Added protein is showing up in foods from breakfast cereal to pasta, but not many condiments … yet. Researchers reporting in ACS Food Science & Technology have now developed an enriched tomato ketchup by incorporating protein extracted from algae. A panel of taste testers preferred the recipes containing up to 3% added algal extract, saying the samples maintained the sweet, tangy taste and reddish appearance expected of the condiment. 

"We wanted to improve the nutritional value of a widely consumed condiment using a sustainable protein source," says Parise Adadi, the corresponding author of the study. "Ketchup is familiar, shelf-stable, and suitable for incorporating functional ingredients." 

Although many protein-added foods get the enrichment from whey, pea, or soy sources, Adadi and colleagues wanted to try a potentially more sustainable alternative: microalgae that are rich in protein. "Chlorella vulgaris can be cultivated rapidly throughout the year using comparatively little land and freshwater, making it a potentially more resource-efficient protein source than many terrestrial crops," says Adadi. 

Previously, another research team incorporated algae proteins into vegan seafood mimics, where the microalgae's fishy taste complimented the squid-ring analogues that they 3D-printed and deep-fried. For ketchup, the challenge was adding algal protein in a way that wouldn't change the condiment's distinct flavor. 

The researchers accomplished this by extracting the proteins from C. vulgaris. Then they developed ketchup recipes containing 1% to 13% algal protein along with typical ingredients such as plum tomatoes, sugar, salt, vinegar, spices, and citric acid. After they bottled and pasteurized the ketchup samples, including a plain ketchup with no added algae, a panel of 15 people tasted them. The panelists shared that: 

  • Samples with 1% and 3% added protein retained the familiar sweet, tangy, and mildly spiced flavor, and had only a subtle algal note. 

  • At 5% and 13% added protein, the algal taste and greenish color became more noticeable, reducing the samples' acceptability despite the higher protein content. 

In addition, compared to the plain ketchup, the samples with 3% and 5% algal extracts contained two to three times more protein, as well as higher amounts of essential amino acids, minerals - particularly sodium and iron - and antioxidants. 

These results suggest that a moderate addition of algal protein could appeal to consumers and enhance nutritional value. The researchers' future work will include larger consumer studies, shelf-life tests, and product development at commercial scales. 

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