Aroma volatile profiles from ripe tomatoes are influenced by physiological maturity at harvest: an application for electronic nose technology

摘要

The effect of physiological maturity at harvest on ripe tomato (cv. Solimar) volatile profiles was studied using ripening response time (in days) to exogenous ethylene treatment (100μl/litre) as a tool to separate immature-green from mature-green fruits. Electronic nose (EN) sensor array and gas chromatography (GC) analyses were used to document volatile profile changes in fruits that required a 1-, 3- or 5-day ethylene treatment to reach the breaker stage. EN output analysis using multivariate discriminant and canonical analyses classified intact tomato and whole tomato homogenate samples that required 3 or 5 days of ethylene treatment as significantly different from those that required only 1 day. The GC aroma profiles from whole tomato homogenate showed that 1-day fruits had significantly higher levels of 1-penten-3-one, cis-3-hexenal, 6-methyl-5-hepten-2-one, 2-isobutylthiazole and geranylacetone than 5-day fruits. Analysis of excised tomato tissues showed that pericarp (including columnella) produced an average 219% greater concentration of the 16 aroma volatiles quantified by GC than locular gel (442 vs. 203μl/litre, respectively). EN analysis concurred with GC by showing greater average Mahalanobis distance between pericarp tissue groupings when compared to locular gel groupings (78.25 and 12.33 units, respectively). Pericarp tissue from the 5-day ethylene treatment showed significantly lower levels of 1-penten-3-one, trans-2-heptenal, 6-methyl-5-hepten-2-one, 2-isobutylthiazole, geranylacetone and beta-ionone than in the 1- and 3-day treatments. Similarly, locular gel from the 3- and 5-day ethylene treatments had significantly lower levels of 1-penten-3-one, 2-isobutylthiazole and 1-nitro-2-phenylethane than 1-day samples. cis-3-Hexenol in locular gel was the only volatile compound that showed significantly higher levels with increasing ethylene treatment. EN analysis showed greater Mahalanobis distances between 1- and 3-day ethylene samples than between 3- and 5-day ethylene samples (32.09 vs. 12.90, 24.14 vs. 6.52, 116.31 vs. 65.04, and 15.74 vs. 13.28 units, for intact tomato, whole tomato, pericarp and locular gel homogenate, respectively).