Walden said there was a need for greater transparency around judges' commercial tie-ins. Prizes for winning challenges included trips to Simon Gault-owned restaurants. "It all feels like a pretty cosy cartel," said Walden. "But that's commercialism."
MasterChef's success - it has around 500,000 viewers each week and a huge social network following - allows it to command huge sums from sponsors and advertisers.
Analysts estimate Count-down's presence on the show would cost it up to $2 million per season.
And TVNZ can command up to $9000 for a 30-second commercial during the show, up from $8500 last year.
The show's commercial partners include Stevens homeware, Regal Salmon and Jetstar. The budget airline features in an upcoming episode when contestants fly to Singapore.
But despite the rumoured million-dollar investment from the supermarket giant, Countdown says it has no input into storylines or how its brand is portrayed.
Countdown spokesman Luke Schepen laughed off suggestions that it could influence the colour of McVinnie's clothes.
"I'm glad he has good fashion sense," he said. "We certainly like green, but I think you might be reading too much into it."
The benefits for Countdown are immediate. After an episode featuring non-perishable ingredients, sales of canned chickpeas leapt by 30 per cent.
A TV executive at another network, who declined to be named, said placement in MasterChef was "clumsier" than in other reality TV shows.
In the Hawke's Bay, MasterChef's visit this week took up the entire front page in the local paper. Vineyard Elephant Hill hosted the show and received extensive coverage.
Hawke's Bay Tourism general manager Annie Dundas said it hadn't forked out any money to attract producers - the restaurants and vineyards had sponsored the exercise.
"MasterChef has always been our target ... it fits the food and wine brand of Hawke's Bay perfectly."