COMPARATIVE ANALYSIS OF LACTIC ACID PRODUCED BY APPLE SUBSTRATE FERMENTATION, USING HPLC AND TECTRONIK SENZYTEC BIOSENSOR

  • D. Vodnar University of Agricultural Sciences and Veterinary Medicine Cluj Napoca
  • Carmen Socaciu University of Agricultural Sciences and Veterinary Medicine Cluj Napoca
Keywords: lactic acid, fermentation, malic acid, apple substrates, HPLC, Biosensor

Abstract

Lactic acid-producing bacteria metabolism play a key role in the production of fermented foods and beverages. Different vegetable substrates are nowadays used to obtain healthy plant-based probiotics. We report here a comparative analysis of lactic acid using High Performance Liquid Chromatography (HPLC) and by Senzytec Biosensor evaluation, from 6 samples of apple pulps and/or peels, spontaneously fermented for 7 and 14 days. After 7 days of fermentation the quantity of lactic acid is higher, dependent on the substrate, better fermentations on pulp-containing samples and on apple variety ( best fermentations on Golden apple substrate). In the second stage fermentation (14 days) a general decrease of organic acids (both malic and lactic acids) was noticed, but the ratio malic:lactic acid decreased also, comparing with the first fermentation stage. These data indicates the preferential consumption of malic acid by lactic bacteria into their metabolic pathways. The combined apple substrate (pulp and peel) proved to be a very good substrate for producing lactic acid. The lactic concentrations obtained by HPLC were generally higher than those obtained by biosensor measurements. The differences between HPLC values and Tectronik Senzytec Biosensor values of lactic acid were nit significant, but dependent on the range of concentrations (from 20 to 200 mg/ml). The biosensor measurements are more reliable at lower lactic concentrations.