pH and trace-elements content in raisin extract industrial-scale alcoholic fermentation

Area of Science:

• Agricultural Science
• Biotechnology
• Food Science

Background:

• Greek raisins are utilized for industrial-scale fermentation.
• Fermentation efficiency is influenced by raisin extract pH and trace-element composition.
• Specific trace elements, particularly copper, can impact yeast performance.

Purpose of the Study:

• To evaluate the suitability of Greek raisins for industrial fermentation based on pH and trace-element profiles.
• To identify key factors influencing ethanol yield and yeast culture longevity.
• To correlate trace-element concentrations, especially copper, with fermentation outcomes.

Main Methods:

• Analysis of Greek raisin varieties for pH and trace-element content (Co, Fe, Zn, Cu, Cd, Pb) using atomic absorption spectroscopy.
• Conducting industrial-scale fermentation trials using raisin extracts.
• Assessing ethanol productivity, yield, and yeast culture stability across different raisin types.
• Experimental fermentation in synthetic media with varying copper concentrations.

Main Results:

• Raisin extracts at pH 3.2 demonstrated significantly higher ethanol productivities and yields.
• A single yeast culture was successfully reused for 300 batches under optimal conditions.
• The Trechumena raisin variety exhibited the lowest copper concentration, while Psilla had seven times more.
• Lower copper content correlated with superior performance in spirit production, confirmed by synthetic media experiments.

Conclusions:

• Optimizing pH to 3.2 and selecting low-copper raisin varieties like Trechumena are crucial for efficient industrial ethanol fermentation.
• Trace element analysis, particularly copper levels, is a key indicator for predicting raisin suitability for fermentation.
• These findings provide a basis for selecting high-quality raisins to improve fermentation processes and product yields.