AUBURN – Surrounded by heaps of groceries, Mary Lou Merrill clutched her coffee can and ignored the clock.

At 7 a.m. Friday, she arrived on the warehouse floor at the Good Shepherd Food-Bank. Her job: sorting, sifting and stacking tons of food, everything from broken cereal boxes and dented coffee cans to taco shells and denture creme.

And she planned to keep at it.

Joined by dozens of other volunteers, the Poland woman planned to work for 32 hours straight.

The food bank is calling it an “inspectathon.”

“We’re cranking out some food today,” said Merrill, who came with her sister, Linda Cotton of Mechanic Falls. “That’s the reason we’re here. They need the help.”

The food bank is facing a shortage of volunteers. Pallets of unsorted food have been stacking up in the Hotel Road warehouse, while some shifts have fallen almost empty of volunteers.

“We have about 50 regulars,” said John Russell, the food bank’s volunteer supervisor and coordinator. “We’d like to double that if we can.”

It’s especially difficult right now, as soup kitchens and food pantries from across Maine prepare for the holidays. For most member charities, the holiday work begins with a trip to a corner of the Auburn warehouse, to a kind of store displaying the sorted food.

“They’re doing their shopping right now and those shelves are pretty bare,” said Rick Small, the food bank’s executive director.

That began to change as the volunteers went to work Friday. By 11 a.m., only four hours after they began, 46 workers had sorted about 25 pallets of food, each weighing roughly 1,000 pounds.

As the day went on, as some volunteers left and others slowed with fatigue, Russell expected the sorting to slow.

Meanwhile, he nurtured a party atmosphere. Using donations he solicited from local businesses, Russell gave away prizes hourly.

It seemed to work.

“I’ve seen a lot of faces today,” he said. The true payoff will come if the people return.

The goal was to create a steady pool of returning volunteers who are trained in inspecting the donations that come in, Russell said.

The volunteer problem started this past summer, when Good Shepherd stopped giving bags of food to eligible volunteers as a thank-you for their work.

Concerned that it could be misinterpreted as payment, the charity’s board decided to halt the policy.

And lest anyone go hungry, the organization brought in an outside group to operate a food pantry, which services individuals and families in a rear corner of the warehouse.

New people have come in, but not enough to eliminate the problem.

“We’ll do whatever we need to do,” Russell said. Through its 600-plus agencies, the food bank distributes enough food each month to make about 1.5 million meals.

Volunteer Sharon Williams of Auburn planned to work 7 a.m. to 7 p.m. on Friday and return for an 8-hour shift on Saturday.

She has known too many people who were helped by the food bank to stay home, said Williams, who has volunteered for about six years.

The official goal of the 32-hour event was to sort about 60,000 pounds of food by the end, but Russell was hopeful that the total would climb higher.

“One hundred thousand would be sweet,” he said.