Mineral Treatment Eliminates Bitterness in Flaxseed Oil

A simple mineral-based treatment has been shown to significantly reduce bitterness in flaxseed oil while preserving its omega-3 fatty acid content, offering a promising solution to a long-standing challenge in plant-based nutrition and food technology.

Researchers from the University of Copenhagen and Aarhus University in Denmark developed a process using food-grade calcium hydroxide — commonly known as slaked lime — to neutralize volatile compounds responsible for the rancid, bitter taste that often develops in flaxseed oil during storage and processing. The treatment, applied at low concentrations and mild temperatures, selectively targets oxidation byproducts without degrading the oil’s valuable alpha-linolenic acid (ALA), an essential omega-3 fatty acid linked to heart and brain health.

Flaxseed oil is one of the richest plant sources of ALA, but its high polyunsaturated fat content makes it highly susceptible to oxidation, leading to unpleasant flavors and reduced shelf life. This has limited its use in functional foods, supplements, and culinary applications despite its nutritional benefits. Previous attempts to stabilize the oil — such as refining, deodorization, or adding synthetic antioxidants — often stripped away nutrients or introduced chemical residues, undermining its clean-label appeal.

In controlled trials, the calcium hydroxide treatment reduced key aldehydes and ketones associated with bitterness by over 70% compared to untreated samples, while ALA levels remained statistically unchanged after four weeks of accelerated storage at 40°C. Sensory panels confirmed a marked improvement in taste and aroma, with treated oil scoring significantly higher for acceptability than control samples.

The method is notable for its simplicity and scalability. Unlike high-pressure processing or enzymatic treatments that require specialized equipment, the mineral approach can be integrated into existing oil refining lines using standard food-grade reactors. Calcium hydroxide is already approved for use in food processing under GRAS (Generally Recognized As Safe) status in the United States and the European Union, minimizing regulatory hurdles for adoption.

“We wanted a solution that was effective, safe, and accessible — something that could work in small-scale mills as well as large industrial facilities,” said Dr. Lena Sørensen, lead author of the study published in Food Chemistry. “Calcium hydroxide is inexpensive, widely available, and reacts specifically with the acidic oxidation products that cause off-flavors. It doesn’t touch the triglycerides or the fatty acid chains we want to preserve.”

The research team tested the treatment on both cold-pressed and expeller-pressed flaxseed oil varieties, finding consistent results across different extraction methods. They also evaluated the impact on oil color, viscosity, and peroxide value — key indicators of oxidative stability — and found no adverse effects. In fact, treated oils showed slower peroxide formation over time, suggesting the treatment may also contribute to improved oxidative stability beyond flavor correction.

Industry analysts note that the global flaxseed market is projected to grow steadily, driven by demand for plant-based omega-3 alternatives to fish oil. However, sensory rejection remains a barrier to wider consumer adoption. A 2023 survey by the International Food Information Council found that over 40% of consumers avoid flaxseed oil due to taste concerns, even when aware of its health benefits.

If adopted widely, this mineral treatment could enable food manufacturers to incorporate flaxseed oil into a broader range of products — including plant-based spreads, dairy alternatives, baked goods, and nutritional supplements — without compromising palatability. It may also reduce waste by extending the usable life of oil batches that would otherwise be discarded due to flavor degradation.

The researchers emphasize that the treatment is not a preservative in the traditional sense but a corrective step applied post-extraction to improve sensory quality. They recommend its use as part of a broader quality control strategy that includes proper seed storage, low-temperature pressing, and protection from light and oxygen.

Further studies are planned to evaluate the long-term stability of treated oil under real-world storage conditions and to explore whether similar mineral-based approaches could be applied to other oxidation-prone oils, such as hemp, chia, or perilla oil. The team has filed a provisional patent for the specific process parameters and is seeking partnerships with food ingredient companies for pilot-scale trials.

As consumer interest in sustainable, plant-based nutrition continues to rise, innovations that address practical barriers like taste and stability — without relying on synthetic additives — are likely to play an increasingly important role in shaping the future of functional foods. This simple mineral treatment offers a rare example of how basic chemistry, when applied thoughtfully, can solve complex problems in food science with minimal technological overhead.