Workers at the Heinz Baked Beans factory in Wigan will go on strike next week in a row over pay.
Unite said its members at the site would walk out for 24 hours from next Wednesday evening and begin a continuous ban on overtime.
The action was agreed at a mass meeting on Saturday after last week's decision to reject a pay offer of 3.3% this year and 3% the following year.
Heinz said the outcome of the ballot was "very disappointing".
A spokesman said its pay offer in the first year equated to 4% "in real terms".
"This is well above the UK average weekly earnings which are increasing by 1.7%, and remains a very fair offer," he added.
"As a package it stands out as one of the best in the food and drink sector, the area and the country."
About 1,200 people are employed at the Greater Manchester factory, which produces beans, soups, pasta meals and baby food.
Unite said the stoppage would lead to two million fewer cans being produced, but Heinz denied this, saying it had "already taken steps to manage stock levels to ensure consumers are not disappointed".
Speaking after the mass meeting, Jennie Formby, Unite's national officer for food and drink, said: "The mood of the meeting was angry and determined.
"Heinz have left our members with no choice but to stand firm and fight for a fair pay deal."
She added: "They are treating its loyal and long-serving workforce disgracefully. It's our members that helped them make its vast profits yet they are still refusing to table an improved offer that reflects their hard work.
"Make no mistake, this strike will hit Christmas production.
"Our members are absolutely determined to win fair pay and we are determined to see that they get it. Unless Heinz forks out a fairer deal, then strike action will go ahead."
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