Effect of autochthonous lactic acid bacteria starters on health-promoting and sensory properties of tomato juices

Strains of Lactobacillus plantarum, Weissella cibaria/confusa, Lactobacillus brevis, Pediococcus pentosaceous, Lactobacillus sp. and Enterococcus faecium/faecalis were identified from raw tomatoes by Biolog System, partial 16S rRNA gene sequence and subjected to typing by Random Amplified Polymorphic DNA-Polymerase Chain Reaction (RAPD-PCR) analysis. Ten autochthonous strains were singly used to ferment tomato juice (TJ) via a protocol which included fermentation at 25 °C for 17 h and further storage at 4 °C for 40 days. Unstarted TJ and TJ fermented with an allochthonous strain of L. plantarum were used as the controls. All autochthonous strains grew well in TJ reaching cell densities ca. 10,000 and 10 times higher than unstarted TJ and TJ fermented with the allochthonous strain. Viscosity of TJs fermented with autochthonous strains was generally the highest, especially when started with W. cibaria/confusa which synthesized exo-polysaccharides. Overall, unstarted TJ and TJ fermented with the allochthonous strain showed marked decreases of ascorbic acid (ASC), glutathione (GSH) and total antioxidant activity (TTA) during storage. On the contrary, several TJs fermented with autochthonous strains, especially with L. plantarum POM1 and POM 35, maintained elevated values of ASC, GSH and TAA. The variation of color indexes mirrored the above behavior. TJs fermented with the above two autochthonous strains were compared to controls based on volatile components through Purge and Trap or Solid Phase Microextraction Gas Chromatography-Mass Spectrometry (PT or SPME-GC/MS) analysis. As shown by Principal Component Analysis a large number of volatiles belonging to various chemical classes markedly differentiated TJs fermented with autochthonous strains with respect to controls.