Potato-like flavor

Musty or potato-like flavor and aroma have been observed as a defect in milk (Hammer and Babel 1957) and Gruyere de Comte cheese (Dumont et al. 1975). This off-flavor results from the production of nitrogenous cyclic compounds by Pseudomonas taetrolens and P. perolens (Morgan 1976). Musty-flavored compounds produced by these organisms include 2,5-dimethylpyrazine and 2-methoxy-3-isopropyl-pyrazine. The Gruyere de Comte with potato off-flavor contained 3-methoxy-2-propyl pyridine, as well as alkyl pyrazine compounds (Dumont et al. 1975). Murray and Whitfield (1975) postulated that alkyl pyrazines are formed in vegetables by condensation of amino acids such as valine, isoleucine, and leucine with a 2-carbon compound. Details of the synthetic mechanism in pseudomonads are unknown. 

Dumont, J. P., Roger, S. and Adda, J. 1975. Identification of a nitrogenous heterocyclic compound responsible for a potato-like off-flavor in Gruyere de Comte. Lait 55, 479-487. 

In an headspace extract of fresh rye bread crust, 3-methylbutanal, (E)-2-nonenal and methional showed the highest FD-factors (Table 4), while 2-acetyl-1-pyrroline, the key odorant of wheat bread crust (cf. Table 3), did not significantly contribute to the rye (rust flavor. Quantitative measurements established [45, 55] that especially the higher odor activity (cf. 3, this chapter) of the boiled potato-like smelling methional in the rye bread crust in combination with the much lower odor activity of the roasty-smelling 2-acetyl-l-pyrroline mainly contribute to the overall flavor differences in rye and wheat bread crusts. 

Pentyl-A-methyl-5-ethyloxazole was identified in french-fried potato flavor and has a strong buttery, sweet and lactone-like flavor. It is probably an Important contributor to the fried food aspect of french-fried potato flavor (37). 

There are many reports of Pseudomonas cultures producing musty, earthy, and potato-like odors ( l-6). The work of Morgan et al. (T) established 2-methoxy-3-isopropyl pyrazine to be partially responsible for these odors. Subsequently, 2-methyoxy-3-isopropyl pyrazine was found in bell peppers (8), a similar compound 2-methoxy-3-secbutyl pyrazine was identified in galbanum oil (9), and several 2-methoxy-3-alkyl pyrazines were identified in various raw botanicals (10). The odor threshold exhibited by 2-methoxy-3-isobutyl pyrazine (1 part in 10 indicates flavor significance for these compounds even at the exceptionally low concentrations in which they occur in foods and other natural products Producing these compounds from microbial fermentations could be an economical source of flavor for the food industry. 

The effect of the retorting process and UHT sterilization on the flavor of green tea drink is shown in figure 17.3. The intensity of off-flavor (potato-like, floral, sweet, heavy, spicy) increased during retorting and sterilization, and the characteristic green... 

Wiley (1947) characterized the odor as pyridinic . According to Mussinan et al. (1976), the flavor is woody, musty, green with a threshold in water of 5.0 ppb. Bentz and Mezzino (1972) (quoted by Maga, 1981a) claimed that mixtures of trimethyloxazole and biacetyl can impart earthy, potato-like or mushroom-like flavor to foods. They reported that, alone, it has a sour and bitter taste and smells like sweet pyridine but, when mixed with diacetyl in molar ratios varying from 1 to 4, an earthy flavor note was predominant. Coleman et al. (1981), who reported it for the first time in baked potatoes, stated that it contributed importantly to the earthy and nutty notes of the total flavor. The flavor has been defined as burnt, nutty, hazelnut (Chemisis, 1970). 

The product is described as having a chocolate note (odor, flavor) at 0.2 ppm in water (Polak s-Douwe Egberts, 1968) and an earthy, baked and potato-like odor (Coleman and Ho, 1980). 

Methoxy-3-alkylpyrazines are often associated with musty-earthy and potato-like odors. 2-methoxy-3-isopropylpyrazine is responsible for the musty, potato-bin odor and contributes to off-flavor notes in wines 2-methoxy-3-isobutylpyrazine is a main constituent of green bell pepper and jalapenios flavor. It is known that alkylpyrazines are formed in thermal reactions but can be also produced by microorganisms, mainly bacteria, such as Pseudomonas species [2]. 

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). 

Three extremely odorous pyrazines, 3-isopropyl-2-methoxypyrazine, 2-s-butyl-3-methoxypyrazine, and 2-isobutyl-3-methoxypyrazine have been shown to be present in green peas, and are likely to be of major significance in the flavor of peas (59). The volatile oil of green bell peppers has been found to contain 2-isobutyl-3-methoxypyrazine as a major component (60,61). The alkylpyrazines in potato chips (62,63) and roasted peanuts (63) have been examined. 2-Isopropyl-3-methoxypyrazine has been characterized in the vacuum steam volatile oil of potatoes (64), 2-ethyl-3-methoxypyrazine in cooked potato (65), and 3-ethyl-2,5-dimethylpyrazine and 2-ethyl-3,5-dimethylpyTazine as the components important to the aroma of baked potato (66). A variety of alkylpyrazines have been identified in roasted sesame seeds (67) and 21 pyrazines have been identified in the aroma components isolated from roasted green tea (68). 

Chestnut has been part of the staple diet in many countries for centuries. It has a sweet and nutty flavor, and its texture is like a firm baked potato and not crunchy compared to other nuts. Chestnut, which is classified as a temperate nut, requires cold winters and warm summers. It has been grown on all continents in northern hemisphere and Austraha [2,3]. hi Asia, the Japanese chestnut Castanea crenata) has been cultivated since the eleventh century and the Chinese chestnut (Castanea mollissima), possibly for 6000 years. In the Mediterranean region, chestnut has been cultivated for at least 3000 years [2]. In Europe, chestnut spreads from south to north and from Mediterranean to Sweden. It was brought to the Alps and Appennines, and new villages were built only where chestnut could grow and produce fruits [4]. 

Pyrazines. Some P. of the types 1-3 are highly active and widely distributed flavor compounds formed either thermally (especially 1 and 2) or biosyn-thetically (3). Alkylpyrazines (1) (see table) have characteristic roast, nut, and potato odors and occur principally in the flavors of coffee, roasted nuts, meat, potatoes, and sea food. 2-Acetylpyrazine (2) has a bread- and popcorn-like odor and is important for... 

For years researchers have investigated the sulfur compounds present in various foods. Cooked foods typically contain numerous sulfur compounds, especially heterocyclic compounds like thiazoles, thiophenes, thiazolines, etc. In 1986, Sha-hidi et al. (7) reported that 144 sulfur compounds had been identified in beef. Other heated food systems like bread, potato products, nuts, popcorn, and coffee also contain many sulfur compounds. Aliphatic thiols have been found in fruits, vegetables, dairy products etc., as well as in heated foods. No discussion of the occurrence of sulfur compounds in foods would be complete without mention of their major role in the various allium species. Indeed, more than half of the volatile compounds reported in garlic, onion, leek, and chive contain sulfur (2). Comprehensive reviews of the literature concerning the role of thiazoles, thiophenes, and thiols in food flavor through 1975 can be found in Maga s series of review articles (3-5). 

Schnermann and Schieberle [54] reported 13 odorants with the highest flavor dilution factors in milk chocolate as 3-methylbutanal (malty) 2-ethyl-3,5-dimetbylpyrazine (potato chip-like) 2- and 3-methylbutanoic acid (sweaty) 5-methyl-(E)-2-hepten-4-one (hazelnut-like) l-octen-3-one (mushroom-Uke) 2-ethyl-3,6-dimethylpyiazine (nutty, earthy) 2,3-diethyl-5-methylpyrazine (potato chip-like) (Z)-2-nonenal (green, tallowy) (E,E)-2,4-decadienal (fatty, waxy) (E,E)-2,4-nonadienal (fatty) 8-decalactone (sweet, peach-like) and 2-methyl-3-(methyldithio)furan. 

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