Associated Laboratory for Green Chemistry - Clean Technologies and Processes

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Effect of a winter savory leaf extract obtained using high hydrostatic pressure on the quality of carrot juice

Publication . Moreira, Sílvia A.; Pintado, Manuela E.; Saraiva, Jorge A.

BACKGROUND: The consumption of vegetable juices has increased due to their characteristics such as freshness/naturalness, high nutritional value, low in calories, and for being a convenient way of consuming bioactive compounds. High hydrostatic pressure (HPP), which has been mainly used to replace thermal processing, is now also being successfully applied as extraction technology to recover bioactive compounds from herbs. The present work aimed to evaluate the effect of supplementation of carrot juice with winter savory leaf aqueous extract on the final juice characteristics. RESULTS: The extract was added to raw carrot juice (1.0 mg mL–1), which was then submitted to HPP and stored for 15 days under refrigeration. Microbial analyses were performed during storage time, as also were analyzed the physicochemical properties such as pH, colour, bioactive compound concentration and antioxidant activity. Supplemented juices presented lower microbial counts than the non-supplemented ones, and, generally, did not present significant changes (P > 0.05) in pH or colour. Concerning the total phenolics and total flavonoids, as well as antioxidant activity, the values were generally higher (P < 0.05) in supplemented juices, which was proven by the high correlation found between total phenolics and ABTS●+ and FRAP assays. CONCLUSIONS: These data suggest that the addition of winter savory leaf extract in carrot juice treated with HPP can effectively improve microbial safety throughout refrigerated storage as well as antioxidant activity, without risking other characteristics of the juice, such as the colour or the acidity.

2021-01-15Journal article

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Optimization of high hydrostatic pressure assisted extraction of stinging nettle leaves using response surface methodology experimental design

Publication . Moreira, Sílvia A.; Pintado, Manuela E.; Saraiva, Jorge A.

High hydrostatic pressure assisted extraction (HPE) is a very promising extraction methodology since it can operate at room temperature and therefore can avoid heat-sensitive compounds changes. Furthermore, it is recognized as a fast technology (only a few minutes) and it is also an already proven environmentally friendly technology. This is the first work to study HPE effect as a new extraction method to obtain improved extracts from stinging nettle, a commonly known weed, traditionally used as folk medicine and with several biological properties proven scientifically. In this work, the HPE process was optimized by an experimental design via response surface methodology using a central composite face-centered design. The effect of pressure level, extraction time, and solvent concentration were evaluated, as also the impact of HPE on total phenolics (TPC), flavonoids, pigments, and antioxidant activity. Results showed that experimental data could be well fitted to second-order polynomial mathematical models, since lack-of-fit values were non-significant and the regression coefficients were above 75%. The optimal conditions for the overall maximization of extraction yield, TPC and antioxidant activity were 200 MPa, 10.2–15.6 min, and 0% ethanol (aqueous extracts), which were tested in a further experiment confirming the predictability of all models (difference by percentage between predicted and experimental optimum were all below 10%. When compared to extraction at atmospheric pressure, HPE allowed increasing the extraction yield about 50.5%; TPC about 84.4%; and antioxidant activity about 77.7%. All the models fitted well the experimental data, being the observed values close to the predicted ones by the model equation.

2020Journal article

Restricted access

Exploring newly synthesized iron chelators as colorimetric/fluorescent sensors in polymer inclusion membranes

Publication . Mesquita, Raquel B.R.; Leite, Andreia; Rangel, Maria; Rangel, António O.S.S.

2020Conference object

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Greener sequential injection method for iron spectrophotometric determination in fresh and marine waters

Publication . Ribas, Tânia C.F.; Mesquita, Raquel B.R.; Moniz, Tânia; Rangel, Maria; Rangel, António O.S.S.

2020Conference object

Open access

Optimization of antioxidant activity and bioactive compounds extraction of winter savory leaves by high hydrostatic pressure

Publication . Moreira, Sílvia A.; Pintado, Manuela E.; Saraiva, Jorge A.

Winter savory is often used in traditional medicine, having several recognized biological properties. This study aimed to evaluate the effect of high pressure-assisted extraction (HPE) and its optimization by response surface methodology to obtain winter savory extracts with a high content of bioactive compounds and high antioxidant activity (the effect of extraction pressure, extraction time, and ethanol concentration were investigated). Results showed that data could be well fitted to second-order polynomial mathematical models for total phenolics, total flavonoids, chlorophylls, carotenoids, and extraction yield, as well as for antioxidant activity. The models predicted optimal conditions ranging 200–500 MPa, extraction time 1–20 min, and ethanol concentration 0–70% (v,v). In comparison with extraction at atmospheric pressure, HPE showed to be more efficient, allowing obtaining an increase of about 40% for all compounds, and an increase of 29, 48, and 70% for antioxidant activity by FRAP, DPPH and ABTS assays, respectively.

2020Journal article

Restricted access