Degradation of curdlan using hydrogen peroxide

Curdlan, a linear glucan interconnected by β-(1 → 3) linkages, is soluble in alkaline solutions but not in water, which limits its wide application, particularly in the food industry. In this study, curdlan was subjected to oxidative degradation using hydrogen peroxide (H₂O₂). The optimal hydrolysis conditions were determined, and the results were as follows: reaction time, 40 min; temperature, 60 °C; H₂O₂ concentration, 1.5% (v/v); and NaOH concentration, 2.5 M. Under these optimised conditions, the maximum dextrose equivalent value (13.49%) was obtained. The composition and the structure of the hydrolysates were characterised by high-performance liquid chromatography and Fourier-transform infra-red spectroscopy, respectively. The hydrolysates were filtered, neutralised with HCl, concentrated to ∼12% (w/v), desalted, and freeze dried to yield a water-soluble, white powder. The (1 → 3)-β-d-glucan oligosaccharide content of the product was 98.6% and the yield was 91.4% (w/w).     

Effects of reaction mixture and other components on the determination of the equilibrium and rate constants of the hydration reactions of anthocyanins

The equilibrium and rate constants of the hydration and deprotonation reactions of anthocyanins show how their color intensity changes with pH. In the cases of several anthocyanins, the constants for each obtained by several methods are different. In an effort to resolve these discrepancies, we have examined the effects of several components of the pH-jump experiments on the values of the constants. Storage of the buffers to be used in pH-jump experiments in Pyrex or borosilicate glass bottles results in increasing Al³⁺ concentration in the buffers over several weeks. When these buffers are used, the anthocyanins with two OH groups on the B ring complex with the Al³⁺ which leads to major changes in their spectra, in the equilibrium position, and in the apparent first-order rate constant. Thus, constants determined on the same anthocyanin using the same buffers stored in glass bottles may be different at different times. During the reduction of the experimental data to the rate and equilibrium constants, two divergences from the expected behavior were found. In the calculation K_a + K_h for the anthocyanin acylated with 4-hydroxy-3,5-dimethoxycinnamic acid (6-O-(4-hydroxy-3,5-dimethoxycinnamoyl)-β-d-glucopyranosyl-(1 → 6)-[β-d-xylopyranosyl-(1 → 2)]-β-d-galactopyranosyl-(1 → O³)-cyanidin), the plotted points appear to fit two straight lines, intersecting at an equilibrium pH near pH 4. In the calculation which leads to the individual constants of both anthocyanins examined here, the points below an equilibrium pH of pH 4 curve upward from the line that describes the points from an equilibrium pH above 4. Differences in the composition of solutions used in pH-jump experiments examined here, include (1) the addition of phosphate to the acetate buffer, (2) the presence of 0.5 M NaCl, and (3) the solution of the anthocyanin in either 0.1 N HCl or 0.1 N HOAc. These changes gave differences that were statistically significant in some of the constants for each of the two anthocyanins examined. The constants were both qualitatively and quantitatively different.     

Determination of l- and d-amino acids in smokeless tobacco products and tobacco

Quantities of free l- and d-amino acids were determined by GC-SIM-MS in 25 European snuff tobaccos (from Germany, England and Sweden) and eight chewing tobaccos (from the Philippines, Africa and Denmark) and compared to those of cigar, cigarillo, and freshly harvested tobacco leaves of cultivars of Nicotiana tabacum L. Amino acids were isolated from tobacco samples by treatment with 70% aqueous methanol and purified by a cation exchanger. Next they were converted into their N(O)-pentafluoropropionylamino acid-(2)-propyl esters, and enantiomers separated and quantified by GC-SIM-MS on a Chirasil^®-l-Val capillary column. Among l-amino acids the most abundant were Pro, Asx and Glx in the low milligram range (about 2–6 mg/g) whereas the other l-amino acids were in the submilligram range. Though native tobacco leaves contained low amounts of few d-AAs (0.2–1.9%), all processed tobacco samples had d-amino acids in varying amounts and patterns.     

Effects of monensin and stage of lactation on variation of blood metabolites within twenty-four hours in dairy cows

Effects of prepartum administration of a monensin controlled release capsule (CRC) and stage of lactation on variation of blood metabolites within 24 h were determined in 16 dairy cows. Cows were fed a total mixed ration ad libitum twice daily at 0700 and 1300 h. At calving, cows were switched from a close-up dry cow diet to a lactating cow diet. Cows were blood sampled every 3 h for 24 h at 3 stages of lactation, including 1 wk before calving (wk −1), 1 wk after calving (wk 1), and 6 wk after calving (wk 6). Serum concentrations of glucose, β-hydroxybutyrate (BHBA), nonesterified fatty acids (NEFA), and urea exhibited significant variation within 24 h. Glucose and NEFA were, respectively, 0.09 and 0.08 mM lower between 1030 and 2230 h than between 2230 and 1030 h. β-Hydroxybutyrate and urea were, respectively, 95.1 and 0.49 mM higher between 1030 and 2230 h than between 2230 and 1030 h. Monensin did not significantly affect glucose, NEFA, and urea in this study. Monensin reduced BHBA at wk 1, but not at wk −1 or wk 6. Glucose was lower and BHBA and NEFA were higher at wk 1 compared with wk −1 and wk 6. Urea was higher at wk 6 compared with wk −1. The variation within 24 h of glucose, BHBA, and NEFA were not affected by monensin and stage of lactation. Diurnal variation of urea was affected by stage of lactation, but not by monensin.     

Colour properties,stability, and free radical scavenging activity of jambolan (Syzygium cumini) fruit anthocyanins in a beverage model system: Natural and copigmented anthocyanins

The colour and stability properties of jambolan anthocyanins, both natural and copigmented forms, were investigated in beverage model as well as their radical scavenging ability. Natural anthocyanins of jambolan revealed low colour intensity due to glycosylation structure of the anthocyanins as diglucoside. The intermolecular copigmentation of anthocyanins with sinapic acid, caffeic acid, ferulic acid, and rosemary polyphenolic extract could enhance the colour intensity, which was observed through spectrometric parameters, such as hyperchromic effect (ΔA_vis-max) and bathochromic shift (Δλ_vis-max). In addition of sinapic acid, caffeic acid, and rosemary polyphenolics also increased the stability of the anthocyanin colour during exposure to white fluorescent light and storage at refrigeration and room temperatures, whereas on high thermal treatments, this phenomenon was not observed. Furthermore, beverage model coloured with natural or copigmented anthocyanins revealed DPPH radical-scavenging activity. The AEAC values indicated that the beverage models with copigmented anthocyanins had higher scavenging activity than the beverage with natural anthocyanins.     

Therapeutic use of phage cocktail for controlling Escherichia coli O157:H7 in gastrointestinal tract of mice

To investigate the therapeutical use of phage mixture for controlling gastrointestinal Escherichia coli O157:H7 cells, in vitro and in vivo experiments were conducted. Three phages, SP15, SP21, and SP22 were selected from 26 phage stock screened from feces of stock animals and sewage influent. Addition of single or binary phage to the E. coli cell batch-culture reduced the turbidity of the culture. However, reascend of the turbidity due to the appearance of phage resistance cell was observed. On the other hand, addition of three phage mixture (SP15-21-22) did not produce reascend of culture turbidity under aerobic condition. Under anaerobic condition, slight reascend of culture turbidity was observed after SP15-21-22 addition. Chemostat continuous culture was operated under anaerobic condition to optimize the titer of phage cocktail and frequency of the addition for controlling E. coli cells. Five-log decrease of E. coli cell concentration after addition of phage cocktail of 10(9) Plaque forming unit (PFU)/ml was observed. However, reascend of cell concentration was observed after 1 d incubation. Repeated addition of phage cocktail was effective to reduce the cell concentration. Suspension of phage cocktail in the buffer containing 0.25% CaCO3 neutralized 9 times much more buffer of pH 2. Based on this in vitro experiment, phage cocktail (SP15-21-22) suspended in the buffer containing 0.25% CaCO3 was orally administrated to the mice in which E. coli O157:H7 cells was administrated in 2-d advance. E. coli and phage concentration in the feces was monitored for 9 d after phage addition. High titer of phage was detected in the feces when the phage cocktail administrated daily. E. coli O157:H7 concentration in the feces has been reduced according to the time period. However, difference of E. coli concentration in the feces of mice administrates with phage and in the control mice without phage addition became slight after 9-d test period. High titer of the phage settled down in the gastrointestinal tracts and reduced the concentration of E. coli cell. Repeated oral administration of SP15-21-22 was effective for rapid evacuation of E. coli O157:H7 from the feces and gastrointestinal tract of mice.     

Vacuolar functions are involved in stress-protective effect of intracellular proline in Saccharomyces cerevisiae

Proline protects yeast cells from damage caused by various stresses. A yeast Saccharomyces cerevisiae mutant with high levels of intracellular proline grown in a minimal medium accumulated proline in its vacuole, but when grown in a nutrient medium, accumulated proline mainly in the cytosol. To understand the role of the proline pool in the vacuole, we examined the stress-protective effect of proline in proline-accumulating yeast cells deficient in vacuolar functions. The disruption of PEP3 encoding a vacuolar membrane protein required for vacuolar biogenesis caused hypersensitivity to heat shock and ethanol stresses, probably due to disappearance of normal vacuoles. The vph1-disrupted cells lacking vacuolar-ATPase activity showed resistance to heat shock without any change in proline localization, but showed severe growth defects in an ethanol-containing medium. These results indicate that vacuolar functions are involved in the stress-protective effect of proline in S. cerevisiae. Also, it appears that excess proline is transported to the vacuole in an ATP-independent manner.     

Structural characterisation and anti-ageing activity of extracellular polysaccharide from a strain of Lachnum sp.

A homogeneous extracellular polysaccharide of Lachnum YM261(LEPS-1) with a molecular weight of 21670 Da was characterised. According to HPGPC, IR, periodate oxidation and Smith degradation, GC-MS and ¹H NMR analysis, the results indicated that LEPS-1 was a glucan linked by the β-(1 → 3)-d-pyran glycosidic bond. The effect of LEPS-1 on anti-ageing in d-gal model mice was also studied. It was found that LEPS-1 significantly increased the activities of antioxidant enzymes (i.e. SOD superoxide dismutase, CAT catalase, GSH-PX glutathione peroxidase) and decreased malondialdehyde (MDA) content in liver, brain and serum of d-gal model mice. These results showed that LEPS-1 had a strong anti-ageing activity.     

Results of an European inter-laboratory comparison study on the determination of the 15 + 1 EU priority polycyclic aromatic hydrocarbons (PAHs) in liquid smoke condensates

A collaborative study on the determination of the 15 + 1 EU priority PAHs in Primary Smoke Condensate (PSC) investigating the performance profile of EU Member States’ laboratories and supporting the work carried out by the European Food Safety Authority on smoke flavourings was organised. Two spiked liquid smoke condensate materials were employed in this study. The results of 25 laboratories from across the European Union, using either high performance liquid chromatography with fluorescence detection or gas chromatography with mass selective detection, were evaluated by application of robust statistics. The assessment of the data indicated broadened Gaussian distributions for all analytes. For benzo[a]pyrene (BaP), benzo[a]anthracene (BaA), chrysene and 5-methylchrysene more than 80% of the respective reported values gave rise to a satisfactory score of |z| ? 2. For benzo[b]fluoranthene, benzo[k]fluoranthene, and dibenzo[a,l]pyrene 70–80%, for the remaining analytes less than 70%, and for dibenzo[a,i]pyrene 52% of the scores were satisfactory. No systematic differences could be detected between values reported by laboratories using methods based on HPLC and the values related to methods based on GC for most of the analytes, except for benzo[k]fluoranthene and benzo[c]fluorene. In both cases laboratories using GC based methods reported about 50% higher values than laboratories using HPLC based methods. The overview on all z-scores sorted by laboratory revealed broad distributions and/or laboratory biases for several laboratories. An assessment of the reported method performance parameters revealed that for the two regulated compounds, BaP and BaA, only two thirds of the reported data were in compliance with Regulation (EC) 627/2006. Overall the methods used in the participating laboratories were – with ample room for improvement – well on the way to comply with European legislation.     

Biosynthesis of poly-gamma-glutamic acid in plants: transient expression of poly-gamma-glutamate synthetase complex in tobacco leaves

Transient expression of genes coding for the poly-gamma-glutamate (gammaPGA) synthetase system (pgs) was investigated in tobacco plants. Three genes of the pgs, pgsA, pgsB and pgsC, were separately placed under the control of the CaMV 35S promoter and introduced into tobacco leaves via Agrobacterium infection. Synthesized gammaPGA in plant tissues was detected immunologically with mouse anti-gammaPGA antiserum which specifically reacts with gammaPGA on a nitrocellulose membrane. Confirmation of gammaPGA biosynthesis in the transient expression analysis in tobacco tissue indicates that subunits of pgs complex were expressed and reassembled in a functional form.     

Identification of the key odorants in raw French beans and changes during cooking

 By application of aroma extract dilution analysis (AEDA) to an extract prepared from raw French beans, 25 odour-active compounds with flavour dilution (FD) factors in the range 4–2048 were detected and subsequently identified. Among them, (Z)-3-hexenal (green, leaf-like), 1-octene-3-one (mushroom-like), 3-isobutyl-2-methoxypyrazine (earthy, beany) and (E,Z)-2,6-nonadienal (cucumber-like) showed the highest FD factors. In an extract prepared from the same amount of cooked beans, 3-isobutyl-2-methoxypyrazine was identified as the most potent odorant, followed by 1,5-(Z)-octadiene-3-one (geranium-like), 3-isopropyl-2-methoxypyrazine (earthy, beany), 3-(methylthio)propanal (methional; cooked potato), 4,5-epoxy-(E)-2-decenal (metallic) and an unknown compound (FD 256) with a smell of geranium leaves. A decrease in (Z)-3-hexenal and 1-pentene-3-one (etheral, pungent) and an increase in methional during cooking were shown to be mainly responsible for the flavour changes induced by cooking the beans. Received: 22 January 1998 / Revised version: 16 March 1998     

Identification of the key odorants in raw French beans and changes during cooking

 By application of aroma extract dilution analysis (AEDA) to an extract prepared from raw French beans, 25 odour-active compounds with flavour dilution (FD) factors in the range 4–2048 were detected and subsequently identified. Among them, (Z)-3-hexenal (green, leaf-like), 1-octene-3-one (mushroom-like), 3-isobutyl-2-methoxypyrazine (earthy, beany) and (E,Z)-2,6-nonadienal (cucumber-like) showed the highest FD factors. In an extract prepared from the same amount of cooked beans, 3-isobutyl-2-methoxypyrazine was identified as the most potent odorant, followed by 1,5-(Z)-octadiene-3-one (geranium-like), 3-isopropyl-2-methoxypyrazine (earthy, beany), 3-(methylthio)propanal (methional; cooked potato), 4,5-epoxy-(E)-2-decenal (metallic) and an unknown compound (FD 256) with a smell of geranium leaves. A decrease in (Z)-3-hexenal and 1-pentene-3-one (etheral, pungent) and an increase in methional during cooking were shown to be mainly responsible for the flavour changes induced by cooking the beans. Received: 22 January 1998 / Revised version: 16 March 1998     

Chemistry and medicinal properties of the Bakul (Mimusops elengi Linn): A review

India is one of the world's biodiversity hotspots and reports confirm that a great variety of fruiting trees are indigenous to this region of the world. Mimusops elengi Linn (family Sapotaceae) commonly known as Bakul is one such tree native to the Western Ghat region of the peninsular India. However, today this tree is also found growing in other parts of the tropical and subtropical regions of the world. The tree is of religious importance to the Hindus and finds mention in various mythological texts. The stem, barks, leaves and fruits are used in various Ayurvedic and folk medications to treat various ailments. In the prehistoric days the ripe fruits were an important source of diet but today no one knows of its dietary use as it is seldom used. Studies suggest the tree contains medicinally-important chemicals, particularly the triterpenes and alkaloids. Preclinical studies in the past five years have shown that the extracts prepared from Bakul possess antibacterial, antifungal, anticariogenic, free radical scavenging, antihyperglycemic, antineoplastic, gastroprotective, antinociceptive and diuretic effects, thus lending pharmacological support to the tree's ethnomedicinal uses in Ayurveda. In this review for the first time attempt is made at addressing the chemical constituents, medicinal uses and validated pharmacological observations of Bakul.     

Structuring dairy systems through high pressure processing

This review highlights the current knowledge on gelation of hydrocolloids induced by high pressure processing (HPP) of dairy products. Pressure-induced gelation of single systems (casein rich, whey protein rich, gelatin, and polysaccharide solutions) as well as rheological and thermo-mechanical effects of HPP on mixture systems are discussed. The mechanism of dairy protein gelation under pressure, their properties and microstructure, and potential application of HPP to improve physical properties of dairy products (cheese, yoghurt, and ice cream) are included. HPP is a promising tool for future manufacturing of structured dairy products with unique sensorial properties.     

Identification of substances responsible for the ‘sawdust’ aroma in oak wood

The unpleasant ‘sawdust’ odour sometimes found in wines aged in new barrels was studied by gas chromatography olfactory detection and mass spectrometry. A particular aromatic zone has several chromatographic peaks, corresponding to certain characteristic odours which can be detected by smelling the gas effluent. These include the subtle rancid, weedy odour of ‘sawdust’. Various carbonyl components have been identified in this particular zone. These include (E)-2-nonenal, 3-octen-1-one, (E)-2-octenal and 1-decanal. These molecules are the primary cause of disagreeable oak wood odours. By measuring (E)-2-nonenal in wines, after derivation by O-(2,3,4,5-pentafluobenzyl)-hydroxilamine (PFBOA), it was possible to correlate the concentration of this unsaturated aldehyde with the intensity of the ‘sawdust’ character noted in tasting. The possible explanations for the presence of these carbonyl compounds are debatable. The carbonyl content varied from one wood sample to another. However, controling the toasting of the wood, both in the laboratory and in the cooperage, produced a major reduction in the extractable (E)-2-nonenal content and eradicated the ‘sawdust’ character of the wine. © 1998 SCI.     

Characterisation of a novel monomeric lectin (AML) from Astragalus membranaceus with anti-proliferative activity

A novel lectin (AML) was isolated from the roots of a Chinese herb Astragalus membranaceus (Fisch.) Bunge, using a combination of ammonium sulphate fractionation and affinity chromatography. AML was found to be a monomeric protein with a molecular mass of 31.5 kDa. Biochemical characterisation revealed that it is a glycoprotein containing 10.7% neutral sugars. The N-terminus of AML was blocked but amino acid sequences of internal tryptic peptides showed moderate sequence identities with some other known lectins. Amongst the various carbohydrates tested, the lectin was best inhibited by d-galactose and its derivatives with pronounced preference for o-nitrophenyl-β-d-galactopyranoside (8.3 mM). The lectin was stable in the pH range of pH 5.0–12.0 and temperatures up to 55 °C for 30 min. AML inhibited the proliferation of HeLa and K562 cell lines. Thus, the lectin displays a high potential for antitumour activity.     

Impact of process conditions on the structure of pre-fermented frozen dough

The volume change of partially fermented dough exposed to refrigeration has been investigated. Lean dough pieces (70 g) were exposed to pre-fermentation at 30 °C during selected time to reach expansion ratios of 2, 3 and 4. The pre-fermented dough were exposed to cooling at 4 °C for 2 h. Dough pieces were then frozen, thawed and baked. The evolution of the volume of the dough during the different stages of the time-temperature history has been measured. Image analysis (cell distribution), of both pre-fermented dough in frozen state and baked bread obtained with these dough, were carried out and used to assess the impact of the degree of pre-fermentation on the stability of the dough and of the baked bread. Results showed that increasing the degree of pre-fermentation results in a reduction in the final dough and bread volume. Freezing applied to pre-fermented dough resulted in a baked bread with larger and less numerous gas cells. However, it was observed that applying a chilling step (4 °C for 120 min) before freezing the pre-fermented dough minimized the loss in bread volume (−40.5% vs. −27.5% in comparison to reference bread - direct baking).     

Survival of Brucella spp. in mineral water, milk and yogurt

Knowledge of the number of organisms in a food product at the time of consumption is crucial to assess the risk from a deliberate contamination of food samples with Brucella. To date, very little data on the survival times of Brucella in different food matrices is available.This study was conducted to assess the survival times of Brucella spp. in water, milk and yogurt. These food products were inoculated with bacteria, serial dilutions of the food samples plated and the number of surviving bacteria counted.Under normal storage conditions Brucella survived in UHT milk for 87 days, for 60 days in water and less than a week in yogurt. Also, when milk was inoculated with low bacterial numbers, Brucella multiplied by five log units within three weeks.Further we could not confirm that a high fat content in food has a protective effect on Brucella survival. Brucella survived in 3.5% and 10.0% fat yogurt for four and two days, respectively.These results show that appropriate methods for the rapid detection of this pathogen from food matrices are required.