Lab-grown fat could enhance cultivated meat

Researchers from Tufts University have bulk-produced fat tissue with a similar texture and make-up to fat tissue that naturally occurs in animals. The study, published in eLife, says the fat tissue could be applied to the production of cultivated meat, giving it a more realistic texture and flavour.

Cultivated meat is still in relatively early stages of development, with many startups yet to bulk produce or gain commercial approval of their products. Most of the products being developed are in the form of an unstructured mixture of cells, lacking the real texture of a fillet or steak, which is naturally created by muscle fibres, connective tissue and fat. For example, cell-grown chicken would be more similar to the texture of chicken nuggets than a slice of chicken breast.

Fat contributes texture and taste to meat, with tests showing that consumers prefer beef containing a higher fat content.

It has been challenging to produce cultured fat tissue in sufficient quantities because the cells in the middle become starved of oxygen and nutrients as the fat grows into a mass. In nature, oxygen and nutrients are delivered through blood vessels and capillaries — something which researchers have no way to replicate at large scale in lab-grown tissue.

The researchers grew fat cells derived from mice and pigs to get around the limitation, first growing them in a flat, two-dimensional layer before harvesting those cells and aggregating them into a three-dimensional mass. The mass used binders such as alginate developed from seaweed and microbial transglutaminase (MTG), both of which are already used in some commercial foods.

The researchers’ goal was to develop a method that is relatively simple.

“Since fat tissue is predominantly cells with few other structural components, we thought that aggregating the cells after growth would be sufficient to reproduce the taste, nutrition and texture profile of natural animal fat,” said John Yuen Jr, a graduate student at Tufts University. “This can work when creating the tissue solely for food, since there’s no requirement to keep the cells alive once we gather the fat in bulk.”

The fat cells had the appearance of fat tissue, but the researchers carried out further tests to see if they reproduced the features of native fat from animals.

To explore the texture, they compressed the fat tissue and saw how much pressure it could withstand compared to natural animal fat. They found that fat bound with alginate withstood a similar amount of pressure to fat tissue in livestock and poultry while fat bound with MTG behaved more like rendered fat, similar to lard or tallow. This suggests that it may be possible to fine-tune the texture of cultured fat using different types and amounts of binders to make it as close as possible to natural fat.

It is also important to consider the molecular composition of fat. Cooking releases compounds that add flavour and aroma to the meat, most of which originate from fat, including lipids and component fatty acids.

The research team examined the composition of the molecules from cell-grown fat and found that a mix of fatty acids from cultured mouse fat differed to native mouse fat, but cultured pig fat had a closer acid profile to the native tissue. This suggests that it might be possible to supplement growing fat cells with different lipids for a closer match to the fatty acid composition of natural meat.

According to David Kaplan, professor at Tufts and director of TUCCA, this method may be translated to large-scale production of cultured fat tissue and bioreactors.

“We continue to look at every aspect of cultured meat production with an eye toward enabling mass production of meat that looks, tastes and feels like the real thing,” Kaplan said.

Image caption: Fat contributes texture and distinct flavour to farm raised beef (shown in main image) and other meats. Researchers have replicated the texture and composition of natural fat in fat tissue grown from cells. Image credit: Mike Silver, Tufts University