Spray-dried zein capsules with coencapsulated nisin and thymol as antimicrobial delivery system for enhanced antilisterial properties

Food grade antimicrobial delivery systems were studied in this work to enhance the effectiveness of antimicrobials inhibiting the growth of Listeria monocytogenes during storage. Corn zein was used as a carrier biopolymer and nisin and thymol as antimicrobials. Capsules produced by spray drying demonstrated different microstructures and release characteristics of nisin at different usage levels of thymol. Better release profiles were achieved when glycerol was additionally used to prepare capsules. Capsules showing sustained release of significant amounts of both antimicrobials effectively inhibited the growth of L. monocytogenes at pH 6.0 and 30 °C in the growth medium. Capsules were also more effective than free antimicrobials in inhibiting the growth of L. monocytogenes in 2% reduced fat milk at 25 °C. Our work showed that engineered delivery systems have promise to fulfill the antimicrobial effectiveness during shelf life storage of foods to ensure microbiological safety.     

Formation and stabilization of antimicrobial delivery systems based on electrostatic complexes of cationic-non-ionic mixed micelles and anionic polysaccharides

Lauric arginate (LAE) is a cationic surfactant that is of great interest to the food industry because of its strong antimicrobial activity. However, its application within foods and beverages is currently restricted because of its limited solubility in aqueous solutions and its bitter taste, which have been associated with its cationic nature. This study examines whether electrostatic complexes between cationic LAE mixed micelles and anionic polysaccharides could be used to improve LAE functionality. Two types of pectin (high and low methoxyl) were titrated into buffer solutions containing either LAE micelles or LAE/Tween 20 mixed micelles (pH 3.5, 50 mM citrate buffer). The electrical characteristics of the micelles or micelle/pectin complexes were assessed by microelectrophoresis measurements, while their stability to aggregation was evaluated by light scattering measurements. LAE micelle/pectin complexes formed large aggregates that rapidly sedimented. On the other hand, mixed micelle/pectin complexes (1:1 LAE/Tween 20, w/w) were stable to aggregation and formed clear solutions. The electrical charge of mixed micelles changed from +8 to -15 mV when the pectin concentration was increased (0.00-0.05 wt %), indicating an electrostatic interaction between anionic pectin molecules and cationic micelles. Lower concentrations of low methoxyl pectin were required (0.01 wt %) to change the net charge of mixed micelles from positive to negative than high methoxyl pectin (0.025 wt %). Our results suggest that the addition of pectin to mixed LAE/Tween 20 micelles leads to the formation of electrostatic complexes that may be useful as functional ingredients in food and other products.     

Impact of tween 20 hydroperoxides and iron on the oxidation of methyl linoleate and salmon oil dispersions

To determine the role of surfactant hydroperoxides on the oxidative stability of fatty acids, the oxidation of methyl linoleate micelles and salmon oil-in-water emulsions was measured as a function of varying Tween 20 hydroperoxide concentrations. Increasing Tween 20 hydroperoxide concentrations from 3.5 to 14.7 micromol hydroperoxide/g Tween 20 decreased the lag phase of headspace hexanal formation but did not increase the total amount of hexanal formed in methyl linoleate/Tween 20 micelles. In the micelle system, Fe(2+) decreased the lag phase of hexanal formation but increased total hexanal concentrations only in micelles with the highest Tween 20 hydroperoxide concentrations (14.7 micromol hydroperoxide/g surfactant). Increasing Tween 20 surfactant hydroperoxide concentrations also increased the oxidation of salmon oil-in-water emulsions as determined by lipid hydroperoxides and headspace propanal. In both the micelle and emulsion systems, the prooxidant effect of Fe(2+) decreased with increasing Tween 20 hydroperoxide concentrations. These data show that surfactant hydroperoxides such as those in Tween 20 could decrease the oxidative stability of lipids in food emulsions.     

Ability of iron to promote surfactant peroxide decomposition and oxidize alpha-tocopherol.

Peroxides are an important factor in oxidative reactions in foods because their decomposition can result in formation of highly reactive free radicals. Emulsifiers such as the Brijs, Tweens, and lecithin were found to contain 4-35 micromol of peroxides/g of surfactant. Peroxide concentrations in Tween 20 micelles increased in the presence of low iron concentrations but decreased when iron concentrations were high, suggesting that iron was capable of promoting both peroxide formation and decomposition. Oxidation of alpha-tocopherol was observed in micelles high in peroxides (Tween 20) but not in micelles where peroxide concentrations were low (Brij). Transition metals accelerated the oxidation of alpha-tocopherol in Tween 20 micelles, whereas EDTA stabilized alpha-tocopherol in the presence of added Fe(2+). These results suggest that surfactant peroxides could decrease the oxidative stability of food emulsions by acting as a source of free radicals, especially in the presence of transition metals.     

Self-diffusion nuclear magnetic resonance,microstructure transitions,and solubilization capacity of phytosterols and cholesterol in Winsor IV food-grade microemulsions

Microemulsions are of growing interest to the food industry as vehicles for delivering and enhancing solubilization of natural food supplements with nutritional and health benefits. The incorporation of molecular phytosterols, cholesterol-lowering agents, in food products is of great interest to the food industry. In this work is demonstrated the use of water dilutable food-grade microemulsions consisting of ethoxylated sorbitan ester (Tween 60), water, R-(+)-limonene, ethanol, and propylene glycol as vehicles for enhancing the phytosterols solubilization. Phytosterols were solubilized up to 12 times more than the dissolution capacity of the oil [R-(+)-limonene] for the same compounds. The solubilization capacity of phytosterols and cholesterol along a dilution line in a pseudo-ternary phase diagram [on this dilution line the weight ratio of R-(+)-limonene/ethanol/Tween 60 is constant at 1:1:3] was correlated to the microstructure transitions along the dilution line. Structural aspects were studied by self-diffusion NMR spectroscopy. The ability of phytosterols to compete with cholesterol for penetration into bile salt micelles in the gut may be limited to rich aqueous systems (O/W microemulsion).     

Growth Responses,Metal Accumulation and Phytoremoval Capability in Amaranthus Plants Exposed to Nickel Under Hydroponics

Surfactant-enhanced solubilization and subsequent biodegradation of phenanthrene and pyrene from aqueous solutions by Arthrobacter strain Sphe3 was investigated. The results show that growth of Arthrobacter strain Sphe3 was increased upon increase in concentration of Tween 20 and Tween 80. Inhibition of bacterial growth was observed with increasing Triton X-100 concentrations, whereas sodium dodecyl sulfate (SDS) totally inhibited this bacterial growth. Phenanthrene and pyrene solubilization was enhanced in the presence of surfactants and found to be linearly proportional to their concentrations, above the critical micelle concentration (CMC). In addition, Tween 20 and Tween 80 enhanced the biodegradation of phenanthrene and pyrene. The high correlation coefficient (R ²) values obtained at all the concentrations studied, suggest that biodegradation kinetics of both phenanthrene and pyrene in the presence of Tween 20 and Tween 80 follow first-order kinetic equation model. Experimental results suggest that Tween 20 and Tween 80 may have great potential for applications in bioremediation of these polycyclic aromatic hydrocarbon (PAH) compounds using Arthrobacter strain Sphe3.     

Influence of surfactant charge on antimicrobial efficacy of surfactant-stabilized thyme oil nanoemulsions

Thyme oil-in-water nanoemulsions stabilized by a nonionic surfactant (Tween 80, T80) were prepared as potential antimicrobial delivery systems (pH 4). The nanoemulsions were highly unstable to droplet growth and phase separation, which was attributed to Ostwald ripening due to the relatively high water solubility of thyme oil. Ostwald ripening could be inhibited by incorporating ≥75% of corn oil (a hydrophobic material with a low water solubility) into the nanoemulsion droplets. The electrical characteristics of the droplets in the nanoemulsions were varied by incorporating ionic surfactants with different charges after homogenization: a cationic surfactant (lauric arginate, LAE) or an anionic surfactant (sodium dodecyl sulfate, SDS). The antifungal activity of nanoemulsions containing positive, negative, or neutral thymol droplets was then conducted against four strains of acid-resistant spoilage yeasts: Zygosaccharomyces bailli, Saccharomyces cerevisiae, Brettanomyces bruxellensis, and Brettanomyces naardenensis. The antifungal properties of the three surfactants (T80, LAE, SDS) were also tested in the absence of thymol droplets. Both ionic surfactants showed strong antifungal activity in the absence of thymol droplets, but no antimicrobial activity in their presence. This effect was attributed to partitioning of the antimicrobial surfactant molecules between the oil droplet and microbial surfaces, thereby reducing the effective concentration of active surfactants available to act as antimicrobials. This study shows oil droplets may decrease the efficacy of surfactant-based antimicrobials, which has important consequences for formulating effective antimicrobial agents for utilization in emulsion-based food and beverage products.     

The release rate of curcumin from calcium alginate beads regulated by food emulsifiers

Curcumin-loaded alginate beads, which contain different food emulsifiers, have been prepared using CaCl? as the cross-linking agent. The controlled release of the curcumin from the beads was investigated at room temperature. For calcium alginate/Span-80/Tween-80 (A/S/T) formulations, almost all of the curcumin loaded in the beads was released into the medium within about 20 h, and the release rates could be regulated by changing the concentration of both Tween-80 and Span-80. However, for the systems of calcium alginate/Q-12A/F-18A (A/Q/F), about 60% of the curcumin loaded in the beads was released at the end of experiments. The studies of scanning electron microscopy indicated that the microstructure of the walls of beads could significantly vary with the concentration or type of emulsifiers. The Fourier transform infrared spectral measurements confirmed that the interactions between calcium alginate and polyglycerol fatty acid esters were stronger than that between calcium alginate and Tween-80/Span-80. The results of swelling studies demonstrated that the initial rates of water uptake for A/Q/F beads were higher than that for A/S/T beads. Moreover, the data of release rates were fitted by an empirical equation, which showed that the release mechanism of curcumin from the alginate gels varied with the composition of emulsifiers for the A/S/T systems. This work provides an important insight into the effect of food emulsifiers on the release rates of the curcumin from calcium alginate beads and will be helpful for the application of the systems in controlled release of other hydrophobic drug.     

Effect of processing on the displacement of whey proteins: applying the orogenic model to a real system

Atomic force microscopy (AFM) has been used to investigate the displacement of a commercial whey protein system and the behavior as compared to that of beta-lactoglobulin (Mackie, A. R.; Gunning, A. P.; Wilde, P. J.; Morris, V. J. Orogenic displacement of protein from the air-water interface by competitive adsorption. J. Colloid Interface Sci. 1999, 210, 157-166). The whey protein isolate (WPI) was displaced from an air-water interface by the surfactants Tween 20 and Tween 60. Displacement data obtained were compared with data obtained for pure beta-lactoglobulin and have shown that WPI was more resistant to displacement from the air-water interface than native beta-lactoglobulin. This was related to the greater surface elasticity of WPI at higher surface stresses. In the presence of Tween 20, WPI was observed to remain on the interface at surface pressures up to 8 mN/m greater than the surface pressure at which complete displacement of beta-lactoglobulin was observed. Displacement of WPI and beta-lactoglobulin films by the surfactant Tween 60 showed similar results. However, because of the lower surface activity of Tween 60, it was not possible to reach surface tension values similar to those obtained for Tween 20. Despite the lower surface activity of Tween 60, WPI was still observed to be present at the interface at surface pressure values greater than those by which beta-lactoglobulin had been completely displaced.     

Iron-accelerated cumene hydroperoxide decomposition in hexadecane and trilaurin emulsions

Free radicals arising from lipid peroxides accelerate the oxidative deterioration of foods. To elucidate how lipid peroxides impact oxidative reactions in food emulsions, the stability of cumene hydroperoxide was studied in hexadecane or trilaurin emulsions stabilized by anionic (sodium dodecyl sulfate; SDS), nonionic (Tween 20), and cationic (dodecyltrimethylammonium bromide; DTAB) surfactants. Fe(2+) rapidly (within 10 min) decomposed between 10 and 31% of the cumene hydroperoxide in Tween 20- and DTAB-stabilized emulsions at pH 3.0 and 7.0 and in the SDS-stabilized emulsion at pH 7.0 with no further decomposition of peroxides occurring for up to 3 h. In SDS-stabilized emulsions at pH 3.0, Fe(2+) decreased peroxides by 90% after 3 h. Decomposition of peroxides in the absence of added iron and by Fe(3+) was observed only in SDS-stabilized emulsions at pH 3.0. These results suggest that peroxide decomposition by iron redox cycling occurs when iron emulsion droplet interactions are high.     

Size, stability, and entrapment efficiency of phospholipid nanocapsules containing polypeptide antimicrobials

The effect of lipid composition [phosphatidylcholine (PC), phosphatidylglycerol (PG), and cholesterol] on size, stability, and entrapment efficiency of polypeptide antimicrobials in liposomal nanocapsules was investigated. PC, PC/cholesterol (70:30), and PC/PG/cholesterol (50:20:30) liposomes had entrapment efficiencies with calcein of 71, 57, and 54% with particle sizes of 85, 133, and 145 nm, respectively. Co-encapsulation of calcein and nisin resulted in entrapment efficiencies of 63, 54, and 59% with particle sizes of 144, 223, and 167 nm for PC, PC/cholesterol (70:30), and PC/PG/cholesterol (50:20:30), respectively. Co-encapsulation of calcein and lysozyme yielded entrapment efficiencies of 61, 60, and 61% with particle sizes of 161, 162, and 174 nm, respectively. The highest concentration of antimicrobials was encapsulated in 100% PC liposomes. Nisin induced more calcein release compared to lysozyme. Results demonstrate that production and optimization of stable nanoparticulate aqueous dispersions of polypeptide antimicrobials for microbiological stabilization of food products depend on selection of suitable lipid-antimicrobial combinations.     

Recovery of uranium (VI) from solution using preculturedPenicillium BIOMASS

PreculturedPenicillium biomass can accumulate U from solutions of uranyl chloride. A 4 g (fresh weight) fungal mass will remove, over a 1 to 4 h period, between 20 and 30 °C, 75 to 90% of the UO₂-ion from 1 to 10 ppm solutions. Accumulation is more or less the same between pH 5.5 to 7.5, and retains over 2/3 of its efficiency at pH 2.5. Boiling, pasteurization and trichloracetic acid pretreatment do not reduce and may increase fungal efficiency. Preculture with Tween 80 improves efficiency by its effect on formation of small beaded mycelial masses.     

Gastrointestinal Release of β‐Glucan and Pectin Using an In Vitro Method

The release of soluble dietary fiber is a prerequisite for viscous effects and hence beneficial health properties. A simple in vitro method was adapted to follow the release during gastrointestinal digestion, and the percentage of solubilized fiber was measured over time. β‐Glucan from oat bran was mainly released during gastric digestion while the release of pectin from sugar beet fiber continued in the small intestine. Unmilled fractions of sugar beet fiber released more soluble fiber than oat bran flakes, probably due to the porous structure of sugar beet fiber as a result of manufacturing processes, but also due to differences in source. Milling to smaller fiber particles significantly improved releasability (from 20 to 55% released β‐glucan and from 50 to 70% released pectin, respectively, after digestion). When milled fibers were included in individual food matrices, the release was reduced by protein and starch matrices (5% β‐glucan and 35% pectin released, respectively) and slowed by fat (45% β‐glucan and 60% pectin released). This may result in a too low or too late release in the upper small intestine to be able to interfere with macronutrient uptake. The method may be suitable for predicting the gastrointestinal release of soluble dietary fibers from food matrices in the development of healthy food products.     

Tween 80对DDTs污染场地土壤的增溶洗脱效果研究

以苏南某滴滴涕类化合物（DDTs）污染场地土壤为研究对象,进行实验室批量洗脱试验,研究了环境友好型表面活性剂Tween 80对土壤中DDTs的增溶洗脱效果及其影响因素。结果表明,Tween 80显著地增加了DDTs表观溶解度,在临界胶束浓度（CMC）以上对DDTs的增溶曲线呈指数衰减函数关系,DDTs各组分洗脱量顺序为4,4′-DDT〉4,4′-DDD〉2,4′-DDD〉2,4′-DDT。Tween 80的浓度、洗脱次数及土壤吸附作用共同影响其对DDTs的洗脱效果。去离子水能有效去除土壤中残留Tween 80,Tween 80解吸附率最高可达72.66%,大大降低了Tween 80二次污染土壤的风险。Tween 80增溶和去离子水解吸附联合过程对DDTs洗脱效果产生显著的协同作用。10 000 mg·L^-1浓度条件下Tween 80对DDTs的去除率最高为72%,其次为8 000 mg·L^-1 的Tween 80水溶液,去除率为66.72%。采用8 000 mg·L^-1的Tween 80溶液进行土壤洗涤处理,结合其他修复技术,可能会是修复DDTs污染土壤的有效技术方案之一。     

Addition of sugars influences color of oil-in-water emulsions

The influence of glucose, fructose, lactose, and glycerol on the color and appearance of surfactant-stabilized oil-in-water emulsions containing a red dye was investigated. A stabilized (Tween-20) oil-in-water emulsion was diluted into sugar solutions to give a range of oil droplet and sugar concentrations. Tristimulus coordinates (L, a, b) and reflectance spectra were measured using a spectrophotometer. With increasing sugar concentration, reflectance spectra shifted to lower reflectance values. Tristimulus coordinates were reduced by approximately 50% for emulsions containing high concentrations of sugar. Adding fructose to emulsions reduced L, a, b values more significantly than adding glucose, lactose, or glycerol. Tristimulus coordinates remained constant when the temperature was raised from 20 to 80 degrees C. The experimental results were explained in terms of the change of relative refractive index at the water-oil interface. The results have important implications for the food industry as they offer a new means to control and optimize the color of food emulsions.     

Effect of beta-cyclodextrin on aroma release and flavor perception

Binding and release of volatile compounds to and from beta-cyclodextrin were measured in model aqueous systems using static equilibrium headspace and dynamic headspace dilution. Beta-cyclodextrin decreased the static equilibrium headspace for some volatiles (e.g., ethyl octanoate and decanone) due to binding, but dilution studies demonstrated that binding was readily reversible. Dynamic release of hydrophobic volatile compounds was similar to that observed from emulsions. When beta-cyclodextrin was added to fat free yogurt, the release of a commercial lemon flavoring was modified and was similar to release from a regular fat yogurt. Sensory difference testing confirmed the release results. The data demonstrate that beta-cyclodextrin can be used to modify flavor delivery in both model and real systems; the effects in the latter are sensorially significant.     

Interfacial shear rheology of aged and heat-treated beta-lactoglobulin films: displacement by nonionic surfactant

Interfacial shear rheology of adsorbed beta-lactoglobulin films (bulk protein concentration 10(-)(3) wt %) has been studied over the temperature range 20-90 degrees C using a two-dimensional Couette-type viscometer. Effects of the type of interface (air-water, triolein-water, and n-dodecane-water), the pH (2.0, 5.6, 6.0, 7.0, and 9.0), and the extent of the heat treatment have been assessed via measurements of changes in the apparent interfacial shear viscosity and elasticity before and after the addition of increasing amounts of nonionic surfactant Tween 20 (polyoxyethylene sorbitan monolaurate). The highest interfacial viscosities were obtained at the n-dodecane-water interface and the lowest at the air-water interface. Competitive displacement of protein from the interface by Tween 20 was easier at the air-water and n-dodecane-water interfaces as compared to the triolein-water interface. The surface shear viscosity was higher and the displacement by Tween 20 more difficult as the isoelectric point of the protein was approached, which is in agreement with the presence of a more strongly cross-linked protein network at the interface. The effect of heat treatment was dependent on the pH of the aqueous solution. No simple relationship between the surface rheological characteristics and the ease of displacement by Tween 20 could be inferred.     

Aminomethylphosphonic acid, a metabolite of glyphosate, causes injury in glyphosate-treated, glyphosate-resistant soybean

Glyphosate-resistant (GR) soybean [Glycine max (L.) Merr.] was developed by stable integration of a foreign gene that codes insensitive enzyme 5-enolpyruvylshikimate-3-phosphate synthase, an enzyme in the shikimate pathway, the target pathway of glyphosate. Application of glyphosate to GR soybean results in injury under certain conditions. It was hypothesized that if GR soybean is completely resistant to the glyphosate, injury could be caused by a metabolite of glyphosate, aminomethylphosphonic acid (AMPA), a known phytotoxin. Glyphosate and AMPA effects on one- to two-trifoliolate leaf stage (16-18-days old) GR and non-GR soybean were examined in the greenhouse. In GR soybean, a single application of glyphosate-isopropylammonium (1.12-13.44 kg/ha) with 0.5% Tween 20 did not significantly reduce the chlorophyll content of the second trifoliolate leaf at 7 days after treatment (DAT) or the shoot dry weight at 14 DAT compared with Tween 20 alone. A single application of AMPA (0.12-8.0 kg/ha) with 0.5% Tween 20 reduced the chlorophyll content of the second trifoliolate leaf by 0-52% at 4 DAT and reduced shoot fresh weight by 0-42% at 14 DAT in both GR and non-GR soybeans compared with Tween 20 alone. AMPA at 0.12 and 0.50 kg/ha produced injury in GR and non-GR soybean, respectively, similar to that caused by glyphosate-isopropylammonium at 13.44 kg/ha in GR soybean. AMPA levels found in AMPA-treated soybean of both types and in glyphosate-treated GR soybean correlated similarly with phytotoxicity. These results suggest that soybean injury to GR soybean from glyphosate is due to AMPA formed from glyphosate degradation.     

Effects of soil mesofauna and farming management on decomposition of clover litter: a microcosm experiment

The effects of soil mesofauna and different farming systems on decomposition of clover (Trifolium repens) litter were investigated in a laboratory experiment. Microcosms were incubated for 16 weeks with fine and coarse litterbags in soils from three types of management systems: fallow, integrated farming and organic farming, the latter two cropped with wheat. The effects were studied by analysing litter mass loss, C and N content, DOC, nitrate and pH in soil leachate, and CO₂ production, as well as mesofauna. Mesofauna significantly accelerated mass loss and C and N release from clover litter in all three soils. With mesofauna access, at the end of the experiment average clover mass loss was almost twice as high and clover C and N content were 60% lower than without mesofauna. Farming systems influenced the decomposition through affecting both element turnover and mesofauna. Although in the first weeks less N was leached from organic farming than from integrated farming soil, cumulative N leaching did not differ between these soils. However, more than 20% less N was leached from the fallow soil than from the field soils. CO₂ production was highest in fallow soil. Here, mesofauna had no effect on this variable. In soil with integrated farming, mesofauna reduced cumulative CO₂ production by 10% whereas in soil from organic farming it increased CO₂ production by 20%. Our data suggest that differences in C and N turnover in different management systems are strongly mediated by soil mesofauna.     

阴/非表面活性剂对菲污染砂土柱淋洗研究

采用玻璃土柱法比较研究了1000、2000、3000和4000mg·L^-1的阴离子表面活性剂十二烷基苯磺酸钠（SDBS）、非离子表面活性剂聚氧乙烯山梨糖醇酐单油酸酯（Tween80）及不同质量配比的混合表面活性剂（SDBS-Tween80）（S∶T=1∶1、1∶2和1∶4）对砂土中菲的柱淋洗。结果表明,SDBS对菲的淋洗曲线总体上呈现先上升到峰值而后下降的变化规律,且呈锯齿形波动;而Tween80与SDBS-Tween80对菲的淋洗曲线具有相似的规律,即淋出液中菲浓度随表面活性剂淋洗液孔隙体积数增大呈现急剧增大、达到峰值后逐渐降低的趋势。淋洗结束时（菲流出浓度接近于0时）,不同浓度的Tween80和SDBS-Tween80对菲的总去除率均可达90.5%以上,而4000mg·L^-1的SDBS对菲的总去除率则仅为76.4%。此外,随着Tween80或SDBS-Tween80浓度增大,菲浓度峰值增大,开始有菲淋出时,菲浓度峰值以及菲流出浓度接近于0时对应的孔隙体积数均减小。菲浓度峰值与表面活性剂浓度呈正相关,累积孔隙体积数与表面活性剂浓度呈负相关。在淋出液累计孔隙体积数相同时,同种表面活性剂对菲的去除率与表面活性剂浓度呈正相关。