Japanese researchers have discovered that common vegetables like garlic and onions can promote the formation of harmful trans fats during high-temperature cooking, challenging our understanding of how these concerning compounds develop in home-prepared meals.
Published in Food Research International | Estimated reading time: 4 minutes
The study, conducted by researchers at Meijo University and Nissui Corporation, reveals that sulfur-containing compounds found naturally in many kitchen staples can transform healthy unsaturated fats into their potentially harmful trans fat counterparts when heated above 140°C (284°F).
The research team, led by Junji Obi and Dr. Masaki Honda, found that two types of sulfur compounds – isothiocyanates and polysulfides – significantly accelerate the conversion of healthy fats into trans fats during cooking. These compounds are abundantly present in popular vegetables from the Allium family (including garlic, onions, and leeks) and Brassica family (such as cabbage, broccoli sprouts, and horseradish).
The findings are particularly relevant given the World Health Organization’s recommendation that trans fat intake should be limited to less than 1% of total daily energy intake. While industrial trans fats in processed foods have received significant attention, this study sheds light on their formation during home cooking.
Through careful laboratory experiments using both pure compounds and real food ingredients, the researchers demonstrated that cooking with garlic and onions at high temperatures can lead to measurable increases in trans fat content. However, they found that adding antioxidants could help mitigate this effect, particularly when cooking with vegetables containing isothiocyanates.
Notably, the study showed that polysulfides – compounds found abundantly in garlic and onions – were more resistant to antioxidant protection, suggesting that lower cooking temperatures may be necessary when preparing these ingredients to minimize trans fat formation.
Key Terms to Know
- Trans Fatty Acids (TFAs)
- A type of fat molecule with a specific chemical structure that has been linked to increased risk of cardiovascular disease when consumed in excess.
- Isothiocyanates
- Sulfur-containing compounds naturally found in vegetables like cabbage and horseradish that can promote chemical changes in fats during cooking.
- Polysulfides
- Sulfur-containing compounds commonly found in garlic and onions that can influence the transformation of fats during the cooking process.
Test Your Knowledge
What temperature threshold was identified as significant for trans fat formation with sulfur compounds?
The study found that trans fat formation significantly increased when cooking temperatures exceeded 140°C (284°F).
Which vegetable family showed the strongest effect on trans fat formation?
The Allium family (including garlic and onions) showed the strongest effect due to their high polysulfide content, which was more resistant to antioxidant protection.
How do antioxidants affect the trans fat formation process differently between isothiocyanates and polysulfides?
Antioxidants significantly reduced trans fat formation with isothiocyanates but had only minimal effect on polysulfide-induced trans fat formation.
What molecular mechanism underlies the formation of trans fats in this cooking context?
The process involves trans-isomerization of unsaturated fatty acids in triacylglycerols (TAGs), where sulfur compounds promote the geometrical reconfiguration of the fat molecules during heating.
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