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Plant Proteins Prevent Damage From Excessive Ice Build-Up and Freezer Burn

Frozen peas.
Credit: PDPics / Pixabay.
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Researchers discovered soy proteins inhibit ice crystals, preserving frozen vegan foods and biological samples. Peptides from hydrolyzed soy slowed ice growth, with larger fractions showing superior potential in this natural preservation dance.

Key takeaways

  • Researchers have found that broken-down soy proteins can hinder ice crystal growth, potentially preserving frozen vegan foods and biological samples.
  • Some animals in cold environments produce antifreeze proteins to prevent freezing, inspiring the frozen food industry's interest.
  • Peptides from hydrolyzed soy protein showed promise in slowing ice growth, with large-size fractions proving more effective.
  • Broken-down soy proteins can prevent ice crystal growth

    Almost everyone has a bag of veggies shoved into the dark recesses of their freezer that’s now essentially an unrecognizable block of ice crystals. And when thawed, foods damaged by excessive ice lose their texture and become mushy. Now, researchers reporting in ACS’ Journal of Agricultural and Food Chemistry have shown that broken-down soy proteins can prevent ice crystal growth and could be especially useful for preserving frozen vegan foods or biological samples.

    Some animals that live in extremely cold environments, such as fish in the deep polar oceans, make antifreeze proteins to keep the liquid in their bodies from freezing. These proteins slow down ice crystal formation and growth, a process that has piqued the interest of the frozen food industry. Recently, researchers discovered that some peptides, which are pieces of broken-down proteins, can also slow ice crystal growth. However, all of the edible peptides tested so far have come from animal sources, including fish, pigs, chickens and cows. So, Tong Wang, Madison Fomich and colleagues at the University of Tennessee wanted to see if breaking down plant proteins could generate similar compounds with ice-crystal-inhibiting properties.

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    The team generated peptides from a commercially available soy protein isolate powder by exposing it to three different hydrolyzing enzymes: alcalase, pancreatin and trypsin. Each resulting mixture of peptides was also separated by size into multiple fractions.

    All of the mixtures slowed ice growth in tests, but the ones produced from alcalase and trypsin were better inhibitors than those from pancreatin. For all three enzymes, most of the activity came from the fraction with the largest peptides. The large-size fractions also ended up including some smaller peptides, which on their own didn’t keep ice crystals from growing; however, the team showed that these small compounds boosted the activity. This study is an initial step toward using soy-derived peptides as a natural, effective way to reduce the ice growth that can lead to freezer burn and thereby increase the shelf life of frozen goods, including vegan and vegetarian products, the researchers say.

    Reference: Fomich M, Día VP, Premadasa UI, Doughty B, Krishnan HB, Wang T. Ice recrystallization inhibition activity of soy protein hydrolysates. J Agric Food Chem. 2023. doi: 10.1021/acs.jafc.2c08701

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