Marigold Petals: From Garden Waste to a Potential Plant-Based Protein Source
Marigolds, commonly used to adorn gardens, festival garlands, and wedding decorations, are now showing potential as a future source of plant-based protein. A study from the University of Georgia has discovered remarkable nutritional content in marigold petals, which are often discarded as waste.
Flower waste is a significant environmental problem. In India, nearly 40% of marigolds are thrown away annually, with similar waste piles generated by the floral trade in the United States. This fact sparked the research team’s curiosity.
‘Billions of dollars’ worth of flowers are discarded every year,’ said Anand Mohan, one of the study’s authors and a professor at the College of Agricultural and Environmental Sciences (CAES). ‘Can you imagine if we could utilise those flowers as food?’
The research shows that dried marigold petals contain almost 10% protein, comparable to popular plant-based sources like quinoa, oats, and wheat. The researchers divided the marigold protein into four types based on extraction fluids. Albumin was the largest fraction, making up about 65% of the total. This albumin proved to be the most functional, excelling in water retention, oil binding, and food emulsification.
A particularly interesting finding for the culinary world is the heat resistance of marigold protein. Marigold albumin remains stable up to approximately 221 degrees Fahrenheit (105 degrees Celsius). This figure is higher than the stability of proteins found in chickpeas and peas. This heat tolerance is crucial for the industrial production of bread, snacks, and processed food products made at high temperatures. Additionally, the strong emulsifying properties of the albumin are highly effective at maintaining consistency in oil-and-water mixtures, such as salad dressings.
Beyond its protein content, marigold petals also offer a savoury (umami) flavour. The presence of glutamic and aspartic acid in the albumin, glutelin, and globulin proteins can enrich the taste of dishes. The petals also exhibit strong antioxidant activity that can slow the rancidity of food fats, and they are rich in fibre and essential minerals like calcium, potassium, and iron.
‘What excites me most about this research is how it challenges the way we think about flowers,’ said Fidele Benimana, the study’s lead author. ‘Most people see marigolds as ornamental plants, but they also contain proteins with unique functional properties that could be useful in food formulations.’
However, the researchers caution that not all marigold types are safe for consumption. The safe varieties are pot marigold (Calendula) and true marigolds from the Tagetes group. This study specifically used Calendula officinalis (common marigold) and extracted only the petals, as the stems and leaves have a bitter taste.
‘I don’t know if marigolds are a super flower. But to me, it seems all these beautiful flowers might be super flowers. You would be surprised how little we actually know about the flowers growing in our own yards,’ Mohan added. ‘Mother Nature still holds many truths we haven’t uncovered. We must look around and reveal them.’
The next research step is to test the performance of marigold protein in real food products on an industrial scale. Converting flower waste into food could help reduce environmental pollution while providing a sustainable alternative plant-based protein source. The study was published in the journal ACS Food Science & Technology.