@article{zhai_pagan-medina_perez-diaz_2023, title={CO2-mediated bloater defect can be induced by the uncontrolled growth of Enterobacteriaceae in cucumber fermentation}, ISSN={["2048-7177"]}, DOI={10.1002/fsn3.3557}, abstractNote={Abstract}, journal={FOOD SCIENCE & NUTRITION}, author={Zhai, Yawen and Pagan-Medina, Christian G. and Perez-Diaz, Ilenys M.}, year={2023}, month={Jul} }
 @article{rothwell_zhai_pagan-medina_perez-diaz_2022, title={Growth of gamma-Proteobacteria in Low Salt Cucumber Fermentation Is Prevented by Lactobacilli and the Cover Brine Ingredients}, ISSN={["2165-0497"]}, DOI={10.1128/spectrum.01031-21}, abstractNote={
            While the abundance of specific ɣ-proteobacteria species varies among vegetable type, several harbor
            Enterobacteriaceae
            and
            Pseudomonadaceae
            that benefit the plant system. It is documented that such bacterial populations decrease in density early in vegetable fermentations.
          }, journal={MICROBIOLOGY SPECTRUM}, author={Rothwell, Madison A. R. and Zhai, Yawen and Pagan-Medina, Christian G. and Perez-Diaz, Ilenys M.}, year={2022}, month={May} }
 @article{zhai_perez-diaz_2021, title={Identification of potential causative agents of the CO2-mediated bloater defect in low salt cucumber fermentation}, volume={344}, ISSN={["1879-3460"]}, DOI={10.1016/j.ijfoodmicro.2021.109115}, abstractNote={Development of bloater defect in cucumber fermentations is the result of carbon dioxide (CO2) production by the indigenous microbiota. The amounts of CO2 needed to cause bloater defect in cucumber fermentations brined with low salt and potential microbial contributors of the gas were identified. The carbonation of acidified cucumbers showed that 28.68 ± 6.04 mM (12%) or higher dissolved CO2 induces bloater defect. The microbiome and biochemistry of cucumber fermentations (n = 9) brined with 25 mM calcium chloride (CaCl2) and 345 mM sodium chloride (NaCl) or 1.06 M NaCl were monitored on day 0, 2, 3, 5, 8, 15 and 21 using culture dependent and independent microbiological techniques and High-Performance Liquid Chromatography. Changes in pH, CO2 concentrations and the incidence of bloater defect were also followed. The enumeration of Enterobacteriaceae on Violet Red Bile Glucose agar plates detected a cell density of 5.2 ± 0.7 log CFU/g on day 2, which declined to undetectable levels by day 8. A metagenomic analysis identified Leuconostocaceae in all fermentations at 10 to 62%. The presence of both bacterial families in fermentations brined with CaCl2 and NaCl coincided with a bloater index of 24.0 ± 10.3 to 58.8 ± 23.9. The prevalence of Lactobacillaceae in a cucumber fermentation brined with NaCl with a bloater index of 41.7 on day 5 suggests a contribution to bloater defect. This study identifies the utilization of sugars and malic acid by the cucumber indigenous Lactobacillaceae, Leuconostocaceae and Enterobacteriaceae as potential contributors to CO2 production during cucumber fermentation and the consequent bloater defect.}, journal={INTERNATIONAL JOURNAL OF FOOD MICROBIOLOGY}, author={Zhai, Yawen and Perez-Diaz, Ilenys M.}, year={2021}, month={Apr} }
 @article{zhai_perez-diaz_2020, title={Contribution of Leuconostocaceae to CO 2-mediated bloater defect in cucumber fermentation *}, volume={91}, ISSN={["1095-9998"]}, DOI={10.1016/j.fm.2020.103536}, abstractNote={Fermented cucumber bloater defect, caused by the accumulation of microbiologically produced carbon dioxide (CO2), creates significant economic losses for the pickling industry. The ability of Leuconostocaceae, indigenous to cucumber, to grow and produce CO2 during a fermentation and cause bloater defect was evaluated. Leuconostocaceae grew and produced over 40% CO2 in cucumber juice medium, used as a model for cucumber fermentation. The inoculation of Leuconostocaceae to 5 Log CFU/g in cucumber fermentations brined with 25 mM calcium chloride and 6 mM potassium sorbate resulted in no significant differences in bloater defect, colony counts from MRS and VRBG agar plates or the fermentation biochemistry; suggesting an inability of the inoculated bacterial species to prevail in the bioconversion. Acidified cucumbers were subjected to a fermentation inoculated with a Leuconostoc lactis starter culture after raising the pH to 5.9 ± 0.4. CO2 was produced in the acidified cucumber fermentations to 13.6 ± 3.5% yielding a bloater index of 21.3 ± 6.4; while 8.6 ± 0.8% CO2 and a bloater index of 5.2 ± 5.9 were observed in the non-inoculated control jars. Together the data collected demonstrate that Leuconostocaceae can produce enough CO2 to contribute to bloater defect, if not outcompeted by the leading lactic acid bacteria in a cucumber fermentation.}, journal={FOOD MICROBIOLOGY}, author={Zhai, Yawen and Perez-Diaz, Ilenys M.}, year={2020}, month={Oct} }
 @misc{zhai_perez-diaz_diaz_2018, title={Viability of commercial cucumber fermentation without nitrogen or air purging}, volume={81}, ISSN={["0924-2244"]}, DOI={10.1016/j.tifs.2018.05.017}, abstractNote={Bloated cucumber defect, resulting from the accumulation of the biologically produced carbon dioxide (CO2) in the fruit, reduces yield and economic gains for the pickling industry worldwide. It was the aim of this review to identify commonalities among effective strategies to reduce bloater defect and determine the theoretical viability of commercial cucumber fermentations without bloater defect and/or purging. This article summarizes the known causes of fermented cucumber bloating defect, including sources of CO2, and the strategies developed to mitigate the production of the carbonic gas such as controlled fermentation, inoculation of selected starter cultures, cover brine acidification and reformulation and the application of air or nitrogen purging. It was understood that microbial activity during fermentation, cucumber tissue respiration, as well as the pressure in the fruits and fermentation tanks, ambient temperature and cover brine composition, impact the levels of dissolved CO2 in the system. Although the biological conversion of oxygen to CO2 reduces the cucumbers internal gas pressure, the dissipation of the gas from the tissue is reduced by brining. Once the gas accumulates in the cucumber tissue in concentrations high enough to displace it, the irreversible formation of hollow cavities or bloaters occurs. Residual CO2 is produced by acid-preserved cucumbers, presumably by tissue respiration, which results in the absence of bloating. Thus, microbial activity seems to contribute most of the CO2 needed for cucumbers to bloat. It is speculated that colonization of the internal cucumber tissue by indigenous microbes, in particular aerobic gram-negative bacteria, results in the localized production of CO2 causing bloating defect early in the fermentation. It is concluded that effective manipulation of the microbiota, reduction of dissolved oxygen levels and the use of adequately selected starter cultures may enable cucumber fermentations of acceptable quality without purging.}, journal={TRENDS IN FOOD SCIENCE & TECHNOLOGY}, author={Zhai, Yawen and Perez-Diaz, Ilenys M. and Diaz, Joscelin T.}, year={2018}, month={Nov}, pages={185–192} }
 @article{zhai_pérez-díaz_diaz_lombardi_connelly_2017, title={Evaluation of the use of malic acid decarboxylase-deficient starter culture in NaCl-free cucumber fermentations to reduce bloater incidence}, volume={124}, ISSN={1364-5072}, url={http://dx.doi.org/10.1111/jam.13625}, DOI={10.1111/jam.13625}, abstractNote={Accumulation of carbon dioxide (CO2) 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 CO2 production and the resulting bloater index in sodium chloride‐free cucumber fermentations brined with CaCl2.}, number={1}, journal={Journal of Applied Microbiology}, publisher={Wiley}, author={Zhai, Y. and Pérez-Díaz, I.M. and Diaz, J.T. and Lombardi, R.L. and Connelly, L.E.}, year={2017}, month={Dec}, pages={197–208} }