6- pentyl-a-pyrone

Fig. 23.4 Organophilic pervaporation (PV) for in situ recovery of volatile flavour compounds from bioreactors. The principle of PV can be viewed as a vacuum distillation across a polymeric barrier (membrane) dividing the liquid feed phase from the gaseous permeate phase. A highly aroma enriched permeate is recovered by freezing the target compounds out of the gas stream. As a typical silicone membrane, an asymmetric poly(octylsiloxane) (POMS) membrane is exemplarily depicted. Here, the selective barrier is a thin POMS layer on a polypropylene (PP)/poly(ether imide) (PEI) support material. Several investigations of PV for the recovery of different microbially produced flavours, e.g. 2-phenylethanol [119], benzaldehyde [264], 6-pentyl-a-pyrone [239], acetone/buta-nol/ethanol [265] and citronellol/geraniol/short-chain esters [266], have been published...

Scheme 23.18 a De novo biosynthesis of coconut-like 6-pentyl-a-pyrone by Trichoderma sp. b Production of macrocyclic musk-like lactones by a combination of microbial co-hydroxylations and co-l-hydroxylations and subsequent chemical conversion steps, c Production of macrocyclic musk fragrances initiated by terminal oxidation of hydrocarbons with Candida tropicalis... 

Trichoderina sp. Coconut, anise, cinnamon 6-pentyl-a-pyrone Sesquiterpenes, cinnamate derivatives... 

Figure 7. Effects of 6-pentyl-a-pyrone on Botrytis rot, 1993 trial, part 1.

The compound 6-pentyl-a-pyrone was extracted from Trichoderma harzianum and analyzed on a Cjg column (A = 300nm). It was separated from other extracted compounds using a 100/0-> 80/20 (at 20 min hold 10 min) water (2.5% acetic acid)/acetonitrile gradient. The pyrone had a retention time of 21 min [1350]. 

Occurrence of 6-Pentyl-a-pyrone in Peach Essence. J. Food Sci. 36, 536 (1971). 

The aroma of peaches is characterized by y-lactones (C6-C12) and 5-lactones (Cio and Cl2). The main compound in the lactone fraction is (R)-l,4-decanolide, which has a creamy, fruity, peach-like odor. Other important compounds should be benzaldehyde, benzyl alcohol, ethyl cinnamate, isopentyl acetate, linalool, a-terpineol, a- and 3-ionone, 6-pentyl-a-pyrone (Formula 18.39, VIII), hexanal, (Z)-3-hexenal, and (E)-2-hexenal. Aroma differences in different varieties of peaches are correlated with the different proportions of the esters and monoterpenes. In the case of nectarines (Prunus persica L., Batsch var. nucipersica Schneid), the lactones y-C8-Ci2 and 5-Cio belong to the compounds with the highest aroma values. 

A fungus widely distributed in the soil, Trichoderma viride, produces an interesting compound with a coconut, peachy aroma in a non-agitated liquid medium containing potato extract and salts(52). After three to four days cultivation, the culture sporulates releasing the metabolite 6-pentyl-alpha-pyrone. The maximum level reported, however, is 0.17 gram/L. 

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