Assessment of "Sugranineteen" Table Grape Maturation Using Destructive and Auto-Fluorescence Methods

Area of Science:

• Viticulture and Oenology
• Plant Physiology
• Agricultural Technology

Background:

• Optimal table grape harvesting relies on maturity indices, traditionally assessed via destructive, time-consuming methods.
• These classical techniques may not capture vineyard heterogeneity, impacting harvest decisions.
• Non-destructive methods offer a rapid, accurate alternative for assessing grape maturity.

Purpose of the Study:

• To evaluate the efficacy of a portable optical sensor (Multiplex® 3) for non-destructive assessment of table grape maturity.
• To establish correlations between sensor-generated indices and key maturity parameters (phenolic compounds, acidity, sugar).
• To provide a rapid and accurate alternative to conventional destructive analysis for grape quality control.

Main Methods:

• Grape samples from a Sugranineteen vineyard were analyzed during ripening.
• Basic maturity indices were measured using wet chemistry.
• Total polyphenols, anthocyanins, and flavonoids were quantified spectrophotometrically.
• Fluorescent readings were obtained from intact grape clusters using the Multiplex® 3 portable optical sensor.

Main Results:

• Strong correlations were found between Multiplex® indices (ANTH_RG, FERARI) and skin anthocyanin content (R² = 0.9613, 0.8713).
• The NBI_R index correlated with total anthocyanins (R² = 0.8032).
• The SFR_R index showed significant links to titratable acidity (R² = 0.6186), sugar content (R² = 0.7954), and the color index of red grapes (CIRG) (R² = 0.7835).

Conclusions:

• The Multiplex® 3 is a viable non-destructive tool for rapid estimation of table grape anthocyanin content.
• This technology offers a significant advancement over traditional destructive methods for grape quality assessment.
• The sensor's ability to correlate with multiple maturity parameters supports its application in viticulture for informed harvesting decisions.