Abstract: In order to improve the quality of grapes during storage and transportation, headspace solid phase microextraction coupled with gas chromatography mass spectrometry (HS-SPME-GC-MS) and E-nose were used to evaluate the quality and flavor compounds of Suffolk Red seedless grapes wrapped with natamycin and epsilon-polylysine preservative paper during cold storage and subsequent shelf life. The results showed that both natamycin and epsilon-polylysine preservative paper, which were obtained by soaking in 500 mg/L natamycin and 500 mg/L ε-polylysine, respectively could obviously inhibit the decay and abscission of Suffolk Red seedless grapes, delay the decrease in grape hardness as well as titratable acid and VC contents, and maintain soluble solid content at a certain level, thereby improving the quality preservation of grapes. These effects were significant compared to the control without any preservative (P < 0.05), whereas natamycin preservative paper was better than ε-polylysine preservative paper. The flavor substances of Suffolk Red seedless grapes were composed of three major classes: esters, aldehydes and alcohols with ethyl acetate, n-hexyl aldehyde, cis-3-hexenal, trans-2-hexenal, 1-hexanol and cis-3-hexen-1-ol being predominant. The relative contents of the major flavor-active esters and alcohols decreased, while the relative content of the major flavor-active aldehydes increased with extended cold storage. During shelf storage, the relative contents of the major flavor-active alcohols and aldehydes decreased, whereas the relative content of the major flavor-active esters increased. The control group showed the largest changes in the relative contents of flavor compounds. The application of biological preservative paper had a positive effect on maintaining the flavor stability of Suffolk Red seedless grapes. Furthermore, natamycin was more effective in maintaining the flavor-active aldehydes and alcohols, whereas ε-polylysine was more effective in retarding the reduction of the flavor-active esters. In addition, principal component analysis (PCA) and linear discriminant analysis (LDA) of electronic nose data enabled to distinguish the flavor of grapes stored cold for different periods during shelf life.

Key words: natamycin, ε-polylysine, preservative paper, grapes, quality and flavor substances