For centuries, the potato has worked in supporting roles. It has been the filling in the samosa, the chips beside the fish, the quiet bulk beneath the aloo tikki.

Nobody has ever cast it as the lead. This month, officials in Ahmedabad allege, it was handed the starring part in a production that ran for five to six months, reviewed only by the critics who matter in street food: the hungry.I find the performance hard to resent.

I find our reaction to it considerably more interesting.THE ROLE OF A LIFETIMEOn October 15, officers from the Ahmedabad Municipal Corporation (AMC) raided a unit and seized about 2,000 kg of suspected ketchup. Officials allege that it contained no tomatoes, only potato powder, starch, water, colour and acetic acid, the sour compound that gives vinegar its bite.

It was sold in 5 kg tins for Rs 105 each, which works out at Rs 21 a kilogram.Tomatoes, meanwhile, averaged Rs 43.70 a kilogram at retail in late June. Whatever else was missing from the tin, the arithmetic was honest.

Potato, starch and a torn sachet: what officials allege went into Ahmedabad’s fake ketchup. (Illustration: Radifah Kabir/India Today) A second raid, reported two days later, found 10,630 kg of suspected adulterated food, including Re 1 ketchup sachets meant for dabeli and vada pav stalls.Laboratory results are pending, so every detail here remains an allegation. The potato, for now, is innocent until proven starchy.FOUR QUALITIES, ZERO TOMATOES Consider how little it takes to be ketchup.

Ask anyone to describe it, and they will offer a red colour, a sour edge, a sweet note and a thick body. That is the entire audition.

Dye supplies the red. Acetic acid supplies the sour.

Sugar supplies the sweet. And starch, the energy store of the potato, supplies the body, because its granules swell and form a gel when heated in water.The finishing touch is physics.

Ketchup is a shear-thinning fluid, which means it flows when shaken or squeezed and thickens again when left alone. It is the only thing in Indian life that refuses to move until it is hit, and then moves far too much.

Red dye, vinegar, sugar and starch can copy ketchup’s colour, sourness, sweetness and thickness, with no tomato in sight. (Illustration: Radifah Kabir/India Today) Starch-thickened sauces behave in a similar way, so a good imitation can pour, cling and settle like the original. Add flavouring, and the tongue gives a standing ovation.I do not blame the diner at the snack stall, who cannot inspect a sachet and should not have to.

I blame the habit. We were never fooled by the potato.

We were already so comfortable with red, sour, sweet and sticky that we had stopped asking for the one thing that makes ketchup ketchup.THE RULEBOOK WILL NOT ASK EITHERIndia does set standards. Ketchup must contain at least 25 per cent total soluble solids, which means everything dissolved in the sauce, mostly sugar and salt, and acidity of at least 1 per cent as acetic acid, according to national rules.

Sugar and vinegar can supply both numbers without a single fruit in the pot. It is rather like checking whether a person is a cricketer by asking whether they own a bat.

Sugar and vinegar can pass the rulebook’s tests. The tomato, left on the side, was never weighed. (Illustration: Radifah Kabir/India Today) The true fingerprint is lycopene, the red pigment of the tomato, and when Consumer Voice tested nine popular brands in 2022, it noted that neither the Bureau of Indian Standards nor the Food Safety and Standards Authority of India (FSSAI) specifies a minimum lycopene level.

In fairness, all nine brands met the minimum requirements. The sealed bottles on your shelf are not the joke here.

The loose tins and sachets that nobody tests are.A TEST OLDER THAN OUR EXCUSESThe most embarrassing part is that the answer has been sitting in a library since 1959. A paper in the journal Food Technology described a rapid way to detect adulterants in tomato ketchup.

It pulled pigments out of the sauce with petroleum ether, a light solvent, and read them in a spectrophotometer, a machine that measures how much light a sample absorbs. Lycopene absorbs light at 503 nanometres.

The more lycopene, the more the tomato content. The authors used it to catch ketchup stretched with carrot, ash gourd, pumpkin, sweet potato, papaya and apple pulp.

It did not test potato powder and dye, but the logic is plain: a sauce with little tomato should show little lycopene. A 1959 paper described a laboratory method that measures lycopene, the tomato’s red pigment, to estimate how much tomato a sauce contains. (Illustration: Radifah Kabir/India Today) That test is 67 years old.

It has never been invited to a street. Meanwhile, FSSAI's online DART list of simple household adulteration checks, which covers items from milk to spices, does not seem to include ketchup.THE RAID ARRIVES AFTER THE DABELII say this with respect for the officers, who did the hard thing.

The case began with one suspicious tin found with a street vendor and, they told Aaj Tak, tracing its source took about three months.A raid, however brave, is a sequel. By the time it opens, the original has long since finished its run on a million plates.THE SOLUTION, SERVED COLDIndia needs three things.

First, a cheap, portable field test for tomato content, checked by food scientists and approved by regulators before an inspector relies on it. Whether one can be made at that price is a question for researchers, and I would like it put to them.

Second, a minimum tomato standard, so that the rulebook finally asks the question the buyer has never been able to. Third, a plain rule that loose sauce declares its tomato content on the tin.Until then, buy sealed, check for an FSSAI licence number, and look for tomato near the top of the ingredients list.

The Ahmedabad laboratory reports may soon tell us exactly what was in those tins. They cannot tell us how long we went without asking.

The potato gave a fine performance. The audience, I fear, had stopped checking the programme.Radifah Kabir is a food and biotechnologist.- Ends