Fresh tomato specific fluctuations in the composition of lipoxygenase-generated C6 aldehydes

Linoleoyl and α-linolenoyl fatty acyl groups are converted to hexanal and hexenal ((Z)-3-hexenal and (E)-2-hexenal), respectively, on the maceration of tomato fruits. These C6 aldehydes greatly contribute to the mix of volatile compounds which determines the flavour of the tomato. Cherry and standard fresh tomatoes were used to study the relationship between fatty acid composition of the intact fruit and the C6 aldehydes produced on maceration. The cherry tomato (var. Cherry Belle) had approximately twice as much α-linolenic acid as the standard tomato (var. Solairo). The enrichment of α-linolenic acid in the cherry tomato compared to the standard tomato was not evenly distributed between the major lipid classes (neutral lipids, glycolipids and phospholipids) but was prominent in the neutral fraction. The linoleic/α-linolenic acid ratio in the cherry and standard tomatoes was 1.75 and 4.1, respectively; this was reflected but not matched by the hexanal/hexenal ratio on macerating these tomatoes (0.1 and 0.27, respectively). Analysis of volatile compounds on macerating tomato fruits was extended to 14 other commercially available varieties which were nominally split into ‘cherry’ (50 g average fruit weight and below) and ‘standard’ (average fruit weight above 50 g) tomatoes. Hexanal/hexenal ratios were remarkably different between ‘cherry’ (0.05–0.1) and ‘standard’ (0.14–0.27) tomatoes. The concept of increasing α-linolenic acid levels in tomatoes to increase desirable flavour is discussed.