Simon Ballance

Sphagnan – a pectin‐like polymer isolated from Sphagnum moss can inhibit the growth of some typical food spoilage and food poisoning bacteria by lowering the pH

Aims:  Investigate if the antibacterial effect of sphagnan, a pectin‐like carbohydrate polymer extracted from Sphagnum moss, can be accounted for by its ability to lower the pH.

Cereal β-glucan quantification with calcofluor-application to cell culture supernatants.

The specific binding of the fluorescent dye calcofluor to cereal β-glucan results in increased fluorescence intensity of the formed complex and is in use for the quantification of β-glucan above a critical molecular weight (MW) by flow injection analysis. In this study, this method was applied in a fast and easy batch mode. In order to emphasize the spectral information of the emission spectra of the calcofluor/β-glucan complexes, derivative signals were calculated. A linear relationship was found between the amplitude of the second derivative signals and the β-glucan concentration between 0.1 and 0.4 μg/mL. The low detection limit of this new method (0.045 μg/mL) enabled its use to study the transport of cereal β-glucans over differentiated Caco-2 cell monolayers. Additionally, the method was applied to quantify β-glucan in arabinoxylan samples, which correlated well with data by an enzyme based method.

Viscosity based quantification of endogenous β-glucanase activity in flour

High molecular weight (MW) is a key parameter for cereal β-glucans physiological benefits like decreased serum cholesterol and attenuated post prandial blood glucose. However, the activity of endogenous flour enzymes during bread production results in a decrease of β-glucan MW. The depolymerization of a standard β-glucan solution by different flour extracts (wheat, barley and rye) was followed by measuring the viscosity decrease with a Rheometer. The slope of the inverse viscosity (1/η) against degradation time was used to quantify β-glucanase activity by comparison with slopes obtained with known concentrations of the β-glucanase Lichenase. Results correlated well with depolymerization rates estimated by HPSEC. The viscosity based method is rapid (20 min per sample), accurate (≤6% variation), and a powerful screening tool for identifying flour fractions with low β-glucanase activity, treatments that can inactivate β-glucanases in flour, or the development of β-glucanase inhibitors for the use in e.g. bread making.

Structural characterization of a branched (1 → 6)-α-mannan and β-glucans isolated from the fruiting bodies of Cantharellus cibarius

A comprehensive characterization of polysaccharides from the chanterelle was performed. Experiments included both linkage analysis by methylation and GC-MS, monosaccharide composition analysis by methanolysis, SEC-MALLS and several NMR experiments including COSY, HSQC, TOCSY, HSQC-TOCSY, NOESY, and HMBC. A 671kDa (1→6)-linked α-d-mannan with single and short (1→2)-linked side chains (WCcF1b) was isolated from the hot water extract, after protease treatment and fractionation by size exclusion chromatography. The hot 1M NaOH extract contained two types of β-glucan; a water soluble (1→6)-linked β-d-glucan with single and short (1→3)-linked β-glucan side chains (ACcSw) and a less branched (1→3)-linked β-d-glucan (ACcIw/ACcId), proposed to contain short side chains in O-4. Chemical shifts assignments of the α-mannan and β-glucan are presented as well as chemical shift values obtained from a (1→6)/(1→3)-β-d-glucan derived from Saccharomyces cerevisiae which was used as reference.

Towards on-line prediction of dry matter content in whole unpeeled potatoes using near-infrared spectroscopy

Prediction of dry matter content in whole potatoes is a desired capability in the processing industry. Accurate prediction of dry matter content may greatly reduce waste quantities and improve utilization of the raw material through sorting, hence also reducing the processing cost. The following study demonstrates the use of a low resolution, high speed NIR interactance instrument combined with partial least square regression for prediction of dry matter content in whole unpeeled potatoes. Three different measuring configurations were investigated: (1) off-line measurements with contact between the potato and the light collection tube; (2) off-line measurements without contact between the potato and the light collection tube; and (3) on-line measurements of the potatoes. The offline contact measurements gave a prediction performance of R(2)=0.89 and RMSECV=1.19. Similar prediction performance were obtained from the off-line non-contact measurements (R(2)=0.89, RMSECV=1.23). Significantly better (p=0.038) prediction performance (R(2)=0.92, RMSECV=1.06) was obtained with the on-line measuring configuration, thus showing the possibilities of using the instrument for on-line measurements. In addition it was shown that the dry matter distribution across the individual tuber could be predicted by the model obtained.

Inter-laboratory evaluation of SEC-post-column calcofluor for determination of the weight-average molar mass of cereal β-glucan.

Even though size exclusion chromatography (SEC) with post column addition of calcofluor (SEC-calcofluor) has been used for the determination of cereal β-glucan molar mass in foods for many years, there is a lack of systematic evaluation of the method. To address this issue a set of suitable β-glucan standards were generated by preparative SEC and their molar mass characteristics were determined by analytical multi-detection SEC (refractive index (RI), light scattering). Each standard was then analysed by SEC-calcofluor at three different labs. As a direct comparison, the analyses were repeated with a RI detector. For SEC-calcofluor accurate measurements of weight average molar mass (Mw) can be made for β-glucan populations within 10-500×10(3)g/mol. Above this molar mass threshold there is an increasing tendency for underestimation of Mw. Precipitation of some β-glucan-calcofluor complexes may have delayed their transport into the detector.

Application of high-performance anion-exchange chromatography with pulsed amperometric detection to compare the kinetic properties of β-glucosidase on oligosaccharides from lichenase digested barley β-glucan

A chromatographic method using HPAEC-PAD was developed to accurately quantify the major oligosaccharides derived from lichenase degradation of barley β-glucan. This method was further used to follow β-glucosidase degradation and product formation as progress curves. This approach allowed us to compare the kinetic characteristics of β-glucosidase on each exclusive oligosaccharide substrate and their mixtures. Our results show that when determining the kinetic parameters of exohydrolases on oligosaccharides following the progress curve for the substrates is necessary since calculations based only on released monosaccharide products may lead to an error. The catalytic activity of almond β-glucosidase on laminaribiose (G3G) was approximately half that measured against cellobiose (3.15 S(-1)). The enzyme had 12 times and 560 times less catalytic activity on 3-O-β-cellobiosyl-D-glucose (G4G3G) and on 3-O-β-cellotriosyl-d-glucose (G4G4G3G) respectively than on G3G. Our approach offers a useful tool for the determination of the kinetics of enzymatic or chemical modification of various carbohydrate substrates.

Impact of hydrothermal and mechanical processing on dissolution kinetics and rheology of oat β-glucan

Highlights • β-Glucan release from oat cell walls during incubation was not complete.• Processing of oats affects the rate and extent of β-glucan release and solution rheology.• The rheology of β-glucan solutions varied depending on oat composition and presence of particulates.• Variations in β-glucan solubility have important implications for physiological activity.

Preparation of high purity monodisperse oligosaccharides derived from mannuronan by size-exclusion chromatography followed by semi-preparative high-performance anion-exchange chromatography with pulsed amperometric detection

Oligosaccharides of ([4)-beta-d-ManpA-(-->](n)) with a degree of polymerisation (DP) of 5, 10 and 15 were generated by partial acid hydrolysis of alginate mannuronan. These were subsequently purified by a combination of size-exclusion chromatography and semi-preparative high-performance anion-exchange chromatography with pulsed amperometric detection. The purity of the isolated oligosaccharides was greater than 96%. With automated operation of the chromatography system, milligram quantities can be generated over a period of a few days. Thus, our methodology now offers some significant advantages over earlier, including our own, protocols focused on uronic acid oligomers, where the final products are either not as pure or more starting material is needed to generate an equivalent yield of product. Removal of ammonium ions in collected fractions after size-exclusion chromatography and prior to freeze-drying was found to be essential to prevent the formation of imines and subsequent Maillard browning products.

The impact of oat structure and β-glucan on in vitro lipid digestion

Graphical abstract The effect of oat β-glucan on lipid digestion relies on the delivery form of the polymer.