Recent breakthroughs: Lab grown STEAKS could soon be on the menu
Lab grown
STEAKS could soon be on the menu: Recent breakthroughs in cultured meat could
pave the way for cuts more complex than burgers
·
To create
cultured meat, researchers take small amounts of tissue from animal
·
After
isolating individual cells, they're put in flasks and fed nutrients, oxygen
·
When grown
on plastic, cells will divide until they exist on all of available surface
·
To get an
organized structure like steak, you need vessels and connective tissue
·
The meat you eat, if you're a carnivore, comes from
animal muscles. But animals are composed of a lot more than just muscle.
They have organs and bones that most Americans do not
consume. They require food, water, space and social connections. They produce
waste.
Farmers spend a lot of energy and resources to grow
complex organisms, creating waste in the process, only to focus on the
profitable cuts of meat they can harvest.
It would be easier, more humane, less wasteful, to
produce just the parts people want.
And with cell biology and tissue engineering, it is
possible to grow just muscle and fat tissue. It's called cultured meat.
Scientists provide cells with the same inputs they need
to grow, just outside an animal: nutrients, oxygen, moisture and molecular
signals from their cell neighbors.
So far researchers have cultivated bunches of cells that
can be turned into processed meat like a burger or a sausage.
+2
· Animal cells alone can replicate most of the
meat experience. But without blood vessels and connective tissue, you don't end
up with an organized, three-dimensional tissue – and that's what you need for
structured cuts of meat, like steak, chicken breast and bacon. Stock image
This cultured meat technology is still in the early
phases of research and development, as prototypes are scaled-up and fine-tuned
to prepare for the challenges of commercialization.
But already bioengineers are taking on the next tougher
challenge: growing structured cuts of meat like a steak or a chicken cutlet.
What meat's made of
If you look at a piece of raw meat under the microscope,
you can see what you're eating on the cellular level.
Each bite is a matrix of muscle and fat cells, interlaced
with blood vessels and enrobed by connective tissue.
The muscle cells are full of proteins and nutrients and
the fat cells are full of, well, fats.
These two cell types contribute to most of the taste and
mouth-feel a carnivore experiences when biting into a burger or steak.
The blood vessels supply an animal's tissue with
nutrients and oxygen while it's alive; after slaughter, the blood adds a
unique, metallic, umami nuance to the meat.
The connective tissue, composed of proteins like collagen
and elastin, organizes the muscle fibers into aligned bundles, oriented in the
direction of contraction. This connective tissue changes during cooking and
adds texture – and gristle – to meat.
The challenge for cellular agriculture researchers is to
emulate this complexity of meat from the bottom up.
We can grow muscle and fat cells in a petri dish – but
blood vessels and connective tissue don't spontaneously generate as they do in
an animal.
How can we engineer biomaterials and bioreactors to
provide nutrient diffusion and induce organization so we end up with a thick,
structured cut of meat?
To create any cultured meat, researchers take small –
think marble-sized – amounts of tissue from a cow, pig or chicken and isolate
individual cells.
Then, bioengineers like me put the cells in plastic
flasks and give them nutrients, oxygen and moisture while housing them at body
temperature.
The cells are happy and can divide exponentially,
creating more and more cells.
Section of turkey stained to show
cellular-level organization skeletal muscle tissue – also known as meat
When grown on plastic, the cells will continue to divide
until they exist on all of the available surface area.
This results in a crowded layer that's one cell thick.
Once the cells stop dividing, they start to mature.
Muscle cells fuse together to create long muscle fibers
and fat cells begin to produce lipids.
Researchers can combine a bunch of these cells together
to create processed meat products, like burgers, hot dogs and sausages.
Animal cells alone can replicate most of the meat
experience.
But without blood vessels and connective tissue, you
don't end up with an organized, three-dimensional tissue – and that's what you
need for structured cuts of meat, like steak, chicken breast and bacon.
To overcome this challenge, scientists can use
biomaterials to replicate the structure and function of blood vessels (for
nutrient and oxygen transfer) and connective tissue (for organization and
texture).
This area of research is called scaffold development.
Scaffolds are the secret ingredient for steaks
The concept of scaffolds originates in the field of
tissue engineering for medical applications. Scientists combine cells and
scaffolds to produce functional biomaterials for research, toxicology screening
or implants.
These biomaterials can take different forms – films,
gels, sponges – depending on what properties are desired in the resulting
tissue.
For example, you could grow skin cells on a flat collagen
film to create a skin graft to help burn victims or bone cells in a hydroxyapatite
sponge for bone regeneration.
For medical applications, scaffolds generally need to be
safe for implantation, must not induce a response from the body's immune
system, be degradable and capable of supporting cell growth.
For food applications, the design considerations of
scaffolds are different. They should still support cell growth, but it's also
important that they are inexpensive, edible and environmentally friendly to
produce.
Some common biomaterials for food applications include
cellulose from plants, a carbohydrate called chitosan from mushrooms and a
carbohydrate called alginate from algae.
Here's one 'recipe' for cultured meat that I've worked on
in the lab. First, create an appropriate scaffold. Isolate chitosan from
mushrooms and dissolve it in water to create a viscous gel.
Put the gel in a tube and expose one end to a cold
substance, like dry ice or liquid nitrogen.
The whole tube of gel will slowly freeze, starting at the
cold end. The frozen gel can then be freeze-dried by a vacuum pulling on the
gel at very low temperatures, ultimately creating a dry sponge-like
material.
The directional freezing process creates a sponge with
small, long, aligned pores resembling a bundle of straws – and also muscle
tissue.·
The simplified process for creating a
chitosan sponge with aligned pores is illustrated in the graphic above
Then, instead of growing meat on flat plastic, you can
transfer the cells to this three-dimensional sponge to provide more surface
area for growing thicker tissue.
The pores can also help distribute nutrients and oxygen
throughout the tissue. So far with this technique, my lab has been able to
produce small bits of meat less than a centimeter square – a little small for a
cookout but a strong start.
Other scaffold possibilities include growing cells within
alginate-based fibers, gels or sponges.
Or technicians can rinse plant cells off of plants in a
process called decellularization and repopulate the cellulose framework that's
left behind with animal cells.
Once researchers find materials and methods that work
really well, we'll work on creating larger batches.
At that point, it'll be a game of scaling up the process
and bringing down the cost so cultured meat products can be cost-competitive
with farmed meat products.
It's always exciting to see startup companies debut their
cultured meatballs, sausages and burgers.
But I'm looking ahead to what's next. With a bit more
research, time, funding and luck, the cultured meat menu 2.0 will include the
steak and pork chops many carnivores know and love.
HOW
IS 'TEST TUBE MEAT' GROWN IN A LABORATORY?
'Test
tube meat' is a term used to describe meat products grown in a laboratory
'Test tube meat' is a term used to describe meat products
grown in a laboratory.
They are made by harvesting stem cells from the muscle
tissue of living livestock.
The cells, which have the ability to regenerate, are then
cultured in a nutrient soup of sugars and minerals.
These cells are then left to develop inside bioreactor
tanks into skeletal muscle that can be harvested in just a few weeks.
Lab-grown beef was first created by Dutch scientists in
2013. A test tube hamburger was served at a restaurant in London to two food
critics.
In March 2017, San Francisco firm Memphis
Meats successfully grew poultry meat from stem cells for the first time.
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