Genotypic and Environmental Contributions to Baked Potato Flavor
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Am. J. Pot Res (2008) 85:455–465 DOI 10.1007/s12230-008-9053-z Genotypic and Environmental Contributions to Baked Potato Flavor Shelley H. Jansky Published online: 24 September 2008 # Potato Association of America 2008 Abstract This study was carried out to determine the relative clones de especialidad. Los atributos de sabor incluyeron contributions of genotype and environment to baked potato calidad de harinoso, dulzura, intensidad de sabor, desabrido flavor variation in standard potato cultivars. In addition, y percepción general de sabor. Se encontraron diferencias relationships between individual flavor components and entre cultivares y ambientes de producción. Las papas overall quality perception scores were determined. The study almacenadas recibieron mayor puntaje en percepción de was carried out for 2 years using stored potatoes. In addition, calidad que las papas frescas. La condición de harinoso fue fresh potato tubers were evaluated in the second year. Taste el atributo del sabor más variable y fue influenciado por el panels evaluated potato varieties within four market classes, genotipo y el medio ambiente. La dulzura e intensidad de russets, whites, reds, and specialty clones. Flavor attributes sabor fueron asociadas positivamente con la percepción de included mealiness, sweetness, flavor intensity, off-flavor, and calidad. Se detectó también una fuerte asociación negativa overall quality perception. Differences among cultivars and entre la falta de sabor y la percepción de calidad. production environments were found. Stored potatoes re- ceived higher quality perception scores than fresh potatoes. Keywords Potato . Solanum tuberosum . Sensory analysis . Mealiness was the most variable flavor attribute and was Baked potato . Sensory panel influenced by both genotype and environment. Sweetness and flavor intensity were positively associated with quality perception. A strong negative association between off-flavor Introduction and quality perception was also detected. Per capita consumption of potatoes in the USA is higher Resumen Este estudio se realizó para determinar la than that of any other vegetable. In 2005, Americans ate contribución relativa del genotipo y el medio ambiente a 61 kg of potatoes per person, of which 21 kg (34%) were la variación del sabor de la papa horneada en cultivares purchased fresh (Economic Research Service, US Depart- estándar de papa. Además se determinó la relación entre los ment of Agriculture). Tomatoes ranked a distant second, componentes individuales del sabor y el puntaje de la with 41 kg consumed per year, of which 8 kg (19%) were percepción de la calidad general. El estudio se realizó por purchased fresh. The most popular way to prepare fresh dos años usando papas almacenadas. Además, tubérculos potatoes is by baking them (Lin and Yen 2004). While frescos de papa fueron evaluados en el segundo año. Los overall per capita consumption of potatoes is expected to paneles sensoriales evaluaron las variedades de papa dentro decrease in the future, the consumption of baked potatoes is de cuatro clases comerciales, rugosas, blancas, rojas y expected to increase. In fact, the largest growth of all potato products among adults is expected to occur for baked S. H. Jansky (*) potatoes (Lin and Yen 2004). Department of Horticulture, Potato breeding programs typically focus on yield, tuber USDA-ARS and University of Wisconsin-Madison, appearance, processing quality, and disease resistance as 1575 Linden Drive, Madison, WI 53706, USA selectable traits (Bradshaw and MacKay 1994; Ross 1986; e-mail: [email protected] Tarn et al. 1992). Flavor, on the other hand, is not an 456 Am. J. Pot Res (2008) 85:455–465 important selection criterion during cultivar development. quality decreases due to the production of organic acids Currently, most breeding programs only require the absence (Cieslik 1997). Levels of methional, an aroma compound, of off-flavor. In recent years, breeders and growers have vary across environments (Duckham et al. 2002; Oruna- expressed a desire to assess cultivar flavor and use this Concha et al. 2001). Because methionine contains sulfur, information in breeding programs to improve the market sulfur application rates may account for some differences in value of potatoes. methional levels (Duckham et al. 2002). Methoxypyrazines Components of flavor include taste, aroma, texture, and may be produced by the tuber or by soil bacteria umami (a Japanese word meaning delicious). The major (Pseudomonas taetrolens) and then absorbed by the tuber, taste (nonvolatile) components in potato tubers are glyco- so soil microbe populations may influence flavor (Buttery alkaloids, sugars, amino acids, lipids, acids, and nucleotides et al. 1973). In addition, high potassium levels in tubers (Maga 1994). Glycoalkaloids can produce a bitter flavor may enhance umami taste intensity (Ugawa and Kurihara when greater than 14 mg/100 g tuber fresh weight (Sinden 1994). Differences in production environment were found et al. 1976). The main contributions of sugars, amino acids, to influence the development of off-flavor in pre-cooked and lipids are the volatile compounds they produce after vacuum-packed potatoes, but specific environmental heating. However, sugars also contribute directly to sweet parameters influencing off-flavor were not determined taste. Phenolic compounds such as chlorogenic acid may (Jensen et al. 1999). contribute negatively to flavor, as a positive correlation Some studies have evaluated the effects of organic between phenolic content and bitterness/astringency has versus conventional production systems on sensory attrib- been reported (Mondy et al. 1971). However, Sinden et al. utes. Using triangle tests, Wszelaki et al. (2005) found that (1976) did not find a strong relationship between phenolic taste panelists were able to distinguish between conven- content and bitterness. Ribonucleotides act as precursors for tionally and organically grown boiled red potatoes if the umami compounds (flavor potentiators). Steamed or boiled skin was left on the tubers while boiling. If the skin was tubers with high levels of guanosine 5′-monophosphate removed during boiling, then differences could not be (GMP) had high quality perception scores in sensory detected. Hajslova et al. (2005) determined that cultivar and analyses (Morris et al. 2007). A positive synergistic effect production year are important influences on sensory quality on flavor occurs when 5′ ribonucleotides interact with of boiled potatoes, but that there is no clear influence of amino acids, especially glutamate. production system (organic versus conventional). In a Baked potatoes produce a complex array of volatile review of studies conducted to evaluate organoleptic quality compounds including lipids, Maillard reaction products, sulfur in organic versus conventional systems, no clear statements compounds, and methoxypyrazines (Oruna-Concha et al. could be made regarding the superiority of one type over 2001). Pyrazines are considered to be among the most the other (Woese et al. 1997). important and characteristic components of baked potato Sensory quality changes during the storage of potato flavor (Oruna-Concha et al. 2001). They are produced by the tubers. In 1981, True and Work (1981) noted that ‘Russet Maillard reaction, in which reducing sugars (glucose and Burbank’ ranked high and ‘Ontario’ ranked low for flavor fructose) interact with amino acids at high temperature. A preference in fresh baked potatoes, but differences were not strong positive relationship between pyrazine levels and baked detected in tubers stored at 8.2°C for 6 months. In a study potato flavor has been reported (Maga and Holm 1992). of pre-peeled boiled potatoes, cultivar and storage time (0, Potato texture is a complex trait, but much variation can 1.5, and 6 months at 4°C) were the primary factors be explained by determining the degree of a tuber’s explaining (68%) variability in taste, color, and texture mealiness or, at the opposite end of the spectrum, waxiness (Thybo et al. 2006). When potato tubers are cooked, fatty (van Marle et al. 1997). A mealy potato is dry and granular, acids degrade to produce aldehydes and ketones, which while a waxy potato is moist and gummy. Texture is contribute to flavor (Duckham et al. 2002). Total levels of influenced, at least in part, by characteristics of starch fatty acids and their flavor products increase during storage grains and cell walls (Martens and Thybo 2000; McComber (Duckham et al. 2002). It is interesting to note that, as et al. 1994; van Marle et al. 1997). Mealiness has been tubers acclimate to cold storage temperatures, their fatty found to be associated with high dry matter content (van acid profiles change. Consequently, both levels and types of Dijk et al. 2002). However, dry matter content does not fatty acids change during storage. There is variation among always explain mealiness. In one sensory analysis study, cultivars in the way their fatty acid profiles are altered ‘Ontario’ was judged to be less mealy than other cultivars during cold storage (Mondy et al. 1963). The types and in the trial, but its total solids content was similar to some levels of other volatile components of flavor also change of those cultivars (True and Work 1981). during storage, presumably due to alterations in enzyme There is evidence that production environment affects activities and levels of flavor precursors, such as sugars sensory quality. As tuber nitrogen levels increase, sensory (Duckham et al. 2002). Levels of glucose and fructose in Am. J. Pot Res (2008) 85:455–465 457 most cultivars increase during storage at less than 10°C testing began, the methods for testing human beings in this (Sowokinos 2001). study were determined to be exempt from review by Potato growers and breeders are interested in considering Institutional Review Board of the Graduate School at the flavor as a marketable trait. In order to breed for improved University of Wisconsin-Madison. A trained taste panel of flavor, the relative contributions of cultivar, production 16 to 20 members evaluated the flavor of tubers baked at environment, and storage environment must be understood. 200°C for 1 h from March 6 to 9, 2006.