Abstract
An alternative methodology is proposed for low temperature winemaking using freeze-dried raw materials. Pine sawdust was delignified and the received porous cellulosic material was applied as immobilization carrier of the psychrotolerant yeast strain Saccharomyces cerevisiae AXAZ-1. The immobilization of yeast cells was examined and verified by scanning electron microscopy (SEM). The immobilized biocatalyst and high-gravity grape must were separately freeze-dried without cryoprotectants and stored at room temperature (20–22 °C) for 3 months. The effect of storage on the fermentation efficiency of the immobilized biocatalyst at low temperatures (1–10 °C), as well as on the aromatic characteristics of the produced wines was evaluated. Storage time had no significant effect on the fermentation efficiency of the biocatalyst resulting in most cases in high ethanol production 13.8–14.8% v/v. The volatile fraction of the produced wines was examined using headspace solid-phase microextraction (HS-SPME) followed by gas chromatography mass spectrometry (GC/MS). GC-MS/SPME analysis along with the organoleptic evaluation revealed in all produced wines a plethora of fresh and fruit aromatic notes. To conclude, fermentation kinetics and aromatic profile evaluation encourages the production of high-quality sweet wines at low temperatures using pine sawdust (Pinus halepensis) entrapped yeast cells as a promoter.
Highlights
Archaeometric studies date vine cultivation earlier and in regions of ancient Mesopotamia [1] while cultivation of grapes is known from Ancient Greece dating back at least 6000 years ago [2]
Tubular cellulose (TC), retrieved from pine sawdust after delignification, is a nano/micro-porous cellulosic material that has been proved to be suitable for use in food processing in support of immobilization [13]
The immobilization capacity of the biocatalyst was illustrated by electron microscopy (Figure 1), showing the delignified pine sawdust before and after immobilization, Mreiscproeocrgtaivniesmlys. 2L0i2k0e, 8w, xise, the fermentation capacity of the immobilized biocatalyst is illustrated in Fig6 uorfe126 showing sugar accumulation along with ethanol production as the biocatalyst was being stored in Froigoumrete2mspheorwatiunrge suupgtaor 9a0ccduamysu. lation along with ethanol production as the biocatalyst was being stored in room temperature up to 90 days
Summary
Archaeometric studies date vine cultivation earlier and in regions of ancient Mesopotamia [1] while cultivation of grapes is known from Ancient Greece dating back at least 6000 years ago [2]. Freeze-drying yields a lightweight, high-quality, and rehydrated product that retains the original shape and most of the original constituents of the starting material [5]. As it has been demonstrated, bioactive compounds and vitamins, which are part of the grape raw material, remain unstable during storage [6]. The development of modern technologies for the preservation of food raw materials through freeze-drying allows the production of wine by freeze-dried grape must at any time of the year with lower costs [4,7]
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