Pasteurizing Fruit Smoothies Could Help Break Down Beneficial Polyphenols

Drinking a smoothie is a popular way to consume fruits and vegetables, many of which are rich in micronutrients called polyphenols. If this beverage is purchased at a store, it’s likely been pasteurized with heat or pressure to prevent harmful bacteria growth and extend shelf-life. Now, a preliminary study in ACS’ Journal of Agricultural and Food Chemistry reports that processing smoothies with high heat could also make polyphenols easier for the gut microbiome to absorb.

Fruits and vegetables are key to a healthful human diet, partly because they contain polyphenols, which can protect against heart disease and neurodegenerative disorders. These beneficial components are released from food during digestion, making them available for absorption by the gut microbiome. Previous research found that food processing techniques like canning and boiling peppers and artichokes may increase the amount of polyphenols metabolized by the gut microbiota, potentially improving the health benefits of these foods. But gaps exist in scientists’ knowledge around other food processing techniques. So, Iziar Ludwig and colleagues investigated how pasteurization could affect polyphenol digestion in the gut microbiome. 

The researchers first prepared a smoothie made up of Granny Smith apples, green celery, green chicory, peppermint and lemon. They split up the smoothie into three parts: One was not treated, and the others underwent either high-pressure or high-temperature pasteurization. Then, the smoothie samples were added to successive solutions meant to mimic the three stages of digestion — oral, gastric and intestinal. Post-digestion pressure- and heat-pasteurized smoothie samples had higher amounts of polyphenolic compounds (21% and 44%, respectively) available for absorption than the untreated sample (17%). The researchers attribute these results to changes in the plants’ cell walls, such as softening or rupturing, induced by pasteurization that could favor the release of polyphenols into the body. 

Finally, to analyze gut microbiome transformations of polyphenols, the digested samples went through a laboratory version of colonic fermentation in vials containing human feces as the microbiota source. The gut microbiota converted most polyphenols into smaller derivatives, such as phenylpropanoic acids. Some of these derivatives have previously demonstrated antidiabetic, anti-inflammatory and chemopreventive effects. The researchers determined that the largest microbiota conversions happened in the high-temperature, post-digestion smoothie sample because it started fermentation with higher overall polyphenol levels. They say this work emphasizes how smoothie processing could lead to new beverage products with enhanced bioaccessibility.

Reference: Matías C, Pereira-Caro G, Sáiz-Abajo MJ, et al. High-pressure and thermal pasteurization applied to smoothies enhances (poly)phenol bioaccessibility along the gastrointestinal tract. J Agric Food Chem. 2025. doi: 10.1021/acs.jafc.4c09166

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