Abstract: This study investigated and compared the inhibitory effect of various polyphenols on the formation of off-odors in thermally processed muskmelon juice using sensory evaluation combined with the Friedman test and multiple comparison analysis. Qualitative and quantitative analysis of the off-odor compounds in muskmelon juice with and without added catechin, genistein, daidzein, phlorotannins or pyrogallol was conducted using headspace solid phase microextraction (HS-SPME) followed by gas chromatography-mass spectrometry (GC-MS), and orthogonal partial least squares discriminant analysis (OPLS-DA) was used to characterize the inhibitory action of each polyphenol on the off-odor compounds. The results revealed that the sensory evaluation was consistent with the instrumental analysis of the types of inhibited off-odor compounds and the percentage inhibition. The five polyphenols at the same concentration of 0.1 mg/mL had different inhibitory effects on the formation of thermally-induced off-odors. Catechin exhibited the strongest inhibitory effect, followed by phlorotannins, daidzein, genistein and pyrogallol, and the effects of catechin, phlorotannins and daidzein were significant (P < 0.05). The combined use of catechin and daidzein could serve as the best way to prevent and minimize the generation of heat-induced off-odors in muskmelon juice. This study provides theoretical guidance to overcome the problem of heat-induced off-odors in muskmelon juice as a representative of thermosensitive fruits and vegetables and to develop deeply processed products.

Key words: muskmelon; thermal processing; off-notes; polyphenols; off-odor inhibition