Enzymatic hydrolysis, grease permeation, and water barrier properties of zein isolate coated paper

An inexpensive zein-lipid mixture was isolated from yellow dent, dry-milled corn. Grease permeation through zein isolate applied to brown Kraft paper was found to be independent of loading levels at zein isolate levels above 30 mg/16 in.(2). The data shows that water vapor transmission rates depended on the amount of coating applied. Triacylglycerols were the most abundant lipid in milled corn but were absent in the zein isolate (perhaps due to hydrolysis by lipases). Zein from the paper was hydrolyzed enzymatically and the hydrolysis monitored by SDS-capillary electrophoresis. At an E:S ratio of 1:100 no further increase in the hydrolysate peak occurred after 10 and 30 min for alpha-chymotrypsin and pancreatin 8 x; however, zein and lipid were still present 1 h after hydrolysis by pancreatin 1 x.     

Influence of acidification and aluminum on the density and biomass of lotic benthic invertebrates

Experiments were carried out in plasticized wooden channels fed by a small creek in the Reserve des Laurentides, 80 km north of Quebec city. Channels were naturally colonized by invertebrates for 65 d before treatment. Treated channels were acidified in August with dilute H₂SO₄ only, or with acid plus a solution of Al sulfate (final concentration of 0.19 mg L^?1). The control channel received creek water only (pH 6.3 to 6.9). The addition of Al had no effect on invertebrate density and biomass. After 73 d of acidification, invertebrate densities were only one third the number found in the control channel. Invertebrate hiomass was not different within channels, although biomass was generally higher in the two acidified channels. Difference in densities between acidified and non-acidified channels was attributed to lack of colonization and not to an increase in drift. Microtendipes, a large and resistant larva of Chironomidae constituted a large fraction of the hiomass, largely outweighing numerous very small larvae. Effects on the density were attributed to the direct effect of low pH and not to indirect action through food limitations.     

Improved method for the synthesis of trans-feruloyl-beta-sitostanol

Phytosterols and phytostanols are known to lower low-density lipoprotein-cholesterol (LDL-C) levels in humans by up to 15%, and at least two products, Benecol and Take Control, are now on the market as naturally derived fatty acid esters of phytostanols (stanol esters) and phytosterols (sterol esters), respectively. A synthetic process was developed to synthesize gram quantities of trans-feruloyl-beta-sitostanol from ferulic acid and beta-sitostanol, with high purity and yields of approximately 60%. The process involves (a) condensation of trans-4-O-acetylferulic acid with the appropriate phytostanol or phytostanol mixture in the presence of N,N-dicyclohexylcarbodiimide and 4-(dimethylamino)pyridine, (b) separation of the trans-4-O-acetylferuloyl products by preparative liquid chromatography, (c) selective deacetylation of the feruloyl acetate, and (d) chromatographic purification of the feruloylated phytostanols. The process was successfully applied to synthesize stanol trans-feruloyl esters from "Vegetable Stanols", a mixture of approximately 70:30 beta-sitostanol and beta-campestanol, in comparable purity and yield.     

Effect of endogenous triacylglycerol hydrolysates on the mechanical properties of Zein films from ground corn

Dry-milled yellow corn and freshly ground food and nonfood grade yellow and white hybrid corn kernels were pretreated in a solution of lactic acid and sodium metabisulfite followed by extraction with 70% ethanol. Zein was precipitated from the extract by reducing the ethanol content of the extract to 40%. Lipid associated with the zein isolates was between 15 and 20% and contained mostly endogenous free fatty acids. The effect of the endogenous free fatty acids on zein isolate films, with and without free fatty acids, was determined by measuring various film properties. Stress-strain measurements indicated 40-200% greater elongation for zein films containing endogenous free fatty acids. Films prepared from zein isolated from preground corn stored for approximately 4 months (27 degrees C, 17% relative humidity) had approximately 3 times greater elongation values than zein films prepared from freshly ground corn.     

Stand structure interacts with previous defoliation to influence herbivore fitness

The intensity and duration of Neodiprion abietis outbreaks have recently increased in forests of North America that were precommercially thinned more than a decade earlier. We tested the hypotheses that changes in stand structure following thinning increase the fitness (i.e., survival rate × fecundity) of N. abietis by either (a) increasing foliar availability and/or quality (i.e., increased availability of primary metabolites and/or reduced foliar defenses) or (b) by reducing any negative effects on foliar quality and/or availability resulting from herbivory that occurred during the preceding season(s). Effects of thinning and previous herbivory on N. abietis and its host plant (Abies balsamea) were determined through (i) a manipulative field experiment that evaluated the effects of experimental defoliation on N. abietis in a thinned stand, (ii) a manipulative field experiment that examined the effects of thinning on N. abietis in undamaged and naturally defoliated stands, and (iii) a field survey to estimate survival of N. abietis in natural populations.Defoliation caused reductions in the availability of different-aged foliage available to larvae and in the fitness of a subsequent N. abietis generation feeding on defoliated branches, but decreases in fitness were smaller in thinned than unthinned stands. In thinned stands, defoliation was associated with increases in foliage production and foliar contents of monoterpenes and nitrogen, as well as with a decrease in foliar contents of water. Conversely, only small changes in plant growth and foliar contents of nutrients and secondary chemicals were observed in defoliated unthinned stands. This suggests that deleterious effects of defoliation on sawfly fitness were offset by an increase in the foliar content of nitrogen, a primary compound known to improve larval growth in sawflies, which supports the hypothesis that thinning moderates negative effects of previous defoliation on sawfly fitness. The present study demonstrates that forestry practices that alter stand structure by reducing tree density may increase herbivory by affecting the way trees respond to insect attack, even after crown closure, with consequences on the buildup of herbivore populations in attacked trees.     

Effect of an Enzyme Preparation Containing Pentosanases on the Bread-making Quality of Flours in Relation to Changes in Pentosan Properties

The effects of a crude pentosanase-containing enzyme preparation were studied on 12 samples of flour varying in quality for French bread making. At the optimal level of addition, the enzyme improved the dough properties, leading to a greater uniformity in quality characteristics and a higher level of quality for all samples. When an excessive amount of enzyme was added, the dough characteristics deteriorated. Changes in the properties of the flour pentosans were studied in the break-making process (kneading, shaping, end of fermentation, baking) using one of the flours, in the absence and presence of pentosanase-containing enzyme preparation at an optimal and excessive levels of addition. Part of the water-unextractable arabinoxylan became extractable during processing of the control sample, but solubilisation occurred to a greater degree with added enzyme. The specific viscosities of water extracts of doughs increased because of the arabinoxylan released from the WUP. Although more arabinoxylan was solubilised at the excessive level of addition, the apparent intrinsic viscosity of dough water-extractable arabinoxylan was greater at the optimum level of addition. These results were essentially confirmed with all the flour samples tested. The effectiveness of the enzyme preparation therefore appeared to be related to the amount and size of the extractable arabinoxylans.     

Angiotensin I converting enzyme-inhibitory peptides from commercial wet- and dry-milled corn germ

Bioprocesses were developed to enhance the value of proteins from deoiled corn germ. Proteins were hydrolyzed with trypsin, thermolysin, GC 106, or Flavourzyme to generate the bioactive peptide sequences. At an enzyme to substrate ratio of 1:100, protein hydrolysis of wet-milled germ was greatest using thermolysin followed by trypsin, GC 106, and Flavourzyme. For the dry-milled corn germ, protein hydrolysis was greatest for GC 106 and least for Flavourzyme. Electrophoretic patterns indicated that the hydrolysis conditions used were adequate for generating low molecular weight peptides for both germs. Unhydrolyzed dry- and wet-milled corn germ did not appear to contain angiotensin I converting enzyme (ACE)-inhibitory peptides. After hydrolysis with trypsin, thermolysin, and GC 106 but not Flavourzyme, ACE inhibition was observed. ACE inhibition was greatest for the GC 106 hydrolysate for both wet- and dry-milled corn germ. Denaturing the protein with urea before hydrolysis, in general, increased the amount of ACE-inhibitory peptides found in the hydrolysate. Membrane fractionations of both the wet- and dry-milled hydrolysates indicated that most of the ACE-inhibitory peptides were in the <1 kDa fraction. Examination of the control total protein extracts (before treatment with proteases) from wet- and dry-milled germ revealed that neither had ACE-inhibitory properties. However, when both total corn germ control protein extracts were fractionated, the <1 kDa fraction of wet-milled corn germ proteins exhibited ACE inhibition, whereas the comparable low molecular weight fraction from dry-milled corn germ did not.     

Interactions between beta-lactoglobulin and aroma compounds: different binding behaviors as a function of ligand structure

Interactions between beta-lactoglobulin (BLG) in its monomeric form and a wide range of aroma compounds were investigated by Fourier transform infrared (FT-IR) and 2D nuclear magnetic resonance (NMR) spectroscopies. A screening of the ligands was carried out by FT-IR through the amide I region changes of BLG upon binding. The location of two binding sites was determined by 2D NMR from the study of 10 selected ligands with different structures. All of the data suggest at least two binding behaviors as a function of the chemical class, the hydrophobicity, or the structure of the ligands. The binding of the elongated aroma compounds, such as 2-nonanone or ethyl pentanoate, within the central cavity involves residues located at the entrance of the calyx and Trp19. The binding onto the protein surface of aroma compounds that have or adopt a compact structure occurs in a site located between strand beta-G, alpha helix, and strand beta-I.     

Comparison of Yield and Composition of Oil Extracted from Corn Fiber and Corn Bran

We recently reported that corn fiber oil contains high levels of three potential cholesterol-lowering phytosterol components: ferulate-phytosterol esters (FPE) (3–6 wt%), free phytosterols (1–2 wt%), and phytosterol-fatty acyl esters (7–9 wt%). A previous study also indicated that corn bran oil contained less phytosterol components than corn fiber oil. The current study was undertaken to attempt to confirm this preliminary observation using more defined conditions. Accordingly, oil was extracted from corn fiber and corn bran prepared under controlled laboratory conditions, using the same sample of corn hybrid kernels for each, and using recognized bench-scale wet-milling, and dry-milling procedures, respectively. After extraction, the chemical composition of the phytosterol components in the oil were measured. This study confirmed our previous observation—that FPE levels were higher in corn fiber oil than in corn bran oil. During industrial wet-milling, almost all of the FPE are recovered in the fiber fraction (which contains both fine and coarse fiber). During laboratory-scale wet-milling, ≈60–70% of the FPE are recovered in the coarse fiber (pericarp) and 30–40% are recovered in the fine fiber. During laboratory-scale dry-milling, <20% of the FPE are recovered in the bran (pericarp), and the rest in the grits. The recoveries of the other two phytosterol components (free phytosterols and phytosterol-fatty acyl esters) revealed a more complex distribution, with significant levels found in several of the dry- and wet-milled products.