The Old Wisdom of Mustard Oil, Now Perfectly Science‑Backed

Monsoon clouds are still hanging over Kolkata, and the air still fills with the smell of ‘Ilish Maach Bhaja’ touching hot rice. But what exactly makes that sharp, nose-tickling, mild pungent flavor so special? And more importantly, how can it be enjoyed without the health concerns that come with high heat cooking?
Let's have a look into the fascinating science behind mustard oil and discover why old cooking techniques might be smarter than you think.
The Magic Molecules Behind That Mustard Punch
When you bite into a perfect shorshe ilish (mustard fish curry), two special compounds create that distinctive taste. The star players are sinigrin and allyl isothiocyanate – but don't worry about the fancy names. Here's what really matters.
Mustard seeds contain sinigrin, which sits quietly until something interesting happens. When you crush the seed and add water, an enzyme called myrosinase springs into action. Think of it like a chemical matchmaker – it transforms the mild sinigrin into allyl isothiocyanate, let's call it AITC, which delivers that familiar nose-prickle sensation.
As explained in Frontiers in Microbiology, intact glucosinolates stay relatively inactive until myrosinase breaks them down. What's fascinating is that these compounds are water-soluble, not oil-soluble, as noted in Molecules (MDPI). This explains why they live in the plant tissue rather than floating in the oil itself.
The conversion from sinigrin to AITC needs two things: moisture and crushed plant tissue. According to Scientific Reports, you can't get that signature mustard flavor without both elements working together.
What's Actually in Your Mustard Oil Bottle
While Bengalis celebrate the season's bounty with ‘hilsa’ or ‘parshe’ taking center stage on their plates, the real aroma, the flavor foundation, comes from the mustard oil itself.
In India, "wood-pressed" or "kolhu" mustard oil gets marketed as traditional cold-pressed oil. The government has clear rules about this. According to the Government of India Gazette - FSSAI, Chapter 2.2, mustard oil can only be labeled "Kachi Ghani/Cold-Pressed" if it contains at least 0.20% natural AITC by weight.
This means the punch in authentic wood-pressed mustard oil comes from AITC molecules, not sinigrin. The oil has already gone through that magical transformation from seed to sharp flavor.
Pratik Dutta Roy of the HealthyFly brand puts it straight, “We see a lot of mustard oil labels around, but we can at least claim that we know what it takes to earn the ‘cold-pressed’ tag. We had to compromise with the very slow speed of production, as the trade-off would have been the quality– if the AITC level goes down it’s no longer a rightful cold-pressed mustard oil, whatever the labels may scream.”
HealthyFly is among the prominent online stores supplying cold-pressed mustard oil to Bengali connoisseurs globally.
How Much Mustard Flavor is Too Much?
In Bengal, the Hilsa fish symbolizes the identity of “Bangals”, the Bengalis who came to India after partition, just as prawns, or chingdi, do for “Ghotis”. Still, when it comes to mustard oil consumption, moderation matters.
The EFSA Journal sets a conservative acceptable daily intake for AITC at 20 micrograms per kilogram of body weight per day. To put this in perspective, a strongly pungent tablespoon of uncooked mustard oil can contain several milligrams of AITC before any cooking losses occur.
Why Heat Changes Everything
Here's where kitchen chemistry gets interesting. AITC boils at around 152°C and is highly volatile, according to PubChem (Allyl Isothiocyanate entry). The Journal of Agricultural and Food Chemistry confirms that AITC breaks down into other compounds when heated extensively.
In simple terms: long, hot cooking drives away the very molecule that gives mustard its character. Deep fried Mach Bhaja definitely loses all AITC. The same is true for mustard paste as well, explaining why our grandmothers always added fresh mustard paste at the end of cooking, not at the beginning.
A good cook, aware of traditional cooking, understands that preserving mustard's essence requires finesse, not just fire.


The Frying Dilemma: Delicious but Demanding
Let's be honest – ‘begun bhaja’ (fried eggplant) and fish fry taste incredible. But repeatedly heating oil creates problems. The FSSAI RUCO booklet and FSSAI SOP on Used Cooking Oil explain that reused oil accumulates total polar compounds. When these exceed 25%, the oil becomes unfit for consumption.
Hang on, breathe easy, this doesn't make your favorite fried foods illegal, but simply suggest a smarter approach: use fresh oil, fry once, eat in modest portions, and then move on.
Smart Strategies for Maximum Flavor
For Fish Curries and Jhols
Bengali traditions consider many rituals incomplete without fish, like the consecration of hilsa pairs in the early season, when the fish often gets cooked oil-free with very less amount of it in a ‘jhol’ with potatoes and eggplant. This traditional approach actually maximizes flavor while minimizing health concerns.
Make fresh mustard paste by grinding seeds with warm water and a pinch of salt. Let this mixture rest for 10-15 minutes so myrosinase can work its magic. Moisture and time favor the conversion process.
Cook your fish gently, then remove the pot from heat before folding in a spoon of the rested paste and a small drizzle of wood-pressed oil. This brief contact with heat preserves aroma while limiting AITC loss.
For Fried Foods
Use fresh oil every time. Fry quickly, drain well, and stop there. The FSSAI RUCO booklet warns against reusing oil beyond the first run. When oil turns dark, foamy, and sticky, it's time for disposal, not reuse. I doubt if you would even try to remember this when sneaking into the crowd thronging your favourite ‘Telebhaja’ (Bengal style fried fritters) shop. But I said it, anyway.
I know you crave that mustard kick; add it after frying. A tiny off-heat drizzle on hot fritters delivers flavor without the chemical breakdown. Doable?
For Everyday Cooking
Treat wood-pressed mustard oil like a condiment rather than a cooking medium– well, when possible. A teaspoon over dal, aloo posto, or a simple cucumber-onion-chili salad provides that signature aroma with minimal heat exposure. The EFSA Journal guidance on total AITC intake encourages us to think of mustard oil as a flavoring agent, not medium or medicine. Well, Bengalis can use generous amounts for that purpose, they have the liberty!
Embrace the Whole Plant
Brassica vegetables like sarson saag, cabbage, and broccoli contain their own glucosinolates plus myrosinase enzymes. According to Frontiers in Nutrition, brief steaming or quick stir-frying preserves more isothiocyanate potential than prolonged boiling.
The strategy? Eat the vegetables for nutrition, use the oil for punctuation.
The Healthy Mustard Oil Game Plan
The Sundarban Hilsa Festival celebrates Bengali river culture with traditional preparations from Hilsa Bhapa to Ilish Paturi. Every bite tells a story of the river. These celebrations remind us that Bengali cuisine evolved not just for taste, but for wisdom.
Bengali kitchens feature not just hilsa but everyday heroes like katla, rohu, koi, tangra, mourola, loite, and chapila fish, often prepared in spicy curries with onions, nigella seeds, turmeric, and mustard oil. Not every dish requires high heat, quite the opposite on the contrary. Each preparation follows principles that modern science now validates.
If you read about the traditional cooking style of the great Thakur Bari, they understood something important: the best flavors come from respecting ingredients rather than overwhelming them. They knew when to use heat, when to hold back, and how to layer flavors for maximum impact.
Science supports what our ancestors have known for generations. Get the most from mustard oil by keeping the drama for the finish, not the frying process. Use genuine wood-pressed (Kachi Ghani/Cold-Pressed) oil sparingly, avoid recycling it for multiple frying sessions, and let seeds and green vegetables carry the health benefits. This gives you authentic shorshe flavor without letting your frying pan have the final say.