Alkaline Isomerization Research Articles

Synthesis of Linoleic Acid of Conjugated Isomers from Sesame (Sesamum Indicum) Seed Oil: Its Use and Effect in a Microstructured Product Type Oil-in-Water Emulsion

The development of functional foods is an area of great interest and innovation in the food industry. The use of conjugated linoleic acid (CLA) in food formulations has been growing in recent years due to its multiple health benefits. In this study, conjugated linoleic acid was obtained from sesame oil, and its use in the formulation of oil-in-water food emulsions was evaluated. Conjugated linoleic acid (CLA) was synthesized from the linoleic acid present in sesame oil using the alkaline isomerization method using proplyeneglycol as a solvent. The effect of alkali concentration (NaOH) and reaction time on the conversion of linoleic acid to CLA was evaluated. A 96.6% conversion of CLA was obtained with a NaOH concentration of 7% and a reaction time of 2 h. Emulsions were prepared using CLA as oil phase and soy lecithin, tween 80, carboxymethylcellulose as emulsifying agents. Emulsions with mixtures of carboxymethylcellulose and tween 80 were stable, presenting a non-Newtonian fluid behavior of pseudoplastic type (n<1). The Ostwald-de-Waele model shows an optimal fit to the experimental data of apparent viscosity (R2>0.99 ), and its microstructural characterization shows a homogeneous particle distribution. These results show that the alkaline isomerization process using propylene glycol as a solvent is an excellent alternative for the synthesis of CLA from vegetable oils such as sesame oil and its application in the development of microstructured products such as functional emulsions, and their subsequent application in the development of new food products with beneficial health characteristics.

Interaction of Organogermanium Compounds with Saccharides in Aqueous Solutions: Promotion of Aldose-to-ketose Isomerization and Its Molecular Mechanism.

This review discusses sugar isomerization with organogermanium compounds. Organogermanium compounds markedly increase the aldose-ketose (glucose-fructose or lactose-lactulose) isomerization ratio, double the initial reaction rate, and significantly reduce the base-catalyzed degradation of sugars. 1H-nuclear magnetic resonance analysis reveals that the affinity of organogermanium compounds with a 3-(trihydroxygermyl)propanoic acid (THGP) structure toward ketoses is 20-40 times stronger than that toward aldoses; thus, such organogermanium compounds form complexes more readily with ketoses than with aldoses. Stable ketose complexes, which contain multiple cis-diol structures and high fractions of furanose structures, suppress the reverse ketose-aldose reaction, thereby shifting the equilibrium toward the ketose side. These complexes also protect sugar molecules from alkaline degradation owing to the repulsion between anionic charges. The increased rate of the initial reaction in the alkaline isomerization process results from stabilizing the transition state by forming a complex between THGP and a cis-enediol intermediate. The cyclic pentacoordinate or hexacoordinate THGP structures give rise to a conjugated system of germanium orbitals, which is extended through dπ-pπ interactions, thereby improving the stability of the complex. Based on these results, we have developed a bench-scale lactulose syrup manufacturing plant incorporating a system to separate, recover, and reuse organogermanium poly-trans-[(2-carboxyethyl)germasesquioxane]. This manufacturing plant can be used as a model of an alkaline isomerization accelerator for continuous industrial production.

Influence of rare sugar syrup on quality attributes and acceptability of bread

SummaryRare sugar syrup (RSS) prepared by alkaline isomerisation of high‐fructose corn syrup (HFCS) contains rare sugars as well as D‐glucose (Glc) and D‐fructose (Fru) and has antiobesity and antidiabetic effects. RSS was used in making bread, and the quality of the final bread product was compared with bread with added sucrose (Suc). 20°Bx RSS‐ and 20°Bx HFCS‐added breads had lower loaf height and volume, moisture content and water activity compared with 20°Bx Suc‐added bread and had higher hardness and gumminess of bread crumb. In contrast, adding 2°Bx RSS did not affect the physical and texture characteristics of the bread. GC–MS analysis of the RSS‐added bread showed that acetol, 3,5‐dihydroxy‐6‐methyl‐2,3‐dihydro‐4H‐pyran‐4‐one, 5‐methylfurfural and acetic acid were the main volatiles, and the amounts were higher than in the Suc‐ and HFCS‐added breads. The addition of 20°Bx RSS resulted in the lowest liking scores for the bread texture, hardness and elasticity. The RSS‐added bread, with a lower evaluation than the 20°Bx Suc‐added bread, was acceptable in overall preference as the 20°Bx HFCS‐added bread. Moreover, after processing, the 20°Bx RSS‐bread retained 86% of the rare sugar D‐allulose with its health functions, so it could be beneficial to consumer health compared with HFCS and Suc.

An Organogermanium Compound Enhances the Initial Reaction Rate of Alkaline Isomerization of an Aldose into a Ketose through Enediol Complex Formation.

We previously demonstrated that the organogermanium compound 3-(trihydroxygermyl)propanoic acid (THGP) enhances the enzymatic and alkaline isomerization of an aldose to a ketose through cis-diol complex formation by multiple mechanisms. Its higher affinity for the ketose than the aldose protects the ketose complex from alkaline decomposition. Furthermore, it has been reported that the aldose-ketose alkaline isomerization pathway includes 1,2-enediol. Therefore, we speculated that the complex-forming ability of THGP could also be applied to enediol, a transient intermediate of alkaline isomerization. To test this prediction, we analyzed the initial rates of glucose or lactose isomerization in a region where there was no substantial difference in pH with and without THGP addition. The results showed that THGP enhanced the rate of fructose or lactulose formation per unit time by approximately 2-fold compared to the control. This finding indicated that THGP could form a complex with the transition state of aldose-ketose alkaline isomerization.

Anion-Specific Effects on the Alkaline State of Cytochrome c.

Specific effects of anions on the structure, thermal stability, and peroxidase activity of native (state III) and alkaline (state IV) cytochrome c (cyt c) have been studied by the UV-VIS absorbance spectroscopy, intrinsic tryptophan fluorescence, and circular dichroism. Thermal and isothermal denaturation monitored by the tryptophan fluorescence and circular dichroism, respectively, implied lower stability of cyt c state IV in comparison with the state III. The pKa value of alkaline isomerization of cyt c depended on the present salts, i.e., kosmotropic anions increased and chaotropic anions decreased pKa (Hofmeister effect on protein stability). The peroxidase activity of cyt c in the state III, measured by oxidation of guaiacol, showed clear dependence on the salt position in the Hofmeister series, while cyt c in the alkaline state lacked the peroxidase activity regardless of the type of anions present in the solution. The alkaline isomerization of cyt c in the presence of 8 M urea, measured by Trp59 fluorescence, implied an existence of a high-affinity non-native ligand for the heme iron even in a partially denatured protein conformation. The conformation of the cyt c alkaline state in 8 M urea was considerably modulated by the specific effect of anions. Based on the Trp59 fluorescence quenching upon titration to alkaline pH in 8 M urea and molecular dynamics simulation, we hypothesize that the Lys79 conformer is most likely the predominant alkaline conformer of cyt c. The high affinity of the sixth ligand for the heme iron is likely a reason of the lack of peroxidase activity of cyt c in the alkaline state.

The Effect of CLA-Rich Isomerized Poppy Seed Oil on the Fat Level and Fatty Acid Profile of Cow and Sheep Milk.

Simple SummaryConjugated linoleic acid (CLA) has attracted significant interest due to its health-related properties. The use of isomerized poppy-seed oil (IPO) enriched with CLA in cow and sheep feed reduced the fat content in milk and favorably modified the fatty acid profile. The content of saturated fatty acids (SFAs) in milk fat, especially medium-chain fatty acids showing adverse atherogenic and thrombogenic effects, decreased, while the content of polyunsaturated fatty acids (PUFAs), including biologically active fatty acids with pro-health properties (i.e., CLA isomers and trans-vaccenic acid (TVA)), increased. In conclusion, IPO with a high concentration of CLA could be used in dairy animal feed to change the nutritional quality and health value of milk, which is beneficial from a human point of view.The aim of the study was to examine the effect of dietary supplementation of isomerized poppy seed oil (IPO) enriched with conjugated dienes of linoleic acid (CLA) on cow and sheep milk parameters (fat content, fatty acid profile, Δ9-desaturase index, and atherogenic index). The process of poppy seed oil alkaline isomerization caused the formation of CLA isomers with cis-9,trans-11, trans-10,cis-12, and cis-11,trans-13 configurations in the amounts of 31.2%, 27.6%, and 4.1% of total fatty acids (FAs), respectively. Animal experiments were conducted on 16 Polish Holstein Friesian cows (control (CTRL) and experimental (EXP), n = 8/group) and 20 East Friesian Sheep (CTRL and EXP, n = 10/group). For four weeks, animals from EXP groups received the addition of IPO in the amount of 1% of dry matter. Milk was collected three times: on days 7, 14, and 30. Diet supplementation with IPO decrease milk fat content (p < 0.01). Milk fat from EXP groups had higher levels of polyunsaturated fatty acids, including FAs with beneficial biological properties, that is, CLA and TVA (p < 0.01), and lower levels of saturated fatty acids, particularly short- (p < 0.01) and medium-chain FAs (p < 0.05). The addition of IPO led to a decrease in the atherogenic index.

Effect of the double bond conjugation on the vascular physiology and nitric oxide production of isomers of eicosapentaenoic and docosahexaenoic acids prepared from shark oil.

A collection of evidence suggests that conjugation of double bonds of eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids, omega-3 polyunsaturated fatty acids (n-3 PUFAs), increases their anticarcinogenic activity; however, the effect of such conjugation on vascular tone activity remains unknown. We propose that the mixture of conjugated PUFAs exerts higher vasorelaxation activity than the corresponding mixture of nonconjugated PUFAs. The vascular response to different concentrations of conjugated and nonconjugated isomers of EPA and DHA, among other fatty acids (FAs) naturally present in shark oil, and the role of nitric oxide (NO) as a vasorelaxant agent were investigated. Both conjugated EPA (CEPA) and conjugated DHA (CDHA) were prepared by alkaline isomerization of all PUFAs contained in shark oil. Different concentrations of conjugated and nonconjugated PUFAs were placed in contact with precontracted aortic rings of Wistar rats to assess their effect on vascular tone. All tested samples exerted a vasorelaxant effect. Compared to nonconjugated PUFAs, conjugated isomers exhibited an increase in the dilatation of the aortic rings (P<0.001) in a dose-dependent manner (P<0.001). In addition, nonconjugated PUFAs produced nitric oxide (NO) in a dose-dependent manner, while conjugated PUFAs did not, suggesting that their dilatation mechanism is not totally dependent on NO.

Efficient Continuous Production of Lactulose Syrup by Alkaline Isomerization Using an Organogermanium Compound.

Lactulose, a keto-type disaccharide widely used in pharmaceuticals and functional foods, is produced by the isomerization of lactose. The organogermanium compound poly-trans-[(2-carboxyethyl) germasesquioxane] (Ge-132) is an effective reaction promoter for the conversion of lactose to lactulose because of its high affinity to ketoses. Herein, an effective method for the continuous production of lactulose syrup was developed using Ge-132 through the alkaline isomerization of lactose in a bench-scale plant. This plant carried out a continuous isomerization process using Ge-132, continuous two-step separation process for separating the sugar and Ge-132, a continuous purification and concentration processes for the lactulose syrup, and separation and purification processes for the recovery of Ge-132. In this bench-scale plant, lactulose-containing syrup (350 g/L lactulose, 92 g/L lactose, and 31 g/L galactose) was prepared. The syrup was produced at a rate of 37.7 mL/h, and the content of residual Ge-132 in the syrup was 2 mg/L. The separation process was a two-step separation system requiring an ordinary electrodialyzer and an electro deionizer, which allowed the separation of more than 99.6 % Ge-132 from the reaction mixture. Moreover, the majority of Ge-132 and sodium hydroxide were recovered through electrodialysis using a bipolar membrane. The proposed system is the first to represent the novel development of an effective continuous production system for lactulose-containing syrup on the basis of the use of organogermanium compounds and incorporation of the electrodialysis technology.

Naturally Occurring Disease-Related Mutations in the 40-57 Ω-Loop of Human Cytochrome c Control Triggering of the Alkaline Isomerization.

Naturally occurring mutations found in one of the two Ω-loop substructures in human cytochrome c are associated with low blood platelet count (thrombocytopenia). Both Ω-loops participate in the formation of conformers associated with cytochrome c peroxidase activity and apoptotic function. At alkaline pH values, the Met80 ligand to the ferric heme iron dissociates, and a lysine residue in the 71-85 Ω-loop coordinates to the iron. The alkaline isomerization has been the focus of extensive kinetic studies, and it is established that a deprotonation triggers the release of the Met80 ligand (p Ktrigger). A second deprotonation stabilizes a pentacoordinate heme form (p Ka2). In this study, site-directed variants at the 41 and 48 positions in the 40-57 Ω-loop and at the 81 and 83 positions in the 71-85 Ω-loop reveal that conformational transitions in the 71-85 Ω-loop, leading to the alkaline or peroxidatic conformers, are controlled by the 40-57 Ω-loop. We find that the variants causing thrombocytopenia, G41S and Y48H, lower the p Ktrigger and increase p Ka2. Our results are presented in a mechanistic framework, depicted by a cube, that accounts for the pH dependencies of the equilibrium and kinetic parameters governing the alkaline transition of the native protein and Ω-loop variants. The data are most consistent with the trigger for Met80 replacement by a lysine being a deprotonation within a hydrogen bonded unit that links the two Ω-loops rather than an individual group. Such a proposal aligns with the entatic contribution made by the same unit in controlling the Met80-Fe(III) bond strength.

Humanlike substitutions to Ω-loop D of yeast iso-1-cytochrome c only modestly affect dynamics and peroxidase activity

Structural studies of yeast iso-1-cytochrome c (L.J. McClelland, T.-C. Mou, M.E. Jeakins-Cooley, S.R. Sprang, B.E. Bowler, Proc. Natl. Acad. Sci. U.S.A. 111 (2014) 6648–6653) show that modest movement of Ω-loop D (residues 70–85, average RMSD versus the native structure: 0.81 Å) permits loss of Met80-heme ligation creating an available coordination site to catalyze the peroxidase activity mediated by cytochrome c early in apoptosis. However, Ala81 and Gly83 move significantly (RMSDs of 2.18 and 1.26 Å, respectively). Ala81 and Gly83 evolve to Ile and Val, respectively, in human cytochrome c and peroxidase activity decreases 25-fold relative to the yeast protein at pH 7. To test the hypothesis that these residues evolved to restrict the peroxidase activity of cytochrome c, A81I and G83V variants of yeast iso-1-cytochrome c were prepared. For both variants, the apparent pKa of the alkaline transition increases by 0.2 to 0.3 relative to the wild type (WT) protein and the rate of opening the heme crevice is slowed. The cooperativity of acid unfolding is decreased for the G83V variant. At pH 7 and 8, the catalytic rate constant, kcat, for the peroxidase activity of both variants decreases relative to WT, consistent with the effects on alkaline isomerization. Below pH 7, the loss in the cooperativity of acid unfolding causes kcat for peroxidase activity to increase for the G83V variant relative to WT. Neither variant decreases kcat to the level of the human protein, indicating that other residues also contribute to the low peroxidase activity of human cytochrome c.

Rare Sugar Syrup Containing d-Allulose but Not High-Fructose Corn Syrup Maintains Glucose Tolerance and Insulin Sensitivity Partly via Hepatic Glucokinase Translocation in Wistar Rats.

Ingestion of high-fructose corn syrup (HFCS) is associated with the risk of both diabetes and obesity. Rare sugar syrup (RSS) has been developed by alkaline isomerization of HFCS and has anti-obesity and anti-diabetic effects. However, the influence of RSS on glucose metabolism has not been explored. We investigated whether long-term administration of RSS maintains glucose tolerance and whether the underlying mechanism involves hepatic glucokinase translocation. Wistar rats were administered water, RSS, or HFCS in drinking water for 10 weeks and then evaluated for glucose tolerance, insulin tolerance, liver glycogen content, and subcellular distribution of liver glucokinase. RSS significantly suppressed body weight gain and abdominal fat mass (p < 0.05). The glucose tolerance test revealed significantly higher blood glucose levels in the HFCS group compared to the water group, whereas the RSS group had significantly lower blood glucose levels from 90 to 180 min (p < 0.05). At 30, 60, and 90 min, the levels of insulin in the RSS group were significantly lower than those in the water group (p < 0.05). The amount of hepatic glycogen was more than 3 times higher in the RSS group than that in the other groups. After glucose loading, the nuclear export of glucokinase was significantly increased in the RSS group compared to the water group. These results imply that RSS maintains glucose tolerance and insulin sensitivity, at least partly, by enhancing nuclear export of hepatic glucokinase.

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.

생물학적 방법을 통한 기능성 이당 lactulose의 생산과 응용 연구

Lactulose (4-O-β-D-galactopyranosyl-D-fructose) is a non-digestible synthetic ketose disaccharide which can used in food and pharmaceutical fields due to its useful functions for encephalopathy, chronic constipation, hyperammonemia, etc. Therefore, the lactulose is regarded as one of the most important disaccharides and have been concentrated much interesting as an attractive functional material in the current industry. From this reason, the research related on the production of lactulose has been carried out various academic and industrial research groups. To produce lactulose, two main methods, chemical production and enzymatic production have been used. Commercially lactulose produced by alkaline isomerization of lactose as chemical production method but it has many disadvantages such as rapid lactulose degradation, purification, and waste management. From these reasons, lactulose produced by enzymatic method which solves these problems has been suggested as a proper method for lactulose production. Two different enzymatic methods have been reported as methods for lactulose production. Lactulose can be obtained through hydrolysis and transfer reaction catalyzed by a β-galactosidase which requires fructose as co-substrate and exhibits a low conversion. Alternatively, lactulose can be produced by direct isomerization of lactose to lactulose catalyzed by cellobiose 2-epimerase which requires lactose as a single substrate and achieves a high lactulose yield. This review summarizes the current state of lactulose production by chemical and biological methods.

Production of Lactulose from Lactose in Subcritical Aqueous Ethanol

AbstractProduction of lactulose from lactose was performed in subcritical aqueous ethanol. The effects of ethanol concentration (0–60% (w/w)) and temperature (160–220C) on the isomerization of lactose were studied. The maximum yield of lactulose (34%) was obtained from the treatment of lactose in 60% (w/w) aqueous ethanol at 200C. The isomerization and hydrolytic reactions of lactose were promoted and suppressed, respectively, by increasing ethanol concentration. The use of higher concentrations of ethanol was restricted due to the low solubility of lactose. Additionally, different feed concentrations (0.5–2.5% w/w) were studied. The maximum lactulose productivity of 63 kg/(h m3‐reactor) was obtained from the treatment employing a 2.5% (w/w) feed concentration, indicating that subcritical aqueous ethanol is promising for the production of lactulose.Practical ApplicationsLactulose is a synthetic disaccharide comprising galactose and fructose. It has been broadly used as prebiotic food additives and drugs against constipation, hepatic encephalopathy and anti‐endotoxin effects. Industrial production of lactulose is currently performed by alkaline isomerization of lactose which has several drawbacks such as high level of by‐products and high cost of downstream processing. Subcritical aqueous ethanol is a novel technique for lactulose production. It can be used to overcome the disadvantages of chemical methods. The simplicity, high productivity, cost‐effectiveness and environmental benignity make this technique applicable to large‐scale lactulose production.

Synthesis, molecular docking and biological evaluation of glycyrrhizin analogs as anticancer agents targeting EGFR.

Glycyrrhizin (GA) analogs in the form of 3-glucuronides and 18-epimers were synthesized and their anticancer activities were evaluated. Alkaline isomerization of monoglucuronides is reported. In vitro and in vivo studies showed that glycyrrhetinic acid monoglucuronides (GAMGs) displayed higher anticancer activities than those of bisglucuronide GA analogs, while anticancer activity of the 18α-epimer was superior to that of the 18β-epimer. 18α-GAMG was firstly nicely bound to epidermal growth factor receptor (EGFR) via six hydrogen bonds and one charge interaction, and the docking calculation proved the correlation between anticancer activities and EGFR inhibitory activities. Highly active 18α-GAMG is thus of interest for the further studies as a potential anticancer agent.

Effectiveness of α-, γ- and δ-Tocopherol in a CLA-Rich Oil.

Conjugated linoleic acid (CLA) is a mixture of positional and geometric isomers of octadecadienoic acid with conjugated double bounds. Positive health properties have been attributed to some isomers, such as anticarcinogenic activity, antiartherosclerotic effects and reduction of body fat gain. Hence, oils rich in CLA such as Tonalin® oil (TO), normally obtained through alkaline isomerization of safflower oil (SO), an oil rich in linoleic acid (LA), are currently used in functional foods. However, special care must be taken to protect them from oxidation to ensure the quality of the supplemented foods. The objective of this work was to evaluate the oxidation and effectiveness of different tocopherol homologues (α-, γ- and δ-), alone or in combination with synergists (ascorbyl palmitate and lecithin), in TO compared to SO at different conditions, ambient temperature (25 °C) and accelerated conditions in Rancimat (100 °C). The oils, the oils devoid of their antioxidants and the latter containing the antioxidants added were assayed. Results showed great differences between SO and TO in terms of formation of hydroperoxides and polymers and also in the effectiveness of tocopherols to delay oxidation. TO showed higher levels of polymerization and, in general, the effectiveness of tocopherol homologues, alone or in combination with synergists, was also lower in the TO.

Isolation and optimisation of the oleaginous yeast Sporobolomyces roseus for biosynthesis of 13C isotopically labelled 18-carbon unsaturated fatty acids and trans 18:1 and 18:2 derivatives through synthesis

An oleaginous and psychrotrophic strain (F38-3) of Sporobolomyces roseus Kluyver & van Niel was isolated from a salt marsh environment in Nova Scotia, Canada following a screening program to select for high producers of 18-carbon unsaturated fatty acids. Fatty acid production was characterised as a function of temperature at 20 g glucose L(-1), and optimal yields were obtained at 14°C, achieving 5.7 g dw biomass and 39.2% total fatty acids by dry weight, with 18:1, 18:2 and 18:3 all-cis fatty acids accounting for 49.4%, 14.3% and 6.7% of total fatty acids (TFA), respectively--the highest reported for this species. Production of 18:3 was inversely correlated to growth temperature, rising from 2% of TFA at 30°C to 8.9% at 6°C. Cultivation of isolate F38-3 on universally (13)C (U-(13)C) labelled glucose and subsequent transesterification and isolation of the fatty acid methyl esters (FAMEs) by preparative chromatography yielded pure, highly (13)C-enriched (>90%) 18:1, 18:2 and 18:3 all-cis FAMEs. The U-(13)C 18:1 FAME was catalytically converted to U-(13)C 18:1 trans-9 and purified to >99.5% purity. The U-(13)C 18:2 was converted by alkaline isomerisation into a 50/50 mixture of 18:2 cis-9, trans-11 and 18:2 trans-10, cis-12 isomers and purified to >95.0% purity. Overall, 10%, by weight, of labelled glucose fed to isolate F38-3 was recovered as fatty acid methyl esters and 7.5% as 18-carbon unsaturated fats, and the final isomerisation reactions resulted in yields of 80% or greater. The ultimate goal of the work is to develop methodologies to produce (13)C-labelled metabolic tracers as tools to study the metabolism of trans fats.

The effects of 90-day feeding of D-psicose syrup in male wistar rats

D-Psicose is a rare sugar present in small quantities in natural products. In a previous study, we showed that D-psicose suppresses increase in plasma glucose and reduces body fat accumulation in rats. Based on acute and chronic toxicity testing in rats, D-psicose is classified as an ordinary and safe substance. Recently, we developed a high D-psicose syrup (PS) made from high fructose corn syrup (HFCS) by the alkaline isomerization method. However, the safety of PS as a food additive has not been demonstrated. In this study, we investigated the effects of 90-day feeding of PS in male Wistar rats. The rats were fed diets containing 3% D-psicose (control) or 4.3% PS for 90 days. The body weight gain and intra-abdominal adipose tissue weight did not differ between the control and PS group. The weights of the tissues did not differ between the two dietary groups. In clinical chemistry and hematological analyses, no differences were found between the control and PS groups. No gross pathological findings were evident at dietary doses of 4.3% PS. Therefore, the present study found no adverse effects of PS in rats fed a diet containing 4.3% PS for 90 days.

A new liquid chromatography method for the simultaneous and sensitive quantification of lactose and lactulose in milk

The disaccharide lactulose is known to have a large influence on human digestion, the effects of which range from prebiotic to laxative action. Lactulose can be derived from lactose by either alkaline isomerization or enzymatic transgalactosylation of fructose. The aim of this study was to establish a new analytical method for the quantification of both disaccharides lactose and lactulose using high performance liquid chromatography (HPLC) and evaporative light scattering detection (ELSD). The new method needs to provide good chromatographic separation of lactose and lactulose while being fast and reliable. Therefore, four analytical methods using different HPLC columns were developed and compared. A HPLC column with an amino-bonded polymeric matrix yielded better results compared to amino-bonded silica-phase resin or cation-exchange resin. The new method had detection limits for lactose and lactulose of 3.8 and 2.5 mg L−1 and was successfully applied to the quantification of lactulose and lactose in commercial milk products.

Solubility of carbohydrates in supercritical carbon dioxide with (ethanol + water) cosolvent

Prebiotic carbohydrates are defined as non-digestible carbohydrates that beneficially affect the host by selectively stimulating the growth and/or activity of a limited number of bacteria in the colon. The present study is focused on two prebiotic ketosugars: tagatose and lactulose, which are currently obtained by alkaline isomerization of their respective aldoses—galactose and lactose. It is a part of a broader research devoted to examining the possibility of complex solid carbohydrate mixtures fractionation using supercritical carbon dioxide and alcohol-type cosolvents. We report new experimental solubility data of tagatose, galactose, lactulose and lactose in supercritical carbon dioxide with ethanol:water (95:5, v/v) used as a cosolvent at T = (60 and 100) °C, P = (10–30) MPa and cosolvent content from 6 to 21% (w/w). The solubility measured was in the range (0.02–1.09) mg g −1. Additionally, the experimental data was correlated using the Soave–Redlich–Kwong cubic equation of state with the modified Huron-Vidal second order (MHV2) mixing rule. The latter employs the mS-UNIFAC, which introduces two new groups in the original UNIFAC parameter matrix to represent the sugar molecules.