longer safe to consume.
Preserving Wasabi Freshness and Color
Proper storage helps maximize freshness and minimize undesirable browning for both authentic and imitation wasabi. Fresh wasabi rhizomes should be kept in the refrigerator, ideally in the crisper drawer, wrapped in a damp paper towel or cloth within an airtight container or unsealed plastic bag. Re-wetting the paper towel every few days helps maintain moisture.
For imitation wasabi pastes sold in tubes, keeping them tightly sealed and refrigerated after opening is recommended to slow oxidation and preserve flavor and color. Wasabi powder has a longer shelf life; store it in an airtight container in a cool, dry place away from direct sunlight to maintain its quality.