The US Food and Drug Administration (FDA) is changing its rules on how food manufacturers notify them of ingredients brought to the market – but the Trump administration has once again punted on defining “ultra-processed foods”, promising more details later.

While the move would close a regulatory loophole, it falls short of the administration’s promises to reform food regulations dramatically even as one of the biggest foodborne illness outbreaks unfolds.

“You have to be kidding. That’s all?” asked Marion Nestle, professor emerita of nutrition, food studies, and public health at New York University. She questioned what took so long for “something so simple and obvious” as closing the loophole and wondered where the proposed definition of ultra-processed foods was – a long-awaited announcement promised earlier this year.

The proposed rule, which was submitted to the Federal Register on Monday, would require companies to submit to the FDA all ingredients in foods that are brought to the market under the Generally Recognized As Safe (Gras) pathway, closing a loophole that allowed food companies to use ingredients that were proven safe either through scientific research or because they were already commonly used.

The framework, put in place in 1958, was meant as an exemption, but it became the main way new substances entered the US food supply, greatly outpacing the food additive petition pathway, Kyle Diamantas, acting commissioner of the FDA, said in a press call on Monday.

“If finalized, this rule would formally transition the Gras framework from a voluntary program to a mandatory notification system,” Diamantas said. It would apply to all ingredients currently on the market using the Gras framework, in addition to new ingredients coming out.

Amaru Sanchez, a food and agriculture lawyer at Akin Gump Strauss Hauer & Feld, noted that “this is a huge deal for the food industry”. It would have ripple effects throughout the food system, with suppliers, companies, retailers and consumers scrambling to understand what the proposed regulation means for them, he said.

It’s not clear if the FDA has the regulatory ability to require this notification, Sanchez said: “It really is the question on everyone’s mind.” In 2021, a federal judge ruled that the FDA had the authority to create a voluntary system – but a mandatory system would be different, he said. And other major legal decisions like the major questions doctrine and the Chevron decisions have dramatically reshaped the legal and regulatory landscape, Sanchez added.

“Maha” came into prominence in part by tapping into public unease about food additives and lack of transparency about the US food system.

Previously, Robert F Kennedy Jr, secretary of the US Department of Health and Human Services (HHS), promised a definition of ultra-processed foods “by April”, but Diamantas said that month that “a definition for ultra-processed foods is really hard”.

There is no scientific consensus on what “ultra-processed foods” are, and it has been difficult to ascertain if they have negative health effects, as Kennedy has repeatedly claimed.

The HHS and the US Department of Agriculture have submitted a proposed definition “aimed at creating a stronger foundation for future federal nutrition research”, Diamantas said on Monday. “Additional information on ultra-processed foods will be shared at a future time.”

If the new Gras rule is implemented, Nestle said, “mandatory notification of new additives is an improvement, but the company is still responsible for the science and will still be hiring its own experts to say the additive is safe”.

Reviewing those notifications and deciding whether the scientific proof of safety is adequate could put strain on FDA staff, she said, who have suffered layoffs and low morale under the Trump administration.

“Also, it would be nice to have a clear statement of what happens if the FDA rejects what the company sends. Does that mean the company cannot use the additive?” she asked.

The regulatory agency will also publish new guidance on biological hazards in ready-to-eat fresh-cut produce on Tuesday, officials said.

The US is currently experiencing one of the largest recorded foodborne illness outbreaks in US history as confirmed cases of cyclosporiasis top 10,000. There is also a salmonella outbreak in eggs and jalapeños, leading to a recall of Taylor Farms products sold in 26 states.