Abstract:
Grape pomace valorization holds great potential for future production of pharmaceutical
ingredients, enzymes, flavors, pigments, phytochemicals, nutraceuticals, biomaterials, and
biofuel. The nutritional compositions of such by-products appear rich in vitamins,
polyphenols, and natural macromolecules of high interest for the food, chemical and
pharmaceutical industry. The objective of this thesis was a valorization of red grape
pomace for recovery of polyphenol through process optimization and kinetics study using
an ethanol-waters solvent. The extraction was carried out using the thermostatic digital
shaker method and the extract was separated from the solvent to determine the yield of
polyphenol by using a rotary evaporator. Grape pomace was analyzed for proximate
composition and found to have:4.076±2.48%moisture,12.8 ±3.05% total proteins, 16.87
±1.05%, total fat 3.67±0.1 total ash , 57.27±3.1 total dietary (<0.08% sucrose ,<0.05 %
glucose & 0.7 %fructose 2.347 ±0.388 mg/l vitamins C. Aso ,Flavonoid, Flavanol, and
polyphenol were analyzed and found to have:46.38±0.507 ,7.816±0.207 ,and 38.476±0.407
mg CE/g ,respectively. The State Ease Design Expert 11.2.0 software and central
composite design (CCD) under RSM was used to determine the influence of extraction
solvent ratio, solid solvent ratio, extraction temperature and extraction time on polyphenol
yield four factors and a central composite design consisting of 30 experimental runs were
performed followed by optimization of total yield polyphenol. This work was deals random
experimental design consisted solvent concentration (30,50, &70%) solvent solid ratio
(20:1,30:1 &40:1), temperature (35
o
c,45
o
c, &55
o
c), extraction time (25,35&45) and it was
conducted with six center point and three replications. The minimum percentage yield was
at 50% solvent concentration/solvent ratio, 30:1 solvent solid ratio, the temperature of 45
ºC and 15 contact time, and the maximum percentage yield was at 70% solvent ratio ,40:1
solvent solid ratio, temperature e 55 ºCand 45 contact time. The kinetics study was
performed on red grape pomace to optimize yield of total polyphenol and the k values
0.0105,0.01106 and 0.01284 were obtained at extract temperature of 35
0
c,45
0
c, and 55
0
c,
respectively, which shows that raising the temperature could enhance the rate extraction of
total polyphenol content.
Keywords: Red grape pomace valorization, polyphenol, thermostatic digital shaker
extraction method, kinetic study.