Year: 2022
Type: dissertation
Abstract: Color is an important sensory feature of food, and often determines its appeal to consumers. Adding color to food products is a very common strategy to enhance consumers expectations. However, legislative action, the continued delisting of synthetic colorants and the growing demand for nature-based products have increased the search for natural colorants in the past few years. Despite their many advantages over synthetic colorants, natural pigments present some limitations such as their low solubility in water, low bioavailability, and lower stability. Therefore, solutions to improve these properties in natural colorants are necessary, and the use of nanoemulsions has been shown to be very effective. In this study, two bio-based emulsifiers, namely rhamnolipids and potato proteins, were used to create colored nanoemulsions containing different natural colors, namely lycopene, β-carotene, curcumin, and chlorophyll. The main goal of this research is to see if these approaches can allow to obtain stable nanoemulsions using natural colors obtained from plants, animals, and, in particular agri-food residues such as tomato waste. To take an even more sustainable approach, a tomato waste crude extract was used to make a nanoemulsion and compared to a commercial extract. A comparison of synthetic and natural β-carotene was also undertaken to further understand the differences in nanoemulsions’ color stability. Droplet sizes, polydispersity index, zeta potential, turbidity, and color of the emulsions were measured during a 30-day period to evaluate their stability. Emulsions produced with potato protein as emulsifier did not present reproducibility, and smaller particle sizes could be obtained by altering the emulsifier type. On the other hand, emulsions produced with rhamnolipids presented particle sizes ranging from 134.9 nm to 318.10 nm and polydispersity index ranging from 0.17 to 0.36, and good stability. The effect of different particle sizes on emulsions color and stability was tested, by varying the sonication duration. Emulsions showed better stability against droplet aggregation and gravitational separation for smaller particle sizes. The lowest color variation was obtained for the smallest droplet sizes kept under refrigeration. Zeta potentials were all smaller than -30 mV, predicting good dispersion stability. Nanoemulsions loaded with natural β-carotene showed better stability to droplet aggregation and less color variation when compared to synthetic β-carotene. Finally, even though very good results were obtained for the commercial lycopene extract obtained from tomato oleoresin, with particle sizes of 134 nm and PDI < 0.3, emulsions produced with this crude tomato waste extract were very unstable. Thus, the study and development of other physical treatments is crucial to obtain stable nanoemulsions consisting of tomato waste pigmented extract.The experimental results presented in this dissertation confirm that rhamnolipids are effective alternatives to produce stable nanoemulsions containing natural pigments, which can then be used in the formulation of natural colored food-products. However, further studies are required to obtain replicas and corresponding statistical confirmation for the most promising systems.
Author: Alves, Mariana Brandão Nogueira
Language: Portuguese
Topic: Proteins in Food Systems
Subfield: Food Science
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W7019160291