Simultaneous determination of galactose, glucose, lactose and galactooligosaccharides in galactooligosaccharides raw materials by high-performance anion-exchange chromatography with pulsed amperometric detection

A dual-mode biosensor based on metal organic framework-coated upconversion composites with near-infrared luminescence and peroxidase-like activity for the detection of alkaline phosphatase and glucose

An abnormal level of alkaline phosphatase (ALP) in serum is related to many diseases, such as breast cancer, prostate cancer, hepatitis, and diabetes. The level of glucose in the blood is related to diabetes or hypoglycemia. Given the close correlation between ALP and glucose in various diseases, it is essential to establish an accurate, sensitive, and selective assay for monitoring the levels of ALP and glucose in serum. As luminescent materials, upconversion nanoparticles (UCNPs) stand out in the design of biosensors because of their high photostability, large anti-Stokes shifts and low background interference. Additionally, metal organic frameworks (MOFs) are a class of functional porous materials, and their adjustable pore size structure and high specific surface area expose many catalytic sites, making MOFs excellent catalysts and ideal materials for constructing artificial enzymes. Herein, a fluorescent and colorimetric dual-mode probe based on a multifunctional composite (UCNP@MOF) with upconversion luminescence and peroxidase-like activity was proposed for the detection of ALP and glucose. Under the optimal conditions, the detection limits of ALP and glucose by the fluorescence method were 0.046 U/L and 0.079 μM, respectively. Furthermore, the method was used to determine ALP and glucose in serum samples, and the detection results were similar to those of commercial kits; moreover, the recoveries were in the range of 92.7-105.4 %, indicating great potential for accurate and sensitive detection of ALP and glucose in biological samples.

Distinguishing α/β-linkages and linkage positions of disaccharides in galactooligosaccharides through mass fragmentation and liquid retention behaviour

Galactooligosaccharides (GOS) are important prebiotics with function closely related to their structure. However, a comprehensive overview of the structure-function relationship is still limited due to the challenge in characterizing multiple isomers in GOS. This study presents a strategy of combining both hydrophilic interaction liquid chromatography (HILIC) retention time and tandem mass spectrometry (MS/MS) fragmentation pattern to distinguish α/β-linkages and linkage positions of disaccharide isomers in GOS through HILIC-MS/MS analysis. The results indicated that the ratio of m/z 203.0524 to m/z 365.1054 could distinguish α/β-linkages, while the ratios of m/z 347.0947 to m/z 365.1054, m/z 245.0642 to m/z 365.1054 and HILIC retention time could distinguish (1 → 2), (1 → 3), (1 → 4) and (1 → 6) linkages. The above rules enabled effective characterization of disaccharides in GOS-containing food samples, including milk powder, rice flour, drink, yogurt. This method can be used in the quality control of GOS and future research on the structure-specific health effects of GOS.

ZIF-8 encapsulated-enzymes integrated nanozyme cascade biocatalysis platform for the colorimetric sensing of glucose and lactose in milk

Cascade biocatalytic reactions have a wide range of applications, especially in the filed of food analysis. Herein, a multi-enzyme composite (ZGGPC) was prepared by in-situ synthesis of Zeolite imidazole framework-8 (ZIF-8) on Prussian blue (PB) modified carbon cloth (CC). The composite encapsulated both glucose oxidase and β-galactosidase simultaneously during the synthesis process. CC and ZIF-8 showed high loading capacity for PB and natural enzymes, respectively. And ZIF-8 also displayed excellent tolerance in protecting enzyme activity under extreme conditions. Based on the cascade biocatalysis, ZGGPC was used to detect glucose and lactose by colorimetric method with detection limits of 1.2 μM and 1.7 mM, respectively. Benefiting from the merits of low cost, easy preparation, and good stability, the sensing system was used to successfully determine glucose and lactose in different milk samples. The present cascade biocatalysis system is hopeful to develop simple and efficient sensing platforms for food analysis.

Insights into the mechanisms underlying the degradation of xylooligosaccharides in UV/H2O2 system

UV/H₂O₂ process is increasingly used to degrade carbohydrates, though the underlying mechanisms remain unclear. This study aimed to fill this knowledge gap, focusing on mechanisms and energy consumption involved in hydroxyl radical (•OH)-mediated degradation of xylooligosaccharides (XOSs) in UV/H₂O₂ system. Results showed that UV photolysis of H₂O₂ generated large amounts of •OH radicals, and degradation kinetics of XOSs fitted with a pseudo-first-order model. Xylobiose (X₂) and xylotriose (X₃), main oligomers in XOSs, were attacked easier by •OH radicals. Their hydroxyl groups were largely converted to carbonyl groups and then carboxy groups. The cleavage rate of glucosidic bonds was slightly higher than that of pyranose ring, and exo-site glucosidic bonds were more easily cleaved than endo-site bonds. The terminal hydroxyl groups of xylitol were more efficiently oxidized than other hydroxyl groups of it, causing an initial accumulation of xylose. Oxidation products from xylitol and xylose included ketoses, aldoses, hydroxy acids and aldonic acids, indicating the complexity of •OH radical-induced XOSs degradation. Quantum chemistry calculations revealed 18 energetically viable reaction mechanisms, with the conversion of hydroxy-alkoxyl radicals to hydroxy acids being the most energetically favorable (energy barriers <0.90 kcal/mol). This study will provide more understanding of •OH radicals-mediated degradation of carbohydrates.

Capillary electrophoresis analysis of industrial galactooligosaccharides

Galactooligosaccharides are added to infant formula to simulate some of the benefits associated with human milk oligosaccharides, in particular to modulate the gut microbiota. During our study the galactooligosaccharide content of an industrial GOS ingredient was determined by differential enzymatic digestion using amyloglucosidase and β-galactosidase. The resulting digests were fluorophore labeled and analyzed by capillary gel electrophoresis with laser induced fluorescence detection. Quantification of the results were based on a lactose calibration curve. Utilizing this approach, the galactooligosaccharide concentration of the sample was determined as 37.23 g/100 g, very similar to earlier HPLC results, but requiring only 20 min separation time. The CGE-LIF method in conjunction with the differential enzymatic digestion protocol demonstrated in this paper offers a rapid and easy to use method to measure galactooligosaccharides and should be applicable to the determination of GOS in infant formulas and other products.

Tripartite Symbiotic Digestion of Lignocellulose in the Digestive System of a Fungus-Growing Termite

Fungus-growing termites are efficient in degrading and digesting plant substrates, achieved through the engagement of symbiotic gut microbiota and lignocellulolytic Termitomyces fungi cultivated for protein-rich food. Insights into where specific plant biomass components are targeted during the decomposition process are sparse. In this study, we performed several analytical approaches on the fate of plant biomass components and did amplicon sequencing of the 16S rRNA gene to investigate the lignocellulose digestion in the symbiotic system of the fungus-growing termite Odontotermes formosanus (Shiraki) and to compare bacterial communities across the different stages in the degradation process. We observed a gradual reduction of lignocellulose components throughout the process. Our findings support that the digestive tract of young workers initiates the degradation of lignocellulose but leaves most of the lignin, hemicellulose, and cellulose, which enters the fresh fungus comb, where decomposition primarily occurs. We found a high diversity and quantity of monomeric sugars in older parts of the fungus comb, indicating that the decomposition of lignocellulose enriches the old comb with sugars that can be utilized by Termitomyces and termite workers. Amplicon sequencing of the 16S rRNA gene showed clear differences in community composition associated with the different stages of plant biomass decomposition which could work synergistically with Termitomyces to shape the digestion process. IMPORTANCE Fungus-farming termites have a mutualist association with fungi of the genus Termitomyces and gut microbiota to support the nearly complete decomposition of lignocellulose to gain access to nutrients. This elaborate strategy of plant biomass digestion makes them ecologically successful dominant decomposers in (sub)tropical Old World ecosystems. We employed acid detergent fiber analysis, high-performance anion-exchange chromatography (HPAEC), high-performance liquid chromatography (HPLC), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), pyrolysis gas chromatography-mass spectrometry (Py-GC-MS), and amplicon sequencing of the 16S rRNA gene to examine which lignocellulose components were digested and which bacteria were abundant throughout the decomposition process. Our findings suggest that although the first gut passage initiates lignocellulose digestion, the most prominent decomposition occurs within the fungus comb. Moreover, distinct bacterial communities were associated with different stages of decomposition, potentially contributing to the breakdown of particular plant components.

Barley Husk Degraded by Fusarium graminearum MH1 Induced Premature Yeast Flocculation

Premature yeast flocculation (PYF) is one of the pivotal problems affecting beer flavor and production. PYF is induced by certain non-starch polysaccharides produced by the degradation of malted barley husks upon the growth of contaminated microorganisms, such as Fusarium graminearum. In this research, the formation mechanism of PYF was uncovered by investigating the secretome of F. graminearum MH1 inoculated to the barley husk. The polysaccharide extract of degraded husk was ultrafiltrated into four fractions and characterized by the minimum PYF concentration, molecular mass distribution, monosaccharide composition, and zeta potential. Among the four fractions, the high-molecular-weight polysaccharide fraction had the highest content of uronic acid and the most negative zeta potential, which contributed to the most severe PYF phenomenon. In addition, the PYF yeast showed a more negative zeta potential than the control yeast during the small-scale brewing process. This is aligned to the negatively charged polysaccharides potentially bonded to the surface of yeast cells through the calcium cation in the same fermentation system, which results in rapid flocculation and precipitation. Approximately 12% of the 214 proteins identified in the Fusarium graminearum MH1 secretome were hemicellulases, which substantially interpreted the mechanism of polysaccharides inducing PYF yeast during beer brewing.

Application of accelerated heteronuclear single quantum coherence experiments to the rapid quantification of monosaccharides and disaccharides in dairy products

Monosaccharides and disaccharides are important dietary components, but if insufficiently metabolized by some population subgroups, they are also linked to disease patterns. Thus, the correct analytical identification, quantification, and labeling of these food components are crucial to inform and potentially protect consumers. Enzymatic assays and high-performance anion-exchange chromatography with pulsed amperometric detection are established methods for the quantification of monosaccharides and disaccharides that, however, require long measuring times (60-180 min). Accelerated methods for the identification and quantification of the nutritionally relevant monosaccharides and disaccharides d-glucose, d-galactose, d-fructose, sucrose, lactose, and maltose were therefore developed. To realize this goal, the NMR experiments HSQC (heteronuclear single quantum coherence) and acceleration by sharing adjacent polarization (ASAP)-HSQC were applied. Measurement times were reduced to 27 and 6 min, respectively, by optimizing the interscan delay and applying non-uniform sampling. The optimized methods were used to quantify d-glucose, d-galactose, d-fructose, sucrose, and lactose in various dairy products. Results of the HSQC and ASAP-HSQC methods are equivalent to the results of the reference methods in terms of both precision and accuracy, demonstrating that these methods can be used to correctly analyze nutritionally relevant monosaccharides and disaccharides in short times.

Influence of Homogenization in the Physicochemical Quality of Human Milk and Fat Retention in Gastric Tubes

BACKGROUND

The retention of human milk nutrients in gastric tubes used to feed premature infants is a challenge to be overcome.

RESEARCH AIMS

To evaluate (1) the performance of six homogenizers (mixing processor, piston valve, ultrasonic bath, ultraturrax, stirring mixer, and ultrasound probe) for the fat retention reduction in gastric tubes; (2) the influence of the best homogenization conditions on the fatty acid and protein profiles of human milk; and (3) the cost/benefit ratio for the inclusion of homogenization as a new step in human milk processing.

METHODS

The influence of different levels and times of homogenization on reducing fat retention of human milk in probes was evaluated in this comparative prospective cross-sectional study. After homogenization, human milk flowed through a gavage and infusion pump apparatus used for feeding. Fat content was quantified before and after feeding. The techniques that reduced fat globule sizes and/or promoted a lower percentage of fat holding were evaluated for efficiency, variations in the fatty acid and protein profiles, and energy density and operating costs.

RESULTS

Homogenization led to a reduction in fat retention in feeding probes. The mixer processor and the ultrasound probe reduced fat retention by 99.23% (SD = 0.07) and 99.95% (SD = 0.02), respectively, and did not negatively influence fatty acid and protein profiles. The mixer processor demonstrated low energy density and low cost for human milk processing.

CONCLUSION

Homogenization promoted reduced fat retention in the feed probe and could help maintain fat nutrients of human milk during enteral feeding.

Comparative Study on Volatile Compounds and Taste Components of Different Durian Cultivars Based on GC-MS, UHPLC, HPAEC-PAD, E-Tongue and E-Nose

In order to comprehensively evaluate the aroma-active substances and taste components of durian, solid-phase microextraction combined with gas chromatography mass spectrometry (SPME/GC-MS), high-performance anion-exchange chromatography with pulsed amperometric detection (HPAEC-PAD) and ultra-high-performance liquid chromatography (UHPLC) were used to test the key components of three popular durian cultivars. A total of 27 volatile compounds, 5 sugars, 27 organic acids and 19 free amino acids were detected in Black Thorn (BT) durian. A total of 38 volatile compounds, 4 sugars, 27 organic acids and 19 free amino acids were detected in Monthong (MT) durian. A total of 36 volatile compounds, 4 sugars, 27 organic acids and 20 free amino acids were detected in Musang King (MK) durian. Finally, the flavor differences of the three durians were evaluated using electronic nose (e-nose) and electronic tongue (e-tongue), and different cultivars were classified through principal component analysis (PCA).

Determination of β-Galactooligosaccharides (GOS) in Infant Formula and Adult Nutritionals: Single-Laboratory Validation, First Action 2021.01

BACKGROUND

β-Galactooligosaccharides (GOS) are typically used in infant formula and adult nutritionals as a source of nondigestible oligosaccharides, which may bring beneficial effects through modulation of the gut microbiota. However, suitable methods for the determination of GOS in products with a high background of lactose do not exist.

OBJECTIVE

The aim of this work was to develop a method suitable for the determination of GOS in infant formula and adult nutritionals and demonstrate suitability through single laboratory validation.

METHODS

Reducing oligosaccharides are labeled with 2-aminobenzamide (2AB), separated by hydrophilic interaction LC, and determined assuming that all oligosaccharides give an equimolar response in the detector. The same sample is analyzed a second time after treatment with β-galactosidase to remove GOS. The difference in the determined oligosaccharides between the two measurements will be the GOS content of the sample. The method was validated in a single laboratory on infant formula and adult nutritionals.

RESULTS

Recoveries were in the range 91.5-102%, relative standards of deviation (RSDr) were in the range 0.7-5.99%, and one sample had an RSDr of 8.30%. Except for the one sample with an RSDr of 8.30%, the performance is within the requirements outlined in the Standard Method Performance Requirements, which specifies recoveries in the range 90-110% and RSDr of below 6%.

CONCLUSIONS

The method is suitable for the determination of GOS in infant formula and adult nutritionals.

HIGHLIGHTS

A method has been developed which is suitable for the determination of GOS in products with a high background concentration of lactose (infant fromula and adult nutritionals). The method does not require access to the GOS ingredient used for the production of the finished product. It is also possible to separately quantify the amount of GOS containing three or more monomeric units in order to support dietary fibre analysis.

Recent approaches for the quantitative analysis of functional oligosaccharides used in the food industry: A review

Functional oligosaccharides (OS) are diverse groups of carbohydrates that confer several health benefits stemming from their prebiotic activity. Commonly used oligosaccharides, fructooligosaccharides and galactooligosaccharides, are used in a wide range of applications from food ingredients to mimic the prebiotic activity of human milk oligosaccharides (HMOs) in infant formula to sugar and fat replacers in dairy and bakery products. However, while consumption of these compounds is associated with several positive health effects, increased consumption can cause intestinal discomfort and aggravation of intestinal bowel syndrome symptoms. Hence, it is essential to develop rapid and reliable techniques to quantify OS for quality control and proper assessment of their functionality in food and food products. The present review will focus on recent analytical techniques used to quantify OS in different matrices such as food and beverage products.

Enhancing the peroxidase activity and decreasing the protease activity of ficin with rational modification and its application to one-step colorimetric detection of glucose

Ficin has dual enzyme activity, i.e., protease and peroxidase-like activity. In some respects, its application is limited by the protease activity of ficin. Herein, we used tris (2-carboxyethyl) phosphine hydrochloride (TCEP) to break the three pairs of disulfide bonds of ficin, and then blocked the free thiol groups with N-ethylmaleimide (NEM) to synthesize ficin-TN. The results showed that ficin-TN had increased peroxidase-like activity and reduced protease activity. According to this phenomenon, we have exploited a colorimetric method with high sensitivity and selectivity for the one-step detection of glucose. Comparing with ficin, ficin-TN has wider detection range (0.1-300 μM) and lower detection limit (88 nM), and our method is simpler and more timesaving than other two-step methods. Furthermore, the actual appliances of ficin-TN for glucose detection in human serum have been illustrated with satisfied result, suggesting that its promising utilization in various fields.

Detection of galactooligosaccharides with high lactose interference in infant formula using a simple single epimer chromatography

Robust and more anti-interference enzymatic quantification of galactooligosaccharide (GOS) is important in consumer protection. However, many methods with harsh conditions could hardly separate GOS's hydrolysates galactose from its structurally similar isomer glucose, since each of them has double epimers, especially to determinate a trace of GOS from large amounts of lactose in the food matrix. The investigation was designed to solve the problem by using High Performance Liquid Chromatography with Evaporative Light Scattering Detector (HPLC-ELSD), applying friendly mobile phase and column. Result showed the content of galactose was seldom affected even by a high content of glucose by integrating the peak area of an excellent resolution single epimer. Moreover, the method existed a good linearity and stability (recovery rate at 90.5-105.1%), which met the statutory limit requirement for the quantitative analysis of concentrated GOS in infant formula. It was also helpful for separating and quantifying other sugar or epimers.

Electrochemical Oxidation of Monosaccharides at Nanoporous Gold with Controlled Atomic Surface Orientation and Non-Enzymatic Galactose Sensing

Non-enzymatic saccharide sensors are of great interest in diagnostics, but their non-selectivity limits their practical diagnostic abilities. In this study, we investigated the electrochemical oxidation of monosaccharides at nanoporous gold (NPG) catalysts with different contributions of surface crystallographic orientations. Fructose elicited no clear electrochemical response, but glucose, galactose, and mannose produced clear oxidative current. The onset potentials for oxidation of these saccharides depended on the surface atomic structure of the NPG. The oxidation potential was approximately 100 mV less positive at the Au(100)-enhanced NPG than at the Au(111)-enhanced NPG. Furthermore, the voltammetric responses significantly differed among the saccharides. Galactose was oxidized at less positive potential and exhibited a higher current response than the other saccharides. This tendency was enhanced in the presence of chloride ions. These features enabled the selective and sensitive detection of galactose at an NPG electrode without enzymes under physiological conditions. A linear range of 10 μM to 1.8 mM was obtained in the calibration plot, which was comparable to those in previously reported enzymatic galactose sensors. Thus, we demonstrated that controlling the crystallographic orientation on the nanostructured electrode surface is useful in developing electrochemical sensors.

Development of amperometric biosensor in modified carbon paste with enzymatic preparation based on lactase immobilized on carbon nanotubes

Abstract

The variety of products derived from milk, without or with lactose, encourages the development of more effective analytical techniques that can be applied to the quality control of both the production line and the final products. Thus, in this work an efficient and minimally invasive method for the detection of lactose was proposed, using a biosensor containing the enzyme lactase (LAC) immobilised on carbon nanotubes (CNTs) that, when reacting with lactose, emit an electrochemical signal. This biosensor was connected to a potentiostat, and its electrochemical cell was composed of the following three electrodes: reference electrode (Ag/AgCl), auxiliary electrode (platinum wire), and working electrode (biosensor) on which graphite (carbon) paste (CP), CNTs, and LAC were deposited. The transmission electron microscopy and scanning electron microscopy were used in the characterisation of the composite morphology, indicating excellent interactions between the CNTs and LAC. The sensitivity of the CP/LAC/CNT biosensor was determined as 5.67 μA cm^-2.mmol^-1 L and detection limits around 100 × 10^-6 mol L^-1 (electrode area = 0.12 cm²) and an increase in the stability of the system was observed with the introduction of CNTs because, with about 12 h of use, there was no variation in the signal (current). The results indicate that the association between the CNTs and LAC favoured the electrochemical system.

Graphic Abstract

Rapid HPLC method for monitoring of lactulose production with a high yield

An HPLC method suitable for rapid monitoring of lactulose production by isomerization from lactose was developed. The separation of lactose and lactulose under hydrophilic interaction liquid chromatography (HILIC) mode was achieved with resolution 1.5 within 5 min. Since isocratic elution was used, there is no extra time necessary for the column equilibration. Application of the method was illustrated on monitoring lactulose isomerization with catalysis of sodium hydroxide in the presence of sodium tetraborate at 70 °C (pH = 11). The conversion yield obtained for lactulose was 86%, and corresponding purity 76%. For the first time, a polyhydroxy stationary phase for separation of lactose and lactulose is reported.