Application of SIFT-MS in Monitoring Volatile Compounds in Fruits and Vegetables

This review article focuses on volatile formation in tomatoes, tomatillos, strawberries, jalapeño peppers, bell peppers, garlic, cocoa beans and liquors, cashew nuts, almonds, pumpkin seeds, and carrots, as measured by Selected Ion Flow Tube Mass Spectrometry (SIFT-MS). The formation of several key volatile compounds occurs due to enzymatic activity, especially by lipoxygenase. (Z)-3-hexenal and hexanal increase after tissue disruption, reach maximum concentration at a similar time and then decrease due to conversion to other compounds, such as (E)-2-hexenal and hexanol. As temperature increases, there is a higher rate of enzyme activity and increased volatility, resulting in an increase in volatile compounds. During frozen storage, (Z)-3-hexenal and hexenol increase initially during storage and then decrease since (Z)-3-hexenal is converted into (E)-2-hexenal while hexenol is degraded into other compounds. In strawberries, damage stimulates the production of LOX-derived volatiles. During the early ripening stage, the concentration of LOX-derived volatiles is high and fruity esters are low, but the concentrations reverse as ripening progresses. During chewing, some volatile compounds in tomatoes and strawberries increase in the mouthspace and nosespace since chewing breaks intact tissue cells and releases LOX enzymes, resulting in the formation of volatile compounds, especially (Z)-3-hexenal and (E)-2-hexenal. Consumption of some foods, such as water, milk, and sodium caseinate solutions, can reduce volatile levels in the mouth, including malodorous garlic breath. The Maillard reaction is responsible for the formation of many volatiles during roasting and increases with temperature and pH. Both roasting and drying promote the formation of furan compounds.