Randy L. Wehling

Comparison of Amylose Determination Methods and the Development of a Dual Wavelength Iodine Binding Technique

ABSTRACT It has long been recognized that limitations exist in the analytical methodology for amylose determination. This study was conducted to evaluate various amylose determination methods. Purified amylose and amylopectin fractions were obtained from corn, rice, wheat, and potato and then mixed in proportion to make 10, 20, 30, 50, and 80% amylose content starch samples for each source. These samples, considered amylose standards, were analyzed using differential scanning calorimetry (DSC), high-performance size-exclusion chromatography (HPSEC), and iodine binding procedures to generate standard curves for each of the methods. A single DSC standard equation for cereal starches was developed. The standard curve of potato starch was significantly different. Amylose standard curves prepared using the iodine binding method were also similar for the cereal starches, but different for potato starch. An iodine binding procedure using wavelengths at 620 nm and 510 nm increased the precision of the method. Whe...

Variation in polyphenol oxidase activity and quality characteristics among hard white wheat and hard red winter wheat samples

ABSTRACT Polyphenol oxidase (PPO) has been related to an undesirable brown discoloration of wheat-based end products. Consumer acceptance and product quality are generally decreased by the darkening phenomena. Two sets of wheat samples (Triticum aestivum L.) were investigated for variation in grain and flour PPO levels. Samples included 40 advanced experimental hard white winter wheat lines grown at two Kansas locations and 10 hard red winter wheat genotypes grown at three Nebraska locations. The variability in grain and flour PPO activities was influenced by growing location and population for the hard white wheat samples. There also was a significant influence of population by growing location interactions on PPO activity in both grain and flour. Genotype and growing location both contributed to variability in flour PPO activity among the hard red wheat samples. The variation in flour PPO activities among growing locations appeared larger than variation produced by genotypes tested for the hard red whea...

HPLC determination of stability and distribution of added folic acid and some endogenous folates during breadmaking

ABSTRACT Bread flour was spiked with folic acid (1.40 mg/lb or 3.08 μg/g of flour) and processed into bread by the sponge and dough method. Changes that occurred to added folic acid and endogenous folate contents through different processing stages, including sponge formation, proofing, and baking, were assessed by reversed-phase ion-pair HPLC combined with UV and fluorometric detection. Sample extraction required α-amylase and rat plasma deconjugase digestion, and sample preparation required purification by solid-phase extraction. Added folic acid was measured by monitoring UV absorption at 280 nm. Four selected forms of endogenous folates including tetrahydrofolate (THF), 5-formyl-THF, 10-formylfolate, and 5-methyl-THF were identified and quantified throughout the bread processing using a fluorescence excitation wavelength of 290 nm and emission wavelength of 350 or 450 nm. Data indicate a relatively good stability of added folic acid and native folates to the baking process, and increased endogenous fo...

Liquid chromatographic method for determining added folic acid in fortified cereal products

Reversed-phase ion-pair high-performance liquid chromatography (HPLC) was coupled with detection by UV absorption (280 nm) for separation and quantitation of added folic acid (FA) in fortified cereal based foods. A simple and rapid liquid-solid extraction method, combined with enzymatic digestion, to recover FA from the sample matrices is also presented. The quantitation of added FA was achieved in products including corn (maize), wheat-, rice- and oat-based cereal breakfast foods fortified at 25% and 100% of the reference daily intake (RDI). The retention time for FA was ca. 15 min, and the detection limit was 2 ng/20 microliters injection for standard FA. When FA was added to unfortified samples of wheat flour at concentrations of 3.08 or 20.0 micrograms/g, recoveries were 93% and 96%, respectively. Comparison of HPLC results with those of a standard microbiological assay has shown quite good agreement (r = 0.998). A solid-phase extraction clean-up procedure has also been developed for use with samples fortified with low levels of FA, where interferences may otherwise hinder quantitation.

Determination of native folates in milk and other dairy products by high-performance liquid chromatography

Folates were measured in dairy products by high-performance liquid chromatography without prior sample clean-up. Detection limits for individual folates range from 0.3 to 7.3 ng/g. The folates were extracted from the sample matrix by adjusting the pH to 4.5 with acetic acid, centrifuging to remove precipitated proteins, and treating with conjugase to remove multiple polyglutamate residues. Folates were separated from other sample components using a reversed-phase column with a methanol-phosphate buffer (pH 6.8), and ion-pairing with tetrabutylammonium ion. Fluorescence was found to be the most useful detection technique. Fluorescence detection of reduced forms of the vitamin was achieved by post-column pH adjustment of the eluent with phosphoric acid, while the parent folic acid molecule required chemical oxidation with hypochlorite in order to obtain a fluorescent response.

Extrusion and Characterization of Starch Films

ABSTRACT Starch plasticized with water, glycerol, and stearic acid was extruded and sheeted into films 0.4–0.6 mm thick. The ingredients were extruded in a conical twin-screw extruder at a temperature profile of 50–120–120–120°C and a screw speed of 45 rpm. The effects of glycerol, water, and stearic acid on selected physical and functional properties of the films were studied. The tensile strength, tensile strain at break, and Youngs modulus were 0.23–2.91 MPa, 45.79–90.83%, and 2.89–37.94 MPa, respectively. Differential scanning calorimetry thermograms exhibited two glass transitions and multiple melting endotherms, including that of amylose-lipid complexes formed during extrusion. The enthalpy of gelatinization of starch in the extruded films was 0.7–4.1 J/g and was dependent largely on the plasticizer content. Fourier-transform infrared spectra revealed significant interactions between the starch and plasticizer but the peaks shifted to higher wave numbers with increasing glycerol content. During ext...

Near-infrared spectroscopic determination of degradation in vegetable oils used to fry various foods.

Near-infrared (NIR) spectroscopic methods for measuring degradation products, including total polar materials (TPMs) and free fatty acids (FFAs), in soy-based frying oil used for frying various foods have been successfully developed. Calibration models were developed using forward stepwise multiple linear regression (FSMLR) and partial least-squares (PLS) regression techniques and then tested with an independent set of validation samples. The results show that the quality of oil used for frying different foods can be measured with a single model. First-derivative treatments improved results for TPM measurement. In addition, PLS models gave better prediction results than FSMLR models. For PLS models, the best correlations (r) between the NIR-predicted data and the chemical method data for TPMs and FFAs in oils were 0.995 and 0.981, respectively. For FSMLR models, the best r values for TPMs and FFAs in oils were 0.993 and 0.963, respectively.

Effect of Extraction Method on the Oxidative Stability of Camelina Seed Oil Studied by Differential Scanning Calorimetry

Camelina seed is a new alternative omega-3 source attracting growing interest. However, it is susceptible to oxidation due to its high omega-3 content. The objective of this study was to improve the oxidative stability of the camelina seed oil at the extraction stage in order to eliminate or minimize the use of additive antioxidants. Camelina seed oil extracts were enriched in terms of natural antioxidants using ethanol-modified supercritical carbon dioxide (SC-CO2 ) extraction. Oxidative stability of the camelina seed oils extracted by ethanol modified SC-CO2 was studied by differential scanning calorimeter (DSC), and compared with cold press, hexane, and SC-CO2 methods. Nonisothermal oxidation kinetics of the oils obtained by different extraction methods were studied by DSC at varying heating rates (2.5, 5, 10, and 15 °C/min). Increasing ethanol level in the ethanol-modified SC-CO2 increased the oxidative stability. Based on oxidation onset temperatures (Ton ), SC-CO2 containing 10% ethanol yielded the most stable oil. Oxidative stability depended on the type and content of the polar fractions, namely, phenolic compounds and phospholipids. Phenolic compounds acted as natural antioxidants, whereas increased phospholipid contents decreased the stability. Study has shown that the oxidative stability of the oils can be improved at the extraction stage and this may eliminate the need for additive antioxidants.

Processing effects on four prebiotic carbohydrates supplemented in an extruded cereal and a low pH drink

Abstract Prebiotic carbohydrates are added as functional ingredients to a variety of processed foods. Data on the stability of prebiotics during food processing in complex matrices remain limited. The objective of this project was to determine the stability of fructooligosaccharides (FOS), inulin, galactooligosaccharides (GOS), and resistant starch (RS2), when added as ingredients (1% w/w) to an extruded cereal and a low pH drink. The cereal was prepared using different screw speeds and barrel temperatures. GOS was not affected by any of the extrusion conditions, whereas inulin decreased significantly at 140 and 170°C. FOS levels decreased in all extrusion conditions, while resistant starch (RS) unexpectedly increased for each of the parameters. The low pH drink was prepared with different sucrose to corn syrup solids (S:CSS) ratios (1:2, 1:1, 2:1) at pH 3.0, 3.5, and 4.0. The 1:1 S:CSS drink at pH 3.0, negatively impacted FOS and inulin. Moreover, FOS levels decreased when exposed to 1:2 S:CSS (pH 3.5 and 4.0) and 1:1 S:CSS (pH 3.0). GOS and RS were unaffected by any drink formulations. As different conditions impact the stability of prebiotics differently, this study addresses the importance of developing product specific processes for each prebiotic when supplemented into a processed food.

High-resolution two-dimensional electrophoresis of wheat proteins

Abstract A high-resolution two-dimensional electrophoretic for separating wheat endosperm proteins is described. Non-equilibrium pH gradient electrophoresis (NEPHGE) and sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS- PAGE) were used to examine proteins in non-fractioned extracts of wheat flours. NEPHGE was conducted in 100-μl capillary tubes at 3000 V, for a total of 4800 V h. The second dimension, SDS-PAGE, was performed as a slab mini-gel (70 × 80 × 1.0 mm) with constant application of 200 V. Image analysis of the two-dimensional separations of three wheat varieties showed approximately 35 and 41% homology of Centurk 78 and Rodeo varieties, respectively, when compared to a reference (Scout 66).