Princeton I-Corps team tackles breast milk shelf-life problem

Written by
Alaina O'Regan, Office of the Dean for Research
May 7, 2024

Soon after the birth of her second child, Katie Silpe started freezing her breast milk for the period ahead when she would return to work. When she thawed the milk later, however, her baby refused to drink it. Detecting a noticeable change in both taste and smell, Katie realized her stored milk was unusable. 

After scouring the internet for solutions, Katie Silpe and her husband Justin Silpe, a postdoctoral research associate at Princeton University, discovered not only that a lot of parents were having difficulties feeding their babies frozen milk, but also that there was a glaring lack of credible information on the topic. 

“A lot of what I found was advice on mommy blogs and Facebook pages suggesting tricks like adding vanilla extract to the milk to get the baby to drink it,” said Katie Silpe, noting that while the freeze-thaw cycle creates an unpleasant smell and flavor, the thawed milk isn’t technically unsafe to drink. “In terms of explanations for why this was happening or actual solutions, there was basically nothing.” 

Justin Silpe realized he might find answers using the same scientific techniques that he used to study bacterial cell communication, his research focus in the lab of Bonnie Bassler, Princeton's Squibb Professor in Molecular Biology, chair of the department, and a Howard Hughes Medical Institute Investigator.

One day, he showed up to the lab with a container of Katie’s breast milk and asked Bassler if he could start a new project.

Justin and Katie Silpe holding their two young daughters and dog in family portrait.

Mother of two Katie Silpe scoured the internet for solutions to improve the shelf-life of frozen breast milk to no avail, sparking the beginning of an innovation journey for her and her husband Justin Silpe, a postdoctoral researcher at Princeton. Photo courtesy of Silpe family

“I was working on things completely unrelated to milk, but Katie and I noticed this huge gap in the scientific literature,” he said. “And Bonnie is generally on board to do new science, especially when it’s for something good that can benefit marginalized groups.” 

Justin Silpe found that the chemical structure of the breast milk was changing in the freezer, and that this change not only affected the smell and flavor, but unexpectedly also caused a loss in nutritional value. 

Silpe and Bassler decided to develop an all-natural, infant-safe powder that can be added to breast milk before storage to retain its structure when frozen, preventing it from going sour and losing vital nutrients. 

The team realized that they would need help to get their innovation out of the lab and into the hands of people who need it, and turned to Princeton University’s Office of Technology Licensing (OTL) for guidance. 

They worked with Cortney Cavanaugh, new ventures and licensing associate at Princeton, to file an invention disclosure and learn about resources available on campus. To get started, Cavanaugh encouraged the team to apply for the National Science Foundation (NSF) I-Corps Northeast Hub four-week Propelus program, which provides researchers with funding, mentorship, and training to develop innovations into real-world products and services for societal benefit.

I-Corps helps participants explore how their innovations can meet a societal need by tapping into industry expertise and talking to potential customers. During the program, the team interviewed healthcare professionals, lactation consultants, pediatricians and working parents affected by the problem. 

One of the experts they met was Maggie Moore, a public health professional who has served in advisory roles for a number of infant and maternal health organizations and who, after chatting with Justin Silpe and Bassler about their mission, decided to join the team full-time. “I’m a big believer in luck and timing, and it’s incredible that I-Corps brought us together,” Moore said. “The reason I signed on in such a big way was the team’s commitment to reaching underserved populations, which includes parents.” 

Three people sitting at a table working together on a laptop in a living room, smiling and chatting

PumpKin co-founders Justin Silpe, Maggie Moore and Bonnie Bassler (left to right) teamed up to improve the shelf-life of breast milk using all-natural ingredients, and participated in NSF I-Corps training programs to bring their innovation to the world. Photo courtesy of researchers

The team is forming a startup called PumpKin, with Bassler in an advisory role, through which they aim to increase access to safe and nutritious breast milk, help parents alleviate stress and meet their breastfeeding goals, and provide scientific information about a topic that has been under-researched for decades. 

Leveraging basic techniques

Milk is composed of “small globs of nutrients suspended in liquid,” according to Bassler. When milk is frozen, these nutrient clusters start to separate and different compounds move around and interact with one another, changing the milk’s chemical structure. 

Leveraging techniques that he often used in Bassler’s lab, Justin Silpe screened thousands of safe and natural ingredients found in existing baby formulas and infant first foods to find out which, if any, could be added to breast milk to help maintain its structure and nutritional value. 

After careful analysis, he developed a mixture of three compounds, which the team is currently refining and testing under guidance from experts and in response to conversations with the Food and Drug Administration (FDA) and other regulatory agencies to ensure its safety. 

“We're creating this for infants, and there is no such thing as being too careful when working with this population,” Moore said. “We’re holding ourselves to the highest possible standard when it comes to safety.” 

Bassler said that the likelihood of a person’s breast milk turning rancid when frozen varies depending on factors such as the presence of enzymes in the milk that cause fat breakdown. But even when frozen milk isn’t turning rancid, it loses nutrients in the freezer. “It’s amazing that when we started this, it was because babies refused to drink the milk because it tasted bad,” Bassler said. “But Justin has since shown that breast milk loses some of its nutritious value when it’s frozen.” 

Bassler, whose expertise lies in bacterial cell communication for development of antibiotics, said this project was completely different from anything ever done in her lab. “When Justin pitched this, however, it was clear that he was passionate and that this was a problem that he could solve, and that it would have immediate significance for parents and children,” she said.

An invisible problem 

The lack of at-home methods to preserve breast milk’s structure and nutrition poses challenges for neonatal intensive care units (NICUs) that rely on donated milk, as well as for parents, especially those working full-time. In fact, the inability to meet breastfeeding goals is a primary reason women leave the workforce after childbirth, according to the World Alliance for Breastfeeding Action.

Bonnie Bassler

Bonnie Bassler, chair of the Department of Molecular Biology at Princeton and adviser for the startup PumpKin. Photo courtesy of researcher

“When Justin brought this topic to my attention, it didn’t take me long to become outraged by how this keeps parents, primarily women, out of the workforce,” Bassler said. “This is a problem that can be tackled with the basic research techniques we use in this lab.” 

Bassler said that part of the reason this widespread issue has flown under the radar for so long is the stigma surrounding it. “People might think, ‘if you can’t feed your baby, you must be a bad mother,’” Bassler said. “So, this topic has been confined to chit-chat over the kitchen table, and more recently, relegated to blogs and social media forums, where misinformation can proliferate. On top of that, women and children’s problems are routinely under-studied in the scientific community and do not receive the investment capital needed to address them at scale.” 

The team is working with Howard Stone, Princeton’s Donald R. Dixon '69 and Elizabeth W. Dixon Professor of Mechanical and Aerospace Engineering and Janine Nunes, director of education outreach at the Princeton Materials Institute and lecturer in chemical and biological engineering, to develop a diagnostic strip that tests for these breakdown products so caregivers can evaluate their milk’s potential shelf life and find out if the nutritional quality has degraded after freezing. The test strips will work similarly to a COVID test, where the user can add a drop of milk to it and the strip will change color in reaction to certain properties. 

It takes a village 

Katie Silpe said she was amazed by the support they received from their community after reaching out to local mom groups for breast milk donations to use for experiments. “The level of response we got was wild,” she said. “Justin and I drove around nearby towns and collected milk samples, and every woman that we talked to wanted to hear about the research and wanted us to keep them updated.” 

She said that engaging in the customer discovery process through the I-Corps program further validated the need for their product. “The conversations we had with moms, pediatricians, lactation consultants, and small business founders like Maggie showed us that this problem was even more widespread than we initially thought,” she said.

Maggie Moore

Maggie Moore, co-founder and CEO of PumpKin, draws from her experience in public health and business to help the team's innovation make an impact for underserved populations. Photo courtesy of Moore

Justin Silpe said that meeting Moore through I-Corps was a life-changing moment. “We understood the research side of it, and we applied for I-Corps very early on to learn how to close the gap of actually getting it on the shelves,” he said. “Maggie has worked in business and public health nutrition for years and has a lot of that expertise, so it’s been incredible to have her on the team.” 

Justin Silpe and Moore recently completed the seven-week intensive National I-Corps Teams program, where they continued their entrepreneurship journey with support from a $50,000 NSF grant provided by the program, alongside their industry mentor Laura Forese, recently retired executive vice president and chief operating officer at New York Presbyterian Hospital.

“Getting to dig even deeper and continue to test our hypotheses in this format was really exciting, and we learned a ton, including from Laura who was an exceptional adviser to us,” Moore said. 

The team has also earned funding from Princeton University's IP Accelerator Fund, Princeton’s Faculty New Venture Assistance Fund, and funding from winning second place at the Keller Center’s Innovation Forum competition. “Princeton has been such an incredibly supportive community and a great place to start this journey,” Moore said. 

After earning NSF funding through I-Corps, the team became eligible for small-business government grants. This month, they were awarded both National Institutes of Health (NIH) and U.S Department of Agriculture (USDA) grants to move their innovations forward. 

Beyond increasing access to safe and nutritious breast milk, the team aims to serve as a trusted source of scientific information about breastfeeding for parents. “If we can make the breastfeeding journey easier for anyone by giving them science-based facts that they can use in their daily lives as parents,” said Katie Silpe, “then we’ll have reached our goal."