Jeff Bezos, founder and chief executive officer of Amazon.com Inc., speaks at the National Press Club in Washington, D.C., on Thursday, Sept. 19, 2019. Andrew Harrer | Bloomberg | Getty Images

Amazon's sprawling marketplace, consisting of millions of third-party sellers, has become a go-to site for many grocery shoppers, especially since the company's acquisition of Whole Foods over two years ago. But an increasing number of consumers are finding that, just as the broader Amazon Marketplace has a major issue with counterfeits and unsafe products, the grocery section is littered with similarly problematic items in the form of expired foods. From baby formula and coffee creamer to beef jerky and granola bars, items are arriving spoiled and well past their sell-by date, Amazon customers say. Interviews with brands, consumers, third-party sellers and consultants all point to loopholes in Amazon's technology and logistics system that allow for expired items to proliferate with little to no accountability. Consumer safety advocates worry that as the marketplace grows, the problem will only get worse. Within Amazon's $900 billion empire, food sellers are among the more than 2.5 million businesses using the site for distribution, a group that now accounts for 58% of the company's total merchandise sold. Third-party merchants sell products, new and used, from all over the world that they purchase from official distributors, flea markets and clearance aisles.

CNBC scanned the site's Grocery & Gourmet category, finding customer complaints about expired hot sauce, beef jerky, granola bars, baby formula and baby food, as well as six-month-old Goldfish crackers and a 360-pack of coffee creamer that arrived with a "rancid smell." A data analytics firm that specializes in the Amazon Marketplace recently analyzed the site's 100 best-selling food products for CNBC and found that at least 40% of sellers had more than five customer complaints about expired goods. Closeout sales and liquidation warehouses can be a hotbed for expired food that ends up on Amazon. In 2017, when Starbucks announced it was shuttering its Teavana locations, many sellers purchased discounted tea-related merchandise from the stores and resold it on Amazon. Today, you can find Teavana products such as rock sugar and fruit teas listed on Amazon even though they were discontinued two years ago. For one Teavana listing, the top customer review says the tea had a "terrible chemical smell" possibly from spoiled fruit. The listing also clearly shows a "not for resale label," which is alarming, said Sarah Sorscher, deputy director of regulatory affairs at the Center for Science in the Public Interest, or CSPI, a consumer advocacy group. The "not for resale" label likely indicates that the product lacks proper nutrition labels or other features that are necessary in direct-to-consumer sales, she said. "At least someone in the supply chain considered these not suitable to be offered for consumption," Sorscher said.

A listing for Teavana tea that shows 'Not for resale' on the package. Amazon

An Amazon seller, who has sold sugar, spices and other food products on the site for the past nine years, told CNBC that Amazon didn't respond to numerous inquiries about the out-of-date Teavana products. Representatives from Nestle, which owns the rights to sell Starbucks coffee and tea, including Teavana, declined to comment. An Amazon spokesperson told CNBC that products sold on the site, including those marked not for resale, must comply with laws and Amazon policies. Third-party sellers are required to provide Amazon with an expiration date if they're selling an item meant for consumption and must guarantee the item has a remaining shelf life of 90 days. Whether that Amazon policy is effective is a big question, says food-safety experts. "There's no indication of how well that policy is enforced," said Thomas Gremillion, director of food policy at advocacy group Consumer Federation of America. "Some sellers could be making a business decision to sell expired products and let Amazon catch some of it and toss it out and persist."

'Stale' Doritos

One third-party listing for Hot & Spicy Doritos, a best-seller in Amazon's chips category and a featured product, has numerous reviews saying the chips were "stale" and set to expire in a matter of days. Popular listings for Fiji water, including one featured by Amazon, show reviews with users claiming they received recycled Fiji bottles filled up with tap water.

An example of a customer complaint about expired coffee creamer. Amazon

An example of expired beef jerky sold on Amazon. Amazon

Angie Atkinson of St. Louis was surprised in February when she received a box of Land O' Lakes Half & Half creamers purchased on Amazon, and opened it to find that every carton was curdled. She looked at the use-by date and was "horrified" when she saw they were already expired. "It didn't occur to me that you could even sell something that was expired," Atkinson said in an interview. "If I had bought it the first time and it was like that, I never would have bought it at all." By the time Andrea Wilson realized her Hostess brownies were more than a year old, she had already eaten one. She contacted Amazon about the order. The issue wasn't resolved until she tweeted at the company. She got her full refund but said she's done buying food on Amazon. tweet "I'm leery now," said Wilson, who lives in the Washington, D.C., area. "It wasn't just a month, it was a whole year, which I thought was pretty extreme." Amazon said in a statement: "With the A-to-z Guarantee, customers are always protected whether they make a purchase from Amazon or a third-party seller." After CNBC brought a number of expired food products to Amazon's attention, the company said it took corrective action to make sure the listings were in line with its standards. Amazon said they were isolated incidents that didn't require enforcement action against the sellers or removal of any products. Many of the identified products continue to receive complaints that they're expired, with some showing negative reviews posted as recently as this week.

An imperfect process

Amazon's spokesperson said the company uses a combination of humans and artificial intelligence to monitor the 22 million-plus pieces of customer feedback received weekly for product quality and safety concerns. Amazon may remove products or suspend an account if the seller violates its policies. "We work hard to make sure customers receive high-quality products when they order from our store," the spokesperson said. "We have robust processes in place to ensure customers receive products with sufficient shelf life. "If customers have concerns about items they've purchased, we encourage them to contact our Customer Service directly and work with us so we can investigate and take appropriate action," the spokesperson added. Regulators and lawmakers are paying closer attention to Amazon's every move now as part of a broader review of Big Tech. Specific to consumer safety, three Democratic senators recently sent a letter to CEO Jeff Bezos after a Wall Street Journal report found thousands of unsafe or banned products on the site. In response to the request, Brian Huseman, Amazon's vice president of public policy, said that "bad actors are constantly attempting to evade our automatic tools and review procedures." Amazon says it feeds data from suspended listings and accounts into its AI systems so they can get better at detection and at blocking suspicious activity. Human moderators can also trigger an investigation if they receive feedback suggesting a product is unsafe. In the food category, Amazon uses a database called "Heartbeat" to monitor customer commentary through reviews, phone calls, emails and seller feedback for safety issues. Even with all these tools, several consultants who advise sellers say Amazon needs to rely on more than just customer complaints and refunds to catch expired foods. They argue that Amazon needs to devise new strategies to police the marketplace more effectively and improve detection of questionable products, while strictly enforcing its policies when third-party sellers break the rules. Sorscher of CSPI says Amazon's technology is clearly coming up short. "Expiration dates are a red flag for what else is harder to see," she said. "If you can't do something as basic as check an expiration date, then what else are you missing?" The analysis that data firm 3PM performed for CNBC on best-selling food products and customer complaints fits with what the firm has seen in other categories.

Jon Derkits, 3PM's chief product officer, worked at Amazon until June, most recently overseeing the electronics section of the third-party marketplace in Canada. He said that in his experience, the company was working to find solutions to food-related issues but there remained big gaps in its inability to prevent the shipment of expired or near expired products. "They hadn't yet earned my trust, as either an Amazon employee or a customer, that I would be safe purchasing a consumable or expiration-dated product from a third-party seller," Derkits said. Food sellers also suffer from a more general problem on Amazon, which is that consumers generally don't know if they're buying from a big seller, small seller or from Amazon itself. Two sellers — one with a perfectly fine item and another with expired products — could be on the same listing competing for the so-called buy box. When shoppers receive expired products from third-party sellers, they often leave negative reviews or seller ratings for the manufacturer, who has nothing to do with the sale. Many food manufacturers feel they're at a loss when it comes to controlling third-party sales of their products on Amazon, said Michael Neuwirth, a spokesman for French food group Danone. "You have two damaged parties in this, one of which is the purchaser, who thinks they're getting the best quality product," Neuwirth said. "Injured party two is the maker of that product whose brand and reputation are now called into question out of no act or fault of their own and, in fact, in a way they can't prevent it." Yet another snag in the review system is that Amazon will cancel certain negative seller reviews if the product delivered was fulfilled by Amazon, meaning that it was shipped from one of the company's warehouses. For example, if a bottle of shampoo sent from an Amazon fulfillment center showed up with a leak, Amazon would cancel the bad review saying, "This item was fulfilled by Amazon, and we take responsibility for this fulfillment experience."

An example of a seller feedback that was cancelled by Amazon. Amazon

Thus, some complaints about expired foods are being canceled even if they're legitimate, and nobody is being held accountable for the mishap. Using software provided by 3PM, CNBC searched for seller feedback containing the word "expired" across a sample of a dozen popular vendors and found that each of these vendors had at least five reviews that were canceled by Amazon. One example of a canceled review that 3PM shared with CNBC reads, "Expired product sent, and return option not available. Salsa was 4 months past expiration date (exp Aug2018, shipped Dec2018)."

Taking back control