The cost of onions has soared 63% over the past year, the biggest increase of any single ingredient in Bloomberg’s Shisa Nyama Index.

Crunching data from the Pietermaritzburg Economic Justice and Dignity group, the gauge tracks the prices of key ingredients in a traditional braai consumed in South Africa, including potatoes, cooking oil, corn meal, carrots, tomatoes, frozen chicken, beef and wors — a sausage made from ground meat offcuts. The overall index rose 12.5% last month, up from 12.4% in August.

To compile its survey, the PMBEJD’s data collectors track the prices of 44 food items on the shelves of 47 supermarkets and 32 butcheries that target the low-income market in the greater areas of Johannesburg, Durban, Cape Town, Pietermaritzburg, Springbok in the far northwest and the far north-eastern town of Mtubatuba.

Data from South Africa’s statistics agency show inflation has largely slowed over recent months and has been in the central bank’s 3% to 6% target band since June. Food inflation has remained elevated, moderating to 8.2% in August from 10% the previous month.

Central Bank Governor Lesetja Kganyago said in a Bloomberg TV interview this week that the bank has more work to do to rein in inflation, with higher food and oil costs posing risks to the outlook.

This has stoked concerns over food prices in the near term, as avian flu and petrol prices risk putting upward pressure on chicken availability and prices, as well as food producer input and delivery costs.

Data from the Bureau of Food and Agricultural Policy shows that the volatility in demand for fresh produce has exacerbated price increases stemming from lower output.

Gift Mlilo, a Johannesburg-based welder, said he mainly eats corn meal and that his vegetable intake is largely restricted to cabbage and tomatoes — which the index shows have fallen in price over the past year.

“We are in deep trouble,” he said. “Employers don’t pay well anymore, and there is no price regulation. Everyone charges what they want, and what will you do if you want to buy food? You have no choice but to buy.”

Read: South Africa’s major food headache – and government’s plan to fix it