豆腐皮废甜浆中大豆低聚糖的树脂脱色研究

从豆腐皮废甜浆中提取的大豆低聚糖粗溶液具有较深的颜色,不符合大豆低聚糖的产品标准。采用静态吸附法和解吸法研究10种树脂对大豆低聚糖溶液中色素的吸附性能及其解吸特性,筛选出脱色效果较好的树脂;同时确定树脂的吸附动力学曲线和吸附等温线模型。结果表明：在所选树脂中大孔吸附树脂DM-130和AB-8对于色素的去除效果最好,脱色率达到70%以上;树脂再生容易,体积分数50%的乙醇溶液几乎可以将色素全部洗脱;树脂对色素的吸附是单分子层吸附,吸附模型符合Langmuir吸附等温线;树脂DM-130和AB-8对大豆低聚糖的吸附率较小,具有实际的应用价值。     

Adsorption isotherm,thermodynamics and kinetics studies of polyphenols separation from kiwifruit juice using adsorbent resin

In this study, the adsorption characteristics of polyphenols in kiwifruit juice were investigated using AB-8 resin, with the aim to separate the polyphenols from kiwifruit juice to prevent astringency and browning during processing and storage. Results showed that the adsorption ability (q_e) of the resin increased with an increase in temperature. The adsorption equilibrium was best described by the Freundlich isotherm (R² > 0.98). Thermodynamic parameters including the changes of enthalpy (ΔH), free energy (ΔG), and entropy (ΔS) were evaluated at 25, 30 and 35 °C. From the enthalpy change (0 < ΔH < 5), the adsorption was endothermic in nature and involved physical adsorption. The result of free energy change (ΔG < 0) demonstrated a spontaneous adsorption process. The pseudo first-order model was found to describe the kinetic data satisfactory. The adsorption mechanism was not limited solely by intra-particle diffusion as shown by the Weber and Morris model.     

Recovery of acetoin from the aqueous solution by means of a novel hyper-cross-linked resin: Equilibrium and kinetics

Acetoin is a high value-added product widely used in the food industry. Recovery of acetoin from the aqueous solution based on a polymeric adsorbent is an efficient method. Hence, a novel hyper-cross-linked resin was prepared and the adsorption behaviors of acetoin on the resin were investigated systematically. The results showed that the maximum adsorption capacity of acetoin onto the resin decreased with increasing temperature, ranged from 192 to 102 mg/g. Batch kinetic experiments revealed that the adsorption process was rapid and the equilibrium was reached in 30 min. The intraparticle diffusion and macropore diffusion models were used to predict the adsorption process. The simulation results showed that the macropore diffusion was the adsorption-rate controlling step. The obtained diffusivity (0.77 × 10⁻⁸ m²/min at the temperature of 293.15 K) had the same magnitude as the acetoin molecular diffusivity, indicating that the mass transfer into the resin pores was occurred by molecular diffusion.     

Cu (II) removal from tequila using an ion-exchange resin

An ion-exchange resin was employed to remove copper from tequila. Elemental analysis, batch and column copper uptake measurements were performed to assess the extent of metal removal; FTIR and XPS were employed to elucidate the copper complexes formed on the surface of resin; GC was used to investigate resin fouling and the extent of methanol removal. A modified Langmuir isotherm was used to explain adsorption equilibrium data. A ligand density of 2.21 mmol/g as sulphonic group, was measured. Maximum copper uptake by resin was 0.59 mmol/g. GC results from column experiments revealed methanol changes from 311 mg/100 ml anhydrous alcohol (AA) to 212 mg/100 ml AA, complying with Mexican regulations. Tequila solution with copper (5.3 l, 7.3 mg/l) was treated to breakthrough point in column experiments reaching 0.5 mg/l of copper at effluent. These results comply with the Mexican regulation for copper concentration (?2 mg/l) showing the promise of resin for industrial applications in removal of copper and methanol from tequila.     

Adsorption of two coffee aromas from synthetic aqueous solution onto granular activated carbon derived from coconut husks

Soluble coffee production requires several processes that cause the loss and degradation of aromas, which reduces the quality of the final product. However, such aromas can be recovered into aqueous solution during the production process. Aromas must be separated from water, and pleasant compounds, such as benzaldehyde, must be separated from unpleasant compounds, such as acetic acid. In this study, the kinetic and thermodynamic parameters of benzaldehyde and acetic acid adsorption from synthetic single-solute aqueous systems onto commercial grade granular activated carbon derived from coconut husks were investigated. The contact time required to attain adsorption equilibrium of benzaldehyde was 6 h, while that of acetic acid was 10 h. Adsorption isotherm data revealed that the adsorption of benzaldehyde and acetic acid was exothermic and spontaneous in nature. Moreover, the isosteric heat of adsorption indicated that the adsorbent surface was energetically heterogeneous. The adsorption equilibrium was fitted according to Langmuir, Freundlich and Temkin isotherms.     

Interaction of apple polyphenols in a multi-compound system upon adsorption onto a food-grade resin

Adsorption of catechin, caffeic acid, chlorogenic acid, phloridzin and rutin from multi-compound model solutions onto Amberlite^® XAD 16HP was studied in laboratory experiments. The adsorption conditions were adapted to those optimal for single compound binding, which were determined in previous studies. The following order of affinity towards the styrene–divinylbenzene copolymer was determined: caffeic acid < catechin < chlorogenic acid < phloridzin < rutin, and the data also reveal significant interactions of the phenolics upon adsorption from multi-compound solutions. The affinity order was successfully derived from differences in the consecutive phases of the adsorption kinetics of individual phenolic compounds. At the very beginning of adsorption polyphenol binding is characterized by processes, which may result in the formation of a subsurface surrounding the resin particles and which precede surface reactions, whereas the final phase is dominated by intraparticle diffusion processes. The results presented in this work contribute to a better understanding of the complexity of adsorption mechanisms and of the influence of adsorption conditions. Thus, detailed evaluation of such complex systems may contribute to optimize the selective recovery of plant secondary metabolites, e.g. by providing phloridzin-enriched extracts with promising health-promoting properties.     

Adsorption of carotenes and phosphorus from palm oil onto acid activated bleaching earth: Equilibrium,kinetics and thermodynamics

In this work, the adsorption of carotenes and phosphorus from crude palm oil onto acid activated bleaching earth was investigated under bleaching conditions, i.e. high temperature (90, 105 and 115 °C) and low pressure (less than 50 mbar). Bleaching earth was added to palm oil in a range of 0.5–3.0 wt%. Results presented in this work suggest that adsorption of β-carotene increases with temperature, while phosphorus adsorption was less affected. Both the pseudo-first-order and the pseudo-second-order kinetic model describe efficiently the β-carotene experimental data. Intra-particle diffusion is involved in β-carotene adsorption mechanism, although it is not the sole rate limiting step in the adsorption onto acid activated bleaching earth. Phosphorus adsorption was too fast resulting in a lack of kinetic data. The equilibrium data were described better by Langmuir and Freundlich models, for β-carotene and phosphorus, respectively. A multi-component Freundlich type isotherm was tested. Its competition coefficients were too low, and it assumed the same form as the monocomponent Freundlich. A thermodynamic study demonstrated that β-carotene and phosphorus adsorption is spontaneous, endothermic and an entropy-driven process. Isosteric heat values suggest that the interactions between adsorbate and adsorbent are heterogeneous.     

Adsorption of rutin onto a food-grade styrene–divinylbenzene copolymer in a model system

Adsorption of quercetin-3-O-rutinoside (rutin) onto Amberlite^® XAD 16HP was studied applying a modified D-optimal design. Temperature, pH value, rutin concentration and resin amount were studied as independent factors determining rutin adsorption. Using the mathematical model resulting from the analysis of the D-optimal design the optimal conditions for rutin adsorption onto the styrene–divinylbenzene copolymer were determined. Furthermore, the model equation was successfully applied to calculate the Langmuir and Freundlich isotherm parameters of this particular solute–sorbent system. In addition, the data obtained from the D-optimal design allowed the calculation of ΔG, ΔH and ΔS for the adsorption process. The results presented in this study are of utmost importance for a better understanding of adsorption phenomena. The more detailed knowledge of such sorbent systems is required to improve the cost-effectiveness of industrial processes for the recovery of secondary plant metabolites, such as polyphenols, based on resin adsorption technology.     

Decaffeination of tea extracts by using poly(acrylamide-co-ethylene glycol dimethylacrylate) as adsorbent

Poly(acrylamide-co-ethylene glycol dimethacrylate) was synthesized by thermal polymerization. The adsorption properties of the polymers for catechins and caffeine were studied. Adsorption kinetics showed the polymers preferred to adsorb the catechins rather than caffeine, and adsorption of catechins and caffeine onto the polymers could be described by the pseudo-second-order model. Isothermal equilibrium curves of catechins and caffeine showed a good fit with Langmuir model. The maximum monolayer adsorption capacity (Q_m) of total catechins (192.85–171.11 mg g⁻¹) was 3.9–5.2-folds of caffeine. Adsorption of catechins and caffeine was spontaneous and exothermic process as the change in free energy and enthalpy were negative. Lower temperature was favorable for the adsorption process. Caffeine and catechins were well separated and recovered by eluting polymers-packed column with gradient ethanol, i.e., 30% ethanol elution for separating caffeine, and 80% ethanol elution for recovering catechins. Thus, the synthetic poly(acrylamide-co-ethylene glycol dimethacrylate) could be used as a new adsorbent candidate for producing the decaffeined catechins.     

Static,Kinetic, and Isotherm Adsorption Performances of Macroporous Adsorbent Resins for Recovery and Enrichment of Bioactive Procyanidins from Cranberry Pomace

This study examined the ability of five Amberlite resins coupled with ultrasound‐assisted water extraction for the recovery and enrichment of bioactive procyanidins and total phenolics from cranberry pomace. Static adsorption showed that XAD‐7HP had the highest adsorption capacity for procyanidins (52.2 mg/g resin) and total phenolics (99.1 mg/g resin) whereas XAD‐761 had the lowest. Adsorption of procyanidins fitted better to pseudo‐second‐order kinetics than pseudo‐first‐order kinetics. Isotherm adsorption on XAD‐7HP suggested that Langmuir isotherm was a better model to describe the adsorption of procyanidins while Kemkin–Pyzhev equation was better for total phenolics based on higher coefficient of determinations (R²). Dynamic tests on XAD‐7HP suggested that the flow rate of 7 and 8 mL/min were the optimum conditions for adsorption and desorption of procyanidins, respectively. Measurements using HPLC revealed that adsorption increased the contents of procyanidins and total phenolics by 4.57‐ and 4.73‐folds, respectively, compared to the initial extracts. This research showed that Amberlite XAD‐7HP resin adsorption coupled with ultrasound‐assisted water extraction is an efficient method to separate and concentrate procyanidins from cranberry pomace.     

Macroporous resin purification of grass carp fish (Ctenopharyngodonidella) scale peptides with in vitro angiotensin-I converting enzyme (ACE) inhibitory ability

The adsorption dynamics and thermodynamics of grass carp fish scale peptides (FSPs) onto non-polar macroporous resins (MARs), DA201-C, have been investigated. The adsorption of FSPs was affected by time, pH and peptide concentration. The adsorption process followed the Langmuir adsorption isotherm, and was endothermic (ΔH < 43 kJ/mol). The predominant force in adsorption of FSPs onto DA201-C was hydrophobic. Depending on this force, the dynamic adsorption and gradient desorption results showed that DA201-C resins were good at desalting and enriching peptides with higher contents of hydrophobic amino acids, and these peptides had higher ACE inhibitory capabilities in vitro. The lowest concentration at which the eluted fraction possessed half of its original ACE activity (IC₅₀) was 0.13 mg/ml. The results indicated that fish scale peptides produced showed good ACE-inhibitory effect in vitro and fish scales are a good source of peptides with in vitro ACE inhibitory activity.     

原花青素在X-5树脂上吸附性能的研究

研究了葡萄籽提取液中的原花青素在X-5大孔吸附树脂上的吸附行为。对静态吸附特性的研究表明,在实验条件下吸附等温线符合Freundlich吸附等温方程式。当平衡质量浓度为180mg/mL时,吸附平衡时间约为3h。对动态吸附特性的研究表明,当以0.5BV/h流量通过吸附床时,动态吸附量比静态吸附量低16%。用40%乙醇溶液洗脱吸附在树脂上的原花青素,洗脱率为86.1%,原花青素含量高于80%。     

纤维素酶在不同长度纤维上的吸附行为

纤维素酶在纤维表面上的吸附是纤维素水解糖化的第一步,探讨了纤维素酶在不同长度纤维上的吸附行为。纤维素酶在纤维上吸附约60 min后可达到平衡,且吸附量随初始酶用量的增加而增多。吸附过程遵循Langmuir等温吸附,且纤维素酶在短纤维上具有最大的吸附量,但在长纤维上具有最大的Langmuir吸附平衡常数,说明纤维素酶在长纤维上能更快地达到吸附平衡。对吸附热力学常数的计算表明,纤维素酶吸附是自发、放热过程,且不可逆吸附。纤维素酶在48目纤维上有最大的吸附焓变,在28目纤维上有最大的吸附熵变。     

离子交换树脂对冰葡萄汁总酸和总酚的静态吸附动力学研究

该实验研究了D354树脂对冰葡萄汁总酸和总酚的静态吸附动力学模型。结果表明,随吸附温度的升高,D354树脂对冰葡萄 汁总酸和总酚的吸附速率显著提高（P＜0.05）。 在0 ℃、10 ℃和20 ℃条件下,D354树脂对冰葡萄汁总酸的最大吸附量分别为151.69 mg/g、 190.09 mg/g及222.16 mg/g;对冰葡萄汁总酚的最大吸附量分别为3.65 mg/g、4.20 mg/g及4.67 mg/g;D354树脂吸附冰葡萄汁总酸和总 酚的过程符合拟二阶动力学模型（R2＞0.9980）,并确定了D354树脂对冰葡萄汁总酸和总酚的拟二阶动力学方程;利用W-M（Weber- Morris）动力学模型对数据拟合（R2＞0.9300）,结果表明整个静态吸附过程受粒内扩散和液膜扩散共同控制。     

Removal of dark colored compounds from date syrup using activated carbon: A kinetic study

Dark colored compounds in date syrup have been removed using powdered activated carbon (PAC) at different operating conditions including different temperatures (30, 40, 50 and 60 °C), as well as different PAC concentrations (0.04, 0.06, 0.08, 0.1 and 0.12 g ml⁻¹). Adsorption isotherms of Langmuir, Freundlich, Tempkin and Harkins–Jura were selected to fit the equilibrium data at different operating temperatures. The isotherms were correlated based on the absorbance intensity and the concentration of a colored compound, which gives the same absorbance intensity as the real date syrup. Among the adsorption models, the Langmuir isotherm best fitted the experimental data with coefficient of 0.99. To study the adsorption kinetics, the pseudo-first order and the pseudo-second order models were evaluated to fit the experimental data. The pseudo-second order equation fitted the experimental data very well.     

Effect of soybean oligosaccharides on blood lipid,glucose levels and antioxidant enzymes activity in high fat rats

The effect of soybean oligosaccharides on blood lipid levels and oxidative stress in rats fed on high-fat diet was investigated. Rats were divided into five groups of 10 animals each. The high-fat group received a high-fat diet containing 18% (w/w) lipid in the diet (36% of total energy). Animals allocated to the soybean oligosaccharides-treatment groups (I, II and III) received the high-fat diet and orally fed with soybean oligosaccharides at a single dose of 150, 300 and 450 mg/kg body weight, respectively. Control rats received basic diet. Results showed that soybean oligosaccharides significantly reduced abnormal blood glucose, lipid level and oxidative stress in animal models at all doses examined. Soybean oligosaccharides were able to reduce oxidative stress and improve abnormal blood lipid levels induced by high-fat diets. In summary, the present study may be important for reverse cardio-cerebrovascular disease.     

树脂法分离纯化荔枝核黄酮

为了分离、纯化荔枝核黄酮,比较了4种大孔树脂的静态吸附过程,筛选出适合吸附荔枝核黄酮的树脂;研究了荔枝核黄酮在大孔吸附树脂上的动态吸附特性,并确定分离荔枝核黄酮的适宜条件。结果表明:HPD800大孔吸附树脂对荔枝核黄酮有较好的吸附分离性能,其对荔枝核黄酮的静态吸附平衡时间为10 h;在25℃条件下,通过吸附等温线,Langmuir模型比Freundlich模型能够更好的描述荔枝核黄酮在HPD800树脂上的吸附平衡过程,所得回归方程为:C/Q=C/434.78+1/1.35×434.78(R2=0.999 3),其相关系数R>0.99。吸附溶液适宜的pH值为5.0。确定树脂柱的较佳操作条件为:流速3.0 mL/min,荔枝核黄酮浓度30.81 mg/mL。     

Inactivation of soybean lipoxygenase in soymilk by pulsed electric fields

The inactivation of soybean lipoxygenase by pulsed electric fields (PEF) was studied. Effects of PEF parameters (treatment time, pulse strength, pulse frequency and pulse width) were evaluated. Soymilk was exposed to pulsed strengths from 20 to 42 kV/cm for up to 1036 μs treatment time in square wave pulse of bipolar mode. Moreover, pulse frequency (100–600 Hz) and pulse width (1–5 μs) was also tested at constant pulsed treatment time of 345 μs and strength of 30 kV/cm. Residual activity of soybean lipoxygenase decreased with the increase of treatment time, pulse strength, pulse frequency and pulse width. The maximum inactivation of soybean lipoxygenase by PEF achieved 88% at 42 kV/cm for 1036 μs with 400 Hz of pulse frequency and 2 μs of pulse width at 25 °C. Inactivation of soybean lipoxygenase by pulsed electric fields was modeled using several kinetic models. Weibull distribution function was most suitable model describing the inactivation of soybean LOX as a function of pulsed electric fields process parameters. Moreover, reduction of soybean LOX activity related to the electric field strength could be well described by the Fermi model.     

葛根多糖纯化工艺及其抗氧化性能研究

目的:以葛根为原料,采用大孔树脂法分离纯化葛根多糖,研究其抗氧化性质。方法:通过对葛根多糖吸附及解吸筛选出最优树脂,分析吸附解吸时间、样液浓度、样液pH以及乙醇的体积分数对多糖纯化的影响,在静态分析条件下再运用层析柱法进行动态纯化,对纯化后的葛根多糖进行抗氧化分析。结果:D101树脂分离纯化效果较好,其对葛根多糖静态吸附和解吸最佳工艺条件吸附时间为8 h,解吸时间为3 h,吸附浓度0.75 mg/mL,样液pH6.0,乙醇解吸体积分数为60%,其对动态吸附和解吸最佳工艺条件为上样液质量浓度1.0 mg/mL,解吸剂体积(60%乙醇)51 mL,在此条件下纯化的葛根多糖纯度达到55.34%。经纯化后的葛根多糖对DPPH·和·OH具有较强的清除作用,最大清除率分别为81.74%和85.11%。结论:大孔树脂法纯化葛根多糖工艺条件合理,且纯化效果好,杂质去除率高,纯化后的葛根多糖抗氧化性得到提高。