Monitoring ester formation during chardonnay juice fermentations in different yeast inoculation levels using solid phase microextraction (SPME) sampling

Volatile esters contribute important floral and fruity sensory properties to wine. Numerous factors influence the biosynthesis and hydrolysis of esters throughout fermentation. In this study, the effect of yeast inoculation levels in Chardonnay juice fermentations was investigated. Ester formations were monitored by solid phase microextraction (SPME) during alcoholic fermentations of Chardormay juice. Repeated batch fermentations were conducted with different inoculation levels (0.25 g dry yeast/L and 0.5 g dry yeast/L). Concentrations of ethyl acetate, ethyl butyrate, isoamyl acetate, ethyl hexanoate, hexyl acetate, ethyl octanoate, and ethyl decanoate after fermentation were significantly higher in high inoculation level fermentation (0.5 g dry yeast/L) than in low inoculation level fermentation (0.25 g dry yeast/L) (t-test, p<0.001). Fermentation progress showed similar profiles in all fermentations. However, yeast cells with low inoculation levels showed longer activity than those with the other fermentation levels.