Dimethyl Dicarbonate Research Articles

Treatment of table olives with 1-methylcyclopropene, heat shock, and dimethyl dicarbonate impacts the microbial fermentation profile and composition of the fruit biofilm

In this study, we used an experimental design to assess the influence of 1-methylcyclopropene (1-MCP), a mild heat shock, and dimethyl dicarbonate (DMDC) on microbial evolution in brines and the biofilm composition of Spanish-style and naturally fermented table olives. Data were statistically analyzed using classical and compositional data analysis (CoDA). In the brines, the natural processing style raised the presence of yeast/fungi, while heat shock increased the populations of lactic acid bacteria populations. The interaction among heat shock, natural fermentation, and DMDC favored the survival of Enterobacteriaceae. Concerning biofilms, the metataxonomic analysis showed that the five most frequently detected bacterial genera were Lactiplantibacillus (66.79%), Secundilactobacillus (15.12%), Pediococcus (7.50%), Marinilactibacillus (4.92%), and Enterobacter (3.88%), while most common fungal genera were Saccharomyces (63.13%), Bannoa (11.49%), Candida (8.34%), Wickerhamomyces (4.15%), and Kluyveromyces (2.04%). Treatments also affected microbial diversity in biofilms. Adding DMDC significantly reduced the number of bacterial taxa compared to untreated olives. Additionally, the Spanish-style processing resulted in lower bacterial diversity. In contrast, fungi displayed an opposite trend, with the highest similarity found in naturally processed olives. CoDA revealed that the bacterial genera Marinilactibacillus and Lactiplantibacillus were characteristic of Spanish-style olives, while Secundilactobacillus and Pediococcus were associated with naturally processed olives. For fungi, Saccharomyces was related to both Spanish-style and naturally processed olives. The results indicate that the treatments influenced bacterial and fungal populations in brines and olive biofilms and their relationships. These effects may help modulate/control the microbial evolution during olive fermentation.

Recent advances in physical/chemical methods as alternatives to SO2 for winemaking: Principles, challenges and perspectives

Sulphur dioxide (SO2) is commonly used in the wine industry to prevent oxidation and maintain microbial stability. However, it can harm consumer health, resulting in a growing demand for chemical-free wine. Therefore, reducing or eliminating the addition of SO2 has become a prevalent trend in the wine industry. In recent years, researchers have made significant progress in finding alternative methods to SO2. This review provides the latest research progress on innovative methods proposed to replace SO2 in winemaking. These include dimethyl dicarbonate, silver nanoparticles, lysozyme, chitosan, phenolic compounds, membrane filtration, ultrasound, ultraviolet irradiation, high pressure, and pulsed electric field. However, these individual antimicrobial methods do not possess the same comprehensive antimicrobial and antioxidant properties as SO2. In the proposed strategy, a promising alternative to SO2 could be to combine physical sterilization technologies with antimicrobial substances. In particular, gentle physical techniques such as pulsed electric field in synergy with natural grape polyphenols can maintain the microbiological stability of wine without the introduction of foreign aid substances, while enhancing the wine's antioxidant properties. In conclusion, while replacing SO2 entirely for wine production remains challenging, the combination of physical sterilization technologies and natural antimicrobial substances shows promise as a viable alternative.

Influence of an indigenous yeast, CECA, from the Ningxia wine region of China, on the fungal and bacterial dynamics and function during Cabernet Sauvignon wine fermentation.

Saccharomyces cerevisiae CECA was a potential indigenous Chinese wine yeast that can produce aroma and flavor in Cabernet Sauvignon wines. High-throughput sequencing combined with metabolite analysis was applied to analyze the effects of CECA inoculation on the native microbial community interaction and metabolism during Cabernet Sauvignon wine fermentation. Fermentations were performed with three different inoculant strategies: spontaneous fermentation without inoculation, inoculation with CECA after grape must sterilization, and direct inoculation of CECA. Results showed that the diversity of bacteria (P = 0.033) is more sensitive to CECA inoculation than fungi (P = 0.563). In addition, CECA inoculation altered the species composition of core microorganisms (relative abundance >1%) and the keystone species (accounting for the top 1% of the most important interactions), as well as of the biomarkers (linear discriminant analysis > 3.0, P < 0.05). Furthermore, the inoculation could change the cluster of metabolites, and these differential metabolite sets were correlated with four fungal taxa of Issatchenkia, Issatchenkia orientalis, Saccharomycetales, Saccharomycetes and two bacterial taxa of Pantoea, Tatumella ptyseos, were significantly correlated. Inoculated fermentation also altered the correlation between dominant microorganisms and aroma compounds, giving Cabernet Sauvignon wines more herbal, floral, fruity, and cheesy aromas. Saccharomyces cerevisiae CECA and dimethyl dicarbonate (DMDC) inhibition treatments significantly altered the microbial community structure of Cabernet Sauvignon wines, which in turn affected the microbial-metabolite correlation. These findings will help winemakers to control the microbial dynamics and functions during wine fermentation, and be more widely used in regional typical wine fermentations. © 2024 Society of Chemical Industry.

Influence and metabolomic basis of an indigenous yeast CECA, from Ningxia wine region of China, on the aroma and flavor of Cabernet Sauvignon wines

In this study, three fermentation treatments of spontaneous fermentation (SF), direct inoculation of CECA (YF), and inoculation with CECA after addition of dimethyl dicarbonate (YDF) were carried out. Multivariate statistical analysis approved that CECA inoculation significantly influenced the composition of 141 metabolites (15 volatile organic compounds (VOCs) and 126 non-VOCs), mainly consisting of 36 acids and derivatives and 25 lipids and lipid-like molecules. YF and YDF wines exhibited similar correlations with aroma types, while there were differences in the kinds and number of VOCs. Moreover, CECA-inoculated fermentation was more favorable to the formation of aftertaste-A, umami, sourness, and richness. The KEGG metabolic pathway analysis indicated that the inoculation strategy significantly affected the amino acid metabolism. The antimicrobial treatment effectively enhanced bitterness, astringency, umami and saltiness while reducing acidity. Further studies are needed to assess the effects of antimicrobial treatment on lipid metabolism.

Effects of the Combined Treatment of Trans-2-Hexenal, Ascorbic Acid, and Dimethyl Dicarbonate on the Quality in Fresh-Cut Potatoes (Solanum tuberosum L.) during Storage.

Fresh-cut potatoes (Solanum tuberosum L.) are susceptible to browning and microbial contamination during storage. In this study, the effects of trans-2-hexenal (E2H), ascorbic acid (VC), dimethyl dicarbonate (DMDC), and the combined treatment of E2H, VC, and DMDC on quality deterioration in fresh-cut potatoes were investigated. The response surface methodology (RSM) demonstrated that E2H, VC, and DMDC concentrations of 0.010%, 0.65%, and 240 mg/L, respectively, were the optimum conditions for fresh-cut potato preservation. Further analysis showed that the combined treatment of E2H, VC, and DMDC was the most effective method of reducing quality deterioration in potatoes compared to the control and individual treatments. Furthermore, the combined treatment of E2H, VC, and DMDC could decrease the accumulation of reactive oxygen species (ROS) via improving antioxidant enzyme activities. Meanwhile, energy-metabolism-related enzyme activities and glutamate decarboxylase (GAD) activity were enhanced, while γ-aminobutyric acid transaminase (GABA-T) activity was reduced via the combined treatment of E2H, VC, and DMDC, which contributed to maintaining high energy levels and GABA content in potatoes. These findings suggested that the combined treatment of E2H, VC, and DMDC could protect membrane integrity through enhancing antioxidant capacity, energy levels, and GABA content to maintain quality in fresh-cut potatoes.

Impact of 1-Methylcyclopropene in Combination with Heat Shock and Dimethyl Dicarbonate on the Physicochemical Profiles of Table Olive Fermentations

AbstractTable olives are the most important fermented vegetable in the Mediterranean countries. In a continuous effort to improve the quality of this food, this work applies an experimental design with four variables to study the use of 1-methylcyclopropene (1-MCP, 2.85 µL/L) in combination with a light heat shock (65 °C, 5 min) and dimethyl dicarbonate (DMDC, 83 mg/L), during the processing of Spanish style and natural table olives. Fruits processed in the Spanish style exhibited higher moisture levels, luminance, and combined acidity. On the contrary, natural olives contained more sugars, had a firmer texture, and displayed a greener colour. Our results show that applying 1-MCP, heat shock, and DMDC can positively impact the processing of Spanish style and natural table olives and influence their physicochemical characteristics. Adding DMDC to the initial brine caused colour degradation but lowered the pH. Using 1-MCP with a light heat shock improved the sugar content and luminance of olives and increased the titratable acidity in the brine. Applying 1-MCP to the Spanish style enhanced the luminosity (brightness) and, when combined with DMDC, led to the lowest pH levels. Further research at an industrial scale is necessary to validate these results and study their influence on microorganisms. These treatments could have applications in developing new table olive processing methods that allow for more predictable products.

Potency of Dimethyl Dicarbonate on the Microbial Inhibition Growth Kinetics, and Quality of Passion Fruit (Passiflora edulis) Juice during Refrigerated Storage.

This study aimed to investigate the effectiveness of dimethyl dicarbonate (DMDC) at various concentrations (0-250 ppm) in inhibiting the growth of Escherichia coli TISTR 117 and spoilage microbes in passion fruit juice (PFJ) and its impact on the physicochemical and antioxidant quality of the juice during refrigerated storage. The highest log reduction in the total viable count, yeast/molds and E. coli was attained in PFJ samples with 250 ppm of DMDC (p ≤ 0.05) added. Microbial growth inhibition by DMDC followed the first-order kinetic model with a coefficient of determination (R2) and inhibition constants (k) ranging from 0.98 to 0.99 and 0.022 to 0.042, respectively. DMDC at 0-250 ppm showed an insignificant effect on pH, °Brix, color (L*, a*, b*), ascorbic acid, total phenolic compound (TPC), total flavonoid content, and antioxidant activity (DPPH, FRAP) (p > 0.05). Control (untreated PFJ), DMDC-250 ppm, and pasteurized (15 s at 72 °C) samples were subjected to 27 days of cold storage at 4 °C. A decreasing trend in pH, total soluble solid, ascorbic acid content, DPPH and FRAP values were observed in all the samples during refrigerated storage. However, the DMDC-250 ppm sample showed a better prospect in physicochemical quality changes compared to the pasteurized and untreated control PFJ samples. ΔE values showed marked changes in the control sample than the DMDC-250 ppm and pasteurized samples at 27 days of storage. Additionally, the total viable count and yeast/mold count were augmented during storage, and an estimated shelf-life of the control, DMDC-250 ppm, and pasteurized samples was approximately 3, 24 and 18 days, respectively. In conclusion, DMDC at 250 ppm could ensure microbial safety without affecting the quality attributes of PFJ during 24 days of storage at 4 °C.

Formation of hepatocyte cytoplasmic inclusions and their contribution to methylcarbamate-induced hepatocarcinogenesis in F344 rats.

Methylcarbamate (MC), a reaction product between dimethyl dicarbonate and ammonia or ammonium ion, is a potent hepatocarcinogen in F344 rats. Various genotoxicity tests have shown negative results for MC. Although previous studies have described the effects of MC on the liver, including the formation of characteristic basophilic cytoplasmic inclusions (CIs) in hepatocytes, the toxicological significance of CIs and their involvement in hepatocarcinogenesis remain unclear. In the current study, to elucidate the mechanisms of MC hepatocarcinogenesis, we examined hepatotoxicity and genotoxicity after 4 weeks of administration of MC using gpt delta rats with an F344 genetic background as a reporter gene transgenic animal model. Histopathologically, single-cell necrosis, karyomegaly, and the formation of CIs positive for Feulgen staining were observed in hepatocytes at the carcinogenic dose, demonstrating the hepatotoxicity of MC. CIs were also detected as large micronuclei in liver micronucleus tests but not in the bone marrow, suggesting that MC could cause chromosomal instability specifically in the livers of rats. Reporter gene mutation assays demonstrated that MC did not induce mutagenicity even in the liver. Immunofluorescence analyses revealed that CIs exhibited loss of nuclear envelope integrity, increased heterochromatinization, and accumulation of DNA damage. An increase in liver STING protein levels suggested an effect on the cyclic GMP-AMP synthase/stimulator of interferon genes innate immune pathway. Overall, these data demonstrated the possible occurrence of chromothripsis-like chromosomal rearrangements via CIs. Thus, the formation of CIs could be a crucial event in the early stage of MC-induced hepatocarcinogenesis in F344 rats.

Influence of an indigenous yeast, CECA, from the Ningxia wine region of China, on the yeast community dynamics and aroma of Cabernet Sauvignon wines

Commercial yeasts are normally used in the wine industry to achieve stable and enhanced wine flavors and aromas, but they can lead to a loss of diversity and a peculiar regional wine style. An indigenous commercial wine yeast, CECA, has been isolated from a well-known wine-producing region, Ningxia, China. As CECA is a young commercial yeast, further research into its characteristics is required. In this study, the performance of CECA in Cabernet Sauvignon wine fermentation, three different fermentation treatments, spontaneous without inoculation, inoculated with CECA, and inoculated with CECA after treatment of the grape must with dimethyl dicarbonate, were performed. During fermentation, six species of yeast identified through a culture-dependent method were also identified with a culture-independent method, although the relative abundance differed between the methods. The floral and fruity were confirmed as characteristics of CECA-inoculated wines using headspace solid-phase microextraction-gas chromatography-mass spectrometry and sensory evaluation. This study enables winemakers to better understand an indigenous commercial yeast, make a peculiar aroma for Ningxia wines and promote the reputation of Ningxia region.

Synergistic effect of electrolyzed water generated by sodium chloride combined with dimethyl dicarbonate for inactivation of Listeria monocytogenes on lettuce.

Electrolyzed water (EW) is recognized as an effective way to control and reduce pathogens in vegetables. However, the disinfection efficacy of EW alone is limited. In this work, the bactericidal activity and biofilm removal capability of EW, generated by adding NaCl to a portable EW generator, were investigated with special reference to Listeria monocytogenes. Furthermore, the impact of EW in combination with dimethyl dicarbonate (DMDC) in reducing the microbial load and improving the overall quality of lettuce during refrigerated storage was evaluated. EW with 0.3% NaCl (SEW) had the highest bactericidal activity against L. monocytogenes. The pathogen treated with SEW exhibited lower superoxide dismutase activity and more leakage of proteins and nucleic acids than in the case of EW. Furthermore, the use of SEW resulted in changes in the cell permeability and morphology of L. monocytogenes. A decrease in adhesion and collapse of the biofilm architecture were also observed, indicating that SEW was more effective for inactivating L. monocytogenes cells compared to EW. For untreated lettuce, the populations of the total plate count and inoculated L. monocytogenes decreased by 2.47 and 2.35 log CFU g-1 , respectively, after the combined SEW/DMDC treatment for 3 min. The use of SEW alone or combined with DMDC did not negatively impact the lettuce color values, titratable acid, ascorbic acid and soluble solids compared to the control group. SEW in combination with DMDC can be used as a novel and potentially effective disinfection strategy for ensuring the safety of vegetable consumption. © 2023 Society of Chemical Industry.

Natural glycolipids inhibits certain yeasts and lactic acid bacteria pertinent to the spoilage of shelf stable beverages

The public health concern around artificial preservatives in food and beverage has contributed to the rising demand for clean-label products, which inevitably require changes in formulation and processing of existing products. Natural glycolipids (NG), derived from Dacryopinax spathularia, is a novel naturally derived preservative shown to be highly inhibitory against spoilage yeasts, Gram-positive bacteria, and to a lesser extent molds. The inhibitory effect of NG against major spoilage microorganisms was determined in acidified beverages (iced tea and sparkling beverage containing fruit juice). Three-strain suspensions of yeasts (Saccharomyces cerevisiae, Zygosaccharomyces bailii and Candida parapsilosis), bacteria (Lactiplantibacillus plantarum, Lactococcus lactis and Gluconacetobacter liquefaciens) and fungal spores (Aspergillus brasiliensis, Byssochlamys nivea and Penicillium roqueforti) were inoculated (100 CFU/mL per species) in commercial beverages. NG was added to beverages at low concentrations ranging from 5 to 15 ppm. Additionally, the combination of NG and dimethyl dicarbonate (DMDC) was tested in the still beverage. The efficacies of NG and NG + DMDC were compared to treatment with 250 ppm sodium benzoate (SB) as determined by log reduction after beverage samples were maintained for 12 weeks at ambient temperature. The applied NG concentrations were lethal to lactic acid bacteria (LAB) and yeasts, thus capable of protecting the beverages from microbiological spoilage for 12 weeks; NG was more effective than SB, which resulted in microbial growth comparable to the control (untreated) samples. NG exhibited mildly microstatic properties against acetic acid bacteria (AAB) and fungal spores. While NG + DMDC treatments improved the inhibition of yeasts and bacteria, there was no observable effect on fungal spores. This study demonstrated that NG can be used alone or combined with DMDC to prevent spoilage in beverages maintained at ambient temperature.

Chemical Methods for Microbiological Control of Winemaking: An Overview of Current and Future Applications

Preservation technologies for winemaking have relied mainly on the addition of sulfur dioxide (SO2), in consequence of the large spectrum of action of this compound, linked to the control of undesirable microorganisms and the prevention of oxidative phenomena. However, its potential negative effects on consumer health have addressed the interest of the international research on alternative treatments to substitute or minimize the SO2 content in grape must and wine. This review is aimed at analyzing chemical methods, both traditional and innovative, useful for the microbiological stabilization of wine. After a preliminary description of the antimicrobial and technological properties of SO2, the additive traditionally used during wine production, the effects of the addition (in must and wine) of other compounds officially permitted in winemaking, such as sorbic acid, dimethyl dicarbonate (DMDC), lysozyme and chitosan, are discussed and evaluated. Furthermore, other substances showing antimicrobial properties, for which the use for wine microbiological stabilization is not yet permitted in EU, are investigated. Even if these treatments exhibit a good efficacy, a single compound able to completely replace SO2 is not currently available, but a combination of different procedures might be useful to reduce the sulfite content in wine. Among the strategies proposed, particular interest is directed towards the use of insect-based chitosan as a reliable alternative to SO2, mainly due to its low environmental impact. The production of wines containing low sulfite levels by using pro-environmental practices can meet both the consumers’ expectations, who are even more interested in the healthy traits of foods, and wine-producers’ needs, who are interested in the use of sustainable practices to promote the profile of their brand.

Dimethyl Dicarbonate as a Food Additive Effectively Inhibits Geotrichum citri-aurantii of Citrus.

Dimethyl dicarbonate (DMDC), a food additive, can be added to a variety of foods as a preservative. This study aimed to evaluate the inhibitory effects of DMDC on Geotrichum citri-aurantii in vitro and in vivo, as well as the potential antifungal mechanism. In vitro experiments showed that 250 mg/L DMDC completely inhibited the growth of G. citri-aurantii and significantly inhibited spore germination by 96.33%. The relative conductivity and propidium iodide (PI) staining results showed that DMDC at 250 mg/L increased membrane permeability and damaged membrane integrity. Malondialdehyde (MDA) content and 2, 7-Dichlorodihydrofluorescein diacetate (DCHF-DA) staining determination indicated that DMDC resulted in intracellular reactive oxygen species (ROS) accumulation and lipid peroxidation. Scanning electron microscopy (SEM) analysis found that the mycelia were distorted and the surface collapsed after DMDC treatment. Morphological changes in mitochondria and the appearance of cavities were observed by transmission electron microscopy (TEM). In vivo, 500 mg/L DMDC and G. citri-aurantii were inoculated into the wounds of citrus. After 7 days of inoculation, DMDC significantly reduced the disease incidence and disease diameter of sour rot. The storage experiment showed that DMDC treatment did not affect the appearance and quality of fruits. In addition, we found that DMDC at 500 mg/L significantly increased the activity of citrus defense-related enzymes, including peroxidase (POD) and phenylalanine ammonia-lyase (PAL). Therefore, DMDC could be used as an effective method to control citrus sour rot.

Effects of dimethyl dicarbonate on improving the aroma of melon spirits by inhibiting spoilage microorganisms

Melon is susceptible to spoilage microorganisms and contains heat-sensitive flavor. Therefore, an ideal spoilage inhibitor should be used in the production of melon spirits. The effects of dimethyl decarbonate (DMDC) on the changes in microorganisms and volatiles were systematically investigated during the fermentation of melon juice. More than 70 volatiles were detected, and most were related to fermentation. DMDC markedly inhibited the microorganisms and altered the types and quantities of flavor substances in final spirits. Isobutanol, isovaleraldehyde, acetal, and other undesirable volatiles related to abnormal fermentation were greatly reduced, while desirable volatiles, such as benzaldehyde and 2-heptanone, were enhanced. In particular, the relative contents of nine-carbon atom compounds, which are key flavor substances of melon, were significantly changed. These changes improved the sensory quality by increasing the melon and flower fragrances while decreasing the sour and pomace notes. Furthermore, adding DMDC did not allow methanol to reach exceed safety levels. Novelty impact statement DMDC markedly inhibited the microorganisms during fermentation and altered the types and quantities of flavor substance in final melon spirits. These changes improved the sensory quality of spirits by increasing the melon and flower fragrances and decreasing the sour and pomace notes. DMDC is an ideal spoilage inhibitor that can be used in the production of melon spirits.

Experimental and Thermodynamic Study on new CO2 absorbents

UNIFAC model is a thermodynamic model for predicting activity coefficients based on the group contribution method, which is very important in predicting gas-liquid equilibrium, especially for CO2-absorbent system. In this research, we used UNIFAC model to regress the interaction parameters of -CH2O versus CO2, -CH2O versus -CO3 in CO2-1, 2-Dimethoxyethane and Dimethyl Carbonate-1, 2-Dimethoxyethane system through experimental and literature data, and predicted the increased solubility of CO2 in the absorbents with increased number of ether bonds and carbon chain. Results revealed the Henry's coefficient of CO2 in CO2- Dimethyl Carbonate system is 1.32 and 1.42 times higher than that in CO2-pentane-3-oxy-1,5-diyl dimethyl dicarbonate and CO2- octane-3,6-dioxy-1,8-diyl dimethyl dicarbonate system at 323.15K, respectively. The gas-liquid equilibrium results calculated by UNIFAC model correspond well with experimental results. This study provides a new idea for designing CO2 new absorbent.

Kinetic study of selected microorganisms and quality attributes during cold storage of mango and passion fruit smoothie subjected to dimethyl dicarbonate

The objectives of this research were to study the effect of DMDC (0–250 ppm) on quality and shelf life of mango and passion fruit smoothie during cold storage. The correlation between microbial population (total microorganisms, yeast and mold, E. coli and S. aureus) and DMDC concentration using zero-order kinetic and first-order kinetic was also determined. In addition, the effect of DMDC compared with pasteurization (90 °C, 100 s) on quality of mixed mango and passion fruit smoothie during the cold storage (4 °C) was studied. The results showed that microbial inactivation was best-described by first-order kinetic model due to a higher coefficient of determination (R2). In addition, DMDC did not affect the decreasing trend of total soluble solid, color difference (∆E*) and total phenolic compound as compared to control during the cold storage. DMDC also hindered the increasing trend in microbial population and prevented the loss of antioxidant activity (DPPH and FRAP assays) and total flavonoid content and decreased the PPO activity as compared with the control during the cold storage. In summary, DMDC showed the potential to maintain the quality and to extend the shelf life of mango and passion fruit smoothie during cold storage.

Kinetic study of microbial inhibition by dimethyl dicarbonate and quality attributes of pomegranate juice during cold storage

This research aimed to study the effect of dimethyl dicarbonate (DMDC, 0–250 ppm) on inhibition kinetic of pathogenic and spoilage microorganisms (Escherichia coli, Saccharomyces cerevisiae and Lactobacillus plantarum) and the effect of DMDC and pasteurization on physiochemical properties (total soluble solid, pH, titratable acidity, ascorbic acid, total phenolic content, anthocyanin content and antioxidant activity), microbial counts and sensory attributes of pomegranate juice during cold storage (4 °C). The results showed that inhibition kinetic of all microorganism tested in this study followed the first-order kinetic. Before storage, no significant differences (p > 0.05) were found in total soluble solid, pH, titratable acidity and antioxidant activity among the treatments. During storage, pH, ascorbic acid, total soluble solid, total phenolic content, anthocyanin content and antioxidant activity of all samples tended to decrease and titratable acidity, total plate count and yeast and mold count showed an increasing trend during cold storage at 4 °C. The shelf life of pomegranate juice was extended by DMDC approximately 8 days compared to control. In addition, DMDC did not significantly affect sensory properties of pomegranate juice (p > 0.05). This research could be used as a guideline for the development of DMDC as a non-heat processing to preserve quality with extended shelf life of juices for health-conscious consumer.

Nickel catalyzed hydrosilane reduction of (het)arenecarboxylic acids into aldehydes

Nickel-catalyzed reduction of (het)arenecarboxylic acids with hydrosilanes in the presence of dimethyl dicarbonate as the activator affords the corresponding aldehydes. The role of the activator is the conversion of the acids into their anhydrides undergoing C–O cleavage. The good yields were achieved in case of substrates bearing electron-donating and electron-neutral groups.

Effects of pretreatment with dimethyl dicarbonate on the quality characteristics of fermented Huyou juice and storage stability

Huyou (Citrus grandis (L.) Changshan-huyou) from ChangShan in Zhejiang, China, is one of the most popular fruits cultivated and consumed worldwide. However, there are no reports on improvement of the edible value through fermentation processing using lactic acid bacteria (LAB). In this study, effects of pretreatment of Huyou juice with dimethyl dicarbonate (DMDC) on quality attributes of the product fermented by Lactobacillus plantarum L1 and Lactobacillus fermentum L2 were investigated using a pasteurized Huyou juice as a control group. The results showed that the application of DMDC to a Huyou juice preparation can ensure the microbiological safety, sensory, and nutritional properties of the products. Furthermore, the flavor of Huyou juice was improved, and the total phenolic and total flavonoid contents (TPC and TFC) increased after the fermentation processing. Compared with the fermented pasteurized Huyou juice, the fermented DMDC-sterilized Huyou juice had better color, which was closer to that of the fresh Huyou juice (p > .05). Moreover, the fermented DMDC-sterilized Huyou juice had a better odor and overall acceptability in the sensory evaluation. Various physicochemical parameters, including the viable cell count, pH, L* value, b* value, vitamin C, TPC, and TFC, of the fermented product treated with DMDC were determined during storage at 4°C. The a* and ΔE* values slowly increased. The viability counts of LAB in both fermented pasteurized and DMDC-sterilized Huyou juices were maintained at 7.0 log CFU/ml after 4 weeks of storage at 4°C. These results indicate that DMDC can be a good alternative for pasteurization at the prefermentation stage of Huyou juice. Practical applications This study compared the effects of pasteurization and dimethyl dicarbonate (DMDC) sterilization on the quality and flavor of Huyou juice and the storage quality of fermented Huyou juice. DMDC could be an ideal alternative for pasteurization for the prefermentation stage of Huyou juice and played a positive role in improving the flavor and quality of fermented Huyou juice. At the same time, it also laid a theoretical foundation for the upgrade and transformation of Huyou (Citrus changshanensis) products.

Inactivation kinetic of selected pathogens of coconut water by dimethyl dicarbonate and microbial shelf life during cold storage

This present work shows the potential of dimethyl dicarbonate (DMDC) as a promising approach to ensure quality and safety of coconut water in term of microbial inactivation and minimal changes in quality parameters during cold storage (4°C). Pathogenic strains including Escherichia coli, Staphylococcus aureus, Salmonella Enteritidis, and Listeria monocytogenes were selected for evaluation of inactivation kinetic with DMDC concentration between 0 and 300 ppm. Physico–chemical properties of DMDC-treated samples were analyzed and shelf-life determination was carried out by monitoring total plate count and yeast and mold count during cold storage (4°C). Results showed that microbial inactivation kinetic was best described by first-order kinetic model according to higher R2 in all strains tested. The DMDC-treated sample did not show any major undesirable effect on quality parameters. Therefore, the shelf life of coconut water could be extended by DMDC while quality parameters are still ensured with guaranteed safety. Novelty Impact Statement According to R2, first-order kinetic was chosen over zero-order kinetic for microbial inactivation of coconut water subjected to DMDC. An extended shelf life of coconut water was also obtained after DMDC treatment with minimal changes in quality. Therefore, this approach substantiates to be highly acceptable with respect to pasteurization in the case of coconut water and can be applied to other juices for industrial perspectives.