Natural pigments recovery from bio-residues: widening the range of safe food colorants
- Autores: Adriana Katherine Molina Vargas
- Directores de la Tesis: Lillian Bouçada de Barros (dir. tes.), Carla Susana Pereira Correia (dir. tes.)
- Lectura: En la Universidade de Vigo ( España ) en 2025
- Idioma: español
- Tribunal Calificador de la Tesis: Pablo Anselmo García García (presid.), Miguel Ángel Prieto Lage (secret.), Natalia Pereira Cruz Martins (voc.)
- Programa de doctorado: Programa de Doctorado en Ciencia y Tecnología Agroalimentaria por la Universidad de Vigo
- Materias:
- Enlaces
- Tesis en acceso abierto en: Investigo
- Resumen
The growing demand for healthier foods reflects a global trend towards adopting lifestyles that promote long-term well-being and aim to prevent the rise of chronic diseases. New food products must not only offer a balanced nutritional profile but also be enriched with bioactive compounds of natural origin that provide additional functional benefits. Among these compounds, natural pigments such as anthocyanins, carotenoids, and chlorophylls, extracted from various plant matrices, stand out. These pigments not only impart color to foods but also possess antioxidant, antimicrobial, and anti-inflammatory properties, contributing to consumer health. However, one of the major challenges in applying natural pigments in the food industry is their instability when exposed to factors such as light, temperature, and pH, which can compromise their functionality and efficacy during processing and storage. In this regard, encapsulation emerges as an effective strategy to protect bioactive compounds, preserving their stability and ensuring controlled release in food products, thereby maximizing their beneficial effects after ingestion.
In this context, research has focused on the extraction and stabilization of natural pigments from food industry by-products, promoting their use not only as colorants but also as ingredients that enhance the nutritional and functional profiles of the food products into which they are incorporated. Various plant matrices were selected, including fruits, leaves, roots, and by-products. Sources of anthocyanins included the fruits of Rubus fruticosus L. var. 'Triple Crown' and the fruits and pomace of Vaccinium corymbosum L. var. 'Legacy'. Carotenoids were obtained from the roots of Daucus carota L., while chlorophylls were sourced from the by-products of Solanum lycopersicum var. 'cerasiforme' and Daucus carota L.
This work has been developed along three main area of research: pigments rich in anthocyanins, carotenoids, and chlorophylls, focusing on their extraction, stabilization, application in food products, and evaluation of their bioaccessibility.
In the first area focused on anthocyanins, the nutritional, chemical, and antioxidant profile of blackberry fruits (Rubus fruticosus L. var. 'Triple Crown') was evaluated. The analysis revealed a high content of anthocyanin compounds, with cyanidin-3-O-glucoside as the predominant component. A solid colorant was developed from the juice of these fruits through encapsulation with maltodextrin, and its stability was monitored over three months, assessing nutritional, chemical, and antioxidant parameters, as well as cytotoxicity to confirm its food safety. The results indicated that the encapsulated colorant was safe for use.
The colorant was subsequently incorporated into kefir, and its effects were evaluated in terms of bioaccessibility, nutritional profile, and chemical composition both on the day of preparation and after seven days of refrigerated storage. A control kefir (KC) was used as a reference. The findings demonstrated that the encapsulated colorant increased tocopherol content and introduced anthocyanin compounds into the kefir, while maintaining high antioxidant activity during storage.
Microbiological analysis revealed that the addition of the colorant slightly affected the viability of yeasts and lactobacilli, causing a slight reduction. However, lactic acid bacteria showed improved stability over time, remaining within the recommended limits to ensure probiotic viability. This suggests that encapsulation not only preserves the anthocyanin compounds but also provides benefits for the stability of certain microorganisms, contributing to the overall quality, nutritional value, and functional properties of the final kefir product.
The second study on anthocyanins focused on blueberry fruits (Vaccinium corymbosum L. var. 'Legacy'), evaluating the nutritional, chemical, antioxidant, antimicrobial, and cytotoxic properties of the fruit and its pomace. After identifying its high nutritional potential, a juice was formulated and enriched with its own solid residue. This pomace was extracted by maceration and incorporated into the juice, which was then encapsulated by thermal gelation with pectin, pasteurized, and freeze-dried, resulting in a solid formulation. This enriched formulation was compared to another without pomace, and both were evaluated over a year for nutritional stability, antioxidant and antimicrobial activity, and microbiological safety. The enriched juice showed a notable increase in anthocyanin compounds, such as malvidin-3-O-glucoside, and higher antioxidant capacity compared to the formulation without pomace. Both formulations were deemed safe for human consumption, and the inclusion of pomace contributed to greater stability of bioactive compounds over time, highlighting its potential as a sustainable ingredient in food production and as a natural colorant.
The second area of research focused on chlorophylls, which were extracted from agricultural by-products of Daucus carota L. and Solanum lycopersicum var. 'cerasiforme' using maceration and ultrasound-assisted extraction techniques. The use of eco-friendly solvents, such as ethanol, was prioritized, demonstrating significantly higher extraction efficiency, yielding 100 times more compared to hexane. The aerial parts of the tomato presented a higher concentration of chlorophylls and their derivatives (211.6±0.3 µg/g) compared to the carrot by-products(110.4±0.4 g/g). Ultrasound-assisted extraction proved to be more effective than maceration, improving the recovery of bioactive compounds. The extraction methodology was optimized using high-performance liquid chromatography coupled to mass spectrometry (HPLC-DAD/ESI-MS), allowing for precise quantification of the yields obtained.
Based on these results, the aerial parts of cherry tomato (S. lycopersicum var. cerasiforme) were characterized, demonstrating their high potential as sources of nutrients, bioactive compounds, and natural colorants. The extracts, rich in chlorophylls, phenolics, and tocopherols, were encapsulated using spray drying with maltodextrin (TAPC) to enhance their stability and functionality. The encapsulated colorant was incorporated into mascarpone cheese (MT) and compared with a control formulation (MC) during 3 days of refrigerated storage.
The results revealed significant differences between the formulations and across the storage period. MT retained moisture better and exhibited stable levels of chlorophyll and phenolic compounds. While -tocopherol slightly decreased during storage, saturated fatty acids remained stable. Colorimetric analysis confirmed a uniform and visually appealing green color, and antioxidant activity (OxHLIA) suggested potential bioactive release over time.
In conclusion, TAPC improved the nutritional, functional, and aesthetic properties of mascarpone, ensuring product stability and safety while offering a promising natural alternative for the food industry.
Finally, the third area of research focused on carotenoids derived from discarded carrots (Daucus carota L.) and their potential as natural colorants in food products through encapsulation. The process involved spray drying using maltodextrin as an encapsulating agent, which preserved and concentrated the bioactive compounds, enhancing their stability during processing and storage. This encapsulated carotenoid pigment was incorporated into mascarpone cheese to evaluate its functional, nutritional, and antioxidant properties.
The results demonstrated significant improvements in the functional properties of the mascarpone. The b* value, indicative of yellow-orange intensity, increased markedly, validating the successful incorporation of carotenoids and enhancing the product's visual appeal. ß-carotene, the main carotenoid responsible for the orange hue, remained stable throughout refrigerated storage, ensuring consistent sensory quality and bioactive functionality.
Microencapsulation effectively protected carotenoids from degradation caused by light and temperature, contributing to their prolonged stability. Nutritional analysis confirmed that the addition of the encapsulated pigment did not significantly alter the composition of lipids, proteins, or carbohydrates in the cheese, maintaining its overall nutritional integrity. Furthermore, the enriched mascarpone exhibited enhanced antioxidant activity, as evidenced by reduced lipid peroxidation and improved oxidative protection.
These findings highlight the potential of agricultural by-products, such as discarded carrots, to produce sustainable, functional food ingredients. Carotenoid encapsulation presents an effective strategy for stabilizing bioactive compounds, improving antioxidant profiles, and enhancing the sensory and nutritional properties of food products, offering significant value for the food industry.
In conclusion, these studies highlight the great potential of natural pigments extracted from fruits and by-products as sustainable alternatives to synthetic colorants in the food industry. Optimizing extraction and encapsulation techniques is key to maximizing the recovery of bioactive compounds, promoting more efficient use of agricultural by-products, and contributing to environmental sustainability. The integration of these pigments into foods not only enriches their nutritional and functional profiles but also meets growing consumer demands for healthier, more natural products. This approach underscores the importance of continued research into these sources of natural colorants, as well as the development of advanced technologies that ensure their stability and long-term commercial viability.
