Supermarket workers are speaking out to CBC's Marketplace about how stores tamper with best-before dates and how it can make food unsafe.

For five years, Mohammad Saffari has worked as a bakery clerk at a Loblaws store in Montreal. He says he was told to change best-before dates on fresh or frozen bakery items such as cheesecakes, muffins and pastries that were weeks or months past the best-before date.

Saffari says he was told to take cheesecakes that had passed their best-before dates and add toppings, so they would appear fresh.

He says cakes were then given a new best-before date and put back on the shelves for sale.

"I decorate it and I'm selling expired stuff for $13.99," he says. "I won't eat this cheesecake myself. But I sell it to you."

'You think other stores don't do it?'

Saffari approached Marketplace after he became frustrated with being asked to change dates. "I couldn't take it anymore," he says. "I was on sick leave for three to four months because of the pressure; because what you're doing you're not proud of and you're forced to do it."

Supermarket insiders say cakes were cut in half or retopped with fresher items and the best-before date extended. (CBC) After speaking up about this on a number of occasions, Saffari decided to secretly record a conversation with his supervisor where he asks about the practice. He shared the recording with Marketplace.

"Every store does the same f---ing thing. You think other stores don't do it?" the supervisor says on tape.

"Everyone f---s with the dates, Mo. Because at the end of the year, the managers, their bonus, you understand?"

Loblaws responds

In an email, Johanne Héroux, a senior director at Loblaws, told Marketplace:

"As a company, we are fully committed to upholding the highest standards in terms of product quality and safety. We have strict protocols in place to ensure their application across all our stores and departments.

"As for the store-specific allegations brought to our attention and in accordance with our zero tolerance policy regarding actions that jeopardize the safety and quality of our products, an investigation was undertaken immediately. Necessary actions will be taken upon completion of the ongoing investigation."

Problems industry-wide

But Saffari is only one of a number of former and current supermarket employees who spoke out about how supermarkets change best-before dates.

Marketplace heard from people who have worked in the bakery, meat and produce departments of a number of different grocery stores, both chains and independent. They described a number of tricks that supermarkets employ to make food appear fresh.

Some insiders told Marketplace that old meat was marinated in sauce to mask the smell. (CBC) These tactics include grinding old meat with fresher meat, marinating old meat in sauces that mask the smell, cutting mould off fruit and vegetables for party trays, and cutting cakes in half to facilitate a faster sale after the best-before has passed.

One insider also says his store took meat that had gone brown from sitting out, and dipped it in blood to make it look redder. Others said they would take mouldy fruit off custard tarts, replace it and glaze it to make it look fresh.

In each of these cases, food was put out with new best-before dates that significantly extended the shelf life.

Food treated this way can harbour microbes that can make you sick, says Keith Warriner, a microbiologist at the University of Guelph.

Best-before dates no guarantee

Best-before dates aren't a guarantee that food is safe to eat. Other factors, such as the way food is stored, can make a big difference.

For dry food, such as cookies, crackers and pasta, best-before dates are a guarantee of freshness and flavour, and don't mean that food past that date is unsafe to eat.

So how do you know that the food you're buying is fresh? Employees recommend buying meat from the back of the shelf, and avoiding pre-marinated or cut foods. They also suggest buying whole cakes, pies and tarts.