Efficient Alkaline Isomerization of Lactose to Lactulose in the Presence of an Organogermanium Compound

Lactulose, a disaccharide widely used in pharmaceuticals and functional foods, is produced by lactose isomerization. Lactose and lactulose have an aldose–ketose relationship. Less than 25 % conversion of lactose into lactulose is achieved using the Lobry de Bruyn–Alberda van Ekenstein transformation with heating, whereas the conversion is increased to 80 % by the addition of an approximately equimolar concentration of the organogermanium compound 3-(trihydroxygermyl)propanoic acid (THGP) to the reaction mixture. To further understand this phenomenon, in this study, we analyzed the affinity between THGP and sugar isomers using ¹H nuclear magnetic resonance spectroscopy. For the dimethyl derivative of THGP with lactose and lactulose, the complex formation ratios at 0.1 M (1:1 mixing ratio) were 14 and 59 %, respectively, with complex formation constants of 1.8 and 43 M^–1, respectively. The complex formation capacity was approximately 24-fold higher for lactulose than for lactose. Moreover, THGP is considered to protect lactulose from alkaline degradation, resulting in high production yield of lactulose. Therefore, we concluded that high affinity for the isomerization product may promote isomerization and that promotion of sugar isomerization using an organogermanium compound is an effective method for converting lactose to lactulose.     

单糖的类型对模拟体系中晚期糖基化终末产物生成的影响

为了研究单糖-赖氨酸模拟体系中单糖类型对晚期糖基化终末产物(AGEs)生成的影响。探讨了葡萄糖、半乳糖、果糖、山梨糖在120 ℃加热0~120 min期间pH、反应颜色、底物消耗、AGEs中间体包括3种二羰基化合物乙二醛(GO)、丙酮醛(MGO)和三脱氧葡萄糖醛酮(3-DG)以及果糖基赖氨酸(FL),以及最终三种AGEs包括羧甲基赖氨酸(CML)、羧乙基赖氨酸(CEL)、吡咯素(Pyr)的变化。结果显示随着反应进行,醛糖体系的pH下降程度以及颜色增加程度高于酮糖体系。反应结束时,葡萄糖-赖氨酸(Glu-Lys)、半乳糖-赖氨酸(Gla-Lys)、果糖-赖氨酸(Fru-Lys)和山梨糖-赖氨酸(Glu-Lys)体系中赖氨酸的损失分别为26.65%、28.95%、11.47%、14.90%;而所有体系中单糖在反应结束时的损失均达到了75.00%以上,要远高于赖氨酸。模拟体系中单糖会出现醛酮转换,但比例低于10%。所有体系中GO和3-DG的含量随着时间的延长而下降,这表明体系中GO和3-DG在反应前20 min内就已大量生成。α-二羰基化合物的生成量远高于FL的生成量。反应结束时,酮糖体系的CML和CEL含量要高于醛糖体系。所有体系中,三种AGEs生成量均为CEL > CML > Pyr。本文表明将来研究食品中AGEs的生成和抑制途径,需重点从中间体途径着手,尤其是α-二羰基化合物。     

Efficient Conversion of D-Glucose to D-Fructose in the Presence of Organogermanium Compounds

D-Glucose and D-fructose are isomers of commonly consumed monosaccharides. The ratio of conversion of D-glucose to D-fructose by glucose isomerase (xylose isomerase) is not more than 50 %. However, addition of an equimolar ratio of the organogermanium compound poly-trans-[(2-carboxyethyl)germasesquioxane] (Ge-132) or its derivative increases the conversion ratio to 80 %. In contrast, use of the Lobry de Bruyn–Alberda van Ekenstein transformation with heating results in a lower conversion ratio, less than 30 %, whereas addition of an equimolar concentration of Ge-132 or its derivative to this reaction mixture increases the ratio to 73 %. Therefore, in this study, we aimed to further analyze the affinity between organogermanium compounds (i.e., Ge-132 and its derivatives) and sugar using ¹H-nuclear magnetic resonance (NMR) spectrometry. For the dimethyl derivative of Ge-132, the complex formation ratios at 0.25 M (mixing ratio 1:1) were 19 and 74 % for D-glucose and D-fructose, respectively. Additionally, the complex formation constants between monosaccharides and Ge-132 were 1.2 and 46 M^-1 for D-glucose and D-fructose, respectively. The complex formation capacity was approximately 40-fold higher for D-fructose than for D-glucose. Therefore, we concluded that the high affinity for the product of isomerization may promote isomerization, and that promotion of sugar isomerization using organogermanium compounds is an effective method for conversion of D-glucose to D-fructose.     

Effects of trypsin‐hydrolyzed wheat gluten peptide on wheat flour dough

BACKGROUND: Gluten peptide was prepared by trypsin hydrolysis and characterized by high‐performance liquid chromatographic analysis. The effects on non‐frozen and frozen doughs of trypsin‐hydrolyzed gluten peptide (THGP) and its combination with ascorbic acid or KBrO₃ were investigated. RESULTS: Molecular analysis of THGP showed a decrease in the high‐molecular‐weight and an increase in the low‐molecular‐weight sodium dodecyl sulfate‐soluble fractions, compared with those of control wheat gluten. The addition of 8% THGP decreased the mixing time and tolerance of the dough, both with and without ascorbic acid or KBrO₃. However, the maximum resistance and extensibility of the rested dough containing 8% THGP, with and without ascorbic acid or KBrO₃, were not significantly different from those of the control dough. The addition of 8% THGP significantly increased the loaf volume of bread baked from non‐frozen dough when combined with 60 ppm ascorbic acid or 30 ppm KBrO₃, but it had a significant effect both with and without ascorbic acid or KBrO₃ on frozen‐dough bread. A large difference in volume was observed between breads made with and without THGP at the oven‐spring, rather than at proofing. CONCLUSION: The addition of 8% THGP increased the loaf volume of bread made from freeze‐damaged dough and this effect increased when THGP was combined with 60 ppm ascorbic acid. Copyright © 2008 Society of Chemical Industry     

Improving the thermostability of β-lactoglobulin via glycation: The effect of sugar structures

This work studied the effects of sugar structure (size, position of carbonyl group, and charge state) on the thermostability of β-lactoglobulin (β-lg) when controlling the glycation extent of reducing sugars to the same level. Ribose, glucose, maltose, maltotriose, fructose and galacturonic acid were selected to react with β-lg at a_w of 0.53 at 45 °C for different periods to reach an average degree of saccharide attached per protein molecule β-lg (average DSP) of 5. β-Lg and the conjugates in pH 3, 5 and 7 were heated. The denaturation temperature was detected by differential scanning calorimeter (DSC), and the solubility was determined by Bradford assay. The results showed that all the conjugates exhibited higher denaturation temperature than β-lg. Larger molecular size, ketose and negative charge had significant effects on increasing the denaturation temperature. β-Lg and the conjugates at pH 3 and 7 could maintain their solubility when increased the temperature from 60 to 90 °C. The conjugates showed better thermostability than β-lg at pH 5 and sugar structure had effects on the improvement. Glycation by sugars with increasing size and negative charge stabilized β-lg. Ketose glycation did not show better thermostability than aldose, but caused more aggregates during mild or short time heating.     

Die Wirkung von Glucoseisomerase auf Oligosaccharide in Stärkehydrolysaten

Action of Glucoseisomerase on Oligosaccharides in Starch Hydrolysates During investigation of glucose isomerization with glucoseisomerase it was found out that in particular circumstances the glucoseisomerase was active not only against glucose, but also against Oligosaccharides, which were present in starch hydrolysates. It was proved that glucoseisomerase was capable of converting small amounts of maltose into an unknown ketodisaccharide and that it was capable of producing ketose residues in molecules of maltose homologous Oligosaccharides. A particularly intensive action of glucoseisomerase on maltose and on maltooligosaccharides was observed when solutions did not contain or contained only small amounts of glucose.     

Substrate specificity of a recombinant d-lyxose isomerase from Providencia stuartii for monosaccharides

The specific activity and catalytic efficiency (k_cat/K_m) of the recombinant putative protein from Providencia stuartii was the highest for d-lyxose among the aldose substrates, indicating that it is a d-lyxose isomerase. Gel filtration analysis suggested that the native enzyme is a dimer with a molecular mass of 44 kDa. The maximal activity for d-lyxose isomerization was observed at pH 7.5 and 45 °C in the presence of 1 mM Mn²⁺. The enzyme exhibited high isomerization activity for aldose substrates with the C2 and C3 hydroxyl groups in the left-hand configuration, such as d-lyxose, d-mannose, l-ribose, d-talose, and l-allose (listed in decreasing order of activity). The enzyme exhibited the highest activity for d-xylulose among all pentoses and hexoses. Thus, d-lyxose was produced at 288 g/l from 500 g/l d-xylulose by d-lyxose isomerase at pH 7.5 and 45 °C for 2 h, with a conversion yield of 58 % and a volumetric productivity of 144 g l^− 1 h^− 1. The observed k_cat/K_m (920 mM^− 1 s^− 1) of P. stuartiid-lyxose isomerase for d-xylulose is higher than any of the k_cat/K_m values previously reported for sugar and sugar phosphate isomerases with monosaccharide substrates. These results suggest that the enzyme will be useful as an industrial producer of d-lyxose.     

Quantitative and qualitative analysis of high molecular compounds in vegetable oils formed under high temperatures in the absence of oxygen

Conditions of deodorization/physical refining of sunflower oil were simulated by high temperature heating in laboratory at 240, 250, and 260 °C. Oxygen atmosphere was excluded by argon atmosphere. Influence of temperature, initial oxidation of incoming oil (peroxide value 2–30 mmol ½ O₂/kg) on geometrical, positional isomerization, and polymerization was measured. The level of initial oxidation of the oil has a significant influence on rate of isomerization, polymerization, and duration of induction period of polymerization reactions. Induction period of polymerization is dependent linearly on temperature at constant hydroperoxide content and is extended with decreasing temperature and lower peroxide value of oil. Significant conjugation took place with geometrical isomerization and resulted in all-trans diene formation. All-trans dienes are incoming reactants for polymerization according to the Diels–Alder mechanism. Suggested “propagation” phase of polymerization took place later. Induction period was observed only in the case of polymerization reactions of triacylglycerols. This is the confirmation of the hypothesis that the cis/trans isomerization, positional isomerization, and polymerization are consecutive reactions in ascending order. Identification of molecular peaks and confirmation of fragments were possible by connecting HPSEC with APCI-MS. Dimers of triacylglycerols (TAG) dominated in studied system. Remaining compounds may have been formed from di-, monoacylglycerols, and other minor constituents of sunflower oil.     

Effect of addition of selected solid cosolutes on viscoelastic properties of model processed cheese containing pectin

The aim of this study was to investigate the effect of various selected solid low-molecular cosolutes (d-glucose, d-fructose, d-galactose, lactose, saccharose; target concentrations in samples 1% w/w) on viscoelastic properties of model processed cheese (40% w/w dry matter and 50% w/w fat in dry matter) without and with pectin addition (target concentrations in final products: 0.2% w/w and 0.4% w/w, respectively). Dynamic oscillation rheometry with parallel plate geometry was used to evaluate the changes in viscoelastic properties of samples. All applied low-molecular cosolutes (1% w/w) decreased the firmness of processed cheese. The nature of cosolute was not significant, i.e. the firmness of final products was declined by various cosolutes to the similar level regardless of their (i) reducing or non-reducing ability; (ii) structure (mono- or disaccharide, aldose or ketose); or (iii) steric arrangement (comparison of two epimers – d-glucose and d-galactose). The reduction of sample rigidity due to cosolute addition was observed in both cases, i.e. in processed cheese without and also with pectin.     

Lactulose as a food ingredient

Lactulose is a synthetic ketose disaccharide that can be obtained from lactose by different methods of synthesis. Chemical methods are based on the isomerization of lactose in the presence of basic catalysts and enzymatic methods using lactose as a galactose donor and fructose as an acceptor. The prebiotic properties of lactulose have been known for more than 50 years and numerous studies have confirmed several health benefits of lactulose as a food ingredient, including selective stimulation of intestinal flora, laxative effect and improvement of calcium absorption. Its use in fermented milk manufacture may reduce the incubation period and favour the growth of bifidobacteria. The synthesis of lactulose‐derived oligosaccharides may provide a new group of prebiotics with properties complementary to those of native lactulose. Copyright © 2009 Society of Chemical Industry     

Modeling Lycopene Degradation and Isomerization in the Presence of Lipids

The kinetics of thermally induced degradation and isomerization of lycopene in olive oil, fish oil, and an olive oil/tomato emulsion were studied in detail. Special attention was paid to the isomerization reactions using a multi-response modeling approach. The type of oil had a significant impact on lycopene degradation kinetics, being faster in fish oil compared with olive oil. The estimated kinetic parameters to describe lycopene degradation in olive oil were not significantly different from those in an olive oil/tomato emulsion. The overall Z-isomer formation and elimination in olive oil, fish oil, and olive oil/tomato emulsion was similar. Only the kinetic parameters for 13-Z-lycopene formation differed significantly in the two oils. Although the isomerization rate constants for the emulsion were lower than for olive oil, the isomerization reactions showed similar temperature dependency. This study shows that the kinetics of thermally induced degradation and isomerization of lycopene in oil and in an olive oil/tomato emulsion can be described using the same model. The food system, however, has an influence on the model parameters, especially on the rate constants.     

Inhibition of aldose reductase and anti-cataract action of trans-anethole isolated from Foeniculum vulgare Mill. fruits

Foeniculum vulgare fruits are routinely consumed for their carminative and mouth freshening effect. The plant was evaluated for aldose reductase inhibition and anti-diabetic action. Bioguided fractionation using silica gel column chromatography, HPLC, and GC-MS analysis revealed trans-anethole as the bioactive constituent possessing potent aldose reductase inhibitory action, with an IC₅₀ value of 3.8 μg/ml. Prolonged treatment with the pet ether fraction of the F. vulgare distillate demonstrated improvement in blood glucose, lipid profile, glycated haemoglobin and other parameters in streptozotocin-induced diabetic rats. Trans-anethole could effectively show anti-cataract activity through the increase in soluble lens protein, reduced glutathione, catalase and SOD activity on in vitro incubation of the eye lens with 55 mM glucose. Trans-anethole demonstrated noncompetitive to mixed type of inhibition of lens aldose reductase using Lineweaver Burk plot.     

Reaction Behavior of Glucose and Fructose in Subcritical Water in the Presence of Various Salts

Glucose and fructose were treated in subcritical water in the presence of alkali or alkaline earth metal chlorides. All salts accelerated the conversion of saccharides, and alkaline earth metal chloride greatly promoted the isomerization of glucose to fructose. In contrast, alkali metal salts only slightly promoted this isomerization and facilitated the decomposition of glucose to byproducts such as organic acids. The selectivity of the glucose-to-fructose isomerization was higher at lower conversions of glucose and in the presence of alkaline earth metal chlorides. The pH of the reaction mixture also greatly affected the selectivity, which decreased rapidly at lower pH due to the generated organic acids. At low pH, decomposition of glucose became dominant over isomerization, but further conversion of glucose was suppressed. This result was elucidated by the suppression of the alkali-induced isomerization of glucose at low pH. Fructose underwent decomposition during the treatment of the fructose solution, but its isomerization to glucose was not observed. The added salts autocatalytically promoted the decomposition of fructose, and the reaction mechanism of fructose decomposition differed from that of glucose.     

Inhibitory efficacy of Ligularia fischeri against aldose reductase and advanced glycation end products formation

The efficacy of Ligularia fischeri (LF) for managing diabetic complications was evaluated by assessing inhibitory effects against advanced glycation end product (AGE) formation, rat lens aldose reductase (RLAR), and 1,1-diphenyl-2-picryl hydrazyl (DPPH) radical scavenging. The ethyl acetate fraction from 70% ethanol extracts of LF showed the highest DPPH radical scavenging activity of 53.90% at a concentration of 3.3 μg/mL. The ethyl acetate fraction exhibited the most potent AGE formation inhibition of 73.57% at a concentration of 55 μg/mL and showed the most potent RLAR inhibition of 88.97% at a concentration of 11.11 μg/mL. The ethyl acetate fraction exhibited the most potent antioxidant and anti-diabetic effects. Nuclear magnetic resonance via bioactivity-guided fractionation of the LF ethyl acetate fraction revealed that 3,4-dicaffeoylquinic acid was the bioactive compound. This compound from LF can be effective for prevention or treatment of diabetic complications.     

Inhibitory effect of polysaccharides from pumpkin on advanced glycation end-products formation and aldose reductase activity

Inhibitors of advanced glycation end-products formation and aldose reductase have been considered to be potential treatment of diabetic complications. This study investigated the abilities of polysaccharides extracted from pumpkin (PPs) to inhibit the formation of advanced glycation end-products and aldose reductase. The results showed that the inhibitory effects of PPs on the formation of advanced glycation end-products were higher than 50%, at 200 μg/ml, stronger than the positive control aminoguanidine, and the inhibitory effects of PPs on aldose reductase were higher than 58%, at 500 μg/ml, but not as potent as the positive control epalrestat. The result of this work suggests that pumpkin polysaccharides displayed therapeutic potential in the prevention and treatment of diabetic complications.     

Isolation and characterisation of an anticoagulant oligopeptide from blue mussel, Mytilus edulis

A potent anticoagulant oligopeptide was isolated from the edible parts of blue mussel (Mytilus edulis). M. edulis anticoagulant peptide (MEAP) with an approximately 2.5 kDa molecular mass was similar to the amino acid sequence of the EF-hand domain of calmodulin from scallop adductor muscle. MEAP could potently prolong both the thrombin time and the activated partial thromboplastin time, and specifically interact with blood coagulation factors: FIX, FX, and FII. MEAP could inhibit proteolytic activation of FX by the intrinsic FXase and formation of FIIa by a prothrombinase complex in dose-dependant reactions. This study elucidated that MEAP prolonged blood clotting by inhibiting activation of FX in the intrinsic tenase complex (FIXa/VIIIa/PLs) and conversion of FII to FIIa in the prothrombinase complex (FXa/FVa/PLs).     

Effect of osmotic pre-treatment and microwave heating on lycopene degradation and isomerization in cherry tomato

Cherry tomato were dehydrated by a combination of different techniques (osmotic dehydration, convective drying, and microwaves assisted air drying) in order to evaluate the effect of the process variables on the degradation and isomerization of lycopene, as well as on the optical properties. Specifically, the effect of prior osmotic treatment, air drying temperature (40, 55, and 80 °C) and level of microwave energy (0, 1, and 3 W/g) were studied. Obtained results showed that the osmotic pre-treatment limited the isomerization during the later stage of drying, whereas both the loss of total lycopene and the trans–cis isomerization, mainly to the 13-cis form, were favored by an increase in temperature and the microwave power. Furthermore, a positive correlation between the degree of isomerization experienced by the samples during drying and the hue (h*) were obtained. This correlation was reflected in the colour of the sample with predominantly more orange tones and less reddish ones.     

Effect of an alkaline salt (papad khar) and its substitute (2:1 sodium carbonate:sodium bicarbonate) on acrylamide formation in papads

The formation of acrylamide in papads processed by flame roasting, frying and microwave roasting as a function of the alkaline salt, papad khar and its substitute, 2:1 sodium carbonate:sodium bicarbonate (w/w) at various concentrations was examined. Addition of papad khar and 2:1 sodium carbonate:sodium bicarbonate makes the product alkaline, which is known to be conducive for the formation of acrylamide. While a correlation was found between acrylamide content and pH with respect to fried and flame roasted papads, microwave roasting did not show any acrylamide formation at all the levels of alkaline salts tested in this study. Flame roasting generated higher levels of acrylamide as compared to frying. Use of microwave roasting is therefore recommended as a consumer-friendly, healthy and safe technology for processing papads.     

Comparison of lycopene stability in water- and oil-based food model systems under thermal- and light-irradiation treatments

Lycopene can undergo degradation via isomerization and oxidation during processing and storage. These degradative reactions affect its bioactivity and health benefit functionality. Degradation kinetics and isomerization of lycopene in water- and oil-based tomato model systems were investigated as a function of thermal treatments and light irradiation. Results showed that 80 and 100 °C heating favoured the stability of lycopene in oil-based tomato products. The high heating temperatures (120 and 140 °C) increased isomerization of lycopene and resulting in degradation of total lycopene and cis-isomers in both water- and oil-based tomato products. However, the levels of degradation of total lycopene contents and cis-isomers were greater in water-based samples than in oil-based model systems under different treatments. Heat and light both promoted lycopene isomerization of the all-trans form to the cis-isomers and further oxidation of cis-isomers. The major effect of thermal degradation and photosensitized oxidation was a significant decrease in the total lycopene content, especially the content of cis-isomers. These research results could be useful in assisting industry to improve processing technology and to improve the nutritional value and health-benefits of tomato-based foods.     

Thermal treatment to form a complex surface layer of sodium caseinate and gum arabic on oil–water interfaces

This study reported an alternative approach to electrostatic interaction to generate a biopolymer complex surface layer on emulsion droplets. By increasing the temperature, a complex surface layer of sodium caseinate (CN) and gum arabic (GA) on emulsion droplets could be formed either through the adsorption of complexes formed in the solution or through direct complexation of CN and GA with the surface. Mixtures of CN and GA were heated at pH 7 and then used to form oil-in-water emulsions at high temperatures. Changes in the average particle size and the ζ-potential of the emulsions indicated that complexes of GA and CN adsorbed to the interface at temperatures above 60 °C. A thick complex surface layer was also observed using confocal laser scanning microscopy. The addition of GA or CN to emulsions made with CN or GA resulted in an apparent binding of GA or CN to the emulsion droplets that depended on the sequence of addition. This temperature-induced formation of a complex surface layer was considered to be due to hydrophobically driven complexation between CN and the protein fraction of GA. The formation of the complex surface layer was dependent on the concentration, the temperature, and the addition order of the second component. This finding may imply an alternative option for the formation of biopolymer multilayers or complex surface layers on colloidal particles.