by Julie Watts and Abigail Sterling

SAN FRANCISCO (KPIX 5) — Have you ever reached to the back of the supermarket cooler to grab the milk with the latest expiration date? Well, buyer beware: those milk dates may be way off.

Alex Snell is something of a milk connoisseur. He’s a cancer survivor and drinks a lot of milk to settle his stomach. Lately, he says his milk has been spoiling way too early.

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“The very first time this happened to me it expired about ten days before the expiration date,” Snell said.

At first Snell thought it was a fluke but one week after buying a new gallon “It had started to curdle,” he said. Then he says it happened a third time and a fourth.

KPIX decided to investigate, putting Snell’s milk to the test. Our first stop — his neighborhood Lucky Supermarket, where we stocked up on Sunnyside Farms, his preferred brand.

Then, we bought the same Sunnyside Farms milk at a different supermarket, Nob Hill Foods. We also picked up a “control” milk there, Clover — Different brand, same store.

Packing each gallon into a cooler of ice, we delivered the samples to Anresco labs in San Francisco to be tested.

Meanwhile, back at the station, we recruited newsroom staffers for three blind taste tests, one on the day we bought the milk, then again in a week and then after two weeks.

Round one, the day we bought milk, all three milks smelled and tasted equally fresh. “It tastes like normal milk,” said Gretchen, one of our testers.

One week later, our tester Scott wasn’t so pleased: “It’s drinkable but I wouldn’t call it fresh,” he said.

Sunnyside Farms from Snell’s Lucky supermarket was getting bad reviews, nine days before the date stamp.

“I would be on the edge of throwing it out,” Scott said.

And so was the Sunnyside Farms from Nob Hill, still eight days before its date stamp. “Yeah, that one doesn’t taste good,” said our taste tester Marian.

The Clover brand from the same Nob Hill Foods got the best reviews even though it was date-stamped for the very next day. “It doesn’t taste quite as fresh as a week ago but it still tastes fine,” said Gretchen.

Our round-three taste test was the clincher.

“One of these smells funny,” said Marian. Two days before the best-by date, Sunnyside from Snell’s Lucky store was already deemed unfit to drink.

“It looks like something I would find in my brother’s college fridge,” said Marian.

Same with the Sunnyside Farms from Nob Hill foods, which still had one day to go.

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“Ew, there are floaties in here. That is nasty,” said Scott.

Once again, our Clover milk from the same store, now one week past its date stamp, was unanimously voted the best of the bunch. Our taste testers were all completely surprised.

“The ones that are dated farthest out should be the freshest. And it should be a consistent thing,” said Scott.

But it turns out that is not necessarily the case. No one regulates best-by or sell-by dates. Dairy processors can set these dates as far ahead as they want. In this case, the Sunnyside Farms milk had a “best by” date, the date you should drink it by, while Clover had a “sell by” date.

“Sell by date is the typical one that is out there,” said Dr. Phillip Tong, an industry expert with the California Creamery Operators Association.

He says the sell-by date is the industry’s voluntary standard.

“It tells the retailer the date that product should be sold at. Milk would still be good if kept cold by the seven days after that sell-by date,” said Dr. Tong.

That could explain why our Clover milk still tasted good one week after its sell-by date.

While you might expect Sunnyside Farms to start souring by its best-by date.

We asked Dr. Tong about that. “Well I think it still provides the consumer with some valuable information, at least it does for me,” said Dr. Tong.

Regardless of taste, our lab tests showed all three milks were well below the legal microbial limit. Why the difference?

“Those counts don’t count all bacteria, unfortunately,” said Dr. Tong.

“There must have been some bacteria that caused our milk to spoil even though the lab didn’t find one,” we asked him. “That’s right, that is right,” he said.

Back in Dublin, Alex Snell is sticking to the smell test.

“I am spending money here and I am pouring it down the drain,” Snell said. He’s switching to another brand.

Sunnyside Farms was quick to conduct an internal investigation when we alerted them. They tell us everything checked out fine. They also told us they are in the process of converting to a sell-by date.

Here’s Sunnyside Farms full statement (PDF):

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In response to our inquiry, Clover Sonoma responded with this statement (PDF)