Scientists discovered a way to keep beneficial bacteria alive in frozen foods by adding a natural ingredient called glycerol to special food mixtures. When they froze and thawed these mixtures multiple times, the bacteria survived much better than before. This research could help food companies create healthier frozen products with live probiotics that actually work. The study tested different amounts of glycerol and found that adding more of it protected the bacteria better, with survival rates jumping from about 7 million to over 9 million bacteria per gram after freezing.

The Quick Take

  • What they studied: Whether adding glycerol (a thick, sweet liquid) to special food mixtures could help keep beneficial bacteria alive through freezing and thawing cycles
  • Who participated: This was a laboratory study testing different food formulas with a specific type of beneficial bacteria called Lactiplantibacillus plantarum P9, not a human study
  • Key finding: Adding glycerol dramatically improved bacteria survival after freezing—bacteria survival increased from 7 million to over 9 million per gram when 40% glycerol was added, compared to no glycerol
  • What it means for you: This research may lead to better frozen probiotic foods that actually contain living, healthy bacteria when you eat them. However, this is early-stage lab research, and we’ll need to see how it works in actual food products before making changes to your diet

The Research Details

Scientists created special food mixtures called high internal phase emulsions (HIPEs)—think of them as tiny droplets of one ingredient suspended in another, similar to how mayonnaise is made. They used soy protein as a binder to hold everything together and added different amounts of glycerol (0%, 20%, and 40%) to see how it affected the mixture. They then froze and thawed these mixtures three times to simulate what happens in a freezer, measuring how well the structure held up and how many bacteria survived the process. They used advanced laboratory techniques to measure droplet size, water content, thickness, and bacterial survival rates.

This research approach is important because frozen probiotic foods are becoming more popular, but freezing traditionally kills many of the beneficial bacteria. By testing different formulas in controlled laboratory conditions, scientists can identify the best recipe before companies spend money developing actual food products. Understanding exactly how glycerol protects bacteria helps scientists design better frozen functional foods.

This is a controlled laboratory study published in a peer-reviewed food science journal, which means experts reviewed the methods. The study used precise scientific measurements and repeated tests. However, this is early-stage research conducted in a lab with isolated bacteria, not in actual food products or in human bodies. The results are promising but need further testing in real-world conditions before being applied to commercial foods.

What the Results Show

The addition of glycerol had dramatic effects on the food mixture’s properties. When scientists added more glycerol, the tiny droplets in the mixture became much smaller (shrinking from about 15 micrometers to about 5 micrometers), which helped protect the bacteria inside. The glycerol also reduced the amount of free water in the mixture, which is important because bacteria need water to grow and can be damaged by ice crystals that form during freezing.

Most importantly, glycerol protected the bacteria during freeze-thaw cycles. Mixtures with 20% or 40% glycerol maintained their structure after three freeze-thaw cycles, while the control mixture (with no glycerol) fell apart and separated. The bacteria survival rates showed the biggest improvement: with no glycerol, only about 7 million bacteria per gram survived freezing, but with 40% glycerol, over 9 million bacteria per gram survived—a 32% increase.

The scientists discovered that glycerol works by preventing large ice crystals from forming. Ice crystals can puncture and damage the delicate structures holding the bacteria. By slowing down ice crystal formation, glycerol keeps the mixture intact and the bacteria protected.

The study also found that glycerol made the food mixture thicker and more gel-like, which helped it maintain its structure better. The hydrogen bonds (molecular connections) in the mixture became stronger and more organized when glycerol was present, creating a denser network that could better withstand freezing. These secondary effects all contributed to the main finding that glycerol protects both the food structure and the bacteria inside.

Previous research has shown that freezing is generally harmful to probiotics, with survival rates often dropping significantly. This study builds on earlier work showing that certain additives can improve probiotic survival by reducing ice crystal formation. The glycerol approach appears to be more effective than some previous methods because it works through multiple mechanisms—reducing water content, preventing ice crystals, and strengthening the food structure all at once.

This research was conducted entirely in a laboratory with isolated bacteria, not in actual food products or in human bodies. The bacteria were tested in a single type of food mixture, so results may differ with other food formulations. The study didn’t test whether the surviving bacteria remain active and beneficial after freezing, only whether they survived. Additionally, the study didn’t evaluate taste, texture, or other qualities that would matter in actual food products. Real-world testing in actual frozen foods and human consumption studies would be needed before these findings could be applied to commercial products.

The Bottom Line

This research suggests that adding glycerol to frozen probiotic foods may help keep beneficial bacteria alive. However, this is early-stage laboratory research. Current recommendation: Continue consuming probiotic foods as part of a healthy diet, but don’t expect major changes based on this single study. Wait for follow-up research in actual food products before making dietary changes specifically based on this finding. (Confidence level: Low to Moderate—promising lab results but needs real-world testing)

This research is most relevant to food scientists and companies developing frozen probiotic products. If you’re interested in probiotics for digestive health, this research suggests future frozen probiotic options may be more effective. People with specific health conditions should consult their doctor before making dietary changes. This research doesn’t apply to people who avoid probiotics or have specific medical reasons to limit them.

This is very early-stage research. It will likely take 2-5 years for food companies to develop actual products using this technology, and several more years for widespread availability. If you want to benefit from probiotics now, traditional refrigerated probiotic products are already available and have established benefits.

Want to Apply This Research?

  • Track your probiotic food consumption weekly (type, amount, and whether refrigerated or frozen) and note any digestive changes. Record this in a simple weekly log to see if you notice patterns over 4-8 weeks.
  • If you use a nutrition app, add a ‘probiotic foods’ category to track your intake. When frozen probiotic products become available, you could use the app to monitor whether you’re consuming them regularly and correlate with how you feel digestively.
  • Create a monthly check-in where you assess digestive comfort, energy levels, and overall wellness. As new probiotic products enter the market, you can test them and track whether they provide benefits compared to your current probiotic sources. Keep notes on product types and your response to them.

This research describes laboratory methods for preserving bacteria in food mixtures and has not been tested in human subjects. The findings are preliminary and based on controlled laboratory conditions. Before making any dietary changes or relying on probiotic products for health benefits, consult with a healthcare provider, especially if you have a compromised immune system, are pregnant, or have specific health conditions. This research does not constitute medical advice. Probiotic effectiveness varies by individual, and more research is needed to confirm these laboratory findings translate to benefits in actual food products and human consumption.