Determination of the Monosaccharide and Alcohol Content of Balsamic and Other Vinegar by Enzymatic Methods

Plessi, Maria; Monzani, Agar; Coppini, Dino

doi:10.1080/00021369.1988.10868629

Cited by 1 publication

(1 citation statement)

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“…In this case there were 12 degrees of freedom (14-2=12) (Table V). The results obtained indicate that the coefficients previously chosen were significant since higher t (12) values were obtained than t-critical (12,0.05) = 2.17. The definitive model can be expressed with the following equation:…”

Section: Acetification Ratementioning

confidence: 80%

Set Up and Optimization of a Laboratory Scale Fermentor for the Production of Wine Vinegar

Tesfaye

García‐Parrilla

Troncoso

2000

Journal of the Institute of Brewing

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A laboratory scale fermenter was used to produce wine vinegar in a submerged culture acetic fertnentation. Tlie aim was to establish the optimal experimental conditions for three important acetification factors in order to obtain high concentrations of acetic acid within the shortest period of time. Tliese factors were stirring speed, substrate loading and working volume. Tlte effect of each single factor taking part in the process and the effect of the possible interaction among these was evaluated. For this purpose an experimental factorial design with a multiple linear regression (MLR) model resolved with a CSS-Statistics programme was applied. Tfie results indicate that to obtain a high fermentation yield the stirring speed was the most important factor and the loading proportion the most important factor to achieve a better rate of acetification.Key Words: Acetic fermentation, fermentor, wine vinegar, factorial design. INTRODUCTIONWine vinegar is the product resulting from the fermentation of wine by acetic acid bacteria. Although it is a spontaneous process which takes place in wines and musts in contact with air, vinegar is far from being the simple spoilage of wine. From an industrial point of view, the process must be controlled in order to obtain the highest degree of acidity in the shortest time as possible. Acetobacter species are the micro-organisms involved in the process and it is clear that those factors which allow better growing conditions for the bacteria will increase the yield and the acetification rate.In the production of vinegar the concentrations of both the substrate (ethanol) and the final metabolic product Another interesting factor is temperature which was optimized3 earlier to obtain maximum specific growth rates, at 30.9°C.To enhance the acetification process it must be considered that the variables involved are related to one another which presents difficulties in an optimization study. For example, the bacterial tolerance to ethanol is up to 12% if the pH is 3.4 but is lowered to 8.2% when the pH is 3.04. Nieto10 suggested that the sensitivity of bacteria to oxygen deficiency increases with a rise in temperature. It is not possible to optimize a single variable while maintaining the others constant. Experimental methods FermentorThe laboratory scale fermentor (B. Braun Biotech, S.A.) employed was a cylindrical concave bottom glass culture vessel of 5 litre capacity with a height-to-diameter ratio of 2:1; an air supply system with air filters and inlet pipe with sparger ring; a refrigeration system with cold water to prevent loss of volatile components; electrical heater jacket 230V and cooling system of the vessel with simple water bath; stirrer with 6-bladed disc impellers; Pt-100 pH-electrode, pO2-electrode; sensor for temperature measurement Pt-100; measurement and control system micro-DCU 300; stirrer speed control MCU-200; and dosing pump-300.Prior to sterilization of the culture vessel, the pH electrode was calibrated at two points (pH 4 or "zero drift" and 7 or "slope") a...

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Section: Acetification Ratementioning

confidence: 80%