Total Polyphenol Yield Research Articles

Valorization of olive oil solid waste using high pressure–high temperature reactor

The production of olive oil leads to considerable amounts of solid wastes rich in bioactive compounds with antioxidant properties, which have been partly used as inefficient polluting heating fuels for many years. This work was aimed to study the effect of extraction time and temperature on phenolics recovery from olive pomace. For this propose, different tests were performed, varying time from 15 to 120 min and temperature from 100 to 180 °C, using a high pressure–high temperature agitated reactor under a modified atmosphere. Total polyphenols, o-diphenols and total flavonoids were quantified. Maximum total polyphenols yield (45.2 mg CAE/g DP) was achieved at 180 °C and 90 min. HPLC analysis showed that oleuropein (2433 mg/100 g DP) and tyrosol (485 mg/100 g DP) were predominant phenolics in the extracts. Methanolic extracts, after additional purification processes, can be used in food, cosmetic and pharmaceutical industries. Solid residues, after phenolics extraction, are considered to have little environmental impact.

Modelling of solid-liquid extraction process of total polyphenols from soybeans

The influence of the solvent, temperature, and extraction time on the extractability of total polyphenols from milled soybeans variety Ika was investigated. The study was performed in order to select the most suitable solvent (water; 50, 60, 70, and 80% aqueous ethanol) for achieving the highest yield of total polyphenols. The most effective solvent (50% aqueous ethanol solution) was used for monitoring the kinetics and modelling of solid-liquid extraction of total polyphenols from soybeans, average particle size 0.459 mm, at solid-liquid ratio of 20 ml/g (ratio of the solvent volume per g of raw material). The total polyphenols content in the soybean extract was determined spectrophotometrically using Folin-Ciocalteu micro-methods at 765 nm. The applicability of different mathematical models (Peleg, Page, and Logarithmic models) to describe the kinetics of the solid-liquid extraction process of total polyphenols from soybeans was studied as well. The results exhibited a significant influence of the solvent and temperature on the kinetics and extraction yield of total polyphenols from soybeans. The best extraction yield of total polyphenols was obtained using 50% aqueous ethanol solution at 80°C after 120 min (4.322 mg GAE/g<sub>db</sub>). The extraction yield of total polyphenols in soybean extracts increased by increasing the extraction temperature and extending the duration of the extraction process. The mathematical models applied showed a good agreement with the experimental results, which allows their application in modelling and optimisation of solid-liquid extraction process for the extraction of total polyphenols from soybeans.

Implementation of response surface methodology to optimise extraction of onion (Allium cepa) solid waste phenolics

An experimental setup based on a 23-full factorial, central composite design was implemented with the aim to optimising recovery of polyphenols from onion solid wastes (OSW). In order to allow for the establishment of a sustainable process, reusable and non-toxic solutions composed of water/ethanol/citric acid were employed as extracting media. The factors considered were (i) the pH of the medium, (ii) the extraction time and (iii) the ethanol concentration. The model obtained produced a satisfactory fitting of the experimental data with regard to total polyphenol extraction (R2 = 0.97, p = 0.0025) and the reducing power of the extracts (R2 = 0.97, p = 0.0033), but not with the antiradical activity (R2 = 0.89, p = 0.0592). The 2nd order polynomial equations obtained after elaboration of the experimental data indicated that all parameters considered were significant in respect with the efficiency of total polyphenol recovery. The highest total polyphenol yield was theoretically predicted to be 9342 ± 1435 mg gallic acid equivalents per 100 g dry weight, under optimal conditions (60% EtOH, pH 2 and 4.2 h). Liquid chromatography-electrospray ionisation mass spectrometry of the optimally obtained extract revealed that the principal phytochemicals recovered were quercetin 3,4′-diglucoside, quercetin 4′-glucoside and quercetin. Simple linear regression analysis between the total polyphenol and the antiradical activity of the OSW extracts showed that there was no correlation in a statistically significant manner, as opposed to reducing power. The recovery of value-added substances from agri-food industrial wastes is an issue with importance pertaining to both the reduction of the waste load released to the environment, and the development of novel, natural food additives with functional properties. Up to date, the examinations pertaining to the clarification of factors that can affect extractability were based on rather unilateral assessment, while it is generally accepted that the retrieval depends on several parameters, which render the phenomenon a particular complexity. In this view, the implementation of factorial design with respect to investigating in parallel several factors pertaining to efficient polyphenol recovery becomes imminent. Thus the establishment of models on such a sound experimental basis is expected to provide a reliable background for more costand resource-effective processes, with a potential direct industrial applicability.

An Investigation on the Recovery of Antioxidant Phenolics from Onion Solid Wastes Employing Water/Ethanol-Based Solvent Systems

Onion solid wastes, composed of the apical trimmings and the outer dry layers of the bulb, were used as raw material for the recovery of antioxidant phenolics by employing acidified water/ethanol-based solvent systems. The extraction efficiency was assessed by measuring the reducing power and the antiradical activity of the extracts, and the total polyphenol yield. Improvement of the extraction yield was based on modifying the solvent composition and the operating conditions (temperature, time). Initial screening of various mixtures showed that significantly higher recoveries (P < 0.001) can be attained by using 60% ethanol containing 0.1% HCl. The assessment of factors affecting yield, including extraction time and temperature, was accomplished using a series of extractions on the basis of a 2 × 3 factorial design model, with time and temperature values varying from 0.5 to 6 h and from 40 to 60°C, respectively. The results obtained showed that improvement of yield is dependent upon increasing extraction time up to 6 hours, whereas increasing the temperature from 40 to 60°C had a negative effect.

Study of solid–liquid extraction kinetics of total polyphenols from grape seeds

Grape seeds are a waste by-product obtained after wine or juice making and present a good source of functional compounds, such as polyphenols. Extraction is a very important step for later use of phenolic components. The effect of different temperatures and solid–liquid ratios on the solid–liquid extraction yield of total polyphenols and the effect of four classes of particle size on the extraction kinetics of total polyphenols with 50% of aqueous ethanol were studied. Temperature, solid–liquid ratio and milling degree had positive influence on extraction rate and extent of extraction. The 1.47–6.68% of total polyphenols per dry matter of grape seeds was extracted during 200 min. Extraction kinetics was estimated using non-experimental two-parameter equation – modified Peleg’s model. Results showed a good prediction of Peleg’s model for extraction kinetics in all experiments ( ρ > 0.994), which gave the possibility for estimation of initial rate and extent of solid–liquid extraction.