Concurrent phase separation and gelation in mixed oat β-glucans/sodium caseinate and oat β-glucans/pullulan aqueous dispersions

The phase separation behavior of mixed oat β-glucans/sodium caseinate and oat β-glucans/pullulan aqueous dispersions at 20 °C has been studied. The concentration of β-glucans required for induction of phase separation and the physical state of the separated phases, as revealed by visual observations and dynamic rheometry, depended on the molecular weight of β-glucans and the initial polymeric composition. For β-glucans with apparent molecular weights (M_w) 35 and 65 × 10³ the β-glucan concentration at which thermodynamic incompatibility occurred decreased from about 2–2.5% (w/w) at low concentrations (∼0.2%) of sodium caseinate or pullulan to about 1–1.5% (w/w) β-glucans at high levels (up to 7.5% w/w) of the second biopolymer; these bi-phasic systems consisted of an upper liquid phase and a lower gel-like phase. For β-glucans with M_w of 110 × 10³, a bi-phasic system with two liquid phases appeared above a certain β-glucan concentration, which decreased from approximately 4% to 1% (w/w) with increasing sodium caseinate levels in the range of 0.2–7.5% (w/w). With further increase in β-glucan concentration, the lower phase turned into a gel, and at even higher β-glucan concentrations, the polymer demixing process was ‘arrested’ by chain aggregation events, leading to a macroscopically single gel phase. Generally, the aggregation of β-glucans seemed to interfere with the phase separation phenomenon resulting in an increase of β-glucan concentration in the lower phase between 5% and 110% and only a slight increase of sodium caseinate or pullulan concentration in the upper phase (<10%), due to kinetic entrapment of the polymeric components into a highly viscous medium.     

Effects of reaction mixture and other components on the determination of the equilibrium and rate constants of the hydration reactions of anthocyanins

The equilibrium and rate constants of the hydration and deprotonation reactions of anthocyanins show how their color intensity changes with pH. In the cases of several anthocyanins, the constants for each obtained by several methods are different. In an effort to resolve these discrepancies, we have examined the effects of several components of the pH-jump experiments on the values of the constants. Storage of the buffers to be used in pH-jump experiments in Pyrex or borosilicate glass bottles results in increasing Al³⁺ concentration in the buffers over several weeks. When these buffers are used, the anthocyanins with two OH groups on the B ring complex with the Al³⁺ which leads to major changes in their spectra, in the equilibrium position, and in the apparent first-order rate constant. Thus, constants determined on the same anthocyanin using the same buffers stored in glass bottles may be different at different times. During the reduction of the experimental data to the rate and equilibrium constants, two divergences from the expected behavior were found. In the calculation K_a + K_h for the anthocyanin acylated with 4-hydroxy-3,5-dimethoxycinnamic acid (6-O-(4-hydroxy-3,5-dimethoxycinnamoyl)-β-d-glucopyranosyl-(1 → 6)-[β-d-xylopyranosyl-(1 → 2)]-β-d-galactopyranosyl-(1 → O³)-cyanidin), the plotted points appear to fit two straight lines, intersecting at an equilibrium pH near pH 4. In the calculation which leads to the individual constants of both anthocyanins examined here, the points below an equilibrium pH of pH 4 curve upward from the line that describes the points from an equilibrium pH above 4. Differences in the composition of solutions used in pH-jump experiments examined here, include (1) the addition of phosphate to the acetate buffer, (2) the presence of 0.5 M NaCl, and (3) the solution of the anthocyanin in either 0.1 N HCl or 0.1 N HOAc. These changes gave differences that were statistically significant in some of the constants for each of the two anthocyanins examined. The constants were both qualitatively and quantitatively different.     

Simultaneous characterisation and quantitation of flavonol glycosides and aglycones in noni leaves using a validated HPLC-UV/MS method

The leaves of Morinda citrifolia L. (noni) have been utilized in a variety of commercial products marketed for their health benefits. This paper reports on a rapid and selective HPLC method for simultaneous characterization and quantitation of four flavonols in an ethanolic extract of noni leaves by using dual detectors of UV (365 nm) and ESI-MS (negative mode). The limits of detection and quantitation were between 0.012 and 0.165 μg/mL. The intra- and inter-assay precisions, in terms of percent relative standard deviation, are less than 4.38% and 3.50%, respectively. The accuracy, in terms of recovery percentage, ranged from 96.66% to 100.03%. Good linearity (correlation coefficient >0.999) for each calibration curve of standards was achieved in the range investigated. The contents of four flavonoids in the noni leaves varied from 1.16 to 371.6 mg/100 g dry weight.     

Amperometric determination of hydrogen peroxide residue in beverages using a Nafion modified palladium electrode

Hydrogen peroxide (H₂O₂) residues are not permitted in food due to health concerns. An amperometric sensor based on a Nafion modified palladium (Pd) electrode was developed for the rapid determination of the H₂O₂ residue in aseptically packaged beverages. A prepared Pd electrode shows a slowly increasing reaction upon repeating the procedure of adding the same concentration of H₂O₂ into the reaction cell unless pretreating the electrode with cyclic voltammetry to obtain reproducible surfaces, whereas a Nafion modified Pd electrode can reach stable reaction to H₂O₂ without any pretreatment. The interference level of ascorbic acid (the ration of electrochemical response to ascorbic acid to the electrochemical response of H₂O₂) was calculated as 0.0004 for the Nafion modified Pd electrode. Interference (99.5%)from ascorbic acid was diminished by Nafion membrane. The response of the sensor to H₂O₂ in distilled water is linear over the range of 0.25–15 μM (r ² = 0.9956). The sensor developed in this study can efficiently determine H₂O₂ residues in commercial beverages with good linear correlation between spiked H₂O₂ concentration and detected H₂O₂ concentration, for winter melon-flavored drink, r ² = 0.9904 in the range of 0.25–15 μM and for lemon-flavored tea, r ² = 0.9927 in the range of 0.25–25 μM.     

Structural characterisation and anti-ageing activity of extracellular polysaccharide from a strain of Lachnum sp.

A homogeneous extracellular polysaccharide of Lachnum YM261(LEPS-1) with a molecular weight of 21670 Da was characterised. According to HPGPC, IR, periodate oxidation and Smith degradation, GC-MS and ¹H NMR analysis, the results indicated that LEPS-1 was a glucan linked by the β-(1 → 3)-d-pyran glycosidic bond. The effect of LEPS-1 on anti-ageing in d-gal model mice was also studied. It was found that LEPS-1 significantly increased the activities of antioxidant enzymes (i.e. SOD superoxide dismutase, CAT catalase, GSH-PX glutathione peroxidase) and decreased malondialdehyde (MDA) content in liver, brain and serum of d-gal model mice. These results showed that LEPS-1 had a strong anti-ageing activity.     

Inactivation of penicillin G in milk using hydrogen peroxide

Milk antibiotic residues have been a public concern in recent years. The Grade A Pasteurized Milk Ordinance mandates that raw Grade A milk will test negative for beta-lactam antibiotic residues before processing. The purpose of this research was to investigate the ability of various levels of peroxide and heat to inactivate penicillin G in raw milk. Whole milk spiked to a mean of 436 +/- 15.1 (standard error of the mean) ppb of potassium penicillin G was treated with hydrogen peroxide at levels of 0.0, 0.09, 0.17, and 0.34%. Samples at each peroxide level (n = 6 per treatment) were treated as follows: 1) incubated at 54.4 degrees C for 3 h, 2) pasteurized at 62.8 degrees C for 30 min, 3) incubated and pasteurized as in treatments 1 and 2, or 4) received no further treatment. A beta-lactam competitive microbial receptor assay was used for quantification of penicillin G. Concentrations of penicillin in selected samples were determined by HPLC for a comparison of test methods. Treatments were evaluated relative to their ability to reduce milk penicillin G levels to below the safe level of 5 ppb. The 0.09% hydrogen peroxide level was ineffective for all treatments. Hydrogen peroxide at 0.17% lowered the mean penicillin G (+/- SEM) from 436 +/- 15.1 to 6 +/- 1.49 ppb using the incubated and pasteurized heat treatment. The 0.34% concentration of hydrogen peroxide was the most effective, inactivating penicillin G to a level well below the safe level of 5 ppb with the pasteurized heat treatment, with or without incubation.     

过氧化氢漂白对开心果中花青素的影响

目的 考察漂白剂过氧化氢及碱液漂白对开心果中花青素的影响,并对漂白工艺的必要性进行探讨.方法 用带有二极管阵列检测器的高效液相色谱仪检测漂白过的开心果果衣中矢车菊素-3-O-葡萄糖苷和矢车菊素-3-O-半乳糖苷含量;对开心果的硬外壳、果衣及果仁的外观进行对比.结果开心果中2种花青素含量对H2O2很敏感.用0.1％过氧化氢漂白30 min,就可使花青素含量减少约60％.当H202浓度为5％以上时,开心果中矢车菊素-3-0-葡萄糖苷含量减少至检测不出,而矢车菊素-3-O-半乳糖苷含量损失达到90％.漂白的动力学过程也指出,反应发生迅速、直接,渗透过程不是反应的限速步骤.碱液与过氧化氢的协同漂白可使开心果外壳漂得更洁白,但果仁中花青素含量损失更多.检测了5种市售漂白过的开心果和2种市售未漂白的开心果,漂白过的开心果中2种花青素均未检出,而未漂白开心果中花青素均有保留.结论 漂白过程破坏了食用部分中的花青素,因而这一工艺步骤是否有必要,值得结合《中华人民共和国食品安全法》和《食品添加剂使用卫生标准》进一步讨论.     

钛盐比色法测定消毒牛奶中残留过氧化氢的含量

介绍用钛盐比色法测定消毒牛奶中残留过氧化氢的含量。方法的检出限为0．36mg／L，回收率为78％～99％。     

Improved yields of cyclic nigerosylnigerose from starch by pretreatment with a thermostable branching enzyme

Cyclic nigerosylnigerose (CNN) is produced enzymatically from starch by the combined action of 6-α-glucosyltransferase and 3-α-isomaltosyltransferase. In our previous study, α-1,6-branching chains found in the structure of amylopectin and glycogen were shown to be favorable for CNN formation by the two enzymes. Therefore, we examined whether the introduction of α-1,6-branch points into starch using the action of branching enzyme (BE) could improve the yield of CNN from starch. Thermostable BE from Geobacillus stearothermophilus TC-91 was prepared as a purified recombinant protein. Pretreatment of amylose with BE considerably increased the CNN yield from 5% to 38%. When BE acted on tapioca starch, the CNN yield was elevated from 47% to 60%. Conversely, BE treatment of waxy corn starch containing very little amylose resulted in a negligible increase in CNN yield. In addition, BE exerted a beneficial effect when starch with a lower degree of hydrolysis was used as a substrate. The present results indicate that the addition of α-1,6-glucosidic linkages to starch using BE is an effective strategy to improve the yield of CNN from starch.     

Functional properties of gelatin from cuttlefish (Sepia pharaonis) skin as affected by bleaching using hydrogen peroxide

Functional properties of gelatin from dorsal and ventral skin of cuttlefish with and without bleaching by H₂O₂ at different concentrations (2% and 5% (w/v)) for 24 and 48 h were studied. Gelatin from skin bleached with 5% H₂O₂ for 48 h showed the highest yield (49.65% and 72.88% for dorsal and ventral skin, respectively). Bleaching not only improved the colour of gelatin gel by increasing the L^∗-value and decreasing a^∗-value but also enhanced the bloom strength, and the emulsifying and foaming properties of the resulting gelatin. Gelatin from bleached skin contained protein with a molecular weight of 97 kDa and had an increased carbonyl content. Fourier transform infrared spectroscopic study showed higher intermolecular interactions and denaturation of gelatin from bleached skin than that of the control. These results indicated that hydrogen peroxide most likely induced the oxidation of gelatin, resulting in the formation of gelatin cross-links, giving improved functional properties.     

Advances in lentinan: Isolation,structure, chain conformation and bioactivities

Lentinan, a β-(1 → 3)-d-glucan isolated from a common edible mushroom, Lentinus edodes, is known as a biologically active macromolecules with very strong host-mediated anti-cancer activity, via activation of the human immune system. However, its widespread medicinal application is hindered by some technical difficulties in its extraction and purification, as well as a lack of thorough understanding of the structure-and-function relationship of this polysaccharide. This review aims at highlighting the different areas of research conducted on lentinan in the past 40 years, including its extraction and purification processes, the analysis of structure, the determination of its chain conformation and conformation transition in solution, as well as its rheological properties and bioactivities especially on anti-cancer treatment. About 156 literatures were cited to summarize the advancement of lentinan in the review paper.     

The influence of Cu(II) ions on physicochemical properties of potato starch oxidised by hydrogen peroxide

The study investigates the influence of Cu(II) ions used as a catalyst on the effectiveness of potato starch oxidation by hydrogen peroxide, and compares the physicochemical properties of the modified starches. The starch was oxidised by H₂O₂ alone and with the addition of Cu(II) ions at three concentrations: 0.1, 0.2 or 0.3 g per 100 g d.m. of starch. The oxidised starches were examined for the content of carboxyl groups, carbonyl groups, amylose and copper, and for water‐binding capacity and water solubility at temperatures of 60 and 80°C. Colour parameters (L*a*b*), susceptibility to retrogradation, thermodynamic characteristics of pasting, intrinsic viscosity and pasting characteristic by RVA were also determined. The results indicate that the concentration of Cu(II) ions added as a catalyst has an effect on both the effectiveness of the oxidation process and the physicochemical properties of starch.     

Molecular characteristics of tara galactomannans: Effect of degradation with hydrogen peroxide

Tara gum (M_w = 1519 × 10³ g/mol) was degraded by hydrogen peroxide in the presence/absence of ascorbic acid, and properties of the products were investigated using gel permeation chromatography, Fourier transform infrared spectroscopy, atomic force microscope, and rheometer methods. Results showed that molecular weight of tara gum decreased with increasing concentration of hydrogen peroxide. The addition of ascorbic acid could sharply increase the degradation rate and degree of tara gum by hydrogen peroxide, which is also confirmed by atomic force microscope. The degradation products kept the structure characteristics of galactomannan. However, they performed different rheological properties. At 1% (w/v) of concentration, DP1 (941 × 10³ g/mol) and DP2 (335 × 10³ g/mol) prepared by H₂O₂ exhibited non-Newtonian behavior, while DP3 (35.1 × 10³ g/mol) and DP4 (14.2 × 10³ g/mol) obtained by hydrogen peroxide plus ascorbic acid displayed Newtonian property. These results may promote the application of tara gum in diverse fields.     

响应面法优化过氧化氢法脱除柿子色素工艺的研究

目的 研究过氧化氢添加量、脱色温度和脱色时间对柿子粉色素脱除效果的影响。方法 采用过氧化氢法对柿子粉的色素进行脱除,并运用响应面法进行工艺条件的优化。结果 在单因素试验的基础上,采用脱色率为评价指标,运用响应面法确定了过氧化氢脱除柿子粉中色素的最佳工艺为过氧化氢添加量为10%,脱色温度40℃,脱色时间52min,在此条件下脱色率为72.13%,多糖保留率为85.75%。结论 采用响应面法优化的柿子粉的色素脱除过氧化氢法工艺条件准确可靠,方便可行,具有参考价值。     

过氧化氢纳米雾化熏蒸对黄豆芽贮藏品质及生理特性的影响

目的 探究过氧化氢(H₂O₂)纳米雾化熏蒸处理对黄豆芽贮藏品质及生理特性的影响。方法 以黄豆品种“绥农53号”萌发的豆芽为试材,分别采用体积分数为0.5%、1.0%、1.5%、2.0%的H₂O₂雾化熏蒸5 min,无熏蒸处理作为对照组(CK),置于2℃,相对湿度为85%环境中贮藏,每隔2 d测定1次黄豆芽的失重率、硬度、脆度、菌落总数、丙二醛(malondialdehyde,MDA)、H₂O₂积累量、总酚含量及褐变数和褐变相关酶活力相关指标。结果 与CK组相比,在贮藏第5 d, 1.5%H₂O₂纳米雾化熏蒸黄豆芽的失重率、菌落总数、褐变指数、MDA含量及H₂O₂积累量分别减少57.9%、22.6%、35.7%、31.0%和25.8%,硬度和脆度较CK组分别提高了25.6%和33.3%。总酚含量减少26.3%,1.5%H₂O₂纳...     

Aqueous extract of citrus peel reduces production of hydrogen peroxide in catechin-enriched green tea

Hydrogen peroxide (H₂O₂) is gradually produced in bottle-packed beverages, including tea and coffee, after the cap has been opened, i.e, through exposure to air, though only a small amount of H₂O₂ is detected in the beverage immediately after the bottle is opened. Since, H₂O₂ is toxic, it is necessary to develop safe and simple ways of reducing its production in bottled beverages. The addition of an aqueous extract of citrus peel reduced the concentration of H₂O₂ in green tea. To characterise the active constituents in the citrus peel, the aqueous extract of the peel was fractionated using chloroform, ethyl acetate, and butanol, in that order, and subjected to gel chromatography. The active constituents in the citrus peel were water-soluble compounds of various molecular weights.     

Production of hydrogen peroxide is responsible for the induction of apoptosis by hydroxytyrosol on HL60 cells

Hydroxytyrosol [3,4‐dihydroxyphenylethanol (3,4‐DHPEA)], a phenolic compound found exclusively in olive oil, exerts growth‐suppressive and pro‐apoptotic effects on different cancer cells. Although some molecular mechanisms involved in the pro‐apoptotic activity of 3,4‐DHPEA have been proposed, the initial stress signals responsible of this phenomenon are not known. Our aim was to assess the involvement of reactive oxygen species as mediators of apoptosis induced by 3,4‐DHPEA on HL60 cells. Apoptosis was determined by analyzing the nuclear fragmentation by both fluorescence microscopy and flow cytometry. The externalization of phosphatidylserine was evidenced using an Annexin V‐FITC kit. The concentration of H₂O₂ in the culture medium was measured by the ferrous ion oxidation‐xylenol orange method. The pro‐apoptotic effect of 3,4‐DHPEA (100 μM) was prevented by N‐acetyl‐cysteine, ascorbate, and α‐tocopherol. Catalase suppressed the 3,4‐DHPEA‐induced apoptosis, while the Fe(II)‐chelating reagent o‐phenantroline showed no effect, suggesting the involvement of H₂O₂ but not of OH^?. Indeed, 3,4‐DHPEA caused accumulation of H₂O₂ in the culture medium. Tyrosol (p‐hydroxyphenylethanol) and caffeic acid, compounds structurally similar to 3,4‐DHPEA but not able to generate H₂O₂, did not induce an appreciable apoptotic effect. This is the first study demonstrating that apoptosis induction by 3,4‐DHPEA is mediated by the extracellular production of H₂O₂.     

Use of hydrogen peroxide and carbonate/bicarbonate buffer for soaking of bacalao (salted cod)

Fillets of cod (Gadus morhua), brined and then dry-salted with NaCl, were cut into portions and desalted with different solutions: carbonate/bicarbonate buffer pH 9.5, tap water, or solutions of 0.25 or 1% hydrogen peroxide. The yield was measured after desalting. The moisture content, water-holding capacity, whiteness, firmness, total volatile basic nitrogen content and microbial load were determined during cold storage. When a pH 9.5 carbonate/bicarbonate buffer solution was used during the early hours of desalting, the yield increased and the product presented better protein functional quality but was highly perishable. When 0.25–1% hydrogen peroxide was used during the early hours of desalting, the microbial content of the end product was considerably lower, as was the yield; the firmness and surface whiteness of the product were improved but its water-binding properties were unaffected.