The Effect of Processing on the Chiral Aroma Compounds in Cherries (Prunus avium L.)

Abstract

Flavor extracts of four different varieties of fresh cherry fruit were obtained using a static vacuum extraction apparatus. The extracts were analysed using GC-MS and three chiral compounds were found in all the cherry varieties: limonene, linalool, and α-terpineol. Multidimensional GC (MDGC), incorporating a cyclodextrin based stationary phase, was used to separate the enantiomers of these chiral compounds. Enantiomeric excesses of (R)-(+)-limonene, (R)-(-)-linalool and (R)-(+)-α-terpineol were found. Each variety of cherry was canned and heat processed in a retort. The canned cherries were then extracted and analysed under similar conditions to the fresh samples. The canned cherries contained the same chiral compounds as found in the fresh. However, the concentration of the chiral compounds changed slightly on processing. Limonene showed a decrease in total concentration whereas α-terpineol increased. Moreover, analysis by MDGC showed a marked decrease in the enantiomeric excess of (R)-(+)-limonene, and small decreases for (R)-(-)-linalool and (R)-(+)-α-terpineol. Chiral compounds are frequently found among the flavor volatiles of fruits and, like many naturally occurring chiral compounds, one enantiomer usually exists with a greater preponderance when compared with its antipode. Chiral odor compounds may show qualitative and quantitative differences in their odor properties (7). For example, (/£)-(+)-limonene has an orange-like aroma while («S)-(-)-limonene is turpentine-like; (£)-(+)-carvone is characteristic of caraway while its enantiomer has a spearmint odor (2). However, other chiral compounds, such as y and 6-lactones, show very little enantioselectivity of odor perception (7). The occurrence of chiral flavor compounds in enantiomeric excess provides the analyst with a means of authenticating natural flavorings, essential oils, and other plant extracts. The advent of cyclodextrin-based gas chromatography'stationary phases has resulted in considerable activity in the analysis of chiral compounds in flavor extracts of fruits, spices and other plants (3-7).

Detection of adulteration in freshly squeezed orange juice by electronic nose and infrared spectroscopy

“…Because of the ultrafiltration and evaporation during the concentration process, the predominant volatile flavour is almost entirely stripped from fresh juice (Johnson & Vora 1983). However, the relative content of α-terpineol and carvone was higher in concentrated juices, which was related to the oxygenolysis of d-limonene during the processing (Pierce et al 1996). Citral, decanal, ethyl butanoate, and ethyl 3-hydroxyhexanoate were considered as important contributors to the citrus aroma, as well as a slight decrease in concentrated juices was similar to the results in the literature (Bai et al 2010).…”

Varietal differences in terpene composition of blackcurrant (Ribes nigrum L) berries by solid phase microextraction/gas chromatography

“…The application of stereospecific analysis of chiral compounds to fruit flavour has been previously reported12, 13 and the analysis of chiral terpenes has proven to be especially useful for assessing quality of fruit aroma 14. However, there have not been any studies on the enantiomeric composition of chiral compounds in the blackcurrant berry.…”

Distribution of enantiomers of volatile organic compounds in selected fruit distillates

“…17 These compounds are commonly formed by anabolic processes and linked to sugar molecules as nonvolatile glycosides in fruits. 20 The found enantiomeric ratio of linalool seems to be almost nonspecific in the studied samples, except for pear brandy, where the dominance of the (R)-enantiomer was observed. Nearly racemic distribution was the most common result observed for the studied terpene compounds, such as linalool, limonene, α-terpineol, and nerolidol.…”

“…In this case, racemization could naturally occur during a fermentation step 19 or a racemic mixture could be already present in raw fruit, e.g., linalool stereoisomers in apricots and plums. 20 The found enantiomeric ratio of linalool seems to be almost nonspecific in the studied samples, except for pear brandy, where the dominance of the (R)-enantiomer was observed. On the contrary, in the case of linalool oxides, the nonracemic mixture was found in all studied distillates.…”