Comparison of MALDI-TOF mass spectrometric to enzyme colorimetric quantification of glucose from enzyme-hydrolyzed starch

Successful quantification of the glucose produced by enzyme hydrolysis of starch was achieved by a matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) protocol, using sorbitol as an internal standard. The starch contents measured by MALDI-TOF MS of corn starch, fiber-enriched oat flour derivatives, oat and barley flours, and barley flour/corn starch composites were evaluated in comparison to a widely accepted and validated method of starch determination, which relies on enzyme colorimetry (EC). The average starch content measured in a series of corn starch samples of different masses was 93 and 101% for EC and MALDI-TOF MS, respectively, values that represent the estimated purity of the sample. There was an agreement of 99% between the starch contents determined by the two analytical methods for complex flour-derived samples. Starch values estimated by MALDI-TOF MS consistently showed a greater degree of variability than those determined by EC, but this limitation was readily compensated by rapid acquisition of multiple mass spectra. This study is the first to report the quantification of glucose by MALDI-TOF MS, and it offers new perspectives into the potential utility of MALDI-TOF MS as a definitive tool for monosaccharide analysis and rapid starch determination in complex samples.     

Resistant Starch Escaped from Ethanol Production: Evidence from Confocal Laser Scanning Microscopy of Distiller's Dried Grains with Solubles (DDGS)

The origin of resistant starch (RS) in distiller's dried grains with solubles (DDGS) of triticale, wheat, barley, and corn from dry‐grind ethanol production was studied. A considerable portion of starch (up to 18% in DDGS) escaped from either granular starch hydrolysis or conventional jet‐cooking and fermentation processes. Confocal laser scanning microscopy revealed that some starch granules were still encapsulated in cells of grain kernel or embedded in protein matrix after milling and were thus physically inaccessible to amylases (type RS1). The crystalline structures of native starch granules were not completely degraded by amylases, retaining the skeletal structures in residual starch during granular starch hydrolysis or leaving residue granules and fragments with layered structures after jet‐cooking followed by the liquefaction and saccharification process, indicating the presence of RS2. Moreover, retrograded starch molecules (mainly amylose) as RS3, complexes of starch with other nonfermentable components as RS4, and starch–lipid complexes as RS5 were also present in DDGS. In general, the RS that escaped from the granular starch hydrolysis process was mainly RS1 and RS2, whereas that from the jet‐cooking process contained all types of RS (RS1 to RS5). Thus, the starch conversion efficiency and ethanol yield could be potentially affected by the presence of various RS in DDGS.     

Dry matter, lipids, and proteins of canola seeds as affected by germination and seedling growth under illuminated and dark environments

The effect of germination and growth under illuminated and dark environments on canola seed reserves was investigated. Depletion of proteins and lipids in whole seedlings and their top (leaf/cotyledons) and bottom parts (stem/roots/seed coat) was independent of light, whereas the protein solubility increased at a faster rate under an illuminated environment than in the dark. A rapid increase in free fatty acids but a net decrease of dry matter content in seedlings grown in the dark environment was observed. The dry matter content of seedlings grown in the illuminated environment increased due to photosynthetic biomass accumulation.     

Effect of Formulation and Processing Treatments on Viscosity and Solubility of Extractable Barley β‐Glucan in Bread Dough Evaluated Under In Vitro Conditions

β‐Glucan shows great potential for incorporation into bread due to its cholesterol lowering and blood glucose regulating effects, which are related to its viscosity. The effects of β‐glucan concentration, gluten addition, premixing, yeast addition, fermentation time, and inactivation of the flour enzymes on the viscosity of extractable β‐glucan following incorporation into a white bread dough were studied under physiological conditions, as well as, β‐glucan solubility in fermented and unfermented dough. β‐Glucan was extracted using an in vitro protocol designed to approximate human digestion and hot water extraction. The viscosity of extractable β‐glucan was not affected by gluten addition, the presence of yeast, or premixing. Fermentation produced lower (P ≤ 0.05) extract viscosity for the doughs with added β‐glucan, while inactivating the flour enzymes and increasing β‐glucan concentration in the absence of fermentation increased (P ≤ 0.05) viscosity. The physiological solubility of the β‐glucan concentrate (18.1%) and the β‐glucan in the unfermented dough (20.5%) were similar (P > 0.05), while fermentation substantially decreased (P ≤ 0.05) solubility to 8.7%, indicating that the reduction in viscosity due to fermentation may be highly dependent on solubility in addition to β‐glucan degradation. The results emphasize the importance of analyzing β‐glucan fortified foods under physiological conditions to identify the conditions in the dough system that decrease β‐glucan viscosity so that products with maximum functionality can be developed.     

Pearling of hull-less barley: product composition and gel color of pearled barley flours as affected by the degree of pearling

Barley grains from two hull-less varieties, Phoenix and Candle, were pearled to various degrees (10-80%). The composition (starch, protein, beta-glucan, lipid, and ash) of pearled grain (PG) and pearling flour (PF) was determined. Effect of pearling on Hunter L, a, and b color parameters of uncooked and cooked (gel) barley flour (milled from PG) was investigated over a 3 day storage at 4 degrees C.     

Viscosity and Solubility of β‐Glucan Extracted Under In Vitro Conditions from Barley β‐Glucan‐Fortified Bread and Evaluation of Loaf Characteristics

Fortifying bread with β‐glucan has been shown to reduce bread quality and the associated health benefits of barley β‐glucan. Fortification of bread using β‐glucan concentrates that are less soluble during bread preparation steps has not been investigated. The effects of β‐glucan concentration and gluten addition on the physicochemical properties of bread and β‐glucan solubility and viscosity were investigated using a less soluble β‐glucan concentrate, as were the effects of baking temperature and prior β‐glucan solubilization. Fortification of bread with β‐glucan decreased loaf volume and height (P ≤ 0.05) and increased firmness (P ≤ 0.05). Gluten addition to bread at the highest β‐glucan level increased height and volume (P ≤ 0.05) to values exceeding those for the control and decreased firmness (P ≤ 0.05). β‐Glucan addition increased (P ≤ 0.05) extract viscosity, as did gluten addition to the bread with the highest β‐glucan level. Baking at low temperature decreased (P ≤ 0.05) β‐glucan viscosity and solubility, as did solubilizing it prior to dough formulation. Utilization of β‐glucan that is less soluble during bread preparation may hold the key to effectively fortifying bread with β‐glucan without compromising its health benefits, although more research is required.     

Isolation and Characterization of High‐Purity Starch Isolates from Regular,Waxy, and High‐Amylose Hulless Barley Grains

Recovering starch from barley is problematic typically due to interference from β‐glucan (the soluble fiber component), which becomes highly viscous in aqueous solution. Dry fractionation techniques tend to be inefficient and often result in low yields. Recently, a protocol was developed in our laboratory for recovering β‐glucan from barley in which sieving whole barley flour in a semiaqueous (50% ethanol) medium allowed separation of the starch and fiber fractions without activating the viscosity of the β‐glucan. In this report, we investigate an aqueous method which further purifies the crude starch component recovered from this process. Six hulless barley (HB) cultivars representing two each of waxy, regular, and high‐amylose cultivars were fractionated into primarily starch, fiber, and protein components. Starch isolates primarily had large granules with high purity (>98%) and yield range was 22–39% (flour dry weight basis). More importantly, the β‐glucan extraction efficiency was 77–90%, meaning that it was well separated from the starch component during processing. Physicochemical evaluation of the starch isolates, which were mainly composed of large granules, showed properties that are typical of the barley genotypes.     

Distribution of Granule Channels,Protein, and Phospholipid in Triticale and Corn Starches as Revealed by Confocal Laser Scanning Microscopy

The morphology and microstructure of starch granules from two cultivars of triticale and from normal corn were characterized using scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM). Compared to numerous pores distributed randomly on the surfaces of corn starch granules, markedly fewer pores were observed on the surfaces of starch granules isolated from Pronghorn triticale, and even fewer on the surfaces of starch granules isolated from Ultima triticale. CLSM with fluorescence staining revealed that starch‐associated protein was predominately distributed on the granule surface and in the internal channels of both triticale and corn starches. However, after triticale starch was treated with SDS or SO₂, the radially oriented, protein‐filled internal channels of the granules were observed more frequently and extended to the central region of granules. Phospholipid was located mainly on the granule surface but also in channels and throughout granules in triticale starches, whereas in corn starch granules, it was mainly in the channels. The amount of protein and phospholipid in chemically and protease‐treated starches varied with starch source and treatment conditions. In treated triticale starches, the nitrogen content was positively correlated with the phosphorus content, indicating a close association between protein and phospholipid within starch granules. Starch‐associated protein and phospholipid may play an important role in maintaining the structural stability of both the granule surface and the internal channels.     

Effect of Health Information on Consumer Acceptability of Bread Fortified with β‐Glucan and Effect of Fortification on Bread Quality

Fortifying bread with β‐glucan reduces bread sensorial properties, though fortification using β‐glucan concentrates of low solubility under the conditions of dough preparation has not been investigated. This study investigated the consumer acceptability and purchase intent of bread fortified with a less soluble β‐glucan concentrate at levels corresponding to 0, 0.75, and 1.5 g β‐glucan/serving bread in relation to the provision of health information, gender, and whole wheat bread consumption. The effect of β‐glucan concentration on the physical properties of the bread produced under pilot plant settings was also investigated. β‐Glucan addition decreased (P < 0.05) loaf volume, increased firmness, and produced a darker, redder bread (P < 0.05), though fortification at 1.5 g β‐glucan/serving bread decreased height as well (P < 0.05). Consumer evaluation (n = 122) revealed that health information increased liking of appearance, flavor, and overall acceptability of the 1.5 g/serving bread to levels similar to or exceeding that of the control. Liking of the 1.5 g β‐glucan/serving bread appearance increased more in women than in men and for consumers who regularly consumed whole wheat bread for perceived health benefits when β‐glucan health information was provided. The provision of β‐glucan health information may be the key to increasing consumer acceptability of bread fortified with β‐glucan.     

Enrichment of tocopherols and phytosterols in canola oil during seed germination

The effect of canola (Brassica napus L.) seed germination under illuminated and dark environments on the total concentration and the composition of tocopherols and phytosterols in seedlings and extracted oil were investigated. During the first 10 days of germination, a decrease in gamma-tocopherol was offset by an increase in alpha-tocopherol, indicating the interconversion of these isomers. From day 10 to day 20 under illumination, there was a net increase in alpha-tocopherol and total tocopherols suggesting the synthesis of new tocopherols, whereas there was no net increase in tocopherols in dark. Tocopherols were mainly concentrated in the leafy seedling tops rather than in the non-photosynthesizing bottoms, whereas phytosterols were equally distributed across both sections. The total tocopherol content of oil extracted from 20-day-old seedlings was 4.3- to 6.5-fold higher than that of intact seeds. On a dry seedling basis, the content and composition of phytosterols did not change significantly (p > 0.05) over the sprouting period, but the concentration of total phytosterols in the oil fraction increased 4.2- to 5.2-fold. The concentration of these valuable phytochemicals in the oil fraction is largely due to the depletion of oil reserves during germination, as well as the de novo synthesis of new alpha-tocopherol stimulated by the presence of light. Germination may represent a viable means to naturally concentrate these high-value constituents in canola oil, offering improvements in oil quality based on the nutritional value and oxidative protection offered by tocopherols and the health benefits provided by both tocopherols and phytosterols.