Abstract:

The purpose of this work was to define optimal conditions for the fermentation of dilute cream by Kluyveromyces
marxianus Y51-6. Optimization of fermentation conditions for improved alcohol content and sensory evaluation was carried
out using an orthogonal array design. A fermentation temperature of 45 ℃, addition of sucrose at 7 g/100 mL, an inoculum
size of 7% (V/V) and 40 h fermentation proved optimal. The fermentation process involved lag phase (0–12 h), logarithmic
phase (12–24 h), stable phase (24–32 h) and declining phase (after 32 h). The pH decreased during the fermentation process,
while acidity and alcohol content increased gradually and color parameters did not change significantly. The results of analysis
by solid-phase micro-extraction (SPME) and gas chromatography-mass spectrometry (GC-MS) showed that 17 components
were detected in unfermented cream, which were dominated by methyl ketones such as 2-heptanone and 2-nonanone. Totally
35 components were detected in fermented cream samples, among which the proportion of methyl ketones was reduced, while
esters and alcohols such as phenylethyl alcohol and ethyl caproate revealed a significant increase.

Key words: Kluyveromyces marxianus, dilute cream, process optimization, solid phase micro-extraction combined with gas chromatography-mass spectrometry