Recovery Of Phenolic Antioxidants Research Articles

Impact of Cold Atmospheric Plasma Pretreatment on the Recovery of Phenolic Antioxidants from Spent Coffee Grounds

AbstractIn the present study, cold atmospheric plasma (CAP) was employed as a pretreatment method for the extraction of phenolic compounds from spent coffee grounds (SCGs). The impact of CAP treatment conditions, i.e., thickness of the SCGs layer (mm), distance between the plasma source and the SCGs layer (mm) and duration of CAP treatment (min), on the total phenol content, in vitro antioxidant activity, as well as caffeine and chlorogenic acid content of SCGs, was investigated. The process parameters were optimized with the aid of response surface methodology (RSM). After optimizing the CAP pretreatment conditions, the CAP-treated SCGs were subjected to ultrasound-assisted extraction using ethanol as the extraction solvent. The optimum conditions for CAP treatment identified, i.e., thickness, 1 mm; distance, 16 mm; and duration, 15 min, led to a significant enhancement in the recovery of bioactive compounds from SCGs compared to those obtained from untreated SCGs. Total phenolic content and antioxidant activity significantly increased (i.e., TPC from 19.0 ± 0.7 to 24.9 ± 1.4 mg GAE/100 g dry SCGs, ADPPH from 106.7 ± 5.01 to 112.3 ± 4.3 μmol Trolox/100 g dry SCGs, AABTS from 106.7 ± 5.01 to 197.6 ± 5.8 μmol Trolox/100 g dry SCGs, ACUPRAC from 17938 ± 157 to 18299 ± 615 μmol Trolox/100 g dry SCGs). A significant increase in caffeine content from 799.1 ± 65.1 mg to 1064 ± 25 mg/100 g dry SCGs and chlorogenic acid content from 79.7 ± 15.3 mg to 111.3 ± 3.3 mg/100 g dry SCGs, was also observed. Overall, CAP pre-treatment can be used to enhance the recovery of bioactive compounds from SCGs.

Modeling and Optimization of Phenolic Compounds from Sage (Salvia fruticosa L.) Post-Distillation Residues: Ultrasound- versus Microwave-Assisted Extraction

The essential oil production of Salvia fruticosa L. generates considerable amounts of post-distillation solid residues (PRES) which are rich in phenolic compounds. In the present work, the recovery of phenolic antioxidants from PRES by using Microwave-Assisted Extraction (MAE) and Ultrasound-Assisted Extraction (UAE) were separately optimized, according to the Box-Behnken experimental design. The optimization was based on extraction yield, total phenolic content (TPC), total flavonoid content (TFC), rosmarinic acid (RMA), carnosol (CARO), carnosic acid (CARA), and antioxidant activity. The optimal processing parameters were 72% and 68% ethanol, a 15- and 10-min extraction time, a 40 °C and 47 °C extraction temperature, and a 1:30 and 1:10 solid-to-solvent ratio, for MAE and UAE, respectively. Results showed that the levels of RMA, CARO, and CARA in UAE extracts were influenced mainly by ethanol concentration, extraction time, and extraction temperature, while MAE extracts were only influenced by the first two factors. Experimenting with the optimal conditions revealed MAE as more effective than UAE in the recovery of RMA and CARA. The experimental values were in good agreement with the predicted ones, indicating model efficacy in MAE and UAE optimization to effectively extract phenolic compounds from PRES for their further application in food and pharmaceutical industries.

A non‐conventional approach for obtaining phenolic antioxidants from red guava (Psidium guajavaL.) by‐products

The recovery of phenolic antioxidants from agro-industrial by-products using non-conventional techniques is a powerful tool to explore the bioactive potential of natural sources. Therefore, it is imperative to analyze the most suitable method to investigate a plant material’s phenolic composition. This study used ultra-turrax (UTE), ultrasonic bath (BUAE), and pressurized liquid (PLE) for soluble phenolic extraction from guava’s pulp and processing waste. UTE at 25°C for 1 h yielded the highest concentration of total phenolics and flavonoids from guava pulp, while PLE for 30 min at 60°C/10 MPa presented the best performance for flavonoids and condensed tannins recovery from guava waste. PLE produced extracts with 39 phenolics and high antioxidant capacity. Besides, scopoletin, resveratrol, and naringin are being reported for the first time in this fruit. These results suggest possible alternatives for the recovery of bioactive compounds, which may be used to develop nutraceuticals and/or functional foods. Practical applications Upon guava processing, 30% of fruit’s total volume is lost in the form of by-products (seeds, peels, and pulp leftovers). Evidence points out that this fraction, along with guava’s pulp, is rich in phenolics with antioxidant properties. An extraction procedure should be conducted to recover these compounds. However, conventional techniques are laborious, time-consuming, and they generally use a large amount of toxic organic solvent. Ultra-turrax—UTE, ultrasonic bath—BUAE, and pressurized liquid—PLE are non-conventional approaches that make possible the reduction of solvents and the recovery of selected phenolics not possible with conventional techniques. These extracts could be further applied to lipid-rich foods as a natural antioxidant system and/or as an ingredient in the development of nutraceuticals and functional foods.

Optimal Aqueous Extraction Conditions as A Green Technique for Recovery of Phenolic Antioxidants from Robusta Dried Coffee Pulp

Coffee pulp, a by-product of coffee processing, contains high level of flavonoids and other phenolic compounds. This by-product also contains high levels of other bioactive compounds such as chlorogenic acids and caffeine, which can be potentially recovered for further applications. This study used water as an inexpensive green solvent, for the maximum recovery of phenolics, major bioactive compounds and antioxidant capacity from coffee pulp. Recovery yield from optimal aqueous extraction was compared with organic solvent extraction. The results showed that temperature, extraction time and solid/solvent ratio significantly affected recovery yields from coffee pulp (P<0.05). Optimal aqueous extraction conditions were 100 °C, 60 min and the ratio of sample to solvent 1:100 g/mL. Under these optimal conditions, recovery yields were similar to those of 50% aqueous acetone extraction. Recovery yields were significantly higher than pure acetone, methanol and ethanol as well as methanol and ethanol in combination with water (50% v/v). Therefore, these optimal aqueous conditions are recommended for recovery of bioactive compounds from coffee pulp for further applications.

Subcritical water enhances hydrolytic conversions of isoflavones and recovery of phenolic antioxidants from soybean byproducts (okara)

This study aimed to enhance the hydrolytic conversions of conjugated isoflavones to non-conjugated aglycones from soybean byproducts (okara) using subcritical water hydrolysis. Processing parameters for temperature, pressure and solid liquid mixing ratio were set as constant variables following the experimental design performed in our previous study for the optimization of isoflavones extraction and kinetics modeling using subcritical water and response surface methododology. Fixed operating conditions were temperature (T: 150°C), pressure (P: 4MPa) and solid liquid ratio (s/l: 20mg/mL), and the reaction time was the sole control variable. The results revealed that prolonging the reaction time increased the concentrations of genistein and daidzein by 6.5 and 9 fold, respectively. Total phenolic contents increased up to 55%, and the antioxidant activities exhibited a strong correlation with isoflavone aglycones and phenolic contents.

Recovery of phenolic antioxidants from Syrah grape pomace through the optimization of an enzymatic extraction process

Phenolic compounds are highly valuable products that remain trapped in grape pomace, an abundant winery by-product. Therefore, efficient extraction procedures of these compounds represent a route for grape pomace valorisation. Here we performed a screening of the factors affecting the aqueous enzymatic extraction of phenolic compounds from Syrah grape pomace, including the following independent variables: temperature, pH, pectinase, cellulase and tannase; and a subsequent optimization through response surface methodology. At the optimal region, the enzymatic treatment enhanced the extraction yield of phenolics by up to 66% and its antioxidant capacity by up to 80%, reducing the incubation time and enzyme doses in respect to previous studies. We found that tannase raises the antioxidant capacity of the extract by the liberation of gallic acid, while cellulose favours the liberation of p-coumaric acid and malvidin-3-O-glucoside. We also tested the procedure in different grape pomace varieties, verifying its wide applicability.

Liberation and recovery of phenolic antioxidants and lipids in chokeberry (Aronia melanocarpa) pomace by solid-state bioprocessing using Aspergillus niger and Rhizopus oligosporus strains

The present study focused on the changes in polyphenols, antioxidant activities and lipid compositions from chokeberry pomace during solid-state fermentation (SSF) with Aspergillus niger and Rhizopus oligosporus. The extractable phenolics increased more than 1.7- fold during both fermentation processes. A similar trend was observed for total flavonoids. The obtained results also indicated that a longer fermentation period resulted in a greater loss of anthocyanins. The free radical scavenging ability of phenolic extracts, evaluated by DPPH and TEAC assays, were significantly enhanced during the SSFs. HPLC-MS analysis of phenolic compounds showed that the amounts of flavonols and cinnamic acids increased while the concentrations of glycosylated anthocyanins decreased substantially. The SSF of chokeberry pomace also resulted in a significant increase in lipids with high linoleic acid content (57–61% of the total fatty acids). The present investigation demonstrated that SSF enriched the chokeberry pomace with phenolic antioxidants and lipids with better nutritional-quality characteristics.

Valorization of Grape by-Products

The by-products of processed grape (grape seeds and grape peels) can be recovered for further food applications. Extracts of grape by-products were obtained with solvents of different polarity (aqueous acetone, methanol and ethanol) and assayed for their total phenolic content and antioxidant activity. The high amount of total phenols was found in grape seeds. Higher yields of phenolic antioxidants were recovered with acetone. The recovery of phenolic antioxidants from the peels and seeds of processed grape could be a valuable alternative to traditional disposal routes (including landfill), in particular for cooking grape varieties. The recycling process could enhance the growth of traditional culinary markets thanks to the new business opportunities for the peel-derived and seed-derived materials.

Recovery of Phenolic Antioxidants and Functional Compounds from Coffee Industry By-Products

The recovery process of the phenolic compounds from the coffee industry by-products and their antioxidant activity were investigated in this work. The coffee by-products (coffee pulp, husk, silver skin, and spent coffee) were obtained from coffee processing industry. The phenolic conserves were extracted using solvent mixture of isoproponal and water. The yield of the conserve was highest in case of silver skin (25%) followed by spent waste (19%) and cherry husk (17%) when pretreated with viscozyme. The conserve enclosed chlorogenic acid as major component when analyzed with high-performance liquid chromatography. The bioactive conserves prepared from coffee by-products possessed 65%–70% antioxidant activity. Apart from these, the coffee by-products encompassed total dietary fiber of 40%–80%. Whereas the soluble and insoluble fiber proportion of the coffee by-product ranged between 16–35% and 18–64%, respectively. The antioxidant activity of coffee by-product fiber ranged from 1.5 to 2.0 mmol trolox/100 g and is analogous to that of widespread fruits and fresh vegetables. The hydration properties such as water holding capacity of each by-product was strictly related to the amount of insoluble fiber and to the granulometry. This is the first report on the isolation of bioactive and functional compounds from coffee by-products and can be a source of new value-added products such as phenolic antioxidant adjunct for food processing.

Recovery of phenolic antioxidants from wine industry by-products

The recovery process of the phenolic compounds contained in the wine industry by-products and their antioxidant activity were examined in this work. To this purpose, a combined process of liquid and supercritical solvent extraction was employed. At first the effect of various process parameters of the liquid solvent extraction––the type of solvent and the pretreatment of the raw material (composition (skins, seeds, stems) and crushing)––on the antioxidant activity of the extract was examined. It was shown that an extract of a higher antioxidant activity was obtained by using ethyl acetate as solvent and raw material free of stems. These extracts were further treated with supercritical carbon dioxide (SC CO2) at various extraction pressures, which resulted in their significant enrichment in phenolic compounds and the improvement of their antioxidant and organoleptic properties, especially at pressures higher than 100 bar. The antioxidant activity of the products was determined by using the Rancimat method, as well as a simple and not time-consuming free radical method. It was proved that both the ethyl acetate extracts and those treated with SC CO2 had antioxidant activity comparable to that of antioxidants commonly used in industry, that is butylhydroxytoluene (BHT), a synthetic antioxidant, and Rosemary extract, a widely known natural one.

Effects of Mode of Sterilization on the Recovery of Phenolic Antioxidants in Laboratory Media Assessed by Nonderivatizing Gas Chromatography-Mass Spectrometry

The effects of autoclaving and filter sterilization on the recovery of butylated hydroxyanisole, butylated hydroxytoluene, tertiary butylhydroquinone, and propyl gallate in laboratory media were investigated by a nonderivatizing gas chromatography-mass spectrometry (GC-MS) method. Lauryl tryptose broth (LTB) or brain heart infusion (BHI) broth were treated with the combinations of the phenolic antioxidants at 200 ppm. The antioxidants were dissolved in 95% ethanol and either added directly to the media followed by autoclaving or filter-sterilized and then added to sterilized media in a flask. Results suggested that antioxidant recoveries were affected by the modes of sterilization as well as by the complexity of the medium. More antioxidants were recovered from the filter-sterilized than from the autoclave-sterilized samples for LTB medium, but no clear difference was seen for BHI broth. The recovery was lowest with butylated hydroxytoluene regardless of medium type or sterilization mode used. The extraction procedure applied as well as the nonderivatizing GC-MS method appeared to be adequate for the simultaneous determination of the four antioxidants.