An investigation into the formation of fumaric acid in apple juice concentrates

In this study, apples inoculated with pure cultures of Rhizopus stolonifer, Penicillium expansum and Lactobacillus plantartrm were utilised as the raw material to produce apple juice concentrate. The effects of microorganisms and various processing treatments on the fumaric acid, lactic acid and pat ulin contents of apple juice were investigated. R. stolonifer was found to be the most responsible causative agent of fumaric acid and lactic acid. L. plantarum also produced certain amounts of lactic acid, but not as much as R. stolonifer. L. plantarum caused a significant decrease in L-malic acid content indicating the occurrence of malolactic fermentation. During this c omplicated biochemical pathway, a small amount of fumaric acid was also for med by L. plantarum. P. expansum produced only patulin, but did not affect the fumaric acid and lactic acid contents. Fumaric acid contents of the sam ples decreased throughout the processing steps excepting evaporation. The f umaric acid contents of the samples increased just after evaporation depend ing on the heat applied. The patulin and lactic acid contents of the sample s also showed a decreasing trend throughout processing. However, L. plantar um caused a significant increase in lactic acid content just after depectin ization depending on whether the appropriate time-temperature conditions fo r incubation were available during depectinization.