Color and appearance factors are the primary quality attributes that can be appraised by consumers of fresh produce at the time of purchase (Gamble et al., 2006; Kramer, 1951). Historically, the snap beans purchased by U.S. consumers were a relatively light shade of green. However, in the 1990s, a major seed company introduced dark green beans to the U.S. fresh market (Brooker and Eastwood, 1992). The company promoted the dark green beans as being more attractive to buyers, but little objective information was available to back these claims. Moreover, it was not known how color might change after the dark green beans were cooked.
The human eye can perceive visual differences in greenness among fresh samples of snap bean pods (Hoffman and Kanapaux, 1955). It is less well understood how these subjective distinctions relate to both objective measures of greenness and subjective ratings for likelihood of purchase. Hoffman and Kanapaux (1955) found a significant correlation (r = 0.906, P ≤ 0.01) between visual color ratings and chlorophyll content of fresh snap bean pods, but chlorophyll is not the only pigment responsible for color in snap beans (Lopez-Hernandez et al., 1993). Brooker and Eastwood (1992) surveyed shoppers for selection preference when comparing fresh pods of the light green ‘Strike’ and the dark green ‘Labrador’ snap beans. They found a slight preference (52.2%) for the light green cultivar, but they did not attempt to relate these preferences to any objective measures of greenness.
Lee (1958) noted that when green vegetables are heated in water, the chloroplasts become swollen and may burst, resulting in a diffusion of green pigment throughout the cells and a more intense green appearance to the surface of the vegetable. Muftugil (1986) found that bean samples blanched with water or steam were more green than raw beans, but cultivars were not compared for possible differential responses.
The objectives of this study were: 1) to perform objective color evaluations on raw and cooked pod samples from several snap bean cultivars with pods representing a range of greenness; and 2) to determine whether consumers could distinguish differences in greenness among raw pod samples from several of these cultivars and, if so, whether these subjective distinctions would relate to both objective measures of greenness and subjective ratings for likelihood of purchase.
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