Pear juice phenolics

Pear Phenolics. The same HPLC analytical system gave good resolution of pear juice phenolics and enabled peak assignments and quantitation to be made in a similar manner to that described for apple phenolics (3,7). It was also necessary to isolate the procyanidins and catechins using the Sephadex clean-up procedure (4) in order to measure their concentration. Figure 6A shows the HPLC separation of cinnamics, flavonols, and arbutin in pear juice while Figure 6B is a HPLC chromatogram of the pear juice procyanidin fraction. 

Spanos, G.A. and Wrolstad, R.E., Influence of variety, maturity, processing and storage on the phenolic composition of pear juice, J. Agric. Food Chem., 38, 817, 1990. 

High-performance LC analysis of phenolics in apples and pear juices are often performed by gradient procedures (49-54), due to the presence of several phenolic classes. Most of the HPLC methods applied to apple phenolics are very similar to that of Oleszek et al. (55). 

Many different sample preparation procedures have been employed, ranging from simple filtration of juice products to solvent extraction, and extraction by SPE using C, 8, Sephadex LH-20 (49,50,52), and Amberlite XAD-2 (51,54,57). The Amberlite XAD-2 cleaning step has been used for many phenolic extracts, especially for fruit purees, to remove the sugars and other polar compounds. However, due to the low recovery rate with Amberlite XAD-2 for certain phenol glycosides, a modified sample preparation technique is needed, especially for quantification of ar-butin in pear juice and blends (54). Figure 6 describes the fractionation procedure for phenolics using a Sephadex LH-20 column (58). 

Figure 7. Effect of processing and storage on the phenolics of pear juice. Unit operations code P, pressed juice H, heat treatment E, enzyme clarification F, fined Ft, filtered B, bottled single-strength juice C, concentrate and CS, stored concentrate.

None of the bottled pear juices or reconstituted pear juice samples showed particular problems of haze or sediment formation (Table IV). SO2 addition, which protected phenolics from oxidation, had no influence on the clarity of these samples. Juice from ripened d Anjou and Cornice fruit had slightly higher % haze readings than juice from unripe fruit. All of these samples were subjected to standard fining procedures which may account for their stability and clarity (6). 

GA Spanos, RE Wrolstad. Phenolics of apple, pear, and white grape juices and their changes with processing and storage. A review. J Agric Food Chem 40 1478—1487, 1992. 

Juice of the sand pear can also be converted into vermouth (Joshi et al, 1999). The complete process is illustrated in Fig. 8.3. Dry and sweet versions, with various alcohol levels, have been prepared (Attri et al, 1993). TSS, acidity, aldehyde, phenol, and ester contents increase as a... 

SPE on a CLX cartridge was applied to separate acidic phenols such as chlorogenic acid (95) from neutral phenols such as (—)-epicatechin (2), (+)-catechin (3), phloridzin (96) and quercitrin (100). The neutral phenols were determined in apple juice by capillary LC with UVD at 280 nm, as an alternative to conventional HPLC. LOD were from 9 pg for 96 to 97 pg for 3. HPLC analysis with MS and DA-UVD showed that apple pomace is a good potential source for phenoUcs. The usefulness of arbutin (9) as specific marker for pear products was placed in doubt (see Section II.A °). 

Commercial pectolytic enzymes used in clarification can cause hydrolysis of hydroxy cinnamic acids in apple, pear and grape juice [183]. In addition, the use of gelatin as a fining agent reduces total phenolics with the polymeric phenolics being the most affected. 

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