Filipa A. Fernandes

The production of citrus juice generates a large quantity of by-products, which are often discarded or used for animal feed. However, several studies have shown its richness in valuable compounds, namely organic acids. Thus, this work intended to valorize orange and lime peels as renewable sources of citric acid. An experimental design combining five levels of the independent variables time (2–45 min), ultrasonic power (50–500 W), and ethanol proportion (0–100%) was implemented and response surface methodology (RSM) was applied to optimize the extraction process. The UPLC-PDA analysis showed that orange peel presented a higher citric acid content than lime. For lime and orange peels, the extraction yield was maximized by sonicating at low power for 5.8 or 35.5 min, using a low ethanol proportion or only water as a solvent, respectively. Overall, optimal UAE conditions were defined for the sustainable extraction of citric acid from citrus by-products, thus contributing to its valorization and upcycling into natural food ingredients.

Haematococcus pluvialis Flotow is a microalga used as a nutraceutical, due to its high content in bioactive compounds, mainly carotenoids, in which astaxanthin stands out [¹]. Furthermore, H. pluvialis has shown a high antioxidant potential, and combined with its intense red colour, this microalga could have dual functionality: as a colourant and a bioactive ingredient [²]. The process to obtain this ingredient involves several transformation steps—namely, lyophilisation and saponification—raising the costs to develop and obtain free astaxanthin, which paradoxically presents greater instability and solubility than its esterified counterpart [³]. Thus, this study provides an alternative approach for the application of red, astaxanthin-rich, H. pluvialis wet paste as a partial substitute for wheat flour (7% and 13% w/w) in the preparation of filloas (Galician pancakes), a typical dessert from the northwestern region of the Iberian Peninsula. To evaluate its power as a natural pigment, the stability of colour over time (3, 6, and 9 days) was measured, and the results were compared with those of a commercial colourant. At the same time, its physicochemical properties such as the microbiological profile were measured to determine its functionality as a food preservative. As a result, redness stability (a*) of 8% higher than that of the commercial colourant was obtained for the maximum concentration of H. pluvialis analysed. The texture showed a significant response (p < 0.02), improving its properties as the concentration of the microalga increased, which showed a tenacity of 3.23 N and extensibility of 15.10 mm during the first 6 days, i.e., a 52% and 19% improvement, respectively, in relation to the control group. In turn, an enrichment of carotenoids, fatty acids, and phenolic compounds, in combination with a potential moderator of microbiological degradation by this unicellular organism, gives added value to this food matrix.

In the present work, sage (Salvia officinalis L.) and basil (Ocimum basilicum L.) were exploited for their preservative purposes, as viable alternatives to artificial ones. The ultrasound-assisted extraction (UAE) of bioactive compounds was pre-optimized using factorial screening analysis, prior to applying response surface methodology (RSM). The obtained extracts were characterized in terms of phenolic compounds by high-performance liquid chromatography coupled to photodiode array detector and mass spectrometer HPLC-DAD-ESI/MS and bioactivities, namely the antioxidant, antimicrobial and cytotoxic potential. In addition, the most promising extracts were incorporated into yogurts, that were further screened for nutritional and physico-chemical properties and microbial load, over a shelf life of 14 days. According to the obtained results, the solvent percentage is the most relevant factor for obtaining rosmarinic acid-rich extract, followed by the extraction time and ultrasonic power. For the antioxidant and antimicrobial activity, sage showed the best result for both analysis and none of the two plant extracts were hepatotoxic. Finally, both extracts did not show changes in the physicochemical and nutritional characteristics of the yogurts and did not interfere with the growth of lactic acid bacteria, an important microorganism during yogurt fermentation. These results highlight the high potential of sage and basil as natural preservatives.

Citric acid, quercetin, dried chestnut flowers and an aqueous extract of chestnut flowers were screened as candidates for preserving a drinkable nutraceutical preparation for 45 days. The assays encompassed antioxidant and antimicrobial activities, nutritional and chemical profiles, and individual profiles of fatty acids and mineral composition, all of which in comparison with a sodium benzoate, a synthetic preservative. The centesimal composition of the nutraceutical formulation was mainly composed of carbohydrates, followed by proteins and fat, with moisture levels between 66% and 71%. Palmitic and stearic acid were the most abundant fatty acids, while calcium and magnesium where the minerals in higher amount. Anthroquinones, followed by flavonoids where the most abundant groups of phenolic compounds. In terms of the preserving effects of the extracts, the chestnut flowers and the citric acid were the most effective natural preservatives, which better preserved phenolic compounds. Furthermore, these two ingredients also revealed the strongest capacity to control the microbial growth in the formulation by inhibiting the growth of food contaminants. In general, these ingredients revealed higher preservation capacity than sodium benzoate, while not altering the nutritional and fatty acid profile. The chestnut flowers and citric acid could be used to preserve foods, food supplements, and nutraceutical formulations after passing the required regulatory procedures for food additives.

Ocimum basilicum var. purpurascens (red rubin basil) is a basil variety rich in anthocyanin compounds, commonly used in the food industry as an aromatic plant. In this study, the nutritional and chemical compositions of red rubin basil leaves were analysed, as well as, the antimicrobial activity and hepatotoxicity of their hydroethanolic extract. Carbohydrates were the main macronutrients present, with glucose being the major free sugar. Quinic acid was the most abundant organic acid, while γ-tocopherol was the highest tocopherol isoform found. α-Linolenic acid was the major fatty acid of the twenty identified compounds. Regarding polyphenols, twenty-six molecules were identified (thirteen non-anthocyanin and thirteen anthocyanin compounds), with rosmarinic acid being the main non-anthocyanin molecule and cyanidin-3-(6,6′-di-p-coumaroyl)-sophoroside-5-glcucoside the most abundant anthocyanin. These compounds could be related to the antimicrobial activity observed in this study. Thus, this variety could be considered a good source of value added molecules for the food industry.

Heat-Assisted Extraction (HAE) was used for the optimized production of an extract rich in anthocyanin compounds from Ocimum basilicum var. purpurascens leaves. The optimization was performed using the response surface methodology employing a central composite experimental design with five-levels for each of the assessed variables. The independent variables studied were the extraction time (t, 20–120 min), temperature (T, 25–85 °C), and solvent (S, 0–100% of ethanol, v/v). Anthocyanin compounds were analysed by HPLC-DAD-ESI/MS and the extraction yields were used as response variables. Theoretical models were developed for the obtained experimental data, then the models were validated by a selected number of statistical tests, and finally, those models were used in the prediction and optimization steps. The optimal HAE conditions for the extraction of anthocyanin compounds were: t = 65.37 ± 3.62 min, T = 85.00 ± 1.17 °C and S = 62.50 ± 4.24%, and originated 114.74 ± 0.58 TA mg/g of extract. This study highlighted the red rubin basil leaves as a promising natural matrix to extract pigmented compounds, using green solvents and reduced extraction times. The extract rich in anthocyanins also showed antimicrobial and anti-proliferative properties against four human tumor cell lines, without any toxicity on a primary porcine liver cell line.