The types of roles that were most likely to be affected were cooks, stores and menu collators.
But the document said staff would be redeployed elsewhere in the DHB or Compass Group where possible.
Food preparation at Hawke's Bay Hospital would also change to a "Cook Chill" method used by Compass Group, which would involve frozen ingredients arriving at the hospital, to be cooked or re-heated in bulk.
"A greater proportion of meal components would be pre-prepared, and then heated on site, than is presently the case."
However, it was proposed Compass Group would continue to source the majority of its ingredients from within Hawke's Bay, such as bread products from Goodman Fielder and Quality bakers, and local fruit and vegetables.
Service and Food Workers Union national secretary John Ryall said the union was opposed to the scheme.
"I don't believe savings come from massive internal re-structuring and privatisation. I think savings come from incremental changes supported by DHB staff and patients," he said.
The eight staff whose jobs were threatened made up about 20 per cent of the DHB's food service work.
"It's a pretty dramatic change to the food service. It's moving from freshly cooked food on the site, to pre-frozen ingredients. It's totally different to what patients in Hawke's Bay are used to."
In March the union presented a petition opposing the scheme to a board meeting, with more than 1000 signatures, mostly from DHB staff.
Hawke's Bay Chamber of Commerce chief executive Wayne Walford said job losses were "never good for the region".
"We're always concerned about the loss of jobs, but we're also concerned about the viability of companies. The companies providing services need to be viable."
Food Hawke's Bay manager Patricia Small said the region did not need "any more job losses".
"Food Hawke's Bay supports the local food sector from growers through to retailers. It would be a concern to us if the local food sector were to suffer from changes proposed to outsource food services to the DHB. Fresh, local produce would undoubtedly be beneficial for patients' well-being. As a region we don't need any more job losses."
The business case was developed for staff and community feedback, to be received by April 24.
Feedback will be considered by the DHB next month. Any changes would probably occur from May next year.