Skin and Flesh Color
Skin and Flesh color will be measured using Minolta spectrophotometer CM-2002 using Hue angle (Fig. 1 & 2).
Peach flesh firmness decreases during maturation of the fruit on the tree. Peaches become more susceptible to bruising during harvest and handling at flesh firmnesses of 6-8 lbf (36 N). At flesh firmness less than 4 lbf (18 N), they can be damaged during the stone removal process at the cannery. In this study, flesh firmness will be measured at two equatorial positions on each fruit using a Fruit Texture Analyzer (Güss Mfg., South Africa) (Fig. 3) with an 8 mm puncture probe and a locally designed Twister. (Fig. 4)
For canning, the peach stone must be mechanically removed from the flesh. The greater the adhesion of the stone to the surrounding flesh, the more difficult the task. Stone adhesion will be measured with an Instron Model 5860 universal testing machine for measuring fruit stone pulling force. (Norwood, MA) (Fig. 5).
Flesh Browning Potential
Browning as a consequence of bruising or processing are due to phenolic oxidation. The destruction of fruit cellular compartmentalization allows phenolic substrates to be accessible to polyphenol oxidases (PPOs) which catalyze the phenolic oxidation. The concentration and composition of phenolic compounds, activity of PPOs and the presence of antioxidants play an important role in fruit browning development.
Characterization of browning will be qualitative evaluation of each cut peach half using a 6 point scale (score 1-6, with 1 = no flesh browning to 6 = severe flesh browning) and measured spectrophotometrically in vitro.
Flesh Anthocyanin Content
Accumulation of anthocyanin in the flesh of peaches is called “bleeding”. In some cultivars this occurs naturally near the stone – pit bleeding.
Bleeding will be scored qualitatively on each cut peach half using a five point scale (1= 0% of the surface pigmented to 5 = 100% pigmented) and measured quantitatively by spectrophotometer with absorbance at 515 nm.
Flesh Total Phenolic Content
High phenol content in fruit flesh has been positively correlated with a high browning potential. Total phenolic content in the peach flesh tissue will be determined by the Folin-Ciocalteu reaction method (Singleton and Rossi, 1965) using gallic acid as a standard. The phenolic content will be expressed as gallic acid equivalents per unit tissue fresh weight.