Volatile organic compounds as markers of quality changes during the storage of wild rocket

Abstract

The quality of leafy green vegetables changes during storage. Leaves become yellow or disintegrate, and an off-odor may develop. In addition, small amounts of volatile organic compounds (VOCs) are released. In this study, the release of acetone, carbon disulfide, dimethyl sulfide, nitromethane, pentane, 3-methylfuran, 2-ethylfuran, and dimethyl disulfide from wild rocket with different initial qualities was monitored during 8d storage at 10°C and correlated to aerobic bacteria counts, yeast and mold counts, and degree of tissue disintegration. The release of VOCs, except for 3-methylfuran, was influenced by the initial quality of the leaves. The release of pentane and 2-ethylfuran was related to the degree of tissue disintegration, and the release of dimethyl sulfide and dimethyl disulfide was related to the total aerobic bacteria count. The results demonstrated that VOCs can be used as markers for monitoring the complex quality changes taking place in packaged fresh produce during storage.

Short-Term Post-Harvest Stress that Affects Profiles of Volatile Organic Compounds and Gene Expression in Rocket Salad during Early Post-Harvest Senescence

“…Physiological changes were reflected in VOC changes, as has been previously shown [11,[20][21][22]. In agreement with previous studies [1,11], isothiocyanates were lost during storage.…”

“…However, this finding contrasts with work in Eruca sativa where isothiocyanates rose during storage [38] and could relate to differences between the two rocket salad species. The differential changes in response to the different stress treatments is consistent with the subtle changes induced by storage at different temperatures [11] and effects of wounding on the release of VOCs [20,39]. These VOC changes indicate that wounding in particular has long-term effects on the bouquet, which could be important in considering post-harvest handling and salad processing.…”

“…Processing and storage also affect microbial growth which could, in turn, affect flavor [6,9]. Specifically, increasing the storage temperature from the optimal 4 to 5 • C to 10 • C results in a rise in microbial growth on rocket leaves resulting in off odors [11,20].…”

“…The analysis of changes in volatile organic compounds (VOCs) can be a very sensitive tool to assess post-harvest changes in rocket salad [11,[20][21][22]. VOC profiles were able to discriminate amongst fresh cut Diplotaxis tenuifolia leaves and those stored for two days or six days at 0 • C to 10 • C. Furthermore, rocket leaves stored under non-isothermal conditions in which a 5 • C storage regime was interrupted after two and six days with 24 h at 13 • C released higher levels of VOCs associated with off odors [22].…”

Low-Cost Quantitation of Multiple Volatile Organic Compounds in Air Using Solid-Phase Microextraction

“…Solid-phase microextraction (SPME) that is based on extraction of VOCs by a micro coating, followed by desorption in a GC injection port, meets these requirements [8]. SPME is widely used for the determination of VOCs in ambient air (Table 1), indoor air and different emissions [9][10][11][12][13][14][15][16][17][18]. Methods based on SPME do not need a pump and a thermal desorption system.…”