EFFECT OF LOW-FREQUENCY ELECTROMAGNETIC PULSED-FIELD STIMULATION ON YEAST FERMENTATION IN PRESENCE OF DICARBOXYLIC AND TRICARBOXYLIC ACIDS

Dicarboxylic and tricarboxylic acids were added to yeast samples suspended in sucrose. The fermentative activity (measured as CO2 production by manometric equipment and referred as mu l CO2/h produced by 100 mg of yeast) was compared: (a) in samples with acid added versus samples without acid; (b) in samples with acid added and submitted to electromagnetic (EM) pulsed field versus nontreated samples; (c) in samples treated with EM pulsed field versus nontreated samples. The following acids are effective in enhancing CO2 production: oxaloacetic (+126.6%), succinic (+47.5%), fumaric (+57.2%), L-malic (+109.8%), and D-malic (+98.9%). alpha-Ketoglutaric (-23.9%) does not enhance fermentative activity. Citric acid (+93.2%) and isocitric acid (+4.6%) stimulate fermentation activity to different percentages. EMF stimulates CO2 production by 52.3% (p < 0.01) With respect to nontreated samples. EMF treatment of yeast added with fumaric (+78.8%, p < 0.01), oxaloacetic (+36.3%, p < 0.01), succinic (+27.9%, p < 0.01), alpha-ketoglutaric (+116.7%, p < 0.01), L-malic (+66.3%, p < 0.01), and D-malic (+49.7%, p < 0.01) acids enhances CO2 production. EMF is also effective in stimulating yeast fermentation in the presence of citric (+23.1%, p < 0.01) and isocitric (+59.8%, p < 0.01) acids.