Scientists sniff out beefy aroma in plant-based burgers

Interest in plant-based meat alternatives has exploded in recent years, thanks to concern about the climate impact of livestock farming and the greater range and quality of vegetarian alternatives available. Many of these vegetarian alternatives closely resemble the taste, smell, appearance and texture of real beef.

Now, US researchers have assessed the aromas of some of these plant-based meat alternatives to find which come close to the real deal.

“During the last several years, increasing awareness of the impact of meat production on climate change, as well as meat shortages during the pandemic, have made people more accepting of plant-based alternatives,” said Dr Lili Zyzak, who led the study. “There are a lot of products out there, and food companies are doing interesting research, but nobody ever publishes anything because it’s a trade secret.”

Plant-based meat substitutes have a long history, and more realistic products have been commercially available for a few decades. However, early versions were very different from meat. In recent years, food scientists – working for both well-established industry giants and tech start-ups dedicated to fake meat – have developed techniques for creating proteins from plants such as soy and pea which taste more like meat.

Raw beefburgers have minimal odour. However, hundreds of volatile compounds are released during cooking, contributing to a savoury, fatty taste and smell. It is a challenge to match this easily identifiable smell using plant proteins and vegetable oils.

“The problem with plant-based burgers is that the plant protein itself contributes a strong odour,” Zyzak explained. “For example, pea protein smells like green, cut grass, so companies have to find a way to mask that aroma. Some use heavy seasonings.”

Zyzak was interested in assessing the aroma of plant-based burgers to better inform consumers about their qualities. She and her colleagues analysed the aroma compounds produced by cooking real beefburgers and eight popular branded plant-based burgers.

First, they cooked the burgers and evaluated the aromas using five descriptors: meaty, fatty, buttery, sweet and roasted. Next, they applied gas chromatography-mass spectrometry combined with olfactometry (measurement of odour composition) to correlate the aromas with specific odour compounds. This required them to inject volatiles from the cooking burgers into the instrumentation, which separated the compounds. Some of the sample was diverted to a sniffing port for human participants to identify which of the five descriptors they smelled. The remaining sample was analysed by mass spectrometry, allowing the researchers to correlate specific compounds with the aroma identified by the participant at a certain time.

This allowed the chemists to identify the compounds that caused the plant-based burgers to differ from a beefburger. They found that Beyond Meat’s Beyond Burger most closely resembled the odour profile of beef, with meaty, fatty, and grilled meat characteristics from the compounds 1-octen-3-ol, octanal, and nonanal. However, it still deviated significantly in smell from the real thing. Another had the closest appearance to a beefburger, but produced a yeasty odour on cooking, with higher levels of methyl butanals and propionic acid. Other patties used heavy seasoning to release the garlicky and barbecue sauce-like aromas associated with burgers.

Ultimately, Zyzak would like to use her findings to produce a mixture of odour compounds that closely mimic hamburger aroma. She is working with a start-up to obtain samples of synthetic meat, which she plans to compare with plant-based and regular burgers.