Pear, Bartlett

During the fall and winter, Matthew MacCartney, the beverage director, mixes Champagne with cubes of Bartlett pear bathed briefly in a pear liqueur. The taste, as simple as something perfectly ripe, is fresher than the sum of its parts. 

Table II. Surface Residues of DDT on Bartlett Pears at Harvest ...

Table IV. Surface Residues of Parathion on Bartlett Pears...

Pears. Triplicate samples of 20 Bartlett pears each were used and a fourth sample was placed in cold storage for subsequent examination, as with the apples. Washing trials were performed in a standard type washer (an Ideal fruit washer with an unheated main tank unit and a water rinse tank unit, Model WKA, manufactured by the Ideal Grader and Nursery Company, Hood River, Ore.). 

Table II. Wash Tests for Removal of DDT Surface Residues from Bartlett Pears...

Riedl, H. and S.A. Hoying. 1980. Impact of fenvalerate and diflubenzuron on target and nontarget arthropod species on Bartlett pears in northern California. Jour. Econ. Entomol. 73 117-122. 

The first example of a cuprate addition to an acceptor-substituted diene was reported by Naf et al. [9], who used lithium di-(Z)-l-heptenylcuprate in a Michael addition to dienoate 1 (Eq. 4.2). The reaction proceeded highly regioselectively, furnishing a 1 1 mixture of the two isomeric 1,6-adducts 2, which were converted into the Bartlett pear constituent ethyl (2 ,6Z)-2,6-dodecadienoate (3) by basic isomerization. 

The flavour of distillates from apple and pear is characterised by typical aroma compounds from these fruits formed by enzymatic degradation of fatty acids to C6-fragments like hexanol, trans-2-hexenol, as well as ethyl esters and acetates of hexanoic acid. In distillates of pears, especially of the variety Bartlett pear, the characteristic pear flavour is mainly dominated by the ethyl and methyl esters of frans-2-czs-4-decadienoic acid and trans-2-trans-A-decadienoic acid [27-29], The biogenesis of these monounsaturated, diunsaturated, and triunsaturated esters may be explained by -oxidation of unsaturated linoleic and linolenic acid in the fruits. The sesquiterpene compound a-farnesene, which is formed during postharvest ripening and storage of Bartlett pears [28], shows that quality and intensity of distilled pear spirits is mainly influenced by the quality and degree of ripeness of the fruits. 

Two catechins, ( + )catechin and ( — )epicatechin, and two leucoanthocyanins were isolated from Bartlett pears by Nortje (165).. Durkee et al. (166) identified arbutin (p-hydroxphenyl-/ -D-glucoside) in mature and immature pears. Several flavanol glycosides such as quercetin 3-glucoside, isorhamnetin-3-glucoside, isorhamnetin-3-rutinoside, isorham-netin-3-galactoside, and quercetin-7-xyloside were identified by Duggan (167). 

Jennings et al (228) fractionated an extract from Bartlett pears into 32 volatile components of which five were found to contribute significantly to the characteristic pear aroma. Later studies indicated that esters of trans-2 cis-4 decadienoic acid and hexyl acetate were significant components of the Bartlett pear aroma (229, 230). More recently, numerous volatiles of Bartlett pears were separated and identified including esters of methyl, ethyl, propyl, butyl, and hexyl alcohols, and Cio to Ci8 fatty acids (231, 232). 

Methanol occurs in some foods. Distilled fruit spirits such as those from the fermentation of Bartlett pears contain some methanol. This has led to European standards for methanol limits in distilled fruit spirits. The levels of methanol can be reduced by appropriate adjustment of fermentation conditions and the distillation processes used.3... 

Glatthar, J., Seen, T., and Pieper, H.J., Investigations on reducing the methanol content in distilled spirits made of bartlett pears, Deutsche Lebensmittel-Rundschau, 97, 209-216, 2001. 

Polyunsaturated aliphatic alkohols, aldehydes, ketones, and esters occur as fragrance components in fats, oils, fruits and plants 158). As an example the synthesis of ethyl (2 ,4Z)-2,4-decadienoate (232, pear ester ), which is responsible for the aroma of bartlett pears 161) is given. 2,4-Diunsaturated ester 232 may be obtained by a number of highly stereoselective syntheses, a lot of them making use of the Wittig reaction. Ohloff and Pawlak condensed 4,5-epoxy-( )-2-pentenal 228 with the ylide generated from 229 (butyllithium/ether) to the alkadiene epoxide 230 which was oxidized with periodic acid to the 2,4-decadienal 231. 231 is subsequently converted with MnOj/NaCN in ethanol to the pear ester 232162) [75 % (Z)-amount of the C-4 double bond] (Scheme 44). 

Figure II. Rates of formation of individual volatiles from ripening Bartlett pear.

Unsaturated esters may also be derived from the products of B-oxidation of unsaturated fatty acids. Methyl-and ethyl decadienoates are known as character impact compounds of Bartlett pears and all presumptive intermediates of the pathway were identified by Jennings et al. (JLZ UL) binoleyl-CoA is transformed into (E,Z)-2,4-decadienoyl-CoA by B-oxidation. The further degradation... 

Oxygen-dependent core breakdown in Bartlette pears 186... 

Figure 10. Browning (A42Q ) of Bartlett pear juice concentrates during...

In the presence of sodium cthoxide, these dienoic acids can be isomerized in high yield to conjugated 2,4-dienoic acids. Surprisingly 6 is isomerized to a mixture of the (2E, 4Z)- and the (2E, 4E)-isomers in a 2 1 ratio. This mixture can be equilibrated mainly to the more stable (2E, 4E)-isomer (867o) by treatment with Ihiophenol in the presence of AIBN (6, 585-586). The ethyl (2E, 4Z)-decadienoate obtained by rearrangement of 6 is a component of the odoriferous principle of Bartlett pears. 

Chang, Y. H., "Chemical Analysis of Acid Precipitated Colloid of Ripe Bartlett Pear Juice". M.S. Thesis. Oregon State University, Corvallis, OR 1979, p. 37-1 6. KLiewer, W. M., Am. J. Enol. Vitlcul. I968, 19, 166. 

Et ester [3025-30-7]. Pear ester. Constit. of odoriferous principle of Bartlett pears. Bpo.05 84-86 . 4-Bromophenacyl ester Mp 72 . 

The o-quinones formed from phenolics further enhance the intensity of browning by oxidation of other substrates, complexing with amino acids and protein, and polymerization. Non-enzymatic discoloration is believed to involve metal-polyphenol complexing as reported in the processed potato (Bate-Smith et al., 1958), cauliflower (Donath, 1962), and asparagus (DeEds and Couch, 1948), conversion of leucoanthocyanidins to pink anthocyanidins in the processed broad bean (Dikinson et al., 1957), green bean puree (Roseman et al., 1957), and canned Bartlett pear (Luh et al., 1960), and protein-polyphenol complexing in chilled or stored beer (Schuster and Raab, 1961). 

---