Methional potato aroma

Raw potato possesses little aroma. Approximately 50 compounds have been reported to contribute to raw potato aroma. Raw potatoes have a high content of LOX, which catalyses the oxidation of unsaturated fatty acids into volatile degradation products (Scheme 7.2) [187]. These reactions occur as the cells are disrupted, e.g. during peeling or cutting. Freshly cut, raw potatoes contain ( ,Z)-2,4-decadienal, ( ,Z)-2,6-nonadienal, ( )-2-octenal and hexanal, which are all products of LOX-initiated reactions of unsaturated fatty acids [188,189]. It is reported that two compounds represent typical potato aroma in raw potato methional and ( ,Z)-2,6-nonadienal [189]. Other important volatiles in raw potatoes produced via the LOX pathway are l-penten-3-one, heptanal, 2-pen-tyl furan, 1-pentanol and ( , )-2,4-heptadienal [189]. Pyrazines such as 3-iso-propyl-2-methoxypyrazine could be responsible for the earthy aroma of potato [35]. Some of the most important character-impact compounds of raw potatoes are summarised in Table 7.8. Aroma compounds from cooked, fried and baked potatoes have previously been reviewed [35]. 

The volatiles that have been established in dilution experiments [76] as important for the aroma of boiled potatoes are listed in Table 6.42. The potato aroma note can be reproduced with an aqueous solution (pH 6) of pyrazines nos. 4 and 5, methional (no. 2), methanethiol (no. 11) and dimethylsulphide (no. 12) in the concentrations given in Table 6.42 [77], Despite its smell of boiled potatoes, methional (no. 11) is not important for the aroma (see below). In the drying process applied for producing a granulate, the concentration of the pyrazines nos. 4 and 5 decrease, and therefore, the intensity of the potato note also decreases [77],... 

An important sulfide is methional (8-37). Methional in beer and wine is formed by the activity of microorganisms. It is partly reduced to the corresponding alcohol methionol (8-13) and reaction with acetyl-CoA yields 3-methylthiopropyl acetate (8-129), which is an important component of various fermented foods. Another ester of acetic acid 3-(methylthio)hexyl acetate is a component that posseses attractive tropical fruity notes on dilution. The less odoriferous (-)-(J )-enantiomer (8-130) is reminiscent of passion fruit, while the (-l-)-(S)-form has a more herbaceous odour. The odour thresholds of these thiols in air are 0.10 ng/1 and 0.03 ng/1, respectively. Both isomers have been found in passion fruit (Passiflora edulis, Passifloraceae), guava Psidium guajava, Myrtaceae) and aromatic white wines. Methyl-3-(methylthio)propionate, or pineapple mercaptan (8-131), has a flavour reminiscent of pineapple. S-Methylthiohexanoate (8-132) is a component of the durian fruit smell. Condensation of methional with ethanol yields (Z)-2-(methylthio)methylbut-2-enal also known as 2-ethylidenemethional (8-133), which is an important component of potato chips aroma. It also occurs in... 

Isopropyl-3-methoxypyrazine and 2,5-dimethylpyrazine, with their typical earthy flavour, have great importance for the aroma of rawpotatoes (Solanum tuberosum, Solanaceae). In addition to these compounds, raw potatoes contain a range of carbonyl compounds and alcohols. A very important component of the aroma of cooked potatoes is methional. 

The aroma of potato chips (French fries) is a mixture of more than 500 compounds. The important components are 2,3-diethyl-5-methylpyrazine, 2-ethenyl-3-ethyl-5-methylpyrazine, (2E,4Z)-deca-2,4-dienal, ( )-4,5-epoxydec-2-enal (8-183), l-octen-3-one, (Z)- and ( )-non-2-enal, 2-methylpropanal, 2-methylbutanal and 3-methylbutanal, biacetyl and 4-hydroxy-2,5-dimethyl-2f/-furan-3-one (furaneol). Another principal component is (Z)-2-(methylthiomethyl)but-2-enal (also known as 2-ethylidene methional, 8-198), which arises in the reaction of methional with acetaldehyde. Both isomers of 2-(methylthiomethyl)but-2-enal are used as flavour enhancers. Less signiflcant compounds are methanethiol and methional. 

Potato flavor is greatly influenced by methods of cooking or preparation. Raw potato contains the characteristic earthy aroma component, 2-ixo-propyl-3-methoxypyrazine. A character impact compound common to boiled and baked potatoes is methional (3-[methylthio]propanal). Baked potatoes contain Maillard products such as 2-ethyl-3-methylpyrazine (earthy, nutty) and 2-ethyl-6-vinylpyr-azine (buttery, baked potato) (34). In potato chips and French-fried potatoes, the potato flavor character of methional is modified by volatile aromatics from frying oils, such as ( , )-2,4-decadienal, and thermally generated alkyl oxazoles possessing lactone-like flavors (34,39). The pyrazines 2-ethyl-3,5-dimethyl and 2,3-diethyl-5-methylpyrazine are described as potato chip like (40). 

---