scholarly journals Extraction of red grape pomace antioxidants with aqueous organic acid solutions using kinetic modelling

2017 ◽  
Vol 62 (3) ◽  
pp. 287-298
Author(s):  
Dimitris Makris
Keyword(s):  
Acetic Acid ◽  
Citric Acid ◽  
Food Industry ◽  
Kinetic Modelling ◽  
Reducing Power ◽  
Grape Pomace ◽  
Antioxidant Compounds ◽  
Aqueous Acetic Acid ◽  
Acid Solutions ◽  
Red Grape

Grape pomace is a food industry residual material which may contain a high load of polyphenolic antioxidants and a number of methods have been implemented for their effective recovery. Nevertheless, eco-friendly processes should embrace environmentally benign and non-toxic solvents. On this basis, this study investigated the extraction of antioxidants, by employing aqueous acetic acid and citric solutions and monitoring the reducing power (PR) of the extracts. The scope was to evaluate the effect of acid concentration on the extraction yield using kinetics. The kinetic model established allowed for the credible comparison of the extraction efficiencies, achieved with acetic acid and citric acid solutions of variable concentration. The results suggested that citric acid solutions were more effective in recovering red grape pomace antioxidants. Using a 4% (w/v) citric acid solution, a maximum PR of 229.8 ?M ascorbic acid equivalents per g of dry pomace could be attained. This investigation demonstrated that aqueous media used for the extraction of antioxidant compounds from food industry wastes could be significantly influenced by the acidifying agent and its concentration.

scholarly journals EXPLOITATION OF AGRI-FOOD SOLID WASTES FOR RECOVERY OF HIGH ADDED-VALUE COMPOUNDS: THE CASE OF GRAPE POMACE AND ONION PEELS

1970 ◽  
Vol 62 ◽  
Author(s):  
Papagiotis Kefalas ◽  
D. P. Makris
Keyword(s):  
Raw Materials ◽  
Reducing Power ◽  
Grape Pomace ◽  
Solid Wastes ◽  
Added Value ◽  
Waste Materials ◽  
Processing Plant ◽  
Food Ingredients ◽  
Pigment Extraction ◽  
Red Grape

Large quantities of both liquid and solid wastes are produced annually by the food processing industry. These waste materials contain principally biodegradable organic matter and their disposal creates serious environmental problems. The waste loads at the processing plant can be significantly reduced through the use of new or modified processing methods or through in-plant treatment and reuse and a variety of processes are being developed towards this direction, aiming at converting the waste materials into bio-fuels, food ingredients and other added-value bio-products. The scope of the present study was an examination on the possibilities of using non-toxic, cheap and readily available means of recovering phenolics from red pomace and onion peels. On such a basis, the solvent systems tested were composed of ethanol, a bio-solvent that can be obtained after fermentation of the sugar-containing raw materials and distillation. In the case of red grape pomace, simple media composed of 60% ethanol were shown to be ideal for recovery of extracts with increased polyphenol concentration and antiradical activity. Higher ethanol content (90%), however, was more effective for pigment extraction. For onion peels, extracts with high flavonol recovery and a reducing power were obtained with a similar medium (60% ethanol/ 0.1% HCl), while optimisation of the extraction conditions with regard to temperature and time, afforded higher yield and more active extracts.

Hydrophobic hydration in aqueous acetic acid and formic acid solutions probed by high pressure

2002 ◽  
Vol 98 (1-4) ◽  
pp. 177-182 ◽  
Author(s):  
Ming-Shan Lin ◽  
Chun-Min Feng ◽  
Hsiang-En Kao ◽  
Yu-Chun Huang ◽  
Hai-Chou Chang ◽  
...  
Keyword(s):  
High Pressure ◽  
Acetic Acid ◽  
Formic Acid ◽  
Hydrophobic Hydration ◽  
Aqueous Acetic Acid ◽  
Acid Solutions

Kinetics of the chromic acid oxidation of alcohols in aqueous acetone solutions

1968 ◽  
Vol 46 (3) ◽  
pp. 441-449 ◽  
Author(s):  
Donald G. Lee ◽  
William L. Downey ◽  
R. Michael Maass
Keyword(s):  
Acetic Acid ◽  
Chromic Acid ◽  
Aqueous Acetone ◽  
Acid Oxidation ◽  
Aqueous Acetic Acid ◽  
Acid Solutions ◽  
Deuterium Isotope Effect ◽  
Chromic Acid Oxidation ◽  
Oxidation Of Alcohols ◽  
Kinetics Of

The rate law for oxidation of 2-propanol by chromic acid in aqueous acetone solutions has been found to be V = k3 [Cr(VI)| [2-propanol]ho, with the magnitude of k3 being over 700 times as great in 93.3% acetone as it is in water. In other respects (primary deuterium isotope effect, Hammett "rho" value, and salt effects) the general features of the reaction strongly resemble those observed in aqueous acetic acid solutions.

Diffusion in Aqueous Acetic Acid Solutions

1956 ◽  
Vol 78 (18) ◽  
pp. 4538-4542 ◽  
Author(s):  
V. Vitagliano ◽  
P. A. Lyons
Keyword(s):  
Acetic Acid ◽  
Aqueous Acetic Acid ◽  
Acid Solutions

13C N.M.R. Spectroscopic Studies on the Reactions of Vanadium(V) With 13C2-Labeled Oxalate in Aqueous and 50% v/v Aqueous Acetic Acid Solutions

1995 ◽  
Vol 48 (4) ◽  
pp. 763 ◽  
Author(s):  
RP Farrell ◽  
PA Lay
Keyword(s):  
Acetic Acid ◽  
Spectroscopic Studies ◽  
Aqueous System ◽  
Aqueous Acetic Acid ◽  
Acid Solutions ◽  
Acetic Acid Medium ◽  
Acid Media ◽  
Coupling Pattern ◽  
Species Being ◽  
Second Peak

13 C n.m.r, spectroscopy has been used to study the reactions of vanadate , H2VO4-, with 13C2-labelled oxalate in aqueous and 50% v/v aqueous acetic acid media. The results of the aqueous system corroborate the natural abundance oxalate 13C n.m.r. studies of Ehde and coworkers ( Ehde, P.M., Petterson , L., and Glaser, J., Acta Chem. Scand., 1991, 45, 998) who report the formation of both mono( oxalato )-, [VO2(ox)(OH2)] - , and bis(oxalato)-vanadium(V), cis-[VO2(ox)2]3-, complexes in solution. At 270 K, pH 3.3, and an n.m.r. operating frequency of 100.16 MHz, the former complex appears as a singlet (167.3 ppm ), while the latter resolves into an AB coupling pattern (169.6, 168.8, 166.6, 165.8 ppm ; Jc -c 85 Hz) owing to the inequivalence of carbons trans and cis to the oxo ligands . In 50% v/v aqueous acetic acid both the mono( oxalato ) singlet (166.8 ppm ) and the bis ( oxalato ) AB coupling pattern (169.2, 168.5, 166.2, 165.5 ppm ; Jc -c ≈ 75 Hz) are present but are somewhat broadened and shifted downfield, which is indicative of other species being present. There is also some resolution of new peaks within the broadened signals. These are believed to be due to the presence of the additional complexes, mainly [VO2(ox)( OAc )]2- and cis-[VO2(ox)( OAc )2]3-, generated in the acetic acid medium. At 298 K, the bis(oxalato) complex exhibits a single 13C peak for the inequivalent carbons at 167.6 ppm because of fluxional behaviour. The mono( oxalato ) complex is in rapid equilibrium with free oxalate, giving a second peak at lower value of 165.7 ppm that is pH-dependent. The mechanisms of the fluxionality of the different complexes are discussed.

Redox switching kinetics of polythionine films in aqueous acetic acid solutions

1993 ◽  
Vol 97 (26) ◽  
pp. 6853-6858 ◽  
Author(s):  
Stanley Bruckenstein ◽  
C. Paul Wilde ◽  
A. Robert Hillman
Keyword(s):  
Acetic Acid ◽  
Aqueous Acetic Acid ◽  
Acid Solutions ◽  
Redox Switching ◽  
Kinetics Of
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