Ohmic-heating treatment as a new process for development of functional ingredients through valorisation of tomato and grape by-products: production, characterization, bioactivity and potential application

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Extraction of tomato by-products’ bioactive compounds using ohmic technology

Publication . Coelho, Marta; Pereira, Ricardo; Rodrigues, António S.; Teixeira, José A.; Pintado, Manuela E.

Tomato peels and seeds are the main by-products of the tomato industry and represent an interesting source of bioactive compounds (BC) including carotenoids, which can be then used as colorant to commercial aquaculture. The aim of the present work was to optimize the extraction of BC from tomato by-products using Ohmic heating (OH) technology. OH extraction experiments were done in the presence of moderate electric fields (MEF) of different intensity (i.e. 4, 6 and 11 V cm−1) to identify the presence of non-thermal effects on the extraction process and its influence on bioactive properties of the extracted compounds. Polyphenol extraction using OH was successfully optimized with the best extraction conditions being 70 °C for 15 min using 70% ethanol as a solvent, which exhibited rutin recovers of 77% higher than control samples. It allowed to recover up to 4.93 μg/gFW lycopene from tomato by-products without resorting to organic solvents. OH can be used as an environmental-friendly, fast and economic process to polyphenols recover from industrial tomato by-products. In addition, the use of different MEF during extraction shows to have a high potential to cause different levels of permeabilization and cell stress that can help to define a selective extraction process of valuable components from tomato by-products.

2019Journal article

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Quercus based coffee-like beverage: effect of roasting process and functional characterization

Publication . Coelho, Marta; Silva, Sara; Rodríguez-Alcalá, Luis Miguel; Oliveira, Ana M.; Costa, Eduardo; Borges, André; Martins, Célia; Rodrigues, António S.; Pintado, Maria Manuela E.

Coffee is one of the world’s most widely consumed beverages but intake it is not encouraged in consumers with some health conditions. In this way, with the growing interest in developing healthier substitutes, a coffee-like beverage obtained from Quercus ilex and Quercus suber acorn´s species, was elaborates maintaining the flavor. Although, this beverage is a promising coffee alternative, little is known about effects of roasting process in its composition. To that end the antioxidant capacity and toxicity of the developed coffee were analyzed and phenolic compounds and fatty acids (esterified and free forms) were characterized through HPLC-DAD and GC-FID, respectively. The results showed that Quercus based beverages presented antioxidant capacity related to their phenolic content, mainly to ellagic acid as the primary phenolic compound identified. Due to this composition, the beverage also presented antimutagenic activity. The main fatty acids in the esterified lipids were mainly oleic, linoleic, palmitic, stearic and cis vaccenic. In the free fatty acids fraction (FFA) they were oleic, linoleic and palmitic acids. Heat processing produced a reduction in total fatty acid concentration in TG and FFA fraction of Q. ilex. Nevertheless, for Q. suber alterations were only found for FFA. Coffee production did not form genotoxic or cytotoxic compounds. Overall, these results show the feasibility of Quercus acorn-based foodstuffs and its potential to produce a functional coffee-like beverage.

2018Journal article

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The use of emergent technologies to extract added value compounds from grape by-products

Publication . Coelho, M. C.; Pereira, R.; Rodrigues, A. S.; Teixeira, J. A.; Pintado, M.E

Background: The current circular economy system-based sustainability and the social lifestyle trends, have led to a developed structure that is restorative or regenerative by purpose and innovation. It substitutes the end-of-life idea of a by-product adding value to it, shifts towards the usage of environmentally friendly solutions, elimi-nating the harmful chemicals, which impair reuse. Scope and approach: Considering the wine production, which is one of the most critical agro-industrial sectors worldwide, generating large amounts of by-products with environmental impact, but also with high economic and nutritional potential. This review aims to evaluate the effects of alternative green technologies on the functionality and recovery of bioactive compounds (BCs) from wine by-products. Key findings and conclusions: These agro-industrial by-products, e.g., skins and pulp remnants, are rich in BCs with health benefits such as supporting the immune system, anti-tumoral, and preventing cardiovascular diseases. Besides, the consumer has increased interest in diet and health, demanding suppliers to consider the reuse of agro-food by-products. Thus, the application of green recovery technologies eliminates the harmful effects comparing to conventional technologies, can be recycled into the food chain as functional additives for different products and applications, guaranteeing the sustainability and reducing the winemaking by-products.

2020Journal article

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Using ohmic heating effect on grape skins as a pretreatment for anthocyanins extraction

Publication . Pereira, Ricardo N.; Coelho, Marta; Genisheva, Zlatina; Fernandes, Jean Michel; Vicente, António A.; Pintado, Manuela E.; Teixeira, José A.

This study aims to obtain aqueous extracts of valuable phytochemicals, in particular anthocyanin’s, from winemaking residues by using grape skins as natural electrical conductors allowing internal heat dissipation through Ohmic Heating (OH) effect. Two different electric pretreatments were evaluated: i) using mild temperatures at 40 °C during 20 min; ii) flash heating from 40 to 100 °C in less than 20 s (no holding time). These pretreatments were followed by aqueous extraction in water at room temperature. Independently of the temperature applied, OH allowed to boost extraction levels increasing concentration of total phenolic compounds, as well as conductivity, soluble solids and red color intensity of the obtained extracts, as shown through principal component analysis (PCA). OH pretreatments at high-temperature short-time (HTST) due to the fast internal heating of grape skin structure allowed increase total concentration of anthocyanins from 756 to 1349 μg/g, with malvidin-3-O-glucoside being the main compound identified and quantified in the aqueous extracts through HPLC analysis (corresponding to about 60% of the total). These results showed that OH bring potential to be an efficient and environmentally friendly technology towards sustainable food processes.

2020Journal article

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Valorization of tomato by-products: influence of ohmic heating process on polyphenols extraction

Publication . Coelho, Marta; Pereira, Ricardo; Teixeira, J. A.; Pintado, Manuela

Current extraction treatments may cause degradation of biocompounds hampering their added value. Phenolic compounds extraction of Lycopersicon esculentum (tomato) by-products was optimized using ohmic heating (OH) as an alternative extraction technology. Design of experiments was applied to evaluate the effect of extraction time, temperature and ethanol concentration and further optimized by a desirability function. The antioxidant activity and characterization of phenolic compounds was performed. A significant increase of phenolics content and antioxidant activity were obtained at 70ºC and 40ºC (p<0.05). The best extraction conditions were 70 ºC, 15 min and 70% of ethanol with a total phenolic content of 2.550 ± 0.072 mg gallic acid equivalents/g(fw). The individual phenolic compounds were identified by HPLC-DAD analysis. In conclusion, OH shows to have a high potential as an environmental-friendly, economical and fast process for the recovery of polyphenols from industrial tomato by-products.

2017Conference object

Open access