Rate Of pH Increase Research Articles

Microcrystallization Effects in Borosilicate Bioactive Glasses: Controllable Release of Bioactive Elements and In Vitro Degradation Properties.

Borosilicate bioactive glasses exhibit excellent bioactivity and degradation properties; however, they suffer from the rapid release of bioactive elements at the initial stage of their degradation. Excessive local concentrations (such as those of B) can affect cell proliferation. Moreover, the degradation and mineralization ability of these glasses deteriorate at the later stages. Aiming to balance the release of bioactive elements during the whole process, herein, a borosilicate bioactive glass 18SiO2-6Na2O-8K2O-8MgO-22CaO-2P2O5-36B2O3 (mol%) was prepared using the melting method. Further, the effects of microcrystallization on the release of bioactive elements and in vitro degradation were studied. Results show that after heat treatment at temperatures over 620 °C, multiple microcrystalline phases, including Ca2SiO4, CaB2O4, and CaMgB2O5, form in the glass. The glass samples heat-treated within the range of 620-640 °C undergo appropriate devitrification degrees, decelerating the rate of pH increase of the immersion solution during the initial stage in comparison to those treated at lower temperatures. This results in a more continuous release of all bioactive elements and allows better control of the overall degradation. Contrarily, the more extensive devitrification degrees of glass samples heat-treated at higher temperatures reverse the pH increase and degradation trends. Since bone marrow mesenchymal stem cells and mouse embryonic osteoblast cells are pH-sensitive, inducing a suitable degree of devitrification proved to favor cell viability and enhance the mineralization capacity. Thus, different microcrystallization degrees provide new approaches for controlling the degradation and release of bioactive elements, resulting in the simultaneous enhancement of biosafety and bioactivity.

Effect on the Quality of Larimichthys crocea Pretreated with Dual-Frequency Orthogonal Ultrasonic-Assisted Immersion with Different Powers during Refrigerated Storage at 4 °C.

In recent years, ultrasonic pretreatment technology has been widely used in the aquatic product preservation industry. Among these technologies, dual-frequency ultrasonic refrigeration is the most common. However, in practical applications, selecting the frequency is relatively simple, and there has been less research on power selection. In this paper, the specific frequency (up and down 20 kHz, around 40 kHz), using different powers of (a) 200 W, (b) 300 W, and (c) 400 W processing, ultrasonic intermittent mode with 30 s on/30 s off cycle, and an ultrasonic processing time of 10 min was examined; the control group (CK) comprised samples without ultrasonic treatment. The samples were stored at 4 °C and then placed in a Polyethylene (PE) bag. The changes in microbiological parameters, physicochemical indices, and protein indices of the samples were monitored every two days. The results show that 400 W ultrasonic treatment can significantly inhibit the growth of TVC during storage. The rate of increase in pH, TVB-N, and TBA values decreased significantly compared with the other groups. Compared with the CK group, the shelf life of the 400 W treatment group was extended by 6 days. Therefore, the 400 W pretreatment method based on orthogonal double frequency has strong application potential for effectively extending the shelf life of refrigerated large yellow croaker.

Compaction, aeration and addition of mycotoxin contaminated silage alters the fermentation profile, mycotoxin content and aerobic stability of ryegrass (Lolium perenne) silage

This study investigated the effect of compaction, aeration and addition of a naturally mycotoxin contaminated ryegrass silage (MCS) containing 1803 µg/kg DM penicillic acid, on the nutritional value and mycotoxin content after ensiling and subsequent aerobic stability of ryegrass Lolium perenne silage (second-cut, June 2020, UK). Mini silos (30 L) were filled with differential compaction (500 kg FW/m3 and 333 kg FW/m3), aeration by injection of air (1L per 48h for 30d then 1L per 7d) and addition of MCS (1.5 g/kg FW ensiled forage) in a 2×2×2 factorial design. During ensilage, mean CO2% (kg FW) in the aerated silos increased with low compaction. Crude protein (CP) increased and ash decreased with aeration. Mean silage fermentation end products acetic (AA), lactic (LA) and propionic acid (PA) concentrations increased with MCS. PA concentration increased with aeration/low compaction. LA decreased and ethanol increased with low compaction. Mycotoxin profiles differed between the silages on opening and after 14-days incubation in aerobic conditions with disappearance of fusarenon X and penicillic acid and appearance of mycophenolic acid and roquefortine C (318 µg/kg DM and 890 µg/kg DM). Addition of MCS, increased the concentration of penicillic acid on opening with an interaction with aeration (80.6µg/kg DM MCS × aerated, 40.0 µg/kg DM in the MCS × sealed). Aerobic stability was affected by aeration and low compaction with reduced time taken to heat to +5°C and +10°C above ambient temperature, higher rate of increase in pH and higher cumulative temperatures to the first peak temperature. Higher mycotoxin concentration at opening had a similar effect increasing time to heat +5°C and +10°C above ambient temperatures in aerobic conditions. Regression analysis showed predominantly direct relationships between silage fermentation end-product concentrations and aerobic stability. This study revealed interactions between silage bacteria and fungi activity from the concentrations of fermentation end-products and mycotoxins during ensilage and subsequent aerobic spoilage. The results supported current best practice for silage making, promoting conditions for improved preservation and aerobic stability. The addition of MCS had unexpected positive effects. However, factors associated with the MCS benefiting aerobic stability were not determined.

Chitosan edible coating: a potential control of toxic biogenic amines and enhancing the quality and shelf life of chilled tuna filets

Edible films and coatings offer great potential to support sustainable food production by lowering packaging waste, extending product shelf life, and actively preserving food quality. Using edible coatings containing plant extracts with antioxidant and antibacterial characteristics could help to enhance the quality and shelf life of fish products. In this study, the combination effect of chitosan with beetroot, curcumin, and garlic extracts on biogenic amines (BAs) reduction, biochemical quality [pH, thiobarbituric acid index (TBA), trimethylamine (TMA), and total volatile base (TVB)], shelf life and sensory characteristics of tuna filets was investigated over 14 days of refrigerated storage compared to control (uncoated) samples. The results showed that the coated samples experienced a lower increase in BAs levels than the control samples. Among the treated samples, chitosan incorporated with curcumin (CH-C) showed the highest reduction in BAs formation (1.45 – 19.33, 0.81 – 4.45, and 1.04 – 8.14 mg/kg), followed by chitosan with garlic (CH-G) (1.54 – 21.74, 0.83 – 5.77, and 1.08 – 8.84 mg/kg), chitosan with beetroot extract (CH-B) (1.56 – 31.70, 0.84 – 6.79, and 1.07 – 10.82 mg/kg), and chitosan without extract addition (CH) (1.62 – 33.83, 0.71 – 7.82 and 1.12 – 12.66 mg/kg) compared to control samples (1.62 – 59.45, 0.80 – 11.96, and 1.14 – 20.34 mg/kg) for histamine, cadaverine, and putrescine, respectively. In addition, the rate of increase in pH, TBA, TMA, and TVB of all coated treatments was lower than in the control samples. Sensory evaluation results revealed that chitosan-treated samples incorporated with beetroot, garlic, and curcumin extracts showed good quality and acceptability characteristics. Overall, chitosan edible coatings incorporated with beetroot, garlic, and curcumin extracts reduced the formation of biogenic amine, delayed biochemical deterioration, and extended the shelf life of tuna filets. Among the treated samples, CH-C demonstrated a remarkable superiority in all the studied parameters. Therefore, this study provides a promising strategy for the incorporation of active compounds in edible coatings to improve the quality and safety of foods during storage.

Effects of Modified Atmosphere Packaging with Different Gas Ratios on the Quality Changes of Golden Pompano (Trachinotus ovatus) Fillets during Superchilling Storage.

The quality changes of golden pompano fillets in air packaging (AP) and modified atmosphere packaging (MAP) with 30% CO2/70% N2, 50% CO2/50% N2, and 70% CO2/30% N2 were evaluated under superchilling (−3 °C). The results showed that the whiteness of fillets decreased during storage. The rate of pH increase of MAP was significantly slower than in AP groups, in which MAP with 70% CO2/30% N2 effectively suppressed the PH. Interestingly, the hardness decreased on day five following the treatments, followed by a relatively stationary trend. MAP could greatly suppress the increase of total volatile basic nitrogen (TVB-N) contents of fillets compared to fillets packed in AP. All MAP groups of fillets maintained first-grade freshness throughout storage, while the AP samples decreased to second-grade freshness on about the 25th day. MAP with 70% CO2/30% N2 and MAP with 50% CO2/50% N2 had the best results in inhibiting protein degeneration and explanation. Unexpectedly, drip loss of fillets in MAP far exceeded the AP group during storage, which causes sensory discomfort. Anaerobic plate count (APC) of fillets in AP exceeded the consumption limit of 6.7 log CFU/g on day 26 (6.75 log CFU/g on the 26th day), whereas the MAP was still microbiologically acceptable after 30 days of storage (6.43, 6.41, 6.22 log CFU/g, respectively). Considering physicochemical and microbiological parameters, the shelf life of fillets packed in AP was 25 days. MAP treatments could prolong the shelf life of fillets by ~4–5 days compared to AP. Overall, MAP with 70% CO2/30% N2 gas ratio was best for inhibiting the quality deterioration of fillets. Furthermore, principal component analysis (PCA) was performed to evaluate the critical indicators of quality deterioration of the fillets. Two principal components were determined by dimensionality reduction, in which the contribution of the first principal component was centrifugal loss > hardness > TVB-N > APC > CO2 solubility > TBARs > drip loss > pH, which mainly reflected the degree of microbial proliferation, protein hydrolysis, and oxidation. The contribution of the second principal component was pH > TBRAs > drip loss > APC > CO2 solubility > TVB-N > hardness > centrifugal loss, indicating a high correlation between lipid oxidation and microbial proliferation index.

Effect of chitosan coating containing Nepeta pogonosperma extract on shelf life of chicken fillets during chilled storage.

Chicken meat is highly susceptible to microbial and chemical spoilage due to its high moisture and protein content. The use of edible coatings contains herbal extracts with antioxidant and antibacterial properties that help to extend the shelf life of meat products. In this study, the effect of chitosan coating (2%) and Nepeta pogonosperma extract (NPe) (0.2% and 0.6%) and their combination on chemical properties (pH, peroxide value (PV), thiobarbituric acid index (TBARS), total volatile basic nitrogen (TVB‐N)) and microbial (aerobic mesophilic and psychrotrophic microorganisms, lactic acid bacteria, Enterobacteriaceae and Pseudomonas sp.) of chicken fillets were studied over a 12‐day refrigerated storage period compared to the control sample. The results of NPe DPPH radical scavenging activity (DRSA) showed that IC50 and total phenolic contents values were 94.65 μg/ml and 113.53 mg GAE/g extract, respectively. Statistical results showed that the rate of increase in pH, PV, TBARS, and TVB‐N of all coated treatments were lower than control. Microbial analysis results showed a decrease in the growth of different bacteria in chitosan‐treated combined with NPe compared to the control sample during chilled storage. Chicken fillets coated with chitosan and 0.6% NPe displayed a longer shelf life compared to other samples.

MgB2 powders and bioevaluation of their interaction with planktonic microbes, biofilms, and tumor cells

Commercial nanopowders of MgB2 were characterized from the viewpoint of granulometric distribution, structure, microstructure, and pH behavior in water. The powders are very different: a higher amount of the MgB2 phase with a lower tendency for agglomeration determines a higher rate of pH-increase. A higher rate of pH-increase usually produces a stronger antimicrobial activity against Staphylococcus aureus, Enterococcus faecium, Escherichia coli, Pseudomonas aeruginosa, Candida albicans, and Candida parapsilosis reference strains. The variation of the pH-increase rate suggests the possibility of temporo-spatial control of MgB2 bioactivity, although the contribution of other factors should not be neglected. Remarkably, the efficiency of the MgB2 powders is higher against biofilms than on microbes in the planktonic state. Further, our experiments confirm the antimicrobial efficiency of MgB2 in the in vitro tests against 29 methicillin resistant clinical S. aureus isolates and 33 vancomycin resistant E. faecium/faecalis strains, but in this case the biofilms are more resistant than planktonic cells. The MgB2 treatment of infected mice led to a significant decrease of E. coli colonization in liver, spleen and peritoneal liquid and it also caused changes in the intestinal microbiota. The activity of powders on HeLa and HT-29 tumor cell lines was assessed by inverted microscopy, flow cytometry, and evaluation of the cellular cycle. MgB2 inhibits tumor cell growth influencing DNA synthesis (S-phase). The obtained results indicate that the tested powders could provide promising solutions for the development of large-spectrum multifunctional antimicrobial and anti-biofilm agents, and/or for anti-cancer therapies.

The Effects of Cold Plasma Application on Quality and Chemical Spoilage of Pacific White Shrimp (Litopenaeus vannamei) during Refrigerated Storage

ABSTRACTPacific white shrimp (Litopenaeus vannamei) is an important species in aquaculture worldwide. Post-mortem changes during cold storage reduce the quality of shrimp and shorten its shelf life. Cold plasma (CP) was applied for 45, 90, and 150s as T1, T2, and T3, respectively, to fresh harvested shrimp. The biochemical parameters and melanosis were analyzed in comparison to metabisulphite treated (TM) and control during 12 days of refrigerated storage. The results highlighted lower rate of increase in pH, total volatile base nitrogen (TVB-N) content, thiobarbituric acid reactive substances (TBARS), free fatty acid (FFA), peroxide value (PV), and fluorescent compounds (FC) in shrimp exposed to CP and metabisulphite compared to control (P < 0.05). Although CP lowered biochemical changes in T1 and T3 shrimp, T2 was the most effective treatment in reducing undesirable changes and improving quality of shrimp. In all storage periods, melanosis was significantly lower in T2, T3, and TM samples. Results demonstrate that CP exposure effectively decreases relative activity of polyphenol oxidase (PPO) enzyme, and prolonging the exposure to CP for 150 s resulted in 50% reduction in enzyme activity. We conclude that application of CP for 90 s was the most efficient circumstance to extend shelf life of white shrimp during cold storage.

Biochemical, Textural and Microbiological Quality of Squid Stored Under Conventional and Slurry Ice During Onboard Fishing

Careful handling of fish and shellfish onboard at the vessel is of prime importance in order to maintain the freshness. Use of slurry ice for onboard fish storage allows rapid heat transfer as well as reduces damage to the product by conventional ice. In the present investigation, the effect of onboard chilling with conventional ice and slurry ice on the quality of squid was evaluated. Samples stored at different time intervals (7th and 11th day) were collected and analyzed for their biochemical, textural and microbiological quality characteristics. Use of slurry ice, immediately after catch of squid reduced the formation of nitrogenous substances as well as the rate of pH increase during storage. Total volatile base nitrogen, tri methyl amine nitrogen and thio-barbituric acid values were within the acceptable limit in both the samples. Texture analysis showed higher hardness, springiness, gumminess and chewiness values for squid samples stored under slurry ice than the samples stored under conventional ice. Further, squid samples stored under slurry ice exhibited higher values of salt content. Microbiological analysis showed significant difference (p < 0.05) in psychrophilic counts of squid stored under slurry ice than the conventional iced ones.

Relationship of temperature and length of storage on ph of internal contents of chicken table egg in humid tropics

All foods have limited shelf life which vary depending on the food and storage conditions. Table eggs are perishable food and storage temperature is an important factor that affects the shelf life. In tropical countries like Nigeria, eggs are usually preserved under ambient condition due to erratic power supply, which reduces the efficiency of refrigeration system. The aim of the present study was to examine the effects of storage periods, temperature and their relationship on the pH of chicken egg internal properties (yolk, albumen and whole egg). Fresh chicken table eggs were randomly allotted to three treatments of storage temperatures; refrigerator (40C ? 2), laboratory (320c ? 4), and poultry store room (370C ? 4). Eggs were assigned to treatments in a completely randomized design, and each treatment was replicated thrice. The pH was measured daily for each storage temperature in all treatments. Storage temperature and periods had significant (P&lt;0.05) effect on pH of measured parameters. The pH values increased with storage temperature and period of storage. The rate of pH increase was significantly (P&lt;0.05) higher in ambient as compared to refrigerator temperature. In this study, only the refrigerator storage has pH values within the range for fresh table eggs. At storage period above three weeks, pH values increased beyond the range for fresh egg. It is validated that storage temperature and period affected egg shelf life, the rate of freshness reduced with increased temperature, thus, storage beyond three weeks of ambient temperature is not advisable in humid tropics.

PH Control during the Struvite Precipitation Process of Wastewaters

The high concentration of phosphorus and nitrogen in wastewater and sludge could be lowered to a certain level by struvite (MgNH4PO4·6H2O) crystallization. One of the main factors for struvite formation is the solution pH. It can be adjusted by non-reagent carbon (CO2) dioxide stripping through the process of aeration. The intensity of the mass transfer between the air and the supernatant of dewatering sludge obtained from wastewater treatment plant is characterized by the volumetric liquid-side mass transfer coefficient, which can be estimated theoretically. It is found that the rate of pH increase depends strongly on the sparging area of the air distribution system while the air flow rate does not influence considerably the Dissolved Oxygen (DO) level which governs the CO2 stripping process. The theoretical calculated values of the volumetric mass transfer coefficient have been compared with those obtained experimentally. Based on the data obtained, relationships of pH/kLa (mass transfer coefficient) were developed. These correlations serve as a tool for prediction of pH during the struvite precipitation process.

Biodiversity of the Surface Microbial Consortia from Limburger, Reblochon, Livarot, Tilsit, and Gubbeen Cheeses.

Comprehensive collaborative studies from our laboratories reveal the extensive biodiversity of the microflora of the surfaces of smear-ripened cheeses. Two thousand five hundred ninety-seven strains of bacteria and 2,446 strains of yeasts from the surface of the smear-ripened cheeses Limburger, Reblochon, Livarot, Tilsit, and Gubbeen, isolated at three or four times during ripening, were identified; 55 species of bacteria and 30 species of yeast were found. The microfloras of the five cheeses showed many similarities but also many differences and interbatch variation. Very few of the commercial smear microorganisms, deliberately inoculated onto the cheese surface, were reisolated and then mainly from the initial stages of ripening, implying that smear cheese production units must have an adventitious "house" flora. Limburger cheese had the simplest microflora, containing two yeasts, Debaryomyces hansenii and Geotrichum candidum, and two bacteria, Arthrobacter arilaitensis and Brevibacterium aurantiacum. The microflora of Livarot was the most complicated, comprising 10 yeasts and 38 bacteria, including many gram-negative organisms. Reblochon also had a very diverse microflora containing 8 yeasts and 13 bacteria (excluding gram-negative organisms which were not identified), while Gubbeen had 7 yeasts and 18 bacteria and Tilsit had 5 yeasts and 9 bacteria. D. hansenii was by far the dominant yeast, followed in order by G. candidum, Candida catenulata, and Kluyveromyces lactis. B. aurantiacum was the dominant bacterium and was found in every batch of the 5 cheeses. The next most common bacteria, in order, were Staphylococcus saprophyticus, A. arilaitensis, Corynebacterium casei, Corynebacterium variabile, and Microbacterium gubbeenense. S. saprophyticus was mainly found in Gubbeen, and A. arilaitensis was found in all cheeses but not in every batch. C. casei was found in most batches of Reblochon, Livarot, Tilsit, and Gubbeen. C. variabile was found in all batches of Gubbeen and Reblochon but in only one batch of Tilsit and in no batch of Limburger or Livarot. Other bacteria were isolated in low numbers from each of the cheeses, suggesting that each of the 5 cheeses has a unique microflora. In Gubbeen cheese, several different strains of the dominant bacteria were present, as determined by pulsed-field gel electrophoresis, and many of the less common bacteria were present as single clones. The culture-independent method, denaturing gradient gel electrophoresis, resulted in identification of several bacteria which were not found by the culture-dependent (isolation and rep-PCR identification) method. It was thus a useful complementary technique to identify other bacteria in the cheeses. The gross composition, the rate of increase in pH, and the indices of proteolysis were different in most of the cheeses.

Enzymatic pH control for biomimetic deposition of calcium phosphate coatings

The current study examines the enzymatic decomposition of urea into carbon dioxide and ammonia as a means to increase the pH during biomimetic deposition of calcium phospate (CaP) onto implant surfaces. The kinetics of the enzymatically induced pH increase were studied by monitoring pH, calcium concentration and conductivity of the aqueous solutions as a function of time, urease concentration and initial concentrations of calcium and phosphate ions. Cryogenic transmission electron microscopy was used to study the process of homogeneous CaP precipitation in solution, whereas CaP deposition on conventional acid-etched titanium and micropatterned polystyrene (PS) surfaces was studied using scanning electron microscopy. The data presented in this study confirm that the substrate–enzyme combination urea–urease offers strong control over the rate of pH increase by varying the concentrations of precursor salts and urease. Formation of biomimetic CaP coatings was shown to proceed via formation of ionic polymeric assemblies of prenucleation complexes. The process of deposition and corresponding coating morphology was strongly dependent on the concentration of calcium, phosphate and urease. Finally, it was shown that the substrate–enzyme combination urea–urease allowed for spatial distribution of CaP crystals along the grooves of micropatterned PS surfaces at low concentrations of calcium, phosphate and urease, stressing the sensitivity of the presented method.

Mechanisms of pH change in wood ant (Formica polyctena) nests

Abstract We conducted a study to determine why the pH of wood ant nest materials is typically higher than that of the surrounding forest soil. An experiment with litter bags demonstrated that the pH of litter increased significantly (after only 7 months) in ant nests. Because the food that foraging ants bring into the nest contains easily decomposed carbohydrates and basic cations (largely in the form of honeydew and prey) that can cause increases in pH, we then estimated the amount of this influ of basic cations and easily decomposed carbohydrates. Based on these estimates, we conducted a second experiment to determine whether addition of field-determined quantities of an easily decomposed carbohydrate (glucose) or a basic cation (Ca2+) would increase the pH of the litter in artificial ant nests in the forest. Both glucose and Ca2+ additions significantly increased the pH of the litter but the increase was greater with Ca2+. The rate of pH increase in the artificial nests was similar to the rate of increase in natural nests. According to our study, ants collect substantial amounts of mineral-enriched materials in this ecosystem, which collectively increase the pH of nest material.

Synthesis of Zn2SiO4:Mn2+ by homogeneous precipitation using propylene glycol-modified silane

Examining the effects of temperature and pH on the hydrolysis of propylene glycol-modified silane (PGMS), which is miscible with water in any ratio, revealed that the hydrolysis progressed very slowly at pH < 4 and room temperature, but was accelerated at higher pH and/or temperature. This study is the first report of the successful synthesis by homogeneous precipitation of Zn2SiO4:Mn2+ phosphor by harnessing the solubility of PGMS in water and its controllable hydrolysis characteristics. Variation of the synthetic conditions showed that both the rate of pH increase and the pH at the time of heating the mixed solution of PGMS, Zn2+, and Mn2+ ions were the most important factors in obtaining the Zn2SiO4 phase. Zn2SiO4:Mn2+ synthesized by homogeneous precipitation exhibited a higher fluorescence intensity than that of samples synthesized using the traditional solid-state reaction method. This was probably because Mn2+, which is an activator, was dispersed more uniformly in the Zn2SiO4 host.

Retardation of quality changes of Pacific white shrimp by green tea extract treatment and modified atmosphere packaging during refrigerated storage

The effect of modified atmosphere packaging (MAP) on the quality changes of Pacific white shrimp (Litopenaeus vannamei) treated with or without green tea extract (1g/L; GTE) in combination with or without ascorbic acid (0.05g/L; AA) during refrigerated storage of 10days was investigated. Shrimp without treatment stored under MAP had lowered psychrotrophic bacteria, enterobacteriaceae and H(2)S-producing bacteria count (P<0.05) but similar lactic acid bacteria count (P>0.05), in comparison with shrimp stored in air (control). The coincidental lowered rate of increase in pH, total volatile base (TVB) content and thiobarbituric acid reactive substances (TBARS) were obtained in shrimp stored under MAP (P<0.05). However, MAP slightly lowered melanosis formation and improved likeness score to some extent. When shrimp were treated with GTE and stored under MAP, the lower microbiological and chemical changes as well as the lowest melanosis formation were observed, compared to shrimp kept under MAP without treatment and the control (P<0.05). GTE treatment in combination with MAP could retard chemical changes and melanosis formation, regardless of AA incorporation (P>0.05). Nevertheless, GTE in combination with AA had higher inhibition on microbial growth and yielded the shrimp with higher likeness, compared with the other treatments (P<0.05). Therefore, shrimp treated with GTE in combination with AA prior to MAP had the lowest losses in quality during refrigerated storage.

Effects of chitosan coating and storage with dry ice on the freshness and quality of eggs

To develop a method that can maintain egg freshness during practical storage conditions, eggs were coated with chitosan and stored with or without dry ice. The physicochemical and microbiological qualities of eggs were evaluated during 14 d of storage at 4 and 23°C without dry ice and at 23°C with dry ice. The combination of chitosan coating and dry ice significantly inhibited a Haugh unit decrease during storage at 23 °C. No difference in functional properties, such as foaming ability, foam stability, and viscosity, among treatments was observed, but chitosan coating and storage with dry ice decreased the rate of pH increase and moisture loss in albumen at d 7 and 14. The eggs treated with chitosan coating and storage with dry ice had a significantly lower number of Salmonella Typhimurium inoculated on the egg surface than did control eggs during storage at 23°C. Results revealed that the combination of chitosan coating and storage with dry ice limited the moisture loss, CO(2) emission, and pH increase, which helped maintaining the freshness of eggs. Microbial growth was also inhibited during storage at 23°C.

Experimental approach of CO 2 biomineralization in deep saline aquifers

We describe an experimental system including monitoring of temperature, pressure, pH, oxidation reduction potential and optical density at 600 nm, designed for studying the role of microorganisms on the geological sequestration of CO 2 and its transformation into solid carbonate phases. Measurements were performed in an artificial ground water (AGW) supplemented with urea (2 g.l − 1 ) and equilibrated at controlled temperatures with a gaseous phase before bacterial inoculation. We used the ureolytic strain Bacillus pasteurii as a model carbonate precipitating bacteria and showed that it can successfully promote strong pH increases by ureolysis in the AGW equilibrated with CO 2 pressures of up to 1 bar. Increasing salinities (5.8, 13.5 and 35.0 g.l − 1 ) have a positive effect on the rate of pH increase, whereas the effect of increasing temperatures (30, 35 and 38 °C) is less important. Calcium is also shown to have a specific positive influence on the rate of ureolysis. The number of viable cells present in solution decreases greatly during the carbonate precipitation event but the population partially recovers once precipitation is over.

Evaluation of antifungal activity of food additives against soilborne phytopathogenic fungi

The efficacy of eight food additives as possible alternatives to synthetic fungicides for the control of soilborne pathogens, Fusarium oxysporum f. sp. melonis, Macrophomina phaseolina, Rhizoctonia solani, and Sclerotinia sclerotiorum was evaluated in this study. A preliminary selection of food additives was performed through in vitro tests. The ED50, minimum inhibition concentration (MIC), and minimum fungicidal concentration (MFC) values showed that ammonium bicarbonate and potassium sorbate were more toxic to soilborne pathogens compared to other food additives with few exceptions and, therefore selected for further testing in soil. The inhibitory and fungistatic efficacy potassium sorbate were higher than that of ammonium bicarbonate in in vitro tests. Potassium sorbate completely inhibited F. oxysporum f. sp. melonis, M. phaseolina, and R. solani at 0.6% in soil tests. In contrast ammonium bicarbonate at 0.6% was inferior compared to potassium sorbate. Ammonium bicarbonate achieved to control all fungi at 2% that is the highest concentration used in this study. Potassium sorbate showed higher toxicity to all fungi compared to ammonium bicarbonate in soil tests. Both ammonium bicarbonate and potassium sorbate increased the pH of soil. The rate of pH increase was higher in ammonium bicarbonate.

Root Substrate pH, Electrical Conductivity, and Macroelement Concentration of Sphagnum Peat-based Substrates Amended with Parboiled Fresh Rice Hulls or Perlite

Substrates were formulated by blending parboiled fresh rice (Oryza sativa) hulls (PBH) or perlite with sphagnum peat (peat) to produce root substrates (substrates) that contained 20%, 30%, 40%, 50%, or 60% (by volume) PBH or perlite with the remainder being peat. After 0 (initial mixing), 4, or 8 weeks in a greenhouse environment, samples were taken and pH, electrical conductivity (EC), nitrate (NO3−), ammonium (NH4+), phosphorus (P), and potassium (K) were determined. As the amount of PBH or perlite in the substrate was increased, the pH increased. After 0 and 8 weeks, the pH of substrates containing up to 30% PBH or perlite had a similar pH. However, the rate of pH increase at these sampling times was higher than that of perlite so that substrates containing 40% or more PBH had a higher pH than equivalent perlite-containing substrates. At the week 4 sampling period, all substrates containing PBH had a higher pH than equivalent perlite-containing substrates. For all sampling times, the difference in pH between equivalent PBH and perlite-containing substrates was not high enough to be of practical significance. For all sampling times, EC increased as the amount of perlite was increased. Depending upon sampling time, the EC decreased or remained unchanged as the amount of PBH was increased. For all sampling times and substrates, EC was within acceptable ranges for unused substrates. Substrates containing PBH had higher NO3− levels than equivalent perlite-containing substrates. The NH4+ level of the substrates decreased as the amount of PBH or perlite was increased. The levels of NO3− and NH4+ were within acceptable ranges for unused substrates. Substrate P and K increased as the amount of PBH in the substrate was increased, but the concentration of P and K remained unchanged or decreased as the amount of perlite was increased. None of the differences between equivalent PBH and perlite-containing substrates was high enough to be problematic with respect to crop production and all of the chemical parameters were within acceptable ranges for unused root substrates.