Identification of Key Off-Flavor Compounds in Thermally Treated Watermelon Juice via Gas Chromatography–Olfactometry–Mass Spectrometry, Aroma Recombination, and Omission Experiments

Abstract

Thermally treated watermelon juice (TW) presents a strong unpleasant smell, resulting in poor consumer acceptance. It is necessary to identify the key off-flavor compounds in TW. Solid-phase microextraction (SPME) and solvent-assisted flavor evaporation (SAFE) coupled with gas chromatography–olfactometry–mass spectrometry (GC–O–MS) were applied to the extraction and analysis of the volatile compounds in TW. Five aroma-active compounds and seven off-flavor compounds were quantitatively analyzed by the standard curve method. Based on the flavor dilution factor (FD), odor attribute, odor activity value (OAV) of volatile compounds, and partial least-squares regression (PLSR) analysis, seven key off-flavor compounds were preliminarily identified as follows: (E)-2-heptenal, decanal, octanol, diisopropyl disulfide, hexanol, (E)-2-decenal, and (E)-2-octenol. Aroma recombination proved that these off-flavor compounds above had a negative impact on the overall flavor in TW. Omission experiments were taken to confirm them further. Finally, octanol, diisopropyl disulfide, and (E)-2-decenal were identified as the most potent off-flavor compounds in TW.

Identification and confirmation of key compounds causing cooked off‐flavor in heat‐treated tomato juice

“…After sterilization, the intensities of the two agreeable notes, grass and fresh, decreased remarkably, while the unpleasant odor attribute, namely cooked off-flavor, showed a significant increase, resulting in a low consumer acceptance. Similar phenomena have also been reported in heat-treated water-melon juice and muskmelon juice (Pang et al, 2019;Yang et al, 2020). In addition, it is worth noting that the intensity of fatty odor decreased after heat treatment.…”

“…For OAV, the contribution of each compound increases linearly with the increasing concentration, which is often inconsistent with the real food matrix. The relationship between the concentration of volatile and its response value is S‐shaped rather than linear (Yang et al., 2020). Therefore, further research is still needed to identify the cooked off‐flavor compounds in HTJ.…”

Key Odorant Differences in Fragrant Brassica napus and Brassica juncea Oils Revealed by Gas Chromatography–Olfactometry, Odor Activity Values, and Aroma Recombination

“…The distillate was concentrated to about 2 mL using a Vigreux column. Approximately 200 μL of the extract was concentrated under a gentle flow of nitrogen (purity ≥99.999%) …”

Genetic Analysis of Fruit Quality Traits in Sweet Watermelon (Citrullus lanatus var. lanatus): A Review

“…Additionally, ( Z )-3-Nonen-1-ol, 2-ethyl-1-hexanol, nonanal, ( E,Z )-3,6-nonadien-1-ol, and nonanol were reportedly dominant VOCs accounting for 81–87% in red-fleshed watermelon and 75–79% in yellow and orange-fleshed watermelon ( Liu et al, 2012 ). Off-flavor VOCs were reported in watermelon, including ( E )-2-heptenal, decanal, octanol, diisopropyl disulfide, hexanol, ( E )-2-decenal, and ( E )-2-octenol ( Yang et al, 2020 ).…”