Effect of hydrocinnamic acids on the growth of lactic bacteria.

Hydroxycinnamic acids, their quinic esters and quinic acid are present in a pple juice and cider. Effects of each of these compounds and of two mixture s on the growth of one strain of two lactic acid bacteria species were stud ied by a four level factorial design. Each design involved three factors. T hus sixteen designs were required to achieve the work described in the pres ent paper. The compounds were the following hydroxycinnamic acids: Ferulic acid, p-Coumaric acid, Caffeic acids, p-Coumaroyl quinic acid, 5'-Caffeoyl quinic acid and the non-phenolic acid: Quinic acid. The two mixtures on an equimolecular basis were: p-Coumaric acid/Quinic acid and Caffeic acid/Quin ic acid. The lactic bacteria species were: Oenococcus oeni and Lactobacillu s plantarum. The factors involved were: pH, tested compound concentration a nd pitching rate. Two growth parameters were examined: apparent growth rate and biomass production. Results showed that esters and Quinic acid were no t active and that bacterial growth was only affected by hydroxycinnamic aci d concentrations. A decreasing inhibitory effect was shown from Ferulic aci d to p-Coumaric acid and Caffeic acid. The two strains behaved differently: both apparent growth rate and biomass production decreased for Oenococcus oeni while only the apparent growth rate was affected for Lactobacillus pla ntarum.