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Assessment of the Validity of Maturity Metrics for Predicting the Volatile Composition of Concord Grape Juice
Author(s) -
Iyer Meera M.,
Sacks Gavin L.,
PadillaZakour Olga I.
Publication year - 2012
Publication title -
journal of food science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.772
H-Index - 150
eISSN - 1750-3841
pISSN - 0022-1147
DOI - 10.1111/j.1750-3841.2011.02592.x
Subject(s) - maturity (psychological) , composition (language) , food science , chemistry , mathematics , chromatography , psychology , art , developmental psychology , literature
Total soluble solids (TSS) are typically used as the sole metric for maturity of Concord grapes. However, the reliability of TSS in predicting the aroma composition of finished juice for grapes sourced from multiple sites has not been investigated. This study sought to determine the validity of TSS in predicting the aroma composition of the juice while also investigating other potentially useful indicators, including pH, titratable acidity (TA), and TSS:TA ratio. Grapes were harvested from 9 sites in the Lake Erie Concord Grape Belt and stratified from north to south and east to west. The key aroma compounds methyl anthranilate (“grapey”) and trans‐ 2‐hexenal (“herbaceous”) were quantified along with several other odorants. It was observed that while TSS was a robust predictor of monomeric anthocyanin content across sites, it was a poor predictor of aroma compounds in the finished juice. Conversely, pH, TA, and TSS:TA ratio were all significantly correlated with methyl anthranilate and trans‐ 2‐hexenal concentrations ( P < 0.05) in samples equal to or exceeding 15 Brix, the industry minimum for grape maturity. These results indicate that parameters related to acidity are better predictors of aroma composition than TSS, which may aid in efforts to minimize herbaceous off‐aromas and optimize the aroma composition of the finished juice. Practical Application: It is critical for the juice industry to have readily measurable parameters in Concord grapes upon harvesting that can predict the aroma composition of the finished juice. To date, total soluble solids (TSS) has been the industry standard for evaluating harvest maturity. Our results indicate that parameters that account for acidity (that is, titratable acidity, pH, and TSS:titratable acidity ratio) are superior in predicting the final juice aroma composition. The implementation of a more reliable predictive index at harvest can reduce the incidence of herbaceous off‐aromas in Concord grape juice, a common consumer complaint for this product.