The in vitro lipolysis and biohydrogenation of monogalactosyldiglyceride by whole rumen contents and its fractions

The contribution of bacterial, protozoal, participate and cell-free fractions of rumen fluid to the lipolysis of monogalactolipid and the hydrogenation of its acyl constituents has been examined. Each of these fractions hydrolysed monogalactolipid and free fatty acids were the major acyl products. Almost all the radioactivity added as monogalactolipid to rumen fluid was distributed between the particulate and bacterial fractions and half to two-thirds of the radioactivity in each of the four fractions was recovered as free fatty acids. Both 16:3 and 18:3, after release from monogalactolipids, were hydrogenated to 16:2 and 18:2 at short incubation times. As incubation was continued there was a rapid decline in dienoic fatty acids and an increase in saturated and monoenoic fatty acids. There was a greater accumulation of trans-18: 1 than cis-18:1. Only the particulate fraction of rumen fluid gave patterns of hydrogenation similar to that obtained with rumen fluid. Bacteria in free suspension had little ability to hydrogenate trienoic fatty acids beyond the dienoic stage and neither protozoa nor the cell-free supernatant gave significant biohydrogenation of trienoic fatty acids. On the other hand, the presence of monoenoic and dienoic fatty acids in the bacterial, protozoal and cell-free fractions isolated from total rumen fluid after incubation with monogalactolipid indicated their transfer to these fractions after biohydrogenation in the particulate fraction.     

Whey protein-derived peptide sensing by enteroendocrine cells compared with osteoblast-like cells: Role of peptide length and peptide composition,focussing on products of β-lactoglobulin hydrolysis

The short-term satiating effect of whey protein intake is higher than that obtained with other dietary proteins. The molecular basis underlying the secretagogue effect of whey proteins on the release of cholecystokinin, a gut hormone involved in appetite suppression, has not been deeply investigated. Using STC-1 enteroendocrine cells we analysed the effects of synthetic peptides and protein hydrolysates. The hypothesis that specific molecular features in terms of short amino acid sequences released after enzymatic digestion may exert a primary role in the cholecystokinin secretagogue activity of dietary proteins was not supported. However, the length of the peptide fragments derived from a protein during enzymatic digestion is relevant to this activity. Regarding the complexities of how food can interact with different cellular systems, our data suggest a novel biological activity of ALPMH, a known bioactive peptide product of β-lactoglobulin digestion, on cell growth and a related signalling pathway in osteoblast-like cells.     

Measurements on disulphide bonds in cereal glutelins

Cereal glutelins were divided by dilute acetic acid extraction into‘soluble’and‘insoluble’fractions. The quantities dissolved in the cases of oats and maize were negligibly small. The S.S bonds of these fractions from wheat, rye, barley, oats and maize have been amperometrically titrated after reaction with sulphite in the absence and presence of guanidine hydrochloride to give, respectively, the accessible and total S.S groups. Accessible S.S groups are believed to be mainly inter-polypeptide chain bonds. The results imply that wheat glutenin resembles the other glutelins in being highly crosslinked. There is some evidence that the density of crosslinking is higher in oats, maize and barley glutelins, provided that the polypeptide chains of the other cereal glutelins are similar in size to those of wheat glutenin.     

Impact of ultrafiltration and nanofiltration of an industrial fish protein hydrolysate on its bioactive properties

BACKGROUND: Numerous studies have demonstrated that in vitro controlled enzymatic hydrolysis of fish and shellfish proteins leads to bioactive peptides. Ultrafiltration (UF) and/or nanofiltration (NF) can be used to refine hydrolysates and also to fractionate them in order to obtain a peptide population enriched in selected sizes. This study was designed to highlight the impact of controlled UF and NF on the stability of biological activities of an industrial fish protein hydrolysate (FPH) and to understand whether fractionation could improve its content in bioactive peptides. RESULTS: The starting fish protein hydrolysate exhibited a balanced amino acid composition, a reproducible molecular weight (MW) profile, and a low sodium chloride content, allowing the study of its biological activity. Successive fractionation on UF and NF membranes allowed concentration of peptides of selected sizes, without, however, carrying out sharp separations, some MW classes being found in several fractions. Peptides containing Pro, Hyp, Asp and Glu were concentrated in the UF and NF retentates compared to the unfractionated hydrolysate and UF permeate, respectively. Gastrin/cholecystokinin‐like peptides were present in the starting FPH, UF and NF fractions, but fractionation did not increase their concentration. In contrast, quantification of calcitonin gene‐related peptide (CGRP)‐like peptides demonstrated an increase in CGRP‐like activities in the UF permeate, relative to the starting FPH. The starting hydrolysate also showed a potent antioxidant and radical scavenging activity, and a moderate angiotensin‐converting enzyme (ACE)‐1 inhibitory activity, which were not increased by UF and NF fractionation. CONCLUSION: Fractionation of an FPH using membrane separation, with a molecular weight cut‐off adapted to the peptide composition, may provide an effective means to concentrate CGRP‐like peptides and peptides enriched in selected amino acids. The peptide size distribution observed after UF and NF fractionation demonstrates that it is misleading to characterize the fractions obtained by membrane filtration according to the MW cut‐off of the membrane only, as is currently done in the literature. Copyright © 2010 Society of Chemical Industry     

Fiber Composition and Digestion Kinetics in Grass Stem Internodes as Influenced by Particle Size

Our objective was to characterize discrete particle fractions in ground grass forage and determine the influence of differences in particle size among fractions on fiber composition and digestion kinetics. Three replicates of reed canarygrass and switchgrass were harvested and the fourth and fifth stem internodes below the panicle were removed, dried, and ground (3 mm). Samples were sieved to a constant weight and particles retained on .3, .425, .6, and .85-mm sieves were analyzed with half of each particle fraction reground to pass a 1-mm Udy mill screen. Particles were analyzed for length, width, and area using an image analyzer, and particle thickness was determined using a light microscope. Volume, surface area, and density measurements of defined particle fractions had an approximate geometric distribution for the four particle fractions, indicating that these measurements are related to particle size estimates based on logarithmic normal distributions. The four particle fractions were similar in composition based on density, crude protein, and fiber estimates. Digestion rate constants were not affected by particle size within the range of the four particle fractions. However, regrinding to pass a 1-mm Udy screen increased digestion rates, indicating that small particle size can affect digestion kinetics. Fiber values from sequential analysis of forage particles not ground to pass a 1-mm screen must be evaluated cautiously, because some potentially soluble components may remain in the residue after each extraction step and result in high analytical values.     

Production of stearate-rich butters by solvent fractionation of high stearic–high oleic sunflower oil

Cocoa butter equivalents (CBEs) are fats with a similar composition and melting profile as cocoa butter (CB), which are usually prepared by blending mid-palm fractions and stearate-rich tropical butters. In this regard, high stearic–high oleic sunflower oil contains disaturated triacylglycerols typically present in CBEs, albeit at a lower concentration than that required to produce a solid fat. Here we have assessed a means to fractionate this oil in order to produce solid fractions that can be used as stearic acid-rich butters appropriate for CBE formulations. Solvent fractionation of high stearic–high oleic sunflower oil was optimised in function of the oil/solvent ratio and temperature. Sunflower stearins with similar melting profiles as cocoa butter were obtained from oils of either 17% or 20% stearic acid in a single step. Different stearin products can be obtained by controlling the oil/solvent ratio and the temperature of fractionation. The use of these fractions as CBE components or confectionery fats is discussed in function of their melting profiles.     

Degradation characteristics of isolated and in situ cell wall lucerne pectic polysaccharides by mixed ruminal microbes

Two pectic polysaccharide fractions were isolated form lucerne (Medicago sativa L) leaves and used in fermentation experiments with mixed ruminal microbes. Both fractions were similar in chemical composition, containing galacturonic acid (52-58 mol%) and the neutral sugars arabinose (14-18 mol%), galactose (6-8 mol%) and rhamnose (8-12 mol%). Fermentation of both fractions was rapid and complete with a half-life of approximately 4 h. Production of total volatile fatty acids matched the degradation profile reaching a maximum level shortly after the rate of degradation began to decrease. The fermentation characteristics of citrus pectin and polygalacturonic acid were similar to those of the lucerne pectic fractions but galacturonic acid was much slower in its rate of degradation while soluble arabinogalactan from larchwood was virtually undegraded. Leaves of early bud stage lucerne and lower nodes and internodes of stems from full bloom lucerne were also fermented by mixed ruminal microbes. Pectic polysaccharides were rapidly and extensively degraded from both tissues. Initial rates were faster for leaves than for stems and the extent of pectic degradation was greater in leaves (8% residual) than in stems (17% residual). Selection of forage lines with increased pectic polysaccharides would provide greater amounts of rapidly available energy that could result in more efficient utilisation of the rapidly degraded protein in lucerne.     

The composition of a gel formed when wheat flour is suspended in phenol-acetic acid-water (1:1:1, w/v/v)

A gel which formed when wheat flour was suspended in phenol-acetic acid-water (1:1:1, w/v/v/) was fractionated into a protein-rich soluble fraction and a carbohydrate-rich insoluble fraction. Gel electrophoresis showed that the soluble fraction contained several proteins and had an amino acid composition with a high content of proline and glutamyl residues and a low content of lysine. The soluble fraction also contained lipids which were mainly phospholipids, phospholipid derivatives and glycolipids and other compounds, which yielded galactose and glucose after acid hydrolysis. The insoluble fraction contained a polysaccharide with similar properties to starch, and lipids which were mainly neutral fats, sterols and sterol esters. Both fractions contained arabinoxylans and mannans. The gel did not contain any nucleic acids. The protein-rich soluble fractions of gels prepared from other wheat flours and air-classified flour fractions, from wheat gluten and from rye and barley flours, showed marked differences in amino acid composition. It is concluded that a heterogeneous class of proteins, rather than specific proteins in fixed proportions, is involved in gel formation.     

Storage Proteins of Glandless Cottonseed Flour

The salt-soluble storage protein isolate of defatted glandless cottonseed flour was separated by gel filtration column chromatography into six fractions (I to VI). Column and thin-layer gel filtration showed that these fractions had molecular weights of >600,000, 280,000, 127,000, 63,500, 10,700, and <2,000, respectively. Treating fraction I protein with dilute alkali dissociated a component that migrated upon gel filtration with fraction VI. Both fractions I and VI were yellow and the color intensified at alkaline pH, suggesting the presence of bound flavonol and gossypol pigments. Because of its large size and low (16.6%) protein content, fraction I was thought to be fragments of membrane and aleurone gram globulins. Gradient polyacrylamide gel electrophoresis (PAGE) showed that the proteins in each fraction being completely recovered from column chromatography were represented in the pattern of the initial isolate. The proteins in fractions II and III have similar ammo acid compositions, except that III is low in methionine, cystine and tryptophan and II is low in tyrosine and phenylalanine. The amino acid composition of fraction I was also similar to fractions II and III, while unique patterns were noted for fractions V and VI. Fraction VI was rich in lysine and arginine.     

Phase Behavior and Mechanical Properties of TripaImitin/Butterfat Mixtures

The functionality of butterfat can be improved by fractionation, a process that can be considered as enrichment of butterfat with long-chain saturated fatty acids. Model hard fractions were produced by adding tripalmitin to butterfat, in ratios from 0.9:0.1 through 0.1:0.9. The model system had very similar thermal behavior and mechanical properties to true fractions. The phase behavior of tripalmitin/butterfat mixtures was determined. Such butterfat fractions have potential as a moisture barrier in edible films and coatings. Tripalmitin-enriched butterfat is an alternative to hard butterfat fractions in some applications.     

Affinity purification and characterisation of chelating peptides from chickpea protein hydrolysates

A chickpea protein hydrolysate produced with pepsin and pancreatin was used for the affinity purification of chickpea chelating peptides. Three chelating peptide fractions were obtained after affinity chromatography with immobilised copper. These peptide fractions showed a higher chelating activity and histidine contents than the original protein hydrolysate. Chelating activity was positively correlated with the histidine content of the purified fractions. Different subfractions were also obtained after gel filtration chromatography from the affinity purified peptide fractions. Some of these subfractions showed a higher chelating activity and histidine contents than the original fractions. These results suggest that a combination of high His contents, around 20–30%, and small peptide size provide the best chelating activities. Thus sequential purification with affinity and gel filtration chromatography is a useful procedure for the purification of chickpea peptides with high chelating activity. These results show that a range of chelating peptides are generated during digestion of the chickpea proteins that, after metal chelation, may prevent the generation of reactive oxygen species (ROS) and favour metal absorption.     

Chemical structure of sulfated polysaccharides from brown seaweed (Turbinaria turbinata)

The chemical structure of three sulfated polysaccharides fractions (TtF1, TtF2, and TtF3) obtained from anion-exchange separation of aqueous extracts of brown seaweed (Turbinaria turbinate) were studied. The infrared spectra patterns showed that the fractions possess functional groups similar to that of sulfated polysaccharides. The sulfated polysaccharides fractions exhibited molecular weights of 223.5, 495.5, and 326.05 kDa, respectively, for TtF1, TtF2, and TtF3. ¹H NMR spectra of TtF2 and TtF3 contain α-anomeric protons (5–5.6 ppm), ring protons (3.4–4.4), and methyl protons (1–1.3 ppm) while that of TtF1 only exhibited ring protons and methyl protons. Rheological data were fitted to power law which revealed that the fractions were Newtonian and/or presented weak pseudoplastic behavior. Consistency values increased with concentration in all fractions. Consistency values of TtF2 were the highest, followed by TtF1 and then TtF3. Thermal degradation patterns of TtF1 and TtF2 were similar but different from that of TtF3. This study confirmed that chemical and physical characteristics of sulfated polysaccharides fractions are interrelated and provided in-depth understanding of sulfated polysaccharides of brown algae.     

Influence of the hydrolysis process on the biological activities of protein hydrolysates from cod (Gadus morhua) muscle

Upgrading of fish protein through limited proteolysis of by‐products and surplus of the food industry generates peptides of interest to food formulation, the animal feed industry and aquaculture. The hydrolysis process has been studied in order to investigate the role of the limiting parameters. Hydrolysates obtained under varying conditions of temperature, pH, time and enzyme concentration were tested on fibroblastic cell cultures and in gastrin radioimmunoassays. Several fractions were shown to contain biologically active peptides such as growth factors or secretagogues (gastrin and cholecystokinin). Under optimum conditions we obtained 160% stimulation of cell growth with only 25 µg ml ⁻¹ hydrolysates, and about 0.25 pg gastrin‐like peptides mg⁻¹ sample. The process of hydrolysis plays a key factor by extending the time of protein degradation in generating these molecules. © 2000 Society of Chemical Industry     

Distribution of hydrophilic and lipophilic antibacterial drugs in skim milk,cream, and casein

This study determined the distribution of drugs to different milk fractions according to their physicochemical properties. Hydrophilic drugs tend to concentrate in skim milk, whereas lipophilic drugs tend to concentrate in cream. The concentration of a drug in casein is related to its degree of binding to milk proteins. Thus, we aimed to determine whether withdrawal time in whole milk differs from that in cream, casein, and skim milk. Amoxicillin and tylosin were selected as prototype hydrophilic and lipophilic drugs, respectively. The study was conducted in vitro and in vivo to determine whether in vitro conditions reflect the distribution of drugs in the different milk fractions in vivo. The in vivo study was conducted using a crossover design on 6 healthy Holstein dairy cattle. First, amoxicillin (i.m., single dose, 14 mg/kg) was administered to cows. Following a 1-wk washout period, tylosin (i.m., single dose, 15 mg/kg) was administered. Concentrations of amoxicillin and tylosin in milk and milk fractions were measured using HPLC-UV. In the in vitro study, 0.04 to 400 μg/g of amoxicillin and 0.05 to 50 μg/g of tylosin were spiked to drug-free milk and the concentrations in milk and milk fractions were measured. In addition, the percentage of total protein in milk and milk fractions was determined. Amoxicillin accumulated more in skim milk than in cream and casein, both in vitro (92%) and in vivo (73%, skim milk-to-whole milk ratio). The distribution of tylosin in whole and skim milk was similar to that of amoxicillin in the in vitro study, in contrast to the accumulation of tylosin in cream seen in vivo. However, the accumulation ratio of tylosin in cream was lower than expected. By either method, tylosin was less concentrated in casein than in skim milk and cream. The percentage of total protein was similar in skim milk and whole milk and higher than in cream. Thus, amoxicillin accumulates less in cream and casein, suggesting that these fractions would pose a lower risk to the consumer. Tylosin was still present at the maximum residue limit (50 μg/kg) 24 h after injection in the casein fraction and 48 h after injection in the cream fraction.     

Influence of dietary fish meal on egg fatty acid composition

Changes in the fatty acid composition of egg-yolk fat of hens fed diets with increasing fish meal content are studied by total fatty acid analysis. The fatty acid composition of the major lipid fractions in egg-yolk fat after feeding a high-level fish meal diet was determined by a combination of thin layer chromatography (t.l.c.) and gas-liquid chromatography (g.l.c.) The changes produced show a fatty acid pattern similar to those of the diets themselves. Long-chain polyunsaturated fatty acids are deposited preferentially in the phospholipids, reaching the highest concentration in cephalin and lecithin.     

Effect of slow desorption on the kinetics of biodegradation of polycyclic aromatic hydrocarbons

The bioavailability to bacteria of 14C-labeled polycyclic aromatic hydrocarbons (PAHs) sorbed onto lake sediments was assessed using a mathematical model and three experimental series. The experiments were performed under similar conditions and included: (1) abiotic desorption of PAHs from sediments by Tenax extraction, (2) mineralization of dissolved PAHs with no sediment present, and (3) mineralization of PAHs sorbed onto sediments. Results obtained from the first two series were used to obtain the parameter values for the model, and the experimental results of the third series were compared to model results. We found that microorganisms were able to promote desorption of the more-labile fractions, but were unable to increase the desorption rate of the slow- and very slow-desorbing fractions. Also, our model predictions indicate that, after very long contact times, and in the concurrence of biodegradation, sorbed PAHs remain not under equilibrium conditions, but rather in a steady state. The net rates of PAH desorption from the three sediment domains considered (fast, slow, and very slow) become similar, and the ratio between the aqueous and the sediment concentration remains constant with time.     

Formation of 2-Pentyl Pyridine During Processing of Soybean Protein Isolates as Affected by pH

Levels of 2-pentyl pyridine (2-pp) in protein fractions from Stressland soybeans increased to 0.868 ppm (±0.027) at pH 7 after removing insoluble components from defatted flours. If similar protein fractions were held at pH 4.5 or pH 9, the 2-pp concentration was 0.182 ppm (± 0.003) or 0.199 ppm (± 0.003), respectively. Soybean cultivars KS4694, Edison, and a type null for lipoxygenase 1, 2, and 3 showed similar changes. The increase at pH 7 occurred in less than 1 h. If the defatted flour solution was not subjected to alkaline extraction to remove insoluble components, the increase of 2-pp at neutral pH did not occur. Thus, the pH conditions should be carefully controlled to produce soybean protein isolates with desired flavor properties.     

Antioxidant activity of ovine casein hydrolysates: identification of active peptides by HPLC–MS/MS

This paper shows the potential role of different ovine casein fractions and their hydrolysates to exert antioxidant activity. ABTS^·+ decolorization assay was used to evaluate the antioxidant activity of the casein fractions (β-, κ- and α_s-caseins) before and after their hydrolysis by pepsin, trypsin and chymotrypsin. Although the antioxidant activity increased in all the fractions after hydrolysis, the effect was particularly remarkable in the κ-casein fraction, which increased its antioxidant activity almost threefold. Further assays in a linoleic acid oxidation system showed that κ-casein hydrolysate inhibited lipid peroxidation. Analysis of the ovine κ-casein hydrolysate by RP-HPLC–MS/MS allowed the identification of 12 peptide sequences with potential antioxidant properties. One of the most abundant peptides, the fragment HPHPHLSF [f(98–105)] was chemically synthesized. Results showed that this κ-casein-derived peptide was a potent inhibitor of linoleic acid oxidation with an activity similar to that obtained with the synthetic antioxidant BHT. Although other peptides might also contribute, HPHPHLSF was the one most likely to be responsible for the activity found in the κ-casein hydrolysate.     

Evaluation of liquid smoke treated ready-to-eat (RTE) meat products for control of Listeria innocua M1

ABSTRACT:  Liquid smoke fractions (S1, S2, S3, and S4) were applied on ready-to-eat (RTE) meat products to control the growth of inoculated Listeria innocua M1. Turkey rolls and roast beef products were dipped in liquid smoke, surface inoculated with L. innocua M1 (10² CFU/25 cm² RTE meat surface), vacuum packaged, and stored at 4 °C. Section 8.5 of USDA's detection and isolation procedure for L. monocytogenes was employed in conjunction with a Micro-ID™ system for L. innocua M1 identification (ID). Products treated with smoke fractions S1, S2, and S3 were negative for L. innocua M1 at 2 and 4 wk during incubation at 4 °C. Products treated with S4 were positive for L. innocua M1 immediately following inoculation and after storage for 2 and 4 wk. Smoke fractions S1, S2, and S3 exhibited pH values lower than 4.6, acidity values higher than 1.5%, and carbonyl concentrations higher than 110 mg/mL. All liquid smoke fractions contained similar phenol concentrations (0.3 to 0.6 mg/mL), suggesting that phenols may have a limited role in the bactericidal effects of liquid smoke fractions against specific microorganisms.     

Evaluation of Wheat Bran Obtained by Tangential Abrasive Dehulling Device

A tangential abrasive dehulling device (TADD) was used to evaluate debranning properties of wheat grain and obtain grain fractions enriched in antioxidants. Effect of grain moisture content and abrasion time on the chemical composition and antioxidant capacity of the fractions were examined. Whole wheat, bran from a quadrumat senior mill, and a commercial aleurone sample were used as references. Total phenolic content (TPC), oxygen radical absorbance capacity (ORAC) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging capacity of the TADD bran extracts were determined and compared to those of the reference materials and butylated hydroxytoluene (BHT). TADD bran fraction obtained at original grain moisture level, 11%, and short abrasion time, 1 min, had the highest ORAC value among the samples examined in this study. Only the sample obtained at 11% moisture level and 1 min abrasion time had similar ORAC, TPC, and DPPH values that are similar to those of the commercial aleurone despite the big difference in their starch content. The effect of grain moisture, abrasion time, and moisture?×?abrasion time interaction had significant effects on the chemical composition and antioxidant capacity of the fractions. This study demonstrated that TADD was very effective in producing wheat grain fractions with high antioxidant content.