Fermented onions make plant-based meat more 'meaty'

Plant-based alternatives such as tempeh and bean burgers provide protein-rich options for those who want to reduce their meat consumption; however, replicating meat’s flavours and aromas has proven challenging. A recent study published in the Journal of Agricultural and Food Chemistry unveils a potential solution: onions, chives and leeks that produce natural chemicals akin to the savoury scents of meat when fermented with common fungi.

When food producers want to make plant-based meat alternatives taste meatier, they often add precursor ingredients found in meats that transform into flavour agents during cooking. Alternatively, the flavouring may be prepared first by heating flavour precursors, or by other chemical manipulations, and then added to products.

Because these flavourings are made through synthetic processes, many countries won’t allow food makers to label them as ‘natural’. Accessing a plant-based, natural meat flavouring would require the flavouring chemicals to be physically extracted from plants or generated biochemically with enzymes, bacteria or fungi. Yanyan Zhang and colleagues at the University of Hohenheim wanted to see if fungi known to produce meaty flavours and odours from synthetic sources could be used to create the same chemicals from vegetables or spices.

The team fermented various fungal species with a range of foods and found that meaty aromas were only generated from foods in the Allium family, such as onions and leeks. The most strongly scented sample came from an 18-hour-long fermentation of onion using the fungus Polyporus umbellatus, which produced a fatty and meaty scent similar to liver sausage.

With gas chromatography–mass spectrometry, the researchers analysed the onion ferments to identify flavour and odour chemicals, and found many that are known to be responsible for different flavours in meats. One chemical they identified was bis(2-methyl-3-furyl) disulfide, a potent odorant in meaty and savoury foods.

The researchers said that alliums’ high sulfur content contributes to their ability to yield meat-flavoured compounds, which also often contain sulfur. These onion ferments could someday be used as a natural flavouring in various plant-based meat alternatives, the team added.

Image credit: iStock.com/matejmm