Cadbury, Coca-Cola Enterprises and Nestlé are all locked in talks with trade unions despite each having offered staff some form of pay rise.
Cadbury's 2.5% pay offer was rejected by Unite without consulting members. The union is holding out for a 5% rise and demanding guarantees that there will be no further site closures or redundancies in the next five years.
In a newsletter for members, Unite said Cadbury had increased its profits by 31% in the past year, while workers had been forced to swallow a pay rise worth "a mere 0.5%".
Tensions are also running high at CCE, where more than 80% of Unite members last week voted in favour of holding a strike ballot.
CCE staff have been offered a 2% pay rise. But they are angry over management's refusal to consult with them about the rise or about changes to its basic pension scheme, according to Unite's national officer for food and drink, Jennie Formby.
Nestlé workers belonging to Unite, the GMB and Usdaw also voted for a strike ballot last week. Staff were angered when Nestlé announced it was freezing basic pay this year although last week it signalled plans for a rise of 1%.
It is understood many of the votes were cast before the 1% offer was made. But shop stewards have indicated that staff are not satisfied with the offer.
"We are not being militant and we want to avoid industrial action," said Formby. "But many of the companies in the grocery sector are doing extremely well and increasing profits despite the recession. We feel that our members should have a share in those profits as they are the people that actually generate the wealth."
Meanwhile, confectioner Tangerine is understood to have resolved a dispute with Unite after engineers at two of its manufacturing sites accepted an undisclosed pay increase.