Sensory and Objective Quality Attributes of Beta-Carotene and Lycopene-Rich Tomato Fruit
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J. AMER. SOC. HORT. SCI. 130(2):244–251. 2005. Sensory and Objective Quality Attributes of Beta-carotene and Lycopene-rich Tomato Fruit John Stommel1 U.S. Department of Agriculture, Agricultural Research Service, Beltsville Agricultural Research Center, Plant Sciences Institute, Vegetable Laboratory, 10300 Baltimore Avenue, Beltsville, MD 20705 Judith A. Abbott and Robert A. Saftner U.S. Department of Agriculture, Agricultural Research Service, Beltsville Agricultural Research Center, Plant Sciences Institute, Produce Quality and Safety Laboratory, 10300 Baltimore Avenue, Beltsville, MD 20705 Mary J. Camp U.S. Department of Agriculture, Agricultural Research Service, Beltsville Agricultural Research Center, Biometrical Consulting Service, 10300 Baltimore Avenue, Beltsville, MD 20705 ADDITIONAL INDEX WORDS. antioxidants, color, Lycopersicon esculentum, pigment, taste panel ABSTRACT. Consumer acceptance of fresh and processed tomato (Lycopersicon esculentum Mill.) products is infl uenced by product appearance, fl avor, aroma, and textural properties. Color is a key component that infl uences a consumerʼs initial perception of quality. Beta-carotene and lycopene are the principal carotenoids in tomato fruit that impart color. Analytical and sensory analyses of fruit quality constituents were conducted to assess real and perceived differences in fruit quality between orange-pigmented, high-beta-carotene cherry tomato genotypes and conventional lycopene- rich, red-pigmented cherry tomato cultivars. Thirteen sensory attributes were evaluated by untrained consumers under red-masking light conditions where differences in fruit color could not be discerned and then under white light. Panelists preferred the appearance of the red-pigmented cultivars when viewed under white light, but scored many of the other fruit-quality attributes of red- and orange-pigmented genotypes similarly whether they could discern the color or not. Irrespective of light conditions, signifi cant genotype effects were noted for fruit appearance, sweetness, acidity/sourness, bitterness, tomato-like fl avor, unpleasant aftertaste, fi rmness in fi ngers, juiciness, skin toughness, chewiness, bursting energy, and overall eating quality. Attributes whose scores differed between white and red-mask- ing lights were intensities of tomato aroma, tomato-like fl avor, sweetness, bursting energy, juiciness, and overall eating quality. The results demonstrated a color bias favoring red-pigmented fruit and highlight the infl uence that color has on perception of tomato fruit quality, particularly on tomato-like fl avor, juiciness, and overall eating quality. Interactions between fruit chemical constituents likely infl uenced perceptions of quality. High-beta-carotene genotypes contained higher levels of sugars and soluble solids and equal or higher titratable acidity than the red-pigmented cultivars. Total volatile levels did not differ among genotypes; however, several individual volatiles were signifi cantly higher in high- beta-carotene genotypes. Trends in consumption of fresh produce are infl uenced by Color is a key component that infl uences a consumerʼs initial consumer perceptions of quality and value. For tomato products, perception of quality in fresh and processed tomato products. objective measurement of fruit chemical constituents, together The color of ripe tomato fruit is due to the colored carotenoids. with sensory evaluation of numerous organoleptic properties, In red fruit, the ratio of lycopene to beta-carotene, and the con- have been developed to help identify and optimize levels of the centration of these carotenoids, determine the hue and intensity attributes that best defi ne appearance, taste, aroma, and texture, of fruit color. Expression of a number of tomato fl esh and skin and contribute to overall fruit quality. Stevens (1979) determined color mutants results in fruit colors that range from green to pale that the fruit sugar and acid content, together with the sugar : yellow to orange to dark red (Stommel, 1992a). acid ratio, were strong determinants of fruit fl avor and consumer It is generally assumed that color infl uences consumer percep- preference. Volatile compounds that contribute to tomato fruit tions of the quality, and often, the identity of foodstuffs. DuBose aroma are also important to fruit fl avor. The levels of these aroma et al. (1980) reported correct identifi cation of fruit-fl avored solu- compounds were later demonstrated to affect the perception tions when “correctly” colored, but misidentifi cation of samples of fruit sweetness and sourness (Baldwin et al., 1998). Efforts with atypical coloration. In that study, as color intensity increased, have been made to characterize and exploit genetic variation for overall acceptability also increased, although at a diminishing tomato fruit quality attributes to improve fruit quality (Causse et rate. In cherry-fl avored sucrose solutions, increasing redness al., 2001; Jones and Scott, 1984; Saliba-Colombani et al., 2001; increased perceived sweetness (Johnson and Clydesdale, 1982) or Stevens et al., 1977). did not affect sweetness but increased fl avor intensity (Philipsen 1995). Several foods prepared with and without added color were judged to have stronger and better aroma and a stronger fl avor Received for publication 17 Dec. 2003. Accepted for publication 9 Aug. 2004. when colored (Christensen, 1983). However, in a subsequent We thank Andrea Blas, Willard Douglas, Mindy Ehrenfried, and Euhnee Park for valuable technical assistance and Sunseeds for supplying seed of ʻCastletteʼ. study, Christensen (1985) reported that added color levels in 1To whom reprint requests should be addressed. Email address: stommelj@ba. cheese and grape-fl avored jelly did not alter perception of aroma ars.usda.gov or fl avor strength. Orange drinks with added red coloring were 244 J. AMER. SOC. HORT. SCI. 130(2):244–251. 2005. BBookook 11.indb.indb 224444 22/15/05/15/05 66:29:11:29:11 PMPM perceived to be sweeter and have greater aroma, but also to have at 0.6-m intervals in single rows on polyethylene-covered raised less natural orange fl avor than less colored samples (King and beds, with beds positioned on 1.5-m centers with trickle irrigation. Duineveld, 1998). Pest control and fertilizer regimes followed standard horticul- We have developed cherry tomato breeding lines that produce tural practices for tomato production in Maryland (University fruit with high levels of beta-carotene. Fruit are orange-pigmented, of Maryland, 2000). Ripe fruit of each genotype were harvested making this material a specialty product for use where additional daily for 5 d, rinsed with tap water, and evaluated by sensory variety, fl avor, or retinoid activity is desired. High fruit beta-caro- panelists on the day of harvest. tene content is due to expression of the Beta gene, which causes SENSORY EVALUATION PANELS. Individuals selected for sensory beta-carotene to accumulate at the expense of lycopene, and results evaluation panels were solicited by e-mail from the ≈1300 cleri- in orange fruit pigmentation. Orange tomato fruit coloration may cal, administrative, technical, and scientifi c staff of the Beltsville also result from expression of the recessive tangerine mutant. Agricultural Research Center (BARC). A total of 120 untrained These orange-pigmented fruit contain little more beta-carotene volunteers who responded affi rmatively to liking and frequently than conventional red-fruited cultivars, but contain lycopene consuming tomatoes participated in the sensory evaluation panels; primarily in the orange-colored cis-form, as opposed to the red- however, seven failed to correctly complete the ballots and were colored trans-lycopene, which is predominant in red fruit. While dropped. There were approximately equal numbers of men and beta-carotene is valued for its retinoid activity and lycopene for women among the volunteers. Panelistsʼ ages were fairly normally its antioxidant properties, cis-lycopene is of considerable interest distributed from the early 20s to mid-60s (years). to the health community since it is presumably more bioavailable Fruit evaluations were conducted in a specially designed taste than trans-lycopene (Boileau et al., 1999). panel facility at BARC with 10 evaluation stations. Each panelist Little information is available in the literature describing the station was outfi tted with an overhead light source, a computer infl uence of tomato color on consumer preferences and their re- monitor with keyboard and mouse for recording sensory attributes, lationship to objective quality measurements. Yellow and orange and a light-masked port for delivery of individual fruit samples tomatoes have long been reputed to be low acid, leading some to the panelist. Lighting conditions that masked color of red- and people to prefer them and others to shun them. However, Wolf et orange-pigmented tomato fruit were created by inserting two lay- al. (1979) tested a large number of home-garden tomato cultivars ers of dark red theatrical gels (medium red fi lter #27; Roscolux, and reported that the yellow and orange tomatoes they tested were Stamford, Conn.) in mini spotlights over each station. Prior to actually more acid than the red cultivars evaluated. In simple conducting formal sensory panels, several staff members who fl avor preference tests, Tomes and Quackenbush (1958) found would not be participating in the panels independently verifi ed statistically equal preference for fruit of an orange-pigmented high- that masked lighting conditions