Preservation Effects of Sourdough Bread Using <i>Lacticaseibacillus</i><i> P</i><i>aracasei </i>and<i> Lactiplantibacillus </i><i>Plan</i><i>trum</i>

The objective of this study was to compare the loaf quality and shelf life of sourdough and yeast-leavened. Sourdough bread is widely consumed in regions such as northern Europe and U.S while sourdough bread relatively unknown in Japan. Sourdough bread was made using novel lactic acid bacteria (LAB): Lacticaseibacillus paracasei NFRI 7415, isolated from traditional Japanese fermented fish, and Laciplantibacillus plantarum, an LAB which, together with L. paracasei, was recently shown to inhibit growth of Escherichia coli. A bread to which LAB were not added was made as a control. Although there were no significant differences in the weight, specific volume and water content among the three samples, the total sugar content of sourdough breads was lower than that of the control: co-fermentation of LAB and yeast appeared to increase sugar consumption. As expected, sourdough bread contained a higher content of organic acid, especially lactic acid. The sample loaves were cut into 1-cm slices and placed in a polypropylene bag, sealed, and stored at 28°C for 6 days. The general bacteria count of the control reached 10 10 cfu/g in 6 days, while the sourdough bread was in the range of 10 5 –10 6 cfu/g. The mold exposure tests showed mixed results, with the sourdough breads showing relatively suppressed growth of incidentally introduced mold, but not inoculated mold. These results indicate that the lactic acid produced by L. paracasei and L. plantarum was effective at inhibiting expansion of toxic bacteria but had no effect on mold to shelf.