Physiological parameters of the grapes—total soluble sugars (TSS), pH, and titratable acidity (percentage malic acid equivalence)—were tested on the first day (before treatment) and on 2 or 4 DPT, and with slight modification based on [19 (link)]. For testing of TSS, 4 un-inoculated grapes from each treatment (ulvan extract or DDW (control)) were randomly selected, placed inside sterilized gauze and collectively crushed, and the filtered juice was collected. Filtered juice of 1 mL from each tested group was placed in a Palette digital-refractometer PR-1 (Model DBX-55, Atago, Japan), and each measurement was repeated in triplicate.
For acidity determination, 7 un-inoculated grapes from every treatment (ulvan extract or DDW (control)) were randomly selected for testing in the following manner: 1 mL of pulp juice was dissolved in 40 mL double-distilled water and determined as malic acid equivalent mass using an automatic titrator (Model 719s, TitrinoMetrohm Ion Analysis Ltd., Herisau, Switzerland).
For acidity determination, 7 un-inoculated grapes from every treatment (ulvan extract or DDW (control)) were randomly selected for testing in the following manner: 1 mL of pulp juice was dissolved in 40 mL double-distilled water and determined as malic acid equivalent mass using an automatic titrator (Model 719s, TitrinoMetrohm Ion Analysis Ltd., Herisau, Switzerland).
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