SAQ employees launched a surprise strike on Friday afternoon.
It is the first of 18 strike days in the mandate they gave themselves in September.
The 5,500 employees of the government-run company have been without a contract since March 31, 2017.
They are calling for more job security for part-time employees, and for more pay for all employees.
In a statement, SEMB-SAQ union president Katia Lelievre denounced disciplinary measures taken on employees who were putting pressure on management.
So far this year SAQ employees have held eleven days of strikes in a bid to pressure management to improve their working conditions.
Three days of negotiations are scheduled for next week.
