Measuring Flesh Color Variability among Processing Clingstone Peach Genotypes Differing in Carotenoid Composition

Abstract

<jats:p>The variability in fresh and processed fruit flesh color of six clingstone processing peach [<jats:italic>Prunus persica</jats:italic> (L.) Batsch] genotypes was measured using CIELAB color variables. The genotypes were selected based on the relative fruit concentrations of β-carotene and β-cryptoxanthin. Significant (<jats:italic>p</jats:italic> &lt; 0.0001) differences were found among the genotypes for the L<jats:sup>*</jats:sup>, a<jats:sup>*</jats:sup>, and b<jats:sup>*</jats:sup> color variables of fresh and processed fruit. Mean color change during processing, as measured by ΔE<jats:sub>LAB</jats:sub>, was greatest for `Ross' and least for `Hesse'. A plot of the first two principal components (PCs) obtained from PC analysis of the L<jats:sup>*</jats:sup>, a<jats:sup>*</jats:sup>, and b<jats:sup>*</jats:sup> variables for fresh and processed fruit revealed three clusters of genotypes that match groupings based on the relative concentrations in fresh fruit of carotenoid pigments. Path analysis showed that variation in β-cryptoxanthin concentration was more precisely determined from color data than β-carotene concentration. Chemical names used: β-β-carotene (β-carotene), (3R)-β-β-caroten-3-ol (β-cryptoxanthin).</jats:p>

Processing‐induced changes in total phenolics and procyanidins in clingstone peaches

“…32 Although phenolic levels were measured in all maturity classifications, the primary interest was in MIII peaches, as this grade is most commonly used in the canning process. Total phenolics were measured in both peeled and unpeeled fruit.…”

“…Following harvest, peaches were divided into four maturity classes, MI, MII, MIII and MIV, on the basis of external skin colour and firmness. 32 Maturity class MIII peaches were stored at three different temperatures for different periods of time. One group of peaches was frozen at À12°C for 0, 1, 2 and 3 months to simulate frozen storage for analytical purposes.…”

Carotenoid cleavage in chromoplasts of white and yellow‐fleshed peach varieties

“…In the case of the two couples of isogenic varieties, a measure of flesh fruit colour is also provided as CIE L * (lightness), a * (green‐red) and b * (blue‐yellow) coordinates. In several studies a * was shown to significantly correlate with total carotenoid content …”

“…Accumulation of substantial carotenoid amounts in fruits of white‐fleshed varieties takes place essentially during the S3 and S4 phases (CIE L *, a *, b * data in Fig. , where a * values can be considered as proportional to total carotenoid content). Accordingly, in Redhaven Bianca CCD4 expression levels were found negligible in the S1 to S3 phases, while showing a dramatic increase during S4 .…”

“…Alternatively, peach CCD4 might recognize neither β‐carotene nor β‐apo‐8′‐carotenal as substrates. This would have significant implications, since β‐carotene is one of the two main carotenoids (the other one being β‐cryptoxanthin, hydroxy‐β‐carotene) that are present in fruit flesh of yellow peach varieties . In fact, in the specific case of Redhaven , β‐carotene accounted for only 5% of total carotenoids in mature fruits (and β‐cryptoxanthin for about 7%), being tetraterpene content mostly due to other xanthophylls .…”