Fruit color development, anthocyanin content, standard quality, volatile compound emissions and consumer acceptability of several 'Fuji' apple strains
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The effect of strain on fruit color development and anthocyanin content, fruit quality, volatile compound emissions and consumer acceptability was evaluated on seven"Fuji" apple strains (Malus domestica Borkh.) at the IRTA (Spain) over a period starting three weeks commercial harvest in 2008 and ending one week after harvest. Based on fruit color, measured with a portable tristimulus colorimeter, and anthocyanin content, the most colored strain was"Zhen Fuji Aztec" (blushed), followed by"Fuji 6629" (also blushed),"Fuji Kiku 8" and"Rubin Fuji" (both striped)."Fuji Chofu 2" (blushed) and"Fuji Suprema" (barely striped) were the least colored strains, although fruit color started earlier in the last one."Ogura" (barely striped) provided intermediate values. The most important increase in anthocyanin content and decrease in hue values was recorded from one week before commercial harvest until harvest, in all strains except"Fuji Suprema". Highly colored strains developed a red color on both sides of the fruit with greater average values for strains with greater colored surfaces than for less colored strains. A medium relationship between hue angle, L* and a*/b* ratio and anthocyanin content was established. Fruit quality parameters for the different harvest dates as fruit firmness, soluble solid content (SSC), titratable acidity (TA), and starch index were similar for the different cultivars and date. Fruit firmness is well maintained across different dates even with high values of starch index. Differences in fruit color, intensity and type, were not related to differences in the fruit quality parameters of the different strains. Ripening time was therefore not related to the intensity or type of fruit color. There are some quantitatively and qualitatively differences among the volatile profiles of all the"Fuji" strains. In quantitative terms, the"Fuji" strain that emitted the lowest total concentration was"Fuji Aztec". There were no statistical differences among the total volatile compound concentrations of"Fuji Kiku 8","Rubin Fuji","Fuji 6629" and"Fuji Chofu 2", which obtained the highest values. The main volatile compound emitted for all of the analyzed strains was the 2-methylbutyl acetate. In general, apples of the most colored strains emitted less volatile compound compared to the least colored. Concerning to consumer acceptability,"Fuji Aztec" strain got the lowest mean score, but there were no differences among the rest of"Fuji" strains. A full-data principal component analysis was run. This analysis showed a high correlation between consumer acceptability and some of the volatile compounds emitted, in addition to fruit that exhibit bigger hue angles on the exposed side (lower red color).