composition of a commercial 'pear essence' derived from fermentation of 'Bartlett' pears, The

Journal of Essential Oil Research: JEOR, May/Jun 2003 by Tucker, Arthur O, Maciarello, Michael J, Rose, Jeanne

Abstract

A commercial `pear essence' derived from fermentation of 'Bartlett' pears was examined by GC/MS. The major components were ethyl (E,Z)-2,4-decadienoate (31.8%), ethyl (E)-2-decenoate (20.5%) and methyl (E,Z)-2,4-- decadienoate (10.3%).

Key Word Index

Pear essence, ethyl (E,Z)-2,4-decadienoate, ethyl (E)-2-decenoate, methyl (E,Z)-2,4-decadienoate

Introduction

The 'Bartlett' pear, also known as `Williams Christbirne' or `Bon Chretien Williams,' or `Beurre William,' originated in about 1770 in England (1,2). Today, it constitutes about 75% of the pears grown in North America (3). The principal volatiles of ripe 'Bartlett' pears include methyl and ethyl esters and C,-C, alcohols (4-17). No reports are known on pear essence' derived from fermentation.

Experimental

Plant material: About 88,000 kg of `Bartlett' pears were fermented for 14 days and distilled in copper stills to yield 60-65% alcohol. This was adjusted with water (which had been purified by reverse osmosis) to 40% alcohol, chilled to O'C, and then settled for several h. At this point, ca. 89 ml of pear essence' floated to the top and was removed, leaving behind the `pear eau de vie' (Lance Winters, private communication).

GC/MS: Mass spectra were recorded ath a 59 70 HewlettPackard Mass Selective detector coupled to a HP 5890 GC using an HP 50 in x 0.2 mm fused silica column coated with 0.33 (mu)m FFAP (crosslinked). The GC was operated under the following conditions: injector temp.: 250 deg C; oven temp. programmed: 60 deg C held for 1 min to 115 deg C at 2.5 deg C/min, then to 210 deg C at 1.0 deg C/min and held for 30 min; injection size: 1(mu)L (~50% solution in spectroscopy grade n-pentane) split 1:10. The MSD El was operated under the following conditions: electron impact source 70 eV, 250 deg C. Identifications were made by retention indices and library searches of our volatile oil library supplemented with those of NBS, NIST and Wiley.

Results and Discussion

The major components in this commercial `pear essence' derived from fermentation of `Bartlett' pears were ethyl (E,Z)2,4-decadienoate (31.8%), ethyl (E)-2-decenoate (20.5%) and methyl (E,Z)-2,4-decadienoate (10.3%) (Table I). These esters are characteristic of `Bartlett' pear aroma (4-17). Whereas decanoic and dodecanoic acid have not been reported in the volatiles of European pears, they are known from apples (14). Ethyl palmitate has not been reported from apples or European pears (4-17) or pear brandy (18-20), but is known from cider (21) and headspace of Asian pears (22). Ethyl myristate is also known from headspace of Asian pears (22). However, the following compounds have not been previously been reported from European pears or pear brandy: methyl undecanoate, methyl 1-undecenoate, 2-methyl acetophenone, ethyl myristate, ethyl palmitate, methyl 9-octadecenoate, ethyl linoleate, and ethyl linolenate.

Acknowledgments

Analytical research was supported by the state of Delaware and the Cooperative State Research, Education, and Extension Service (#801-15-01C).

References

1. H. Kessler, Bimensorten der Schweiz. Buchverlag Verbandsdruckerei, Bern (1948).

2. J. Seitzer, Farbtabein der Birnensorten. Verlag Eugen Ulmer, Stuttgart (1957).

3. D. C. Elving, A. Dale, K. H. Fisher, N. Miles and G. Tehrani, Fruit cultivars. Ministry Agr. Food Ontario Publ. 430 (n.d.).

4. W. G. Jennings and M. R. Sevenants, Volatile esters of Bartlett pear. III. J. Food Sci., 29, 158-163 (1964).

5. W. G. Jennings, R. K. Creveling, and D. E. Heinz, Volatile esters of Bartlett pear. IV. Esters of trans:2-cis:4-decadienoic acid. J. Food Sci., 29, 730-734 (1964).

6. D. E. Heinz and W. G. Jennings, Volatile components of Bartlett pear. V. J. Food Sci., 31, 69-80 (1966).

7. R. K. Creveling and W. G. Jennings, Volatile components of Bartlett pear. Higher boiling esters. J. Agr. Food Chem., 18, 19-24 (1970).

8. W. G. Jennings and R. Tressl, Production of volatile compounds in the ripening Bartlett pear. Chem., Mikrobiol., Technol. Lebensm., 3, 52-55 (1974).

9. N. Ghena, M.-E., Ceausescu, and N. Braniste, Determinarea substantelor aromatice la sou#il de par Williams. Lucrari Stiintifice. Ser. B. Hort. Bucuresti, Inst. Agron. "N. Balcescu," 20-21, 119-122 (1977-78).

10. L. F. Russell, H. A. Quamme, and J. I. Gray, Qualitative aspects of pear flavor. J. Food Sci., 46, 1152-1158 (1981).

11. R. Romani, J. Labavitch, T. Yamashita, B. Hess, and H. Rae, Preharvest AVG treatment of 'Bartlett' pear fruits: Effects on ripening, color change, and volatiles. J. Amer. Soc. Hort. Sci., 108, 1046-1049 (1983).

12. H. A. Quamme, Decadienoate ester concentrations in pear cultivars and

seedlings with Bartlett-like aroma. HortScience, 19, 822-824 (1984). 13. H. Shiota, Changes in the volatile composition of La France pear during maturation. J. Sci. Food Agric., 52, 421-429 (1990).

14. N. M. M. Paillard, The flavour of apples, pears and quinces. In: Food flavours. Part C. The flavours of fruits. Edits., I. D. Morton and A. J. Macleod, p. 1-41, Elsevier Sci. Publ. BV, Amsterdam (1990).