Effect of enzymes on strawberry volatiles during storage, at different ripeness level, in different cultivars, and during eating.

UNLABELLED: Strawberry samples with enzyme activity and without enzyme activity (stannous chloride added) were measured for real-time formation of lipoxygenase (LOX) derived aroma compounds after 5 min pureeing using selected ion flow tube-mass spectrometry (SIFT-MS). The concentration of (Z)-3-hexenal and (E)-2-hexenal increased immediately after blending and gradually decreased over time, while hexanal concentration increased for at least 5 min in ground strawberries. The formation of hexanal was slower than the formation of (Z)-3-hexenal and (E)-2-hexenal in the headspace of pureed strawberries. The concentration of LOX aldehydes and esters significantly increased during refrigerated storage. Damaging strawberries increased the concentration of LOX aldehydes but did not significantly affect the concentration of esters. The concentrations of many of the esters were strongly correlated to their corresponded acids and/or aldehydes. The concentration of LOX-generated aldehydes decreased during ripening, while fruity esters increased. Different varieties had different aroma profiles and esters were the greatest percentage of the volatiles. The aroma release of some of the LOX-derived aldehydes in the mouthspace in whole strawberries compared to chopped strawberries showed that these volatiles are formed in the mouth during chewing. The persistence of LOX-derived compounds was higher than esters after swallowing. The mouthspace after and before swallowing persistence ratio of esters decreased as the chain length of the acid part of the ester compounds increased in whole strawberries.

PRACTICAL APPLICATION: The storage studies showed that the concentrations of fruity and fresh volatiles increased during ripening and storage while damaging only increases the fresh volatiles. The nose, mouth, and headspace information can be used in the flavor industry to improve the formula of natural strawberry flavor by considering human perception during eating.