Researchers in the US have developed a two-step fermentation method that can improve the aroma of plant proteins, paving the way for more appealing plant-based foods.

The team, based at Ohio State University, designed a process to counter the odours that typically form during plant cultivation and extraction.

Their results showed their approach could remove between 95-99% of key smells, significantly outperforming one-stage fermentation across all proteins. Because smell greatly influences flavour perception, common plant protein scents – often described as beany, grassy, earthy, sulfurous or cereal-like – can stand in the way of consumers choosing plant-based foods, the researchers explained.

Depending on the product, successful fermentation can take anywhere from a few hours to an entire day. Manpreet Kaur, lead author of the study and a PhD student in food science and technology at Ohio State, said that adding the second step does not overcomplicate this process. This means future plant-based proteins created using the team’s method will not cost consumers more or take longer to produce.

“We are using the same things that are used in the normal fermentation process,” explained Kaur. “The only thing changed is how we utilise the bacteria.”

In the experiment’s first stage, researchers added a type of beneficial bacteria, Lactobacillus plantarum, to their microbial cultures, allowing it to ferment and begin breaking down the compounds responsible for foul smells.

In stage two, they used a traditional yogurt culture containing a variety of common bacteria known for developing and modulating desirable aromas to complete the fermentation process.

The researchers then applied this method to solutions containing eight different plant proteins: 9% soy, pea, chickpea, mung bean, faba bean, rice, barley-rice and hemp.

According to the team, in each test, human sensory evaluation results revealed consistent and often near-complete reductions in smells.

Kaur’s team also found that adding certain ingredients could affect the outcome of the process. For example, while the natural sugar allulose could enhance Lactobacillus plantarum activity, strawberry preserves aided the performance of the bacteria in the yogurt. In contrast, non-fermentable additives, such as pectin, xanthan gum and oil, were introduced with only minimal effects on odour reduction. 

The team says the work can not only advance the field’s understanding of how fermentation can be used to mitigate sensory challenges, but also offers a practical solution for development of flavourful plant-based dairy snack alternatives.