Microbial community characterization and its role in volatile compound production during inoculated and spontaneous fermentation of kiwi wine (Actinidia deliciosa cv. Tsechelidis)

Abstract

Kiwi wine is a relatively new fermented beverage developed to valorize the over-supply of kiwifruit production. Similarly to winemaking, the juice is fermented with yeast under controlled conditions (temperature, period of fermentation, and maturation). Fermentation may take place either by the naturally occurring microorganisms (spontaneously) or by the addition of selected strain(s), such as Lalvin RC212 (Saccharomyces cerevisiae, inoculated fermentation). In this study, the microbial community of both kiwi wine fermentation strategies was studied, applying modern molecular approaches. The selected microorganisms, Saccharomyces cerevisiae, total yeasts, Enterobacteriaceae and Lactobacillus were quantified using quantitative Polymerase Chain Reaction (qPCR) throughout the fermentation and maturation period. Additionally, the transcriptomic profile of Lalvin RC212 during inoculated fermentation was investigated. Genes involved in key metabolic processes, affecting the wine organoleptic profile were quantified via qPCR. ADH1, BAT1, ATF1, and ALD6 were chosen based on their role in amino acid catabolism (Ehrlich pathway), production of volatile compounds, and acetic acid. Furthermore, the aromatic profile of kiwifruit juice and inoculated and spontaneous fermentations was examined through Headspace-Solid Phase Micro-Extraction (HS-SPME) technology coupled with Gas-Chromatography and Mass-Spectrometry (GC-MS). Statistical methods were implemented to explore correlations and patterns between kiwi juice or fermentation method and volatile compounds. The results were compared with previous studies using fruits and wines of several kiwi cultivars. Our experiment is considered innovative because this is the first report utilizing the Greek kiwi cultivar “Tsechelidis”.