Say what you will about "big food," but they will be around to be sued in 20 - 50 years. It means they have incentives to actually careful about what they to do people.
Just because I sell something doesn't make me exempt from the legal consequences of my actions prior. If I negligently claim that a product will make you healthier and it cripples you, then you can sue me regardless of whether I still own the product. Similarly, I could be prosecuted for dishonest advertising type offences (which aren't wiped clean simply by selling a business!).
You might be talking about a products liability type claim.
Only an incompetent acquirer would take liability for any latent claims in a target acquiree. Most likely they will get strong warranties from the seller about the existence of claims and rely on their own due diligence to ensure they aren't buying a product which is likely to cripple people in the future.
In 90% of cases the seller will retain liability for incidents which pre-date the sale of their business.
Actually, yes, selling your stake in the corporation that was the legally-responsible actor does mean that you are no longer at any financial risk for the actions of the corporation prior to you selling it, at least not in the main way that you were prior to selling it (that the consequences imposed on the corporation would reduce the value of your equity stake.)
If you manage to sell the corporate entity to a third party without making any warranties about latent claims, you will not be concerned about the corporation's liability. And the purchaser of that corporation is pretty foolish.
However you are still responsible for your own personal liability when you operated the company. Did you breach your directors' duties? Did you commit fraud? Did you sign a guarantee for the obligations of the corporation?
There are three ways to become personally liable off the top of my head. I'm sure there are several more.
However, the enumeration of those other avenues to liability is valuable.
The corporate veil may protect them from liabilities of the company (barring fraud/breach of directors' duties), however in this particular instance we have a founder, Rob Rhinehart, who seems to have done most of his marketing and made most of his claims personally. That is, Rob, not Soylent Nominees Ltd, made the statements.
Therefore, if he has breached laws, civil penalty provisions or acted negligently in doing so, he is personally liable.
Source: I recently acted for a home owner who sued her (incorporated) builder in negligence (for building a house which fell down). The company was unfortunately insolvent. Luckily, the founder/director of the company made a number of claims about the expertise and abilities of the building company on the company website (which he hosted personally). We sued the director personally.
Sure, they are going to want to differentiate from existing Big Food products (so do new Big Food products), but otherwise, the trust factors are pretty much the same.