Large Consumer Panel Studies

In a study by Fellers et al. (40), 30 Florida-processed grapefruit juices were obtained from the U.S. retail market during 1983 for flavor and chemical and physical analyses of quality factors, including limonin by the EIA method. Six juices of each of five types were used: frozen concentrated, grapefruit juice from concentrate packed in glass, cartons, and cans and grapefruit juice (canned directly from freshly harvested fruit). Ten products were evaluated by grapefruit juice users at each of three metropolitan test locations in the United States. Two of the five juice types were tested at each location. Each sample was tested by 108 consumers with each testing no more than two samples. Consumers evaluated samples on a nine-point hedonic scale (1 = dislike extremely, 9 = like extremely) for overall flavor and on a five-point scale (— 2 = not at all enough; 0 = just right; +2 = much too much) for the attributes of sweetness, tartness, bitterness, aroma, and color.

Correlation analysis revealed no significant association (P > 0.05) between overall flavor and limonin content (EIA). However, the bitterness attributed, overall and for each product type, was somewhat too much (P < 0.05) and correlated significantly (P < 0.01) with limonin concentration.

A serious problem apparently arose from the inability of consumers to differentiate bitterness from tartness. There was a significant positive correlation between tartness and bitterness (r = — 0.66; P < 0.01) as judged by the consumers and negative correlation between sweetness and bitterness (r = 0.55; P < 0.01); in addition, tartness correlated directly (P < 0.05) with both limonin and naringin content. However, bitterness, as measured by the consumer, also correlated directly at the 99% confidence level with limonin and naringin content.

In another study (6), the effect on flavor of limonin addition to grapefruit juice was determined. Using a single commercial Florida frozen concentrate, limonin levels (HPLC) of 2.3, 7.1, 8.8, 9.2, and 11.0 /¿g/mL were obtained in the respective reconstituted juices at 10.0° Brix with a Brix:acid ratio of 8.5. The target limonin levels were 2, 5, 7,10, and 15 /¿g/mL. A stock solution of limonin in distilled water (obtained by slow addition of limonin to boiling water) was used to spike the juice. Both grapefruit juice users and nonusers at shopping malls in three large U.S. cities participated in the large consumer study. An overall flavor score was obtained on each product using a nine-point hedonic scale (1 = dislike extremely; 9 = like extremely); a five-point scale (— 2 = not at all enough; 0 = just right; + 2 = much too much) was used to rate bitterness, sweetness, tartness, aroma, and color; finally, after each panelist had finished rating their two samples, they were asked which of the two samples was preferred. P < 0.05 was chosen as the level for significance.

Overall flavor means for all panelists (users and nonusers) varied within an acceptable range from the low end of the like moderately flavor category to the top end of the like slightly category (Table 1). The product having the highest limonin level (11.0 /¿g/mL) was assessed as having a flavor significantly inferior to the two products having

Table 1. Mean Flavor Score Values and Preference Ratings by Consumer Panels for Grapefruit Juice with Varying Limonin Contents

Limonin Concentration (//g/mL by HPLC)

Table 1. Mean Flavor Score Values and Preference Ratings by Consumer Panels for Grapefruit Juice with Varying Limonin Contents

Limonin Concentration (//g/mL by HPLC)

Consumers

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