Inactivation efficacy of plasma-activated water: influence of plasma treatment time,exposure time and bacterial species

This study aimed to evaluate the influence of plasma treatment time, bacterial exposure time to PAW and bacterial species on the inactivation efficacy of plasma-activated water (PAW), with additional investigation of the inactivation mechanisms of PAW. Six bacterial species, including Listeria innocua, Staphyloccus aureus, Escherichia coli, Pseudomonas fluorescens, Shewanella putrefaciens and Aeromonas hydrophila were selected as the representative bacteria. The initial bacterial concentration was around 7 log CFU ml⁻¹ after mixing with PAW, and the inactivation efficacy was measured after different exposure times during the 4 °C storage. Scanning electron microscopy (SEM) images of the bacteria after PAW treatment were carried out to inspect the cell structure damage, and physicochemical properties of PAW, including pH, conductivity and long-living reactive species of H₂O₂, , and , were examined. The results showed that the inactivation efficacy of PAW was positively correlated with plasma treatment time and bacterial exposure time, and for the species examined in this study, the Gram-negative species were more sensitive to PAW than the Gram-positive species. Cell structure damage, including shrinkage, distortion, or holes, was observed after PAW treatment. The pH of PAW was acidified to 2.5–2.9, and conductivity was significantly increased to 518.0 μs cm⁻¹. and H₂O₂ were reduced during the 48 h storage, while an increased concentration was observed for . This study demonstrated that the processing parameters of plasma treatment time, exposure time and characteristics of bacteria can significantly affect the inactivation efficacy of PAW.     

Mechanisms of molecular and structural interactions between lentil and quinoa proteins in aqueous solutions induced by pH recycling

There has been a growing interest in plant proteins due to their beneficial health effects, low cost and variety of applications in food industries. The low solubility of lentil proteins (LPs) is one of the significant factors that limit their use in food applications. Quinoa proteins (QPs), which have high water solubility, were combined with LPs at pH 12 to generate LP-QP complexes to generate pH-based soluble protein compounds. The LP-QP complexes demonstrated a large surface charge with an increase solubilisation of the protein complexes by more than 85%, together with resistance to protein aggregation. The combination of LPs to QPs led to a significant increase (P < 0.05) in unique tertiary and secondary protein structures as determined by the protein–protein interaction (PPI) technique involving pH recycling. Interactions between LPs and QPs affected the surface morphology of the protein complexes formed. Electrostatic interactions, hydrophobic forces and hydrogen bonding were indicated to play key roles in the PPIs. The capacity of pH cycling to illustrate the above protein interactions shows that this is a robust approach for assessing the emulsion and foaming properties of food proteins.     

橄榄油与椰子油混油基对类蛋黄酱乳液流变及冻融稳定性的影响

以类蛋黄酱体系为研究对象，运用Turbiscan、流变仪、粒度仪、显微镜研究在pH 3条件下橄榄油与椰子油不同比例复配（10∶ 0、9∶ 1、8∶ 2、7∶ 3）的混油基对于乳清分离蛋白-蛋黄卵磷脂稳定的乳液体系流变性质及冻融稳定性的影响。结果表明：随着椰子油比例增加，乳液黏度增加，弹性模量增加，橄榄油与椰子油质量比7∶ 3复配混油基制得的乳液具有最大的黏度和最高的弹性模量；所有乳液在4~40 ℃弹性模量下降，说明乳液在贮存、冷藏运输过程中内部结构完整，乳液具有良好的稳定性;蛋黄卵磷脂能够提高含椰子油（饱和脂肪酸含量高）乳液的冻融稳定性，并且椰子油比例越大（饱和程度越高），冻融稳定性提高效果越好;乳液冻融稳定性从高到低依次为橄榄油与椰子油质量比为7∶ 3>8∶ 2>9∶ 1>10∶ 0。     

Changes of the cell surface hydrophobicity of Lactobacillus acidophilus La‐5 in response to pH,temperature and inulin

The main topic of this study was to study how cell surface hydrophobicity (CSH) could change in response to pH, temperature and inulin; Lactobacillus acidophilus La‐5 was used as a model microorganism. pH, temperature, inulin and incubation time (exposure to prebiotic or incubation at pH 4.0 and 9.0) were combined through a full factorial design and a Central Composite Design; the results were analysed using a multifactorial anova (first step) and a stepwise regression (second step). Temperature and pH significantly affected CSH: an increase in the temperature determined a significant increase in CSH, whereas the correlation pH vs. CSH was negative, as an increase in pH caused a significant decrease in CSH. Inulin played a significant role, but its effect could be influenced by temperature, pH and exposure time. This study is the first approach on the effects of some environmental factors on CSH and suggests that the culturing conditions and/or the exposure to some prebiotics could modify it with positive or negative effects.     

Decay of Ozone in Water: A Review

Scientific publications on ozone decay kinetics in water report very wide result variations, depending on a multiplicity of factors, such as ozone concentration, pH, temperature, alkalinity, fluid-dynamic conditions, presence of UV radiations, and concentration of organic and inorganic carbon. This paper intends to provide an engineering-oriented review that summarizes and compares the main results reported in the recent literature so that the condensed information can guide the reader in getting operational indications to assist applications and research.     

Effect of dextran glycation on nanofibril assembly of soya β‐conglycinin at pH 2.0 and the pH stability of nanofibrils

In this study, we investigated the effects of dextran glycation on soya β‐conglycinin self‐assembly into nanofibrils at 85 °C and pH 2.0, as well as their stability at pH 2.0–10.0. Although the hydrolysis rate of β‐conglycinin decreased, glycation significantly increased the structural change rate in the initial stage of nanofibril formation and the growth of nanofibril. It is suggested that the glycation of three subunits (α′, α, β) in β‐conglycinin may promote fibril assembly because the extension regions of α′ and α subunits play an important role in affecting the rate of structural changes in fibril formation. At neutral pH, conjugate nanofibrils are highly dispersible and transparent and remained greater structural stability compared with mixture. The improvement stability of conjugate nanofibrils may be contributed to dextran which provides some steric hindrance to prevent the aggregation of nanofibrils; this would also facilitate the application of soya β‐conglycinin nanofibrils in food industry.     

Beet tissue ensiling: An alternative for long-term storage of sugars in industrial beets for nonfood use

Industrial beets have significant potential to compete against corn grain as an important source of sugars for nonfood industrial processes including microbial bioconversions. However, dependable, long-term storage techniques are necessary to extend processing campaigns and meet increasingly-important industry requirements such as carbon footprint reductions. This work evaluated the potential of industrial-beet tissue ensiling as an alternative for long-term sugar storage. Ground industrial-beet tissue was ensiled for 8 wk at 23 °C and various combinations of pH, moisture content (MC), and sugar:solids (SSR). The pH, MC, and SSR values ranged from 2.0 to 6.8, 50%–85%, and 38%–76%, respectively, according to a central composite rotatable design. Response surface methodology was used to model and illustrate effects of parameter combinations on beet sugar retention. MC and pH had statistically significant effects on sugar retention in beet tissue silage, whereas SSR had no significant effect. Only some combinations of pH ≤ 4.0 and MC ≤ 67.5% enabled the highest sugar retentions in ensiled tissue (≥ 90%). Moreover, tissue ensiled at pH ≤ 3.0 and MC ≤ 67.5% showed increases of ≤ 7% over initial sugars after 3 d of ensiling, suggesting that highly acidic conditions may partially hydrolyze beet tissue cellulose and/or hemicellulose during storage. In contrast, tissue ensiled at some combinations of pH < 6.5 and MC > 67.5% only achieved sugar retentions of < 30% at 8 wk. Sulfuric acid cost estimates (on a dry-sugar basis) to achieve effective pH (2.0–4.0) for sugar retentions ≥ 90% range from $4.9 Mg⁻¹ to $18.6 Mg⁻¹.     

Factors that influence the performance of two-chamber microbial fuel cell

The two-chamber microbial fuel cell (MFC) was operated in batch mode, using acclimated hydrogen-producing mixed bacteria as the anodic inoculum, artificial sucrose wastewater as the substrate (sucrose concentration 10.0 g/L). The performance of the MFC was analyzed at different anodic pH microenvironments, such as the initial pH of the anolyte of 8.57, 7.3, 7.0 and 6.0, respectively, while anodic pH-controlled of 7.3 and 7.0. It showed that the best performance was obtained when the MFC was carried out at anodic pH-controlled of 7.3. Taking the interaction of factors into consideration, we adopted response surface methodology (RSM) to investigate the effects of sucrose concentration, operating temperature and ferrous sulfate concentration on the performance of MFC. The optimum condition for maximum output voltage of the two-chamber MFC (external resistance 1000 Ω) was thus obtained.     

Preparation and properties of novel pH‐sensitive core−shell microspheres for enhanced oil recovery

A novel pH‐sensitive core?shell microsphere was synthesized by growing sodium acrylate as a shell on crosslinked polyacrylamide particles as the core by surface‐initiated atom transfer radical polymerization. The structures and characteristics of the microspheres were confirmed by Fourier transform infrared spectroscopy, ¹H NMR spectroscopy, SEM, transmission electron microscopy and AFM. The viscosity and size of the microspheres in response to changes in pH value were also investigated. As a kind of potential profile control and flooding agent, the performances of permeability reduction and enhanced oil recovery were studied in designed experiments. © 2017 Society of Chemical Industry     

Evaluation of pH‐treated fish sarcoplasmic proteins on rheological properties of fish myofibrillar protein mediated by microbial transglutaminase

Fish sarcoplasmic protein (SP) could be exploited in the water‐holding agent for fish protein gels, except that the gel strength is reduced. The adjustment of pH could modify protein interactions to overcome the inferior effect. Fish SP solutions were adjusted to pH 3 or 12, neutralised to pH 7 and lyophilised to be pH‐treated SPs. These SPs along with lyophilised untreated SP (Normal SP) were incorporated into fish myofibrillar protein (MP) with microbial transglutaminase (MTG). The denaturation temperature (T_d) of MP mixed with normal SP was 66 °C with the lowest shear stress value. The denaturation of MP mixed with pH‐treated SP reduced to be 57 °C, resulting in increased shear stress. The cooking loss of MP gel was reduced by adding pH‐treated SPs, while the breaking forces were similar to control. The result indicated that pH‐treated SPs could be used to reduce cooking loss of MTG‐mediated MP gels without affecting the gelling properties.