2- Methylisoborneol

The characteristic earthy and harsh flavor and aroma of roasted Ro-busta coffees is largely attributed to 2-methylisoborneol. Amounts found in green Robusta coffee beans were 0.03 to 0.3 ppb, and this could be completely removed by steam heating or roasting.26 There is approximately ten times as much 2-methylisoborneol in roasted Robusta coffee beans than in similarly treated Arabica coffee.27... 

Rouge, F., Gretsch, C., Christensen, K., Liardon, R., Thermal stability of 2-methylisoborneol in Robusta coffee. Colloq. Sci. Int. Cafe, 15th(Vol.2), 866, 1993. (CA121 33729q)... 

Fig. 1. Structures of geosmin and 2-methylisoborneol, the two most common causes of off-flavor in farm-raised channel catfish.

For example, in channel catfish Ictalurus punctatus) aquaculture ponds in the southeastern USA, some species of cyanobacteria produce earthy and musty metabolites such as geosmin and 2-methylisoborneol (MIB) (Fig. 1). These compounds are rapidly absorbed across the gills of the catfish and accumulate in the flesh of the catfish, thereby rendering them unpalatable and unmarketable. 

Many papers from the patent literature on pyrethroids and juvenile hormones cannot be included in this Report. Papers have reported the synthesis and activity of monoterpenoid juvenoids, including geranyl pyridyl ethers " and geranyl alkyl ethers and amines and their epoxides. Further papers in this section include a report of the potent lung toxicity of perillaketone, the observation that the malodorous water contaminant 2-methylisoborneol has the l-R-exo configuration, and that fenchyl methyl L-aspartylaminomalonate is 2 x 10" times sweeter than sucrose. ... 

Jelen, H.H., Majcher, M., Zawirska-Wojtasiak, R., Wiewiorowska,M., Wasowicz, E. (2003) Determination of geosmin, 2-methylisoborneol, and a musty-earthy odor in wheat grain by SPME-GC-MS, profiling volatiles, and sensory analysis. J. Agric. Food Chem. 51 7079-7085. 

SBSE was recently applied [152] to the analysis of off-flavor compounds, including 2-methylisoborneol (2-MIB) and geosmin, in drinking water. These organic compounds cause taste and odor problems at very low concentrations and are notoriously difficult to extract. Detection limits by SBSE ranged from 0.022 to 0.16 ng/L. The recoveries ranged from 89 to 109% with relative standard deviations of 0.80 to 3.7%. 

Dichloroanisole 2.3.6- Trichloroanisole 2.4.6- Trichloroanisole 2.3.4.6- Tetrachloroanisole Pentachloroanisole 2.4.6- Tribromoanisole Geosmin 2-Methylisoborneol l-Octene-3-ol Octa-1,3-diene a-Terpineol 4.4.6- Tri methyl-1,3-dioxane... 

Mycotoxins may include butanol, estrogenic compounds (e.g., zearalenone), heptanone, lactones, lactams (patulin), stachybotrylactones, stachybotry-lactams, 2-pentylfuran, 2-hexanone, 2-methyl-1-propanol, 3-methylfuran, 2-methylisoborneol, 3-methyl-2-butanol, and macrocyclic trichothecenes (Satratoxins F, G. and H, Roridine, Verrucarinj, and Trichoverrols). 

Pendleton, P., Wong, S., Schumann, R., et al. (1997). Properties of activated carbon controlling 2-methylisoborneol adsorption. Carbon, 35, 1141—9. 

Conte, E. D., Shen, C. Y., Perschbacher, P. W., and Miller, D. W. 1996. Determination of geosmin and methylisoborneol in catfish tissue (Ictalurus punctatus) by microwave-assisted distillation—solid phase adsorbent trapping, J. Agricul. Food Chem., 44 829-835. 

Volatile fungal metabolites contribute to the organoleptic properties of several other foodstuffs. Surface mould ripened cheeses such as Brie and Camembert are produced using Penicillium camembertii and, more commonly, P. caseicolum. Oct-l-en-3-ol accompanied by smaller amounts of octa-l,5-dien-3-ol and 3-one are major contributors to the aroma. These organisms also have the ability to produce 2-alkanones from fatty acids and these contribute to the odour of the cheese. 2-Methylisoborneol (7.70) and 2-methoxy-3-isopropylpyrazine (7.71) have been detected in mature cultures. An unpleasant earthy flavour encountered in some aged cultures has been attributed to the excessive produetion of 7.71. 

Methylisoborneol (MIB, Section 5,B.44), which could be responsible for the earthy, musty smell of roasted robustas (Vitzthum et al., 1990) has been found by Grosch et al. (1993) and Rouge et al. (1993) in... 

Very recently, Cantergiani et al. (2001) (Figure 2,11) investigated the composition of the volatile fraction of a Mexican green coffee with a pronounced earthy/mouldy off-flavor. The three components responsible were determined by GC-olfactometry, isolated, concentrated and finally characterized by GC/MS as geosmin (Section 5,B.46), 2-methylisoborneol (Section 5,B.44) and 2,4,6-trichloroanisole (Section 5,H.82), The concentrations were lower in the reference than in the defective samples. The... 

The pure substance has a camphor-like odor, which becomes musty, earthy, tarry and mouldy on dilution. The flavor is woody, camphoraceous, earthy, mouldy, borneol-like for the (1/ )- isomer and more fenchol-like for the (lS -isomer (Chemisis, 1994). For Vitzthum et al. (1990), it is responsible for the earthy, musty smell of robusta coffee, with an odor threshold of 0.005 ppb in coffee beverages and 0.0025 ppb in water. Other thresholds in water quoted by these authors vary from 0.0014-0.1 ppb. For Rouge et al. (1993, see above) 2-methylisoborneol is not responsible for the robusta flavor character in a brew. 

Bade-Wegner H., Holscher W. and Vitzthum O.G. (1993) Quantification of 2-methylisoborneol in roasted coffee by GC-MS. 15th Int. Colloq. Chem. Coffee (Montpellier, 6-11.6.1993) (ASIC, 1993), 5.37-44. 

This particular type of Wagner-Meerwein shift has special recognition due to its importance in the field of terpene chemistry. For example, the conversion of a-methylcamphene into 4-methylisoborneol involves both a Nametkin and a Wagner-Meerwein rearrangement. In the Meinwald rearrangement both 1,2- and 1,3-shifts occur to give different products (Scheme 2.24). 

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