Stability of natural food colorants derived from onion leaf wastes

• Published in: Food chemistry 2022-08, Vol.386, p.132750-132750, Article 132750
• Main Authors: Prodromidis, Prodromos, Mourtzinos, Ioannis, Biliaderis, Costas G., Moschakis, Thomas
• Format: Article
• Language: English
• Subjects: Anthocyanins - analysis; Color; Color stability; Cyclodextrins; Food Coloring Agents - chemistry; FT-IR spectroscopy; Onion leaf waste, natural colorants, cyclodextrins; Onions; Plant Extracts - chemistry; Plant Leaves - chemistry; Spectroscopy, Fourier Transform Infrared; UV–Vis spectroscopy
• ISSN: 0308-8146; 1873-7072
• DOI: 10.1016/j.foodchem.2022.132750

•Green extraction of colorants from onion wastes (OWE)•High temperature extraction assisted the pyranoanthocyanins formation.•OWE-cyclodextrins-complex formation was confirmed by spectroscopy (FT-IR, UV)•The color intensity was enhanced after storage, UV-irradiation and heat treatment. Plant anthocyanins have widely been employed as natural food colorants. However, their instability restricts many of their applications in food industry. In this study, anthocyanins were extracted from onion outer scales, using aqueous solutions with or without added cyclodextrins (CDs). The results indicated that when cyclodextrins were included in the extraction medium, the anthocyanins were stable or even had improved and augmented color intensity upon storage or following thermal and UV-light treatments over a broad pH range (2.0–7.0). FT-IR and UV–Vis spectroscopy measurements confirmed the formation of inclusion complexes between CDs and anthocyanins and the presence of pyranosyl groups (pyranoanthocyanins) upon heating. Overall, the stability of onion anthocyanins under various environmental stresses, often encountered during food processing and storage, indicates that the natural color extract from onion outer scales can be of value as an interesting colorant alternative for food applications.