Previously, it has not been possible to obtain a concentrated ripe Bartlett pear essence. From studies of Bartlett pear aroma characteristics, it was found that methyl and ethyl decadienoates are the components contributing to the characteristic ripe Bartlett pear aroma. It was also found that only perfume-like aroma products, lacking in typical Bartlett pear aroma, could be obtained in the early pear essence recovery trials. Thus, a laboratory scale fruit essence recovery unit was designed and built to study the difficulties in pear essence recovery. Water was first used to calibrate the unit, then, apple juice was applied as a testing model to establish the basic essence recovery effectiveness of the unit. It was found that the high heat provided by the reboiler, would drive the high-boiling, low-volatile pear aroma components upward to the fractionating column top where they could be recovered as overhead product. The high-boiling compounds were found in the reboiler discharge water in the low-heat tests. A good, strong and characteristic ripe Bartlett pear essence was obtained in the high-heat pear essence recovery test. A concept of separating low-boiling alcohols from high-boiling esters, to avoid the interference from low-boiling alcohols in the concentrating high-boiling esters. was substantiated through developing a two-stage essence recovery unit. Characteristic Bartlett pear essence of 100 fold was produced successfully in the two-stage test. Along with the organoleptic evaluation, the essence product was also analyzed by GC-MS and UV spectrometry to confirm the presence of "decadienoates" — characteristic Bartlett pear aroma components. This is the first time that a typical and good quality ripe Bartlett pear essence of 100 fold has been recovered. / Graduation date: 1981

Two methods of separating sugars and acids of Bartlett pears were compared to decide upon a working method for later studies involving identification and quantitation of sugars and acids during ripening of pears and in the production and storage of pear concentrate. The first method involved precipitation of acids with saturated lead acetate followed by several washings of the precipitate with 85% ethanol for complete removal of sugars. In the second method acids were bound to an anion exchange resin column (Dowex 1-X8), sugars washed off with deionized water, and the acids later eluted with strong formic acid. Gas Chromatographic and Mass Spectrometric (GC-MS) analyses of Trimethylsilyl (TMS) ethers of sugars separated by either method resulted in the identification of fructose, glucose, sorbitol, sucrose, mesoinositol and xylose. Inaddition, galactose, reported as a trace sugar in pears, was identified by gas chromatography, however, confirmation by mass spectrometry could not be obtained. Similar analyses of TMS derivatives of acids separated by lead salts precipitation indicated that a complete separation of sugars from acids was not achieved, resulting in co-chromatography of fructose with citric acid and presence of other unidentified peaks with characteristic ions of TMS sugars in their mass spectra. GC-MS analyses of TMS derivatives of acids separated by ion exchange, on the other hand, indicated complete separation of sugars from acids and the following acids were identified: glycolic, succinic, phosphoric, malic, citric, quinic, mucic, and chlorogenic. Notably, phosphoric acid, which has not been reported in pears, was separated by both lead salt precipitation and ion exchange and identified by GC-MS. However, some of the trace acids which have been reported in pear juice or pear must were not detected in Bartlett pears. The internal standard method was used for gas chromatographic quantitation of four major sugars (fructose, glucose, sorbitol, and sucrose) and four major acids (citric, malic, phosphoric, and quinic) of pears in the following studies. Bartlett pears attained their highest sugar content (13.5 g/100 g fruit) on the fourth day of ripening (66 [greater than or equal to] 2°F ) and at a penetrometer reading of 6 lbs. Sucrose and fructose rose by 0.75% and 1.3% respectively and then decreased, however, sucrose declined more rapidly. Sorbitol and glucose, on the other hand, both decreased steadily by about 0.5%. The total acidity rose by about 1.2 meq/100 g fruit until the fourth day and then followed a near linear decline. The decrease in malic and citric acids accounted for the decline in total acidity, phosphoric and quinic acids undergoing little change. Apart from the hydrolysis of a small amount of sucrose at the depectinization and concentration steps, little change was found to occur in the sugar and acid levels during the production of a concentrate from the juice of Bosc and Cornice pears. Accelerated storage (98°F) of pear concentrate for sixteen weeks resulted in about 6% loss of total sugars. About 2.5% of this loss was accounted for by the loss of sucrose. The remainder was due to the loss of fructose, glucose and, to a much lesser extent, of sorbitol. Fructose and glucose levels underwent erratic fluctuations during this study. This is thought to be due to hydrolysis of sucrose and Maillard browning reactions of reducing sugars occurring simultaneously. / Graduation date: 1978

Ultrafiltration of d'Anjou pear juice in the batch mode with a Romicon HFXS MXII pilot-scale ultrafilter produced a "sparkling clear", light-colored permeate which was sterile, essentially free of pectin, and lower in phenolics than the feed juice. Retention characteristics of PM-50, PM-30 and PM-10 hollow fiber membranes were tested at a volume concentration ratio of 1.14. No differences in retention characteristics were found; the membranes were completely permeable to sugars, malic acid and α-amino compounds and semipermeable to pectic substances and phenolics. Filtration temperatures of 15°C, 30°C and 50°C did not affect retention characteristics. The higher temperature did reduce the number of microorganisms in the retentate. Transmembrane pressures, varying from 103 to 153 kPa, also did not affect composition of the permeate. The effects cf filtration time (as volume concentration ratio) were tested with a PM-50 membrane at 50°C with a transmembrane pressure of 153 kPA. Flux declined as the log of volume concentration ratio. With increasing filtration time, retention efficiency for pectic substances and phenolics decreased. The permeates became more golden in color but remained clear. Loss of efficiency was attributed to concentration polorization. Pectic substances were thought to be the major contributor to the formation of the gel layer. / Graduation date: 1982

Graduation date: 1982

Graduation date: 1979

Thesis (D. Sc.)--Cornell University. / "Extracted from the Proceedings of the Philadelphia Academy of Sciences, Sept. 28, 1886. p. 322-341." Also available in digital form on the Internet Archive Web site.

[No abstract available] / Land and Food Systems, Faculty of / Graduate

Thesis (Ph. D.)--Oregon State University, 2008. / Printout. Includes bibliographical references. Also available on the World Wide Web.

Thesis (Ph. D.)--Oregon State University, 2008. / Printout. Includes bibliographical references. Also available on the World Wide Web.

Polyphenol oxidase (PPO) from d'Anjou pears was purified and some molecular properties were studied. The extraction of PPO was accomplished in the presence of the phenolic binder AG 2X-8 and Triton X-100. Chlorophyll pigment was removed by chromatography resulting in a clear, colorless enzyme extract. Three fractions of pear PPO were purified by hydrophobic interaction chromatography on Phenyl Sepharose CL-4B, followed by chromatography on DEAE-cellulose and hydroxylapatite (HA). The best resolution was achieved when the columns were developed at room temperature. Reproducibility of the entire scheme was excellent with chromatography on the hydrophobic resin as a key to the procedure's success. The three fractions of pear PPO were homogeneous when stained for protein with the silver stain after polyacrylamide gel electrophoresis and corresponded to relative mobilities of 0.41 (HA 1), 0.43 (HA 2), and 0.73 (DEAE 3). However, other minor protein bands were noticed on lithium dodecyl sulfate, LDS, electrophoresis. Dimethylsulfoxide, DMSO, was found to significantly increase the PPO activity over the control. An 80% increase in enzyme activity was observed when 5% DMSO was added to the enzyme fraction. Chlorogenic acid reacted with one of the purified fractions (HA 2) at pH 7 to yield 5 additional PPO bands upon electrophoresis. However, no electrophoretic changes were observed with another fraction (DEAE 3) or when 2,3-dihydroxybenzaldehyde was reacted with the two PPO fractions. The molecular weights of the three multiple forms of pear PPO were similar and were 45,300 ± 5% daltons by Sephacryl S-300 gel filtration and 59,600 ± 3% daltons by LDS electrophoresis in 10% and gradient polyacrylamide slab gels. The isoelectric points of the three PPO fractions were: HA 1, pi 4.3 and 4.5; HA 2, pi 4.5 and 4.7; and DEAE 3, pI 6.9. The three fractions differed in amino acid composition with HA 1 having a higher proportion of hydrophobic amino acids and less charged residues than either HA 2 or DEAE 3. All three forms of PPO contained a high proportion of the acidic amino acids and/or their amides, and glycine. / Graduation date: 1983