Fruit Flavors - American Chemical Society

Chapter 24

2,5-Dimethyl-4-hydroxy-3(2H)-furanone and Derivatives in Strawberries During Ripening

Downloaded by UNIV LAVAL on July 12, 2016 | http://pubs.acs.org Publication Date: May 5, 1995 | doi: 10.1021/bk-1995-0596.ch024

Carlos Sanz, Daryl G. Richardson, and Ana G. Pérez Department of Horticulture, Oregon State University, Agriculture and Life Science 4017, Corvallis, OR 97331

Content of Furaneol and derivatives in seven strawberry varieties were assessed during ripening. In most cases content of these compounds sharply increased along fruit ripening with maximum values at the overripe stage. The largest amount of Furaneol, mesifurane and Furaneol glucoside were found in overripe strawberries of cultivars Douglas (22.89 μg/g F W ) , Pajaro (39.13 µg/g F W ) , and Totem (16.51 μg/g FW), respectively. Results obtained showed quantitative differences among varieties that could be related to their organoleptic properties. The best correlation values were found between Furaneol content and strawberry aroma for Parker (r=0.741) and Benton (r=0.733) strawberries.

It seems to be a general phenomenon that increase in berry size, obtained by breeding, inevitably leads to deterioration of the aroma of berries. Thus, the pleasant and herbaceous aroma of wild strawberries is not found in most cultivated varieties. Strawberry aroma is mainly determined by a complex mixture of esters, aldehydes, alcohols and sulfur compounds which have been extensively studied (1-5). Two compounds, 2,5-dimethyl-4-hydroxy-3(2H)-furanone (Furaneol, I) (6-7) and 2,5-dimethyl-4-methoxy-3(2H)-furanone (mesifurane, II) (8) are considered to be among the most important volatiles reported in wild strawberries. These two compounds have not been found in all cultivated varieties (9), although factors such as Furaneol water-soluble nature (8-10) and thermal unstability (11-12) could well account for the failure of some authors to detect Furaneol. Both, Furaneol and mesifurane, have strong, sweet and pleasant odours. Furaneol imparts caramel burnt sugar notes at high concentrations and becomes fruity, strawberry-like at lower concentrations (13), and mesifurane is described as having a more sherry-like aroma (14). Kallio et al. (15) found in artic

0097-6156/95/0596-0268$12.00/0 © 1995 American Chemical Society Rouseff and Leahy; Fruit Flavors ACS Symposium Series; American Chemical Society: Washington, DC, 1995.

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2,5-Dimethyl'4-hydroxy-3(2H)-fiiratwne in Strawberries 269


bramble good correlation between Furaneol content and the aroma evaluations, and a certain influence of the content of mesifurane on the overall impression of taste. There are several studies identifying the presence of Furaneol, mesifurane (16-17) and Furaneol glucoside (III) (18) in strawberries. However, no study has focused on the production of these three compounds during fruit ripening, and due to the lack of a reliable quantitative method of analysis their actual contribution to strawbeny aroma is still not well known. In this work a new analysis procedure, involving H P L C separation and quantitation of Furaneol, Furaneol glucoside and mesifurane, is used to determine the amount of these three compounds in seven strawberry cultivars during ripening. The relation of Furaneol and mesifurane contents to aroma evaluations is also assessed. Experimental Fruits. Fruits from seven strawberry (Fragaria ananassa Duch.) cultivars, Chandler, Parker, Douglas, Pajaro, Benton, Redcrest and Totem, grown at the O.S.U. horticultural research fields in Corvallis (OR, U S A ) , were used in this study. Strawberries were harvested at four ripening stages: white (I), pinky (II), bright-red (III, ripe) and dark-red fruits (IV, overripe), and immediately frozen, and kept at -25°C. Preparation of samples for H P L C . Strawberries were cut symmetrically in four pieces. Four pieces from four different fruits, approximately 15 g, were thawed and ground in a Sorvall Omni-mixer with 15 m L of distilled water. Celite (1.5 g) was added and mixed with the homogenate, and allowed it to stand for 5 min. This mixture was vacuum filtered through a Whatman No 1 filter paper (Whatman Int. Ltd., Maidstone, U K ) , and the solid phase washed three times with 5 m L distilled water. Five m L of this filtered extract was clarified, removing pulp, fat, protein, and carotenoids, by first adding 0.25 m L of Carrez I solution, and then 0.25 m L of Carrez II solution added slowly with gentle mixing, according to Wallrauch (79). After standing for 5 min, the mixture was centrifuged at 2500 χ g for 5 min. The supernatant was filtered through a 0.2 μπι nylon membrane (Alltech Associates, Inc., Deerfield, II) before H P L C analysis. H P L C analysis. Quantitative H P L C analysis of strawberry extracts was accomplished with a Beckman 334 liquid chromatograph (Beckman Instruments Inc., Berkeley, C A ) , Hitachi 100-10 detector (Hitachi Ltd., Tokyo, Japan), and Shimadzu C - R 3 A integrator (Shimadzu Co., Kyoto, Japan). Analysis was carried out using a reverse phase Econosil C18 column (25 cm χ 4.6 mm, 10 μπι, Alltech) coupled to a ODS-5S guard column (3.0 cm χ 4.6 mm, Bio-Rad, Richmond, C A ) . The mobile phase consisted of: A ) 0.2M sodium acetate/acetic acid (pH 4) buffer (acetate buffer) and B) methanol, with the following chromatographic conditions: 0-2 min, isocratic 10% methanol; 2-18 min, gradient 10-12% methanol; 18-36 min, isocratic 12% methanol; flow rate, starting 1.5 mL/min and increased to 2.0 mL/min in 0.5 min at 18 min; detector, U V 280 nm; and injection volume, 20 μL·

Rouseff and Leahy; Fruit Flavors ACS Symposium Series; American Chemical Society: Washington, DC, 1995.


270 FRUIT FLAVORS


24.

SANZ ET AL.

2,5-DimethyU4-hydwxy'3(21I)-furanone in Strawberries 271

Sensory evaluation. Extracts from each strawberry variety at different maturity stages were evaluated by means of a 16-point scale for strawbeny aroma and overall aroma intensity. Samples were assessed by 18 judges at room temperature. A random three-digit code was given to each sample, and they were served in a random presentation, either three or four samples at a time. Each sample, 25 m L of strawberry extract, was presented in a 75 m L odorless glass jar covered with black opaque paper. Linear regression coefficients for furaneol and mesifurane contents against strawberry aroma and overall aroma intensity were calculated.


Results and discussion. H P L C analysis. Gas liquid chromatography is the most frecuently used method for the separation of aroma compounds of strawberry. However, this technique has been proved to be inadequate for the determination of compounds such as Furaneol due to the thermal unstability of this compound under normal G C conditions (12, 20). This can explain the low reproducibility of the results found in early reports on Furaneol content in fruits (7-8, 21). H P L C analysis seems to be a more suitable technique to determine the actual content of Furaneol, mesifurane and Furaneol glucoside in fruits, as it has been shown in recent studies of Furaneol content on grapefruit and pineapple (22-23). Nevertheless no method for the simultaneous determination of the three compounds in strawberry has been reported. Figure 1 shows a typical H P L C chromatogram from a strawberry extract, where Furaneol glucoside, Furaneol and mesifurane were resolved into unique peaks at retention times of 10.0, 12.2 and 30.3 min, respectively. The analytical method used is faster than traditional methods involving liquid-liquid extraction (7-8, 21), and avoids any kind of concentration procedure which could cause alterations in the aroma composition. Furaneol and Derivatives Content during Ripening. In order to understand the aroma of a fruit is necessary to know not only the nature of constituents, but how the significant components change in kind and quantity during the development of the fruit. Using the analitical procedure described above, Furaneol and derivatives content were determined in seven strawberry varieties during ripening (Figures 2 and 3). In all studied varieties only when fruits reached a certain degree of ripeness, the biosynthesis of the three compounds was enhanced. Furaneol, Furaneol glucoside and mesifurane content sharply increased at the last ripening stage. These results seem to agree with those reported on the formation of methyl and ethyl esters during strawberry ripening (5). However there are other groups of compounds such as amyl, isoamyl and hexyl esters whose contents remain constant or decrease at the last maturity stages, as reported in Chandler strawberries (5). Although the biogenetic pathway of Furaneol is still unknown, the reason for the presence of this compound and derivatives only at the last ripening stages could be the lack of the forming enzyme activity in unripen fruits, as proposed Yamashita et al. (24) for volatile esters.



272

FRUIT FLAVORS

MATURITY STAGE

FURANEOL

|

MATURITY STAGE

|

MESIFURANE

FURANEOL

GLUCOSIDE

Figure 2.-Content in Furaneol, mesifurane and Furaneol glucoside in Californian varieties during ripening. Each bar represents the mean of six analyses. Means for the same compound with the same letter are not statistically different at significance level ρ=0.05.



24. SANZ ET AL.

l^DimethyU^hydroxy^il^furanone in Strawberries 273

MATURITY STAGE

MATURITY STAGE

TOTEM

330

j^j

FURANEOL

f~]

MESIFURANE

I

II

III

I

FURANEOL

GLUCOSIDE

IV

MATURITY STAGE

Figure 3.-Content in Furaneol, mesifurane and Furaneol glucoside in strawberry varieties from Oregon (Benton, Redcrest) and British Columbia (Totem) during ripening. Each bar represents the mean of six analyses. Means for the same compound with the same letter are not statistically different at significance level p=0.05.



274

FRUIT FLAVORS

Among the seven strawberry cultivars studied, four were Californian varieties, Chandler, Parker, Douglas and Pajaro, two were from Oregon, Redcrest and Benton, and Totem was from British Columbia. Most studies, dealing with the quantitative comparison of volatiles, have found great differences among cultivars (4, 9, 17, 25). In this work, a quite similar pattern on the formation of the three compounds under investigation was found for all the Californian varieties (Figure 2). In these four strawberry cultivars, low amounts of Furaneol, Furaneol glucoside and mesifurane were found to be present in the fruits in early ripening stages (I and II), while almost total absence of these three compounds was determined for Redcrest, Benton and Totem at the same stages (Figure 3). A t the commercial maturity stage (stage III) Parker showed the highest content in the three compounds, and at the overripe stage (IV) the largest amount in Furaneol and mesifurane were determined in Douglas and Pajaro, respectively. In these varieties, the amounts of Furaneol (22.89/xg/g FW) and mesifurane (39.13 /xg/g F W ) are the greatest values so far reported in strawberries, only comparable to values described for cultivar Confitura by Douillard and Guichard (9). These results were expected, since this is the first non-gas chromatographic analysis of these compounds in strawberries. Similar differences are found when H P L C quantitation data of Furaneol in pineapple (7, 23) are compared to those obtained by G C analysis (26). Strawberry varieties from Oregon (Redcrest and Benton) and British Columbia (Totem) are mainly used for the processing industry. Redcrest, a strawberry with very poor organoleptic properties, had the lowest levels in Furaneol and derivatives of the seven studied cultivars. Benton is considered to be a high flavor variety, suitable to be used for jam production specially because its high content in organic acids (27). Furaneol and mesifurane content in Benton strawberries stage III were among the highest determined, but only a slight increase was observed in the production of these products at stage IV. Low levels of Furaneol glucoside were determined in this cultivar. Strawberries from cultivar Totem were characterized by having excellent organoleptic characteristics at the last ripening stage (IV). Maximum values of Furaneol glucoside were found in this cultivar (16.5 μg/g FW), which also showed large amounts of Furaneol (21.61 ttg/g F W ) and mesifurane (18.51 /ig/g FW). Given these high contents and that Furaneol has a considerably low threshold concentration (0.03 ppb), while mesifurane has a threshold of 0.01 ppm (28), the excellent aromatic quality of this strawberry cultivar reported in a previous study (29), would be confirmed. Sensory evaluation. Sensory evaluation data from the four maturity stages for each strawberry variety were pooled in order to carry out regression analysis of Furaneol and mesifurane contents against values for strawberry aroma and overall aroma intensity. In general terms, the content of Furaneol and mesifurane describes better the strawberry aroma than the overall aroma intensity. On the other hand, there are better correlations for Furaneol content and both attributes than for mesifurane, with the exception of Parker (strawberry aroma and overall intensity) and Benton (strawberry aroma). Kallio et al. (75) also found better correlations for Furaneol content than for mesifurane against character of odor in the sensory analysis of different varieties of arctic bramble. The best correlation values between Furaneol content and strawberry aroma were found for Parker (r=0.741) and Benton (r=0.733) strawberries. Rouseff and Leahy; Fruit Flavors ACS Symposium Series; American Chemical Society: Washington, DC, 1995.

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2,5-Dimethyl-4-hydroxy-3(2R)-furanone

in Strawberries 275


Literature cited. 1. Mc Fadden, W.H., Teranishi, R., Corse, J., Black, D.R.; Mon, T.R. J.Chromatog. 1965, 18, 10-19. 2 Drawert, F.; Tressl, R.; Staudt, G.; Köppler, H. Z. Naturforsch. 1973, 282, 488491. 3. Dirinck, P.; Schreyen, L.; Schamp, N.M. J. Agric. Food Chem. 1977, 25, 759763. 4. Dirinck, P.; De Pooter, H.L.; Willaert, G.A.; Schamp, N.M. J. Agric. Food Chem., 1981, 29, 316-321. 5. Pérez, A.G.; Rios, J.J.; Sanz, C.; Olías, J.M. J. Agric. Food Chem. 1992, 40, 2232-2235. 6. Sundt, E. Proc. Scand. Symp. Aroma Research, Naeringsmiddelindustrien. 1970, 23, 5-13. 7. Pickenhagen, W.; Velluz, Α.; Passerai, J.P.; Ohloff, G. J. Sci. Food Agric. 1981, 32, 1132-1134. 8. Pyysalo, T.; Honkanen, E.; Hirvi, T. J. Agric. Food Chem. 1979, 27, 19-22. 9. Douillard, C.; Guichard, E. Sciences des Aliments. 1989, 9, 53-76. 10. Hirvi, T.; Honkanen, E.; Pyysalo, T. Lebensm. Wiss. Technol. 1980, 13, 324325. 11. Flath, R.A.; Forry, R.R. J. Agric. Food Chem. 1970, 18, 306-309. 12. Shu, C.K.; Mookherjee, B.D.; Ho, C.-T. J. Agric. Food Chem. 1985, 33, 446448. 13. Re, L.; Maurer, B.; Ohloff, G. Helv. Chim. Acta. 1973, 56, 1882-1894. 14. Hunter, G.L.K.; Bucek, W.A.; Radford, T. J. Food. Sci. 1974, 39, 900-903. 15. Kallio, H.; Lapveteläinen, Α.; Hirvi, T.; Honkanen, E. In Analisis of Volatiles; Schreier, P., Ed.; W. de Gruyter, Berlin, 1984, pp 433-446. 16. Hirvi, T.; Honkanen, Ε. Z. Lebensm. Unters Forsch. 1982, 175, 113-116. 17. Douillard, C.; Guichard, E. J. Sci. Food Agric. 1990, 50, 517-531. 18. Mayerl, F.; Näf, R.; Thomas, A.F. Phytochemistry. 1989, 28, 631-633. 19. Wallrauch, S. Flusiges Obst. 1984, 51, 64-65. 20. Williams, A.A.; Mottram, D.S. J. High Res. Chromatog. 1981, 4, 421-422. 21. Schreier, P. J. Sci. Food Agric. 1980, 31, 487-494. 22. Lee, H.S.; Nagy, S. J. Food Sci. 1987, 52, 163-165. 23. Wu, P; Kuo, M.C.; Zhang, K.Q.; Hartman, T.G.; Rosen, R.T.; Ho, C.-T. Perfum. Flavor. 1990, 15, 51-53. 24. Yamashita, Y.; lino, K.; Yoshikawa, S. Nippon Shokuhin Kogyo Gakkaishi 1979, 26, 256-259. 25. Hirvi, T. Lebensm. Wiss. Technol. 1983, 16, 157-161. 26. Wu, P.; Kuo, M.C.; Hartman, T.G.; Rosen, R.T.; Ho, C.-T. J. Agric. Food Chem 1991, 39, 170-172. 27. Reyes, F.G.; Wrolstad, R.E.; Cornwell, C.J.J.Assoc. Off. Anal. Chem. 1982, 65, 126-131. 28. Honkanen, E.; Hirvi, T. In Food Flavors. The Flavor of Fruits; Morton, I.D.; MacLeod, A.J., Eds.; Elsevier, Amsterdam, 1990, pp 125-193. 29. Skrede, G. J. Sci. Food Agric. 1980, 31, 670-676. RECEIVED March 30, 1995


Fruit Flavors - American Chemical Society

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