A report commissioned by the NHS last year found that up to 40% of patients are malnourished in hospital and one in 10 would have a shorter stay in hospital if the food was better.
Grossman and a posse of Britain's best chefs will be asked to create menus suited to individual patients' needs in a long awaited initiative to improve food in Britain's hospitals.
Extensive trials of new menus will be held as part of the £40m revamp.
The first step will be to survey NHS trusts and to talk to caterers and to patients about their ideas.
Around £500m is spent on 300 million NHS meals every year.
Mr Grossman told the BBC the initiative would be based on practical suggestions.
He said: "It is not a gimmick, it is not a celebrity exercise, it is not a joke, it is not trivial - it is incredibly important to a lot of people.
"I have been asked to come in to chose a team of chefs, to co-ordinate their work and to draw up a set of practical recommendations that will then be put into effect.
"I believe passionately that everybody should be able to get good food.
"This is not party politics, it is about delivering better food to a lot of people who need it."
Damning report
A report commissioned by the NHS last year found that up to 40% of patients are malnourished in hospital and one in 10 would have a shorter stay in hospital if the food was better.
There are also concerns that poor quality is creating huge waste in the NHS.
The Department of Health report said: "These standards are not good enough.
"The food is variable in quality, it is not provided in a way which is sufficiently responsive to patients, and too much of it is wasted as a result."
The NHS will make food available on a 24-hour basis and is introducing ward housekeepers whose job it is, is to ensure food is the right quality and quantity.
A pilot scheme in place at Nottingham City Hospital has already introduced a ward housekeeper.
They wait on patients and help them decide what to eat, suggesting snacks as an alternative to a main meal. The amount of food wasted has decreased by 40%.
An NHS spokeswoman said the scheme was part of a wider initiative.
"There will be a variety of chefs but Loyd Grossman will be the figurehead," she added.
By next year hospitals will have a 24-hour "ward call" service similar to hotel room service, giving them round-the-clock access to meals from the new menu.
At present, meals are served at rigid times and patients have complained that they are often left without food if they miss the set meals.
Ward housekeepers will also be appointed to ensure quality, and hospital food will be subjected to regular inspections, with patients asked for their views.