Nada El Darra

Changes in polyphenol profiles and color composition of freshly fermented model wine due to pulsed electric field, enzymes and thermovinification pretreatments.

This work compares the effects of three pretreatments techniques: pulsed electric fields (PEFs), enzymes treatment (ET) and thermovinification (TV) on the improving of extraction of main phenolic compounds, color characteristics (L(∗)a(∗)b(∗)), and composition (copigmentation, non-discolored pigments) of freshly fermented model wine from Cabernet Sauvignon variety. The pretreatments produced differences in the wines, with the color of the freshly fermented model wine obtained from PEF and TV pretreated musts being the most different with an increase of 56% and 62%, respectively, compared to the control, while the color only increased by 22% for ET. At the end of the alcoholic fermentation, the contents of anthocyanins for all the pretreatments were not statistically different. However, for the content of total phenolics and total flavonols, PEF and TV were statistically different, but ET was not statistically different. The contents of flavonols in musts pretreated by PEF and TV were significantly higher comparing to the control. An increase of 48% and 97% was noted respectively, and only 4% for ET. A similar result was observed for the total phenolics with an increase by 18% and 32% respectively for PEF and TV, and only 3% for ET comparing to the control. The results suggest that the higher intensity and the difference of color composition between the control and pretreated freshly fermented model wines were not related only to a higher content of residual native polyphenols in these freshly fermented model wines. Other phenomena such as copigmentation and formation of derived pigments may be favored by these pretreatments.

Pulsed Electric Field-Assisted Cold Maceration of Cabernet franc and Cabernet Sauvignon Grapes

The effect of pulsed electric field treatment on the cold maceration (6 days at 6ºC) of Cabernet franc and Cabernet Sauvignon grapes was investigated. The parameters of grape juice pH, Brix, color intensity, anthocyanin and total polyphenol contents, and free radical scavenging activity were determined during the entire period of cold maceration. The high pulsed electric field treatment (5 kV/cm, 1 ms, 48 kJ/kg) enhanced significantly the extraction of flavonoid (quercetin 3-β-D-glucoside and epicatechin gallate) components after subsequent cold maceration of red grapes. The high treatment also enhanced the color intensity (75% for Cabernet franc and 68% for Cabernet Sauvignon) and increased the anthocyanin content of juice (from 87 to 172 mg/L for Cabernet franc and 168 to 269 mg/L for Cabernet Sauvignon). The moderate pulsed electric field treatments (400 and 800 V/cm, 50 to 100 ms) were less effective for polyphenol extraction but consumed less energy (3 to 40 kJ/kg). The wines obtained from treated Cabernet franc and Cabernet Sauvignon musts had higher phenolic content and color intensity during the alcoholic fermentation period than wines obtained from the untreated musts.

Effect of pulsed electric field treatment during cold maceration and alcoholic fermentation on major red wine qualitative and quantitative parameters

This work studies the effect of pulsed electric field (PEF) treatment at moderate and high field strengths (E=0.8kV/cm & 5kV/cm) prior and during alcoholic fermentation (AF) of red grapes on improving different parameters of pre-treated extracts: pH, °Brix, colour intensity (CI), total polyphenols content (TPI) of Cabernet Sauvignon red wine. Similar trends were observed for treating grapes using moderate and high electric field strength on the enhancement of CI and TPI of the wine after AF. The application of PEF using moderate strengths at different times during cold maceration (CM) (0, 2 and 4days) was more efficient for treatment during CM. The treatment during AF showed lower extraction rate compared to treating during CM and prior to AF. Our results clearly show that the best time for applying the PEF-treatment through the red fermentation is during the CM step.

Valorization of industrial waste using energy saving procedures. Phenolic compounds purification from grape by-products by Accelerated Solvent Extraction (ASE)

The attention given by scientists these days to environment-friendly and energy saving procedures led us to work on the optimization of phenolic compounds extraction from waste industrial products using green technology methods. The growing attention towards phenolic compounds is basically due to the bioactivity of those molecules and their potential application in several industries such as pharmaceutical, nutraceutical and agriculture. In this paper we describe the extraction of phenolic compounds from grape by-products using Accelerated Solvent Extraction which was conducted and followed by a quantitative and qualitative study of the extracts in order to investigate the best extraction parameters. The extraction process using this energy saving method, showed that the optimal conditions are a 70% ethanol/water mixture (v/v) and a 140°C temperature. The quantity of the extracted phenolic compounds was determined by the Total Phenolic Index (TPI), while the qualitative study by High-Performance Liquid Chromatography (HPLC). The results showed that phenolic compounds content, quantity and diversity in each sample was dependent on the extraction temperature.

Effect of the Extraction Process on the Biological Activity of Lyophilized Apricot Extracts Recovered from Apricot Pomace

The preservation of polyphenols in fruits by lyophilization has gained great interest in the recent decades. The present study aims to assess the impact of the pre-treatment extraction methods heat-assisted extraction (HAE) and infrared (IR) on lyophilized apricot pomace extracts. Then to test the conservation of polyphenols quantities as well as their bioactivities (antiradical and antibacterial) in lyophilized extract. An aqueous extract was obtained through either heat-assisted extraction or infrared pre-treatments then lyophilized to obtain a dried form. Results showed that the content of polyphenols, the antiradical and antibacterial activities in lyophilized extracts exhibited a slighter decrease in infrared sample compared to the heat-assisted extraction ones. The High-performance liquid chromatography (HPLC) analysis showed that lyophilized extracts IR and HAE preserved the same phenolic molecules (rutin, catechin and epicatechin) detected in liquid extracts (IR and HAE) with a smaller yield. Lyophilization can be used as a widely process in the food industry to conserve many bioactive molecules.

A Comparative Study of the Phenolic and Technological Maturities of Red Grapes Grown in Lebanon

Grape harvest date is determined according to the technological and phenolic maturities. These parameters were calculated for different red grape (Vitis vinifera L.) varieties (Cabernet Sauvignon, Merlot, Syrah, Cabernet Franc) over four years (2008, 2009, 2010, and 2011) (642 samples). Titratable acidity and sugar content of the grapes were used to determine the technological maturity, whereas Glories (1 and 2) and ITV (Institut Technique de la Vigne et du Vin) methods were used to monitor their phenolic maturity. The ITV method allows the monitoring of phenolic maturity by the quantification of total polyphenol index and anthocyanins, while the Glories method enables the quantitative evolution of extractable anthocyanins and tannins of the grapes. A correlation was shown between the harvest dates obtained by both ITV and Glories (R2 = 0.7 – 0.93). Phenolic maturity of grapes can, therefore, be optimized by the application of both ITV and Glories. Similarly, a correlation was observed between technological and phenolic harvest dates. The effect of climate on the phenolic content of grapes was also studied. The highest temperatures (up to 25 °C) accompanied by the lowest rainfall (null value), induced the maximal concentration of polyphenols in grapes. Thermal and water stresses were also shown to enhance the grapes’ polyphenolic production.