By 2050, the world population is expected to increase to about 10 billion people. Food production will have to keep pace with this growth. The oceans, with their huge, often untapped potential as food sources, are becoming more and more important to us humans. Sustainable use of marine resources is essential.

Algae are at the bottom of the food chain in the ocean and can be produced with little effort and very sustainably. A new study by the Leibniz Center for Tropical Marine Research (ZMT) in collaboration with the Marine Botany Group of the University of Bremen uses sea grapes (Caulerpa lentillifera), a species of Indo-Pacific algae. Algae products can be improved nutritionally. The study was published in the journal Algae Research.

Algae have a valuable nutritional profile: low in calories, but high in protein and unsaturated fatty acids, as well as many mineral salts, vitamins and trace elements. Also called “green caviar”, sea grapes have high antioxidant potential. They are characterized by their special shape: small, round balls hanging from the panicle are slightly salty and explode in the mouth like caviar.

Cultivation of sea grapes began quite by accident in the 1950s when fish farmers in the Philippines discovered that this algae could grow well in fish ponds. Meanwhile, sea vegetables are also cultivated in Japan and Vietnam, among other places.

When green algae like sea grapes are exposed to high levels of light radiation, they produce harmful free radicals. To protect themselves, algae produce more antioxidants such as vitamins C and E, β-carotene and various polyphenols, making their nutritional profile particularly valuable to us. Such antioxidants are important components of the human diet and are thought to have beneficial effects on many diseases in humans, such as diabetes and cardiovascular disease. Can farmers use increased light to cost-effectively improve sea grape quality? That was the question posed by Lara Stuthmann, a marine biologist at ZMT and lead author of the study.

For the study, he exposed sea grapes to five different light intensities for 14 days each. Subsequently, the antioxidant content was determined photometrically. Lara Stuthmann compared the results with different fruits, such as pomegranate, goji berries and arono, which are known for their high antioxidant content and are therefore considered “superfruits”.

In fact, targeted irradiation can more than double the antioxidant content of sea grapes to the level found in pomegranate seeds. “Light irradiation has great potential as a cheap and simple means of increasing the antioxidant content of algae. This application can also be considered for other algae,” says Stuthmann. “However, depending on the level of radiation, bleaching of sea grapes can also occur.” Therefore, the light irradiation and treatment time should be adjusted depending on the intended use of the algae – for example, as cosmetics or food.

More than 10,000 different species of algae are known, but only eight different species of algae are kept in more than 90% of algae cultures. Many are dried before consumption to remove certain molecules such as carrageenan or agar, which are used as gelling and thickening agents. Few are suitable for direct consumption.

Bremen University Dr. “What makes sea grapes special compared to most macroalgae is their growth habit and consistency, which makes them a very pleasant palate experience. They are easy to reproduce and grow quickly,” said Karin Springer. is the author of the study. “Sea grapes can therefore find a place on German menus as a source of protein, antioxidants and other nutrients.”

Sea grapes are in high demand in Japan, Vietnam and China and are eaten raw with various sauces, in salads or with sushi. In Europe, they are not yet recognized as food. Nevertheless, they are already sold in some places, including in Bremen, and various high-end chefs have recognized the potential of these algae for their dishes.

Sea grapes may also be suitable for growing in integrated aquaculture, which combines different farming animals and plants. These constitute a natural cycle in which feed residues and biological waste materials are optimally used. For example, ZMT is experimenting with seaweed farms in Vietnam to co-cultivate sea grapes with shrimps or sea snail Babylonia aerolata, which is considered a delicacy in Vietnam.

Provided by the Leibniz Center for Tropical Marine Research (ZMT).