Grapes fractions

There are two methods available for aroma recovery. In one method, a portion of the water is stripped from the juice prior to concentration and fractionally distilled to recover a concentrated aqueous essence solution. Apple juice requires 10% water removal, peach 40%, and Concord grape 25—30% to remove volatile flavor as an essence. Fractional distillation affords an aqueous essence flavor solution of 100—200-fold strength, which means the essence is 100 to 200 times more concentrated in flavor than the starting juice. A second method of essence recovery is to condensate the volatiles from the last effect of the evaporator they are enriched in volatile flavor components (18). 

Rozenberg O, Howell A and Aviram M. 2006. Pomegranate juice sugar fraction reduces macrophage oxidative state, whereas white grape juice sugar fraction increases it. Atherosclerosis 188(1 ) 68-76. 

Fractionation of Grape Seed Proanthocyanidins for Bioactivity Assessment... 

The aim of this chapter is to highlight recent advances in fractionation techniques for grape seed PAs, using as examples methods we are using for large-scale fractionation into monomers, oligomers, and polymers for assessment of bioactivity and bioavailability in animal model studies of Alzheimer s disease. Our methods represent modifications/combinations of previously described approaches. We first discuss the available methods and modifications and then present a case study for the fractionation of MegaNatural-AZ GSE. 

Methods used for the detection of PAs in cmde or partially purified extracts can also be adapted for post-column analysis after fractionation (see below). Direct quantitative analysis of PAs in crude grape phenolic extracts is often impossible due to the complex sample matrix. Thus, fractionation or purification is often necessary before analysis. The Folin-Ciocalteu and Pmssian Blue assays are widely used for the quantification of total polyphenols in plants [27,28]. These methods are not specific for PAs due to the reaction of other phenolic compounds with these reagents. 

Saucier C, Mirabel M, Daviaud F et al (2001) Rapid fractionation of grape seed proanthocyanidins. 1 Agric Food Chem 49 5732-5735... 

Labarbe B, Cheynler V, Brossaud F et al (1999) Quantitative fractionation of grape proanthocyanidins according to their degree of polymerization. J Agric Food Chem 47 2719-2723... 

Repeated TLC of active, pooled fractions from Red Flame grapes revealed major spots with Ry s corresponding to those of catechin and epi-catechin, identical color reaction with p-toluenesolfonic acid spray reagent, and coelution of trimethylsilane (TMS) derivatives by GC with reference samples of these flavans. However catechin and epicatechin were assayed with the bacterial strains described and no activity was detected. TMS-derivatized samples of active grape flavans were examined by GC-MS, but a search for the molecular ions of a number of known wr-inducing phenolics yielded negative results. 

In the search for LHR air-inducers, each phenolic aglycone or other fraction to be tested was dissolved in DMSO and diluted in pH 5.50 or 5.70 MS medium to a final concentration of 0.1% DMSO (phenolic glycosides and the grape flavan fractions were dissolved directly in pH 5.50 or 5.70 MS medium). Subsequent experiments revealed a more acidic pH optimum for... 

Gas Chromatography. In our GC analyses, N,0-bis-(Trimethylsilyl) Trifluo-roacetamide (BSTFA)-derivatized standards of known wtr-inducing pheno-lics failed to correspond in retention time to any of the derivatized samples of the most active grape flavan fractions. Catechin and epicatechin were tentatively identified by GC. 

Ferret, C., Pezet, R., and Tabacchi, R., Fractionation of grape tannins and analysis by matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry, Phytochem. Anal, 14, 202,... 

Extraction and Fractionation of Flavonoids from Grape and Wine.264... 

Mass spectrometry methods based on soft ionization techniques, 59,61,88,89 matrix-assisted laser desorption ionization/time-of-flight (MALDI-TOF), have been successfully applied for the direct analysis of grape and wine extracts and for monitoring flavonoid reactions in model solution studies. They give access to the molecular weights of the different species present in a fraction or extract and, through fragmentation patterns, provide important information on their constitutive units. Description of the various MS techniques can be found in Chapters 1 and 2. 

Vidal, S. et al., Fractionation of grape anthocyanin classes using multilayer coil countercurrent chromatography with step gradient elution. J. Agric. Food Chem. 52, 713, 2004. 

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