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Scientists smell the meaty aroma in plant-based burgers

Researchers at the University of Eastern Kentucky conducted an analysis of the flavor compounds produced by cooking real and vegetable burgers to identify the compounds that cause the vegetable patties to differ in odor from their conventional counterparts.

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

Now, US researchers have reviewed the flavors of some of these plant-based meat alternatives to find ones that come close to the real deal.

“In recent years, increasing awareness of the impact of meat production on climate change and the meat shortages during the pandemic has made people more accepting of plant-based alternatives,” said Dr. Lili Zyzak, who led the investigation. “There are a lot of products and food companies 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 several decades. However, early versions were very different from meat. In recent years, food scientists — working for both established industrial giants and tech start-ups focusing on fake meats — have developed techniques to make proteins from plants like soy and peas that taste more like meat.

Raw beef burgers have minimal odor. However, during cooking, hundreds of volatile compounds are released that contribute to a savory, greasy taste and smell. It is a challenge to match this easily recognizable scent with vegetable proteins and vegetable oils.

“The problem with vegetable burgers is that the vegetable protein itself gives off a strong odor,” explains Zyzak. “For example, pea protein smells like green grass clippings, so companies have to find a way to mask that aroma. Some use heavy herbs.”

Zyzak was interested in assessing the aroma of plant-based burgers to better inform consumers about their qualities. She and her colleagues analyzed the flavorings produced by cooking real beef burgers and eight of the brand’s popular plant-based burgers.

First, they cooked the burgers and evaluated the flavors against five descriptors: meaty, fatty, buttery, sweet, and roasted. They then applied gas chromatography-mass spectrometry in combination with olfactometry (measurement of odor composition) to correlate the aromas with specific odor compounds. This required them to inject volatiles from the cooking burgers into the instruments, which separated the compounds. A portion of the sample was diverted to a sniff port for human participants to identify which of the five descriptors they were smoking. The remaining sample was analyzed by mass spectrometry, which allowed the researchers to correlate specific compounds with the aroma identified by the participant at any given time.

This allowed the chemists to identify the compounds that made the plant-based burgers differ from a beef burger. They found that Beyond Meat’s Beyond Burger most closely resembled the odor profile of beef, with meaty, fatty and grilled meat characteristics of the compounds 1-octen-3-ol, octanal and nonanal. However, it still differs significantly in smell from the real thing. Another was most similar to a beef burger, but produced a yeasty odor when cooked, with higher levels of methylbutanals and propionic acid. Other patties used heavy spices to release the garlicky and barbecue sauce-like flavors of burgers.

Ultimately, Zyzak wants to use her findings to produce a blend of fragrances that closely mimic the hamburger flavor. She is working with a start-up to obtain samples of synthetic meat, which she wants to compare with plant-based and regular burgers.