Effect of Low-Frequency Electromagnetic Pulsed Field Stimulation on Yeast Fermentation in Presence of Dicarboxylic and Tricarboxylic Acids

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Abstract
Dicarboxylic and tricarboxylic acids were added to yeast samples suspended in sucrose. The fermentative activity (measured as C02 production by manometric equipment and referred as μl 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%). a-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), α-ketoglutaric(+ 116.7%, p < 0.01), L-malic (+ 66.3%, P < 0.01), and D-malic (+ 49.7%, p < 0.01) acids enhances C02 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.