Analytical Services

• Carbohydrate composition
• Stereochemistry of sugar residues
• Polysaccharide linkage analysis

GC is the method of choice for glycosyl-residue identification (i.e., the sugar components that make up polysaccharides and oligosaccharides). Two basic derivitization techniques allow for the necessary volatilization and ultimate separation of each glycosyl residue that is released from the polymers by the initial acid hydrolysis. The standard alditol acetate derivitization (or acetylation) technique is highly reproducible and enables the identification of neutral sugar components. A TMS-methyl glucoside techniques expands the analysis to the acidic components, such as the galacturonic acid residues that constitute common pectin. A variation of this second technique is used to determine the d or l configuration of each sugar component.

In addition to glycosyl-residue identification, the methylation of polysaccharides prior to acid hydrolysis and acetylation facilitates the identification of the glycosyl residue linkage points. This is essential to understanding the nature and identity of the polysaccharides.

• Molecular weight
• Starch chain length distribution
• Oligosaccharide distributions
• Preparative separations

HPAEC provides an indirect assessment of oligosaccharide size by comparison to known standards. This also allows for the determination of chain length distributions in mixtures of similar oligosaccharides, such as starch hydrolysates. In addition, HPSEC may be used for the estimation of the size range of large polysaccharides, such as intact pectin or fiber, and for comparison to degraded products of these important food components. In some cases these techniques may be used for preparative separation of products for further analysis.

• Thermal transitions
• Reaction kinetics

THERMAL TRANSITIONS

Exothermic (crystallization) and endothermic (melting) event of food and non-food materials. Glass transition of pure or composite materials

REACTION KINETICS

Gelatinization degree, Degree of cooking, extent of reaction.

• Characterization of water-solid interactions
• Water sorption of molecules

• Anomeric configuration
• Sequence

The WCCR houses a 300 MHz Varian NMR for the analysis of soluble oligosaccharides and polysaccharides. Higher field systems are also available through the Purdue NMR facility if needed. NMR provides valuable structural information for carbohydrate research; such as glycosyl residue anomeric configurations, the presence and relative abundance of non-carbohydrate substitutions (such as acetyl groups or methyl ethers) on polysaccharides, and even the sequence of the glycosyl residues in a mixed polymer.

• Viscoelastic measurements
• Starch pasting
• Rheological analysis
• Gelation kinetics

VISCOELASTIC MEASUREMENTS

Viscoelastic properties of food and non-food materials under small oscillations. Stress relaxation and Creep Tests under small and large strains controlled. Flow curves of liquid materials at a large of shear rates using rotational and capillary viscometry. Determination of yield stress for plastic materials. Determination of thixotropy of time-dependent food and non-food materials.

RHEOLOGICAL ANALYSIS

Determination of rheological models for non-Newtonian liquid and viscoelastic food and non-food materials. Determination of relaxation times spectra. Effect of temperature on rheological properties of foods and non-food materials. Determination of Glass Transition Temperatures (Tg) of Food and non-Food materials.

GELATION KINETICS

Gelation of food and non-food materials using small strain oscillatory tests.

• Thermal transitions
• Reaction kinetics

A Fourier-transform infrared spectrometer (FT-IR) is an instrument capable of performing rapid, nondestructive mid-infrared (MIR) spectroscopic analysis of samples. An infrared spectrum contains features arising from vibrations of molecular bonds, and the MIR region (400-4000 cm-1) is highly sensitive to the precise sample composition. Data obtained from an FT-IR are absorption spectra that provide information on numerous compounds, including quantitative, qualitative, physical, and chemical information related to individual components. The intensity of absorption is directly proportional to the concentration of the absorbing compound. This is useful for generating standard curves and determining total concentration of the compound of interest, using partial least squares (PLS) techniques. The wavenumber positions of absorbance peaks, peak intensities, and peak widths are useful for functional group and sample identification. Wavenumber positions of absorbance bands are specific to the functional groups in a sample, thus each sample has a unique “fingerprint” absorbance spectrum. Group wavenumbers, or wavenumber regions in which functional groups absorb infrared radiation regardless of other molecular structures, are useful for determining the presence or absence of specific functional groups in a sample. Absorbance peak widths are influenced by the number and strength of functional group interactions with neighboring molecules, and the overlap of functional group absorbance peaks often occurs with increasing the complexity of samples. To facilitate the interpretation of complex spectra, chemometrics approaches are commonly used. Chemometrics algorithms utilize statistical and mathematical techniques to analyze chemical data. Common chemometric approaches include pattern recognition (e.g. hierarchical cluster analysis, principal component analysis, soft independent modeling of class analogies) and multivariate calibration and prediction (e.g. partial least squares, principal components regression). FT-IR instrumentation and multivariate statistical analysis techniques allow for the detection of constituents present in very low concentrations, as well as subtle compositional differences between and among multiconstituent specimens. Discriminant analysis (DA) is used to differentiate between sample types. The FT-IR instrument accessories enable the analysis of solid, powder, viscous, and liquid samples by transmission, ATR, and/or DRIFTS analysis. The FT-IR microscope also enables surface mapping and analysis of smaller samples.