Location: Food Science ResearchTitle: Evaluation of the use of malic acid decarboxylase-deficient starter culture in NaCl-free cucumber fermentations to reduce bloater incidence
|ZHAI, YAWEN - North Carolina State University|
|Perez Diaz, Ilenys|
|DIAZ, JOSCELIN - North Carolina State University|
|LOMBARDI, RACHEL - North Carolina State University|
|CONNELLY, LAUREN - North Carolina State University|
Submitted to: Journal of Applied Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/25/2017
Publication Date: 1/1/2018
Citation: Zhai, Y., Perez Diaz, I.M., Diaz, J., Lombardi, R.L., Connelly, L.E. 2018. Evaluation of the use of malic acid decarboxylase-deficient starter culture in NaCl-free cucumber fermentations to reduce bloater incidence. Journal of Applied Microbiology. 124(1):197-208. https://doi.org/10.1111/jam.13625.
Interpretive Summary: Efforts to improve/optimize low salt cucumber fermentations to reduce formation of hollow cavities in the finished preserve are underway. The impact of using unique starter cultures for such fermentations derived from Lactobacillus plantarum and the application of fermentation cover brine reformulation for NaCl-free cucumber preservation was studied. This publication discusses the results of such efforts and the optimization strategies currently under consideration. Essentially it was learned that the starter culture of choice needs to outcompete the natural microbiota to make an impact in the reduction of the hollow cavity formation defect. A combination of high levels of a dominant starter culture with cover brine acidification was found to aid in minimizing the defect, but insufficient to eradicate it.
Technical Abstract: AIMS: Accumulation of carbon dioxide in cucumber fermentations is known to cause hollow cavities inside whole fruits or bloaters, conducive to economic losses for the pickling industry. This study focused on evaluating the use of a malic acid decarboxylase (MDC)-deficient starter culture to minimize carbon dioxide production and the resulting bloater index in sodium chloride-free cucumber fermentations brined with calcium chloride. METHODS AND RESULTS: Attempts to isolate autochthonous MDC-deficient starter cultures from commercial fermentations, using the MD medium for screening, were unsuccessful. The utilization of allochthonous MDC-deficient starter cultures resulted in incomplete utilization of sugars and delayed fermentations. Acidified fermentations were considered, to suppress the indigenous microbiota and favour proliferation of the allochthonous MDC-deficient Lactobacillus plantarum starter cultures. Inoculation of acidified fermentations with L. plantarum alone or in combination with Lactobacillus brevis minimally improved the conversion of sugars. However, inoculation of the pure allochthonous MDC-deficient starter culture to 10^7 CFU per ml in acidified fermentations resulted in a reduced bloater index as compared to wild fermentations and those inoculated with the mixed starter culture. CONCLUSIONS: Although use of an allochthonous MDC-deficient starter culture reduces bloater index in acidified cucumber fermentations brined with calcium chloride, an incomplete conversion of sugars is observed. SIGNIFICANCE AND IMPACT OF THE STUDY: Economical losses due to the incidence of bloaters in commercial cucumber fermentations brined with calcium chloride may be reduced utilizing a starter culture to high cell density.