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1 mm diameter, cylindrical probe pressed into the pulp of each fruit at a speed of
0.1 m/min.
chemical Analyses
All chemical assays were once replicated within the same sample. Tomatoes were
cut and peeled and immediately homogenized by a Waring blender.
Dry matter and pH determinations were performed as reported in [18]. An
aliquot of the homogenized tomato tissues was used to measure the soluble solid
content (SSC) with a BS model RFM 81 refractometer.
About 10 g of homogenized flesh was used for the determination of titratable
acidity and acidic profile. Titratable acidity was determined according to AOAC
methods (AOAC. 1980. Official Methods of Analysis, 13th ed. N° 46024 and N°
22061. Association of Official Analytical Chemists, Washington. DC).
The Total Phenolic Content was determined in tomato extracts by the Fo-
lin-Ciocalteu based method [19], using gallic acid (GA) as a standard for the
calibration curve. Results were calculated as gallic acid equivalent (GAE) in fresh
fruit (mg g-1). A calibration curve (0-500 mg l-1 of GA) was made prior to the
determinations. Samples were read in a KONTRON Uvikon 941 Plus spectro-
photometer.
Citric, tartaric and oxalic organic acids were determined from an aqueous
extract of the homogenized pulp (10 g plus 20 mL H2O), homogenized for 30
seconds with an Ultra-Turrax, then centrifuged at 5600 × g for 20 min, and fil-
tered through 0.45 µm filter. The extracts were analyzed by HPLC at 20°C, using
0.02 M H3PO4 as mobile phase (flow rate: 0.6 mL/min) on an Inertsil ODS-3
column of 0.46 × 25 cm dimension with 5 µm of particle diameter, using detec-
tion by a UV-VIS spectrophotometer set at 210 nm. Retention times of standards
were: tartaric acid 8.9 min, oxalic acid 9.8 min, citric acid 21.9 min.
Ascorbic acid (vitamin C) was determined from an aqueous extract of the
homogenized pulp (10 g plus 20 mL metaphosphoric acid 6% in H2O), homog-
enized for 30 seconds in an Ultra-Turrax, then centrifuged at 5600 × g for 20
min, and filtered through a 0.45 µm filter. The extracts were analyzed by HPLC
at 20°C, using 0.02 M H3PO4 as mobile phase (flow rate: 0.6 mL/min) on an In-
ertsil ODS-3 column of 0.46 × 25 cm dimension with 5 µm of particle diameter
detected by a UV-VIS spectrophotometer set at 254 nm. Under these conditions,
ascorbic acid has a retention time of 8.6 minutes.
Compounds were identified following HPLC by comparing their reten-
tion times with those of commercial standards. Compounds were quantified by
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