Valorizations of Marigold Waste for High-Value Products and Their Industrial Importance: A Comprehensive Review

Abstract

The municipal authorities in developing nations face serious challenges in marigold flower garbage management. The primary issue is that they never are reused after prayers. Flower waste of Tagetes erecta, T. patula, and Calendula officinalis L. are commonly used for carotenoid and flavonoid extractions and, subsequently, used for incense stick and biogas production. Marigold plants are also used for phytoremediation during their growth stage. The lutein industry is booming due to its increasing market demand, expected to reach ~2121.2 billion tons by 2022, where marigolds are a major contributor globally. The process of isolating lutein from saponified marigold oleoresin yields a product with 70–85% purity. Lutein is a major xanthophyll (70–88%) of marigold petals, and a maximum of 21.23 mg/g of lutein was extracted. This review discusses the properties of selective marigold species, their compositions, and the extraction of different flavonoids and carotenoids, especially lutein. Moreover, different extraction methods of marigold lutein, the collection of marigold waste, and their subsequent utilization to derive several value-added products are discussed. Among physical treatments, ultrasonic-assisted extraction and enzymatic treatment with 5% solids loading were the maximum-yielding methods.