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Quantification of 3-deoxyglucosone (3DG) as an aging marker in natural and forced aged wines

Publication . Oliveira, Carla M.; Santos, Sónia A. O.; Silvestre, Armando J. D.; Barros, António S.; Ferreira, António César S.; Silva, Artur M. S.

The Maillard reaction product 3-deoxyglucosone (3DG) was quantified in wines, by high-performance liquid chromatography-mass spectrometry analysis after derivatization with ortho-phenylenediamine. Both sweet red Port wines and dry white wines were analysed during natural and forced aging. In natural aging, and for dry white wines, 3DG is negatively correlated to age (r = −0.939), while for sweet red Port wines, 3DG is positively correlated to age (r = 0.782). The same tendency was observed during a wine forced aging protocol. For a dry white wine, with higher levels of α-amino acids, 3DG is consumed (kconsumption 0.077–0.098 day−1) along the time protocol, while for a sweet red Port wine, with lower levels of α-amino acids, an accumulation of 3DG is observed with time (kformation 0.041–0.060 day−1). These results suggest that 3DG content can be used as an aging marker, as it has discriminated dry white and sweet red Port wines from different ages and cultivars. Analysis of wine-model solutions allowed verifying that the fructose content has a higher effect on 3DG formation than glucose, as well as that an increase on amino acids content does not lead to an increase of 3DG yields.

2016Journal article

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Adaptation of Saccharomyces cerevisiae to high pressure (15, 25 and 35 MPa) to enhance the production of bioethanol

Publication . Ferreira, Ricardo M.; Mota, Maria J.; Lopes, Rita P.; Sousa, Sérgio; Gomes, Ana M.; Delgadillo, Ivonne; Saraiva, Jorge A.

Saccharomyces cerevisiae is a yeast of great importance in many industries and it has been frequently used to produce food products and beverages. More recently, other uses have also been described for this microorganism, such as the production of bioethanol, as a clean, renewable and sustainable alternative fuel. High pressure processing (HPP) is a technology that has attracted a lot of interest and is increasingly being used in the food industry as a non-thermal method of food processing. However, other applications of high pressure (HP) are being studied with this technology in different areas, for example, for fermentation processes, because microbial cells can resist to pressure sub-lethal levels, due to the development of different adaptation mechanisms. The present work intended to study the adaptation of S. cerevisiae to high pressure, using consecutive cycles of fermentation under pressure (at sub-lethal levels), in an attempt to enhance the production of bioethanol. In this context, three pressure levels (15, 25 and 35 MPa) were tested, with each of them showing different effects on S. cerevisiae fermentation behavior. After each cycle at 15 and 25 MPa, both cell growth and ethanol production showed a tendency to increase, suggesting the adaptation of S. cerevisiae to these pressure levels. In fact, at the end of the 4th cycle, the ethanol production was higher under pressure than at atmospheric pressure (0.1 MPa) (8.75 g.L−1 and 10.69 g.L−1 at 15 and 25 MPa, respectively, compared to 8.02 g.L−1 at atmospheric pressure). However, when the pressure was increased to 35 MPa, cell growth and bioethanol production decreased, with minimal production after the 4 consecutive fermentation cycles. In general, the results of this work suggest that consecutive cycles of fermentation under sub-lethal pressure conditions (15 and 25 MPa) can stimulate adaptation to pressure and improve the bioethanol production capacity by S. cerevisiae; hence, this technology can be used to increase rates, yields and productivities of alcoholic fermentation.

2019Journal article

Restricted access

Combined effect of pressure and temperature for yogurt production

Publication . Lopes, Rita P.; Mota, Maria J.; Sousa, Sérgio; Gomes, Ana M.; Delgadillo, Ivonne; Saraiva, Jorge A.

Fermentation under non-conventional conditions has gained prominence in the last years, due to the possible process improvements. Fermentation under sub-lethal pressures is one of such cases, and may bring novel characteristics and features to fermentative processes and products. In this work, the effect of both pressure (10–100 MPa) and temperature (25–50 °C) on yogurt production fermentation kinetics was studied, as a case-study. Product formation and substrate consumption were evaluated over fermentation time and the profiles were highly dependent on the fermentation conditions used. For instance, the increase of pressure slowed down yogurt fermentation, but fermentative profiles similar to atmospheric pressure (0.1 MPa) were obtained at 10 MPa at almost all temperatures tested. Regarding temperature, higher fermentative rates were achieved at 43 °C for all pressures tested. Moreover, the inhibitory effect of pressure increased when temperature decreased, with complete inhibition of fermentation occurring at 50 MPa for 25–35 °C, contrasting to 43 °C where inhibition occurred only at 100 MPa. Therefore, an antagonistic effect seems to occur, since yogurt fermentation was slowed down by pressure increasing, on one hand, and by temperature decreasing, on the other hand. Additionally, some kinetic parameters were calculated and fermentation at 43 °C presented the best results for yogurt production, with lower fermentation times and higher lactic acid productivities. Interestingly, fermentation at 10 MPa/43 °C presented the optimal conditions, with improved yield and lactic acid production efficiency, when compared to fermentation at 0.1 MPa (efficiency of 75% at 10 MPa, against 40% at 0.1 MPa). As the authors are aware, this work gives the first insights about the simultaneous effect of pressure and temperature variation on a microbial fermentation process, which can be combined to modulate the metabolic activity of microorganisms during fermentation in order to improve the fermentative yields and productivities of the desired product.

2019Journal article

Open access

Physicochemical and microbial changes in yogurts produced under different pressure and temperature conditions

Publication . Lopes, Rita P.; Mota, Maria; Pinto, Carlos A.; Sousa, Sérgio; Silva, José A. Lopes da; Gomes, Ana M.; Delgadillo, Ivonne; Saraiva, Jorge A.

Variations on fermentation conditions (temperature, pressure, etc.) can bring novel characteristics to fermentative processes and the respective final products. Regarding yogurt, both bacteria metabolism and physical properties of gel may be affected, resulting in different yogurts. Therefore, lactic acid fermentation was performed under different combinations of pressure (0.1, 10 and 30 MPa) and temperature (35, 43 and 50 °C), and microbiological and physical properties of the yogurts obtained were analyzed. Fermentation conditions affected the microbial growth, with Streptococcus thermophilus being more sensitive to the combination of high temperatures and pressures than Lactobacillus bulgaricus. Regarding physical properties, both syneresis and texture were influenced by fermentation conditions. Yogurts fermented at 10 MPa presented interesting features, with syneresis similar to control yogurts and a firm texture. Therefore, the fermentative conditions can be changed not only to regulate the fermentation kinetics, but also to produce a final product with different properties. Therefore, this approach opens the possibility of applying this type of strategy to a wide range of food fermentative processes, with potential to improve food quality and to create and develop food products with novel characteristics.

2019Journal article

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Effect of emergent non-thermal extraction technologies on bioactive individual compounds profile from different plant materials

Publication . Moreira, Sílvia A.; Alexandre, Elisabete M. C.; Pintado, Manuela; Saraiva, Jorge A.

Extraction is the first step for isolation and purification of interesting bioactive compounds, by mixing of the plant material with an adequate solvent. Those bioactive compounds are, usually, secondary metabolites, such as phenolic acids and flavonoids which are present in closed insoluble structures, making its extraction a challenge. There are many different traditional extraction methods, such as Soxhlet, heat reflux, and maceration. Nevertheless, due to several disadvantages, they are being replaced by new methods, using emergent technologies, such as high hydrostatic pressure, ultrasounds, pulsed electric fields, and supercritical fluids. The use of novel technologies allows enhancing mass transfer rates, increasing cell permeability as well as increasing secondary metabolite diffusion, leading to higher extraction yields, fewer impurities on the final extract, extractions at room temperature with thermo-sensitive structures preservation, use of different non-organic solvents, low energy consumption, short operation time, and have no significant or lower effect on the structure of bioactive compounds. This paper aims to review the effect of the main emergent extraction technologies (high hydrostatic pressure, pulsed electric fields, ultrasounds, and supercritical fluid assisted) on the individual profile of bioactive compounds from plant material.

2019Journal article

Restricted access