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1.
Food Chem Toxicol ; 48(12): 3471-6, 2010 Dec.
Article in English | MEDLINE | ID: mdl-20870004

ABSTRACT

Grape skin extracts of Riesling Vitis vinifera L. grapes from conventionally or organically managed cultivars were compared on the basis of their phenolic content, antioxidant capacity, antimicrobial and antimutagenic properties and pesticide loads. Promising results on their biological properties suggest that those extracts would be valuable as food preservatives. The antioxidant capacity of conventional extracts was significantly higher, according to the higher content in catechin, epicatechin and procyanidin B. Pesticide loads did not affect the antimutagenic or antimicrobial properties of the extracts. Both extracts inhibited the growth of Gram-positive foodborne pathogens such as Staphylococcus aureus, Enterococcus faecalis and Enterococcus faecium to similar extents. Possibly as a result of higher amounts of quercetin and its derivatives, higher antimicrobial effects against Listeria monocytogenes and Salmonella typhimurium were observed for the organic white grape skin extracts. Conventional or organic extracts did not show remarkable antimutagenic effects when tested against the mutagen IQ by means of the Ames test. Due to the presence of fungicides, the conidial germination of Penicillium expansum, Penicillium chrysogenum and Aspergillus niger, were inhibited by 95% by conventional GSE, while negligible effects were observed with organic grape extracts. The latter, however, showed inhibitory effects against Trichoderma viridie and Aspergillus versicolor.


Subject(s)
Food, Organic/analysis , Pesticide Residues/analysis , Phenols/analysis , Phenols/pharmacology , Vitis/chemistry , Antioxidants/analysis , Antioxidants/pharmacology , Bacteria/drug effects , Carbohydrates/analysis , Chromans/analysis , Chromatography, High Pressure Liquid , Flavonoids/analysis , Fruit/chemistry , Fungi/drug effects , Indicators and Reagents , Methanol , Nitrogen/analysis , Plant Extracts/analysis , Potassium/analysis , Solvents , Spectrometry, Mass, Electrospray Ionization , Ultraviolet Rays , Vitis/microbiology
2.
J Agric Food Chem ; 56(22): 10761-6, 2008 Nov 26.
Article in English | MEDLINE | ID: mdl-18950186

ABSTRACT

Chinese purple corn extracts ( Zea mays L., Zhuozhou, Hebei, China) (EZPC) were selected among five Chinese purple corn hybrids due to their higher anthocyanin content, and their thermal stability was evaluated. The total anthocyanin content and total phenolic content of EZPC were 304.5 +/- 16.32 mg of cyanidin-3-glucoside equiv/100 g of dry seeds and 489.8 +/- 24.90 mg of gallic acid equiv/100 g of dry seeds, respectively. Moreover, the individual anthocyanins of EZPC were determined by HPLC-DAD/ESI-MS analysis. Seven main compounds were determined, including cyanidin-3-(malonylglucoside), cyanidin-3-O-glucoside-2-malonylglucoside, cyanidin-3-O-glucoside, peonidin-3-O-glucoside, peonidin-3-(malonylglucoside), pelargonidin-3-(6''-malonylglucoside), and peonidin-3-(dimalonylglucoside). The thermal stability of EZPC was studied by differential scanning calorimetry. Thermodynamic analysis showed that the conversion of EZPC followed an Arrhenius relationship, where the delta enthalpy (H) and activation energy (E(a)) were 97.0 J/g and 204 +/- 2.72 kJ/mol, respectively. Furthermore, the relationships between the degree of conversion of EZPC and time or temperature were reported. This study demonstrated that the evaluated Chinese purple corn hybrids are a natural source of anthocyanins and are stable over a wide range of temperatures and times.


Subject(s)
Anthocyanins/analysis , Hot Temperature , Zea mays/chemistry , Anthocyanins/chemistry , Chromatography, High Pressure Liquid , Drug Stability , Phenols/analysis , Spectrometry, Mass, Electrospray Ionization , Thermodynamics
3.
J Agric Food Chem ; 55(4): 1289-94, 2007 Feb 21.
Article in English | MEDLINE | ID: mdl-17253716

ABSTRACT

High-pressure/high-temperature properties of vitamins in food are important with respect to the new pressure-assisted thermal sterilization method utilizing pressure-induced adiabatic temperature changes. Riboflavin, thiamin, and thiamin monophosphate (TMP) stabilities were assayed in the temperature range from 25 to 100 degrees C under normal pressure (0.1 MPa) and high pressure (600 MPa) in acetate-buffered (pH 5.5) model solutions, some with added fructose, hemoglobin, or ascorbic acid. Thiamin and riboflavin stabilities were also assayed in minced fresh pork fillet and in rehydrated pork reference material with and without pressure treatment at 600 MPa in the temperature range from 20 to 100 degrees C. In pork, the vitamins proved to be sufficiently stabile for high-pressure/high-temperature processing. Under similar conditions, vitamin decay in model solutions was up to 30 times faster, especially that of TMP. Thus, it appears that it may not be possible to draw conclusions for the pressure behavior of real food matrices from the results of investigations in food models. A further consequence is that caution is necessary when supplementing foods with synthetic B vitamins preceding high-pressure/high-temperature processing.


Subject(s)
Food Handling/methods , Hot Temperature , Meat/analysis , Pressure , Riboflavin/analysis , Thiamine/analysis , Animals , Drug Stability , Swine , Thiamine Monophosphate/analysis
4.
Biochim Biophys Acta ; 1764(3): 552-7, 2006 Mar.
Article in English | MEDLINE | ID: mdl-16446130

ABSTRACT

Application of high pressure can be used for gentle pasteurizing of food, minimizing undesirable alterations such as vitamin losses and changes in taste and color. In addition, pressure has become a useful tool for investigating structural changes in proteins. Treatments of proteins with high pressure can reveal conformations that are not obtainable by other physical variables like temperature, since pressure favors structural transitions accompanied with smaller volumes. Here, we discuss both the potential use of high pressure to inactivate infectious TSE material and the application of this thermodynamic parameter for the investigation of prion folding. This review summarizes our findings on the effects of pressure on the structure of native infectious scrapie prions in hamster brain homogenates and on the structure of infectious prion rods isolated from diseased hamsters brains. Native prions were found to be pressure sensitive, whereas isolated prions revealed an extreme pressure-resistant structure. The discussion will be focused on the different pressure behavior of these prion isoforms, which points out differences in the protein structure that have not been taken into consideration before.


Subject(s)
Hot Temperature , PrPSc Proteins/chemistry , Prion Diseases/metabolism , Animals , Brain/metabolism , Cricetinae , Pressure , Protein Conformation , Protein Denaturation , Protein Folding
5.
J Biol Chem ; 280(11): 9842-7, 2005 Mar 18.
Article in English | MEDLINE | ID: mdl-15598650

ABSTRACT

Crude brain homogenates of terminally diseased hamsters infected with the 263K strain of scrapie (PrP(Sc)) and purified prion fibrils were heated or pressurized at 800 megapascals and 60 degrees C for 2 h in different buffers and in water. Prion proteins (PrP) were analyzed for their proteinase K resistance in immunoblots and for their infectivity in hamster bioassays. A notable decrease in the proteinase K resistance of unpurified prion proteins, probably because of pressure-induced changes in the protein conformation of native PrP(Sc) or the N-truncated PrP-(27-30), could be demonstrated when pressurized at initially neutral conditions in several buffers and in water but not in a slightly acidic pH. A subsequent 6-7 log(10) reduction of infectious units/g in phosphate-buffered saline buffer, pH 7.4, was found. The proteinase K-resistant core was also not detectable after purification of prions extracted from pressurized samples, confirming pressure effects at the level of the secondary structure of prion proteins. However, opposite results were found after pressurizing purified prions, arguing for the existence of pressure-sensitive beta-structures (PrP(Sc)(DeltaPsen)) and extremely pressure-resistant beta-structures (PrP(Sc)(DeltaPres)). Remarkably, after the first centrifugation step at 540,000 x g during isolation, prions remained proteinase K-resistant when pressurized in all tested buffers and in water. It is known that purified fibrils retain infectivity, but the isolated protein (full and N-truncated) behaved differently from native PrP(Sc) under pressure, suggesting a kind of semicrystalline polymer structure.


Subject(s)
Brain/metabolism , Prions/chemistry , Animals , Biological Assay , Cricetinae , Endopeptidase K/chemistry , Endopeptidase K/pharmacology , Hydrogen-Ion Concentration , Immunoblotting , Polymers , PrPSc Proteins/chemistry , Pressure , Protein Conformation , Protein Denaturation , Protein Structure, Secondary , Protein Structure, Tertiary , Scrapie , Temperature , Time Factors
6.
Appl Environ Microbiol ; 70(1): 603-6, 2004 Jan.
Article in English | MEDLINE | ID: mdl-14711694

ABSTRACT

Lactobacillus plantarum CNRZ 1228 exhibited heme-dependent catalase activity under environmental conditions similar to those encountered during sausage fermentation. The 1,455-bp catalase gene (katL) was cloned and encoded a protein of 484 amino acids. Expression of katL in a heterologous host showed that katL encodes a functional catalase. PCR screening of selected strains of lactic acid bacteria for katL indicated the presence of similar genes in other strains of lactobacilli.


Subject(s)
Catalase/metabolism , Cloning, Molecular , Escherichia coli/enzymology , Hemin/metabolism , Lactobacillus/enzymology , Animals , Catalase/genetics , Enterococcus/enzymology , Enterococcus/genetics , Escherichia coli/genetics , Lactobacillus/genetics , Meat Products/microbiology , Molecular Sequence Data , Sequence Analysis, DNA
7.
J Gen Virol ; 85(Pt 1): 261-264, 2004 Jan.
Article in English | MEDLINE | ID: mdl-14718641

ABSTRACT

High hydrostatic pressure is a mild technology compared with high temperatures and is commonly used for food pasteurization. Crude brain homogenates of terminally diseased hamsters infected with scrapie 263K strain were heated at 60 degrees C and/or pressurized up to 1000 MPa for 2 h. Prion proteins were analysed for their proteinase K sensitivity using a Western blot technique. PrP(Sc) pressurized with 500 MPa or above proved to be proteinase K sensitive. To test the remaining infectivity of the pressurized material, hamsters were infected intracerebrally. Results showed a greatly delayed onset of disease (from 80 up to 153 days) when samples had been pressurized at 500 MPa and above. An increase in the survival rate was also observed: 47 % survival over 180 days was seen following infection with homogenates pressurized at 700-1000 MPa.


Subject(s)
Endopeptidase K/metabolism , Hot Temperature , PrPSc Proteins/metabolism , PrPSc Proteins/pathogenicity , Animals , Brain/metabolism , Cricetinae , Disinfection/methods , Hydrostatic Pressure , Scrapie/metabolism , Scrapie/mortality
8.
J Agric Food Chem ; 51(27): 8093-7, 2003 Dec 31.
Article in English | MEDLINE | ID: mdl-14690402

ABSTRACT

Peptides containing the cyclic product of glutamine at the N terminus are usually biologically active. If the cyclization of glutamine was associated with a volume reduction, pressure should displace the equilibrium in the direction of the lower volume. Here, results in model solutions and in whey are discussed, showing that the theorized cyclization of glutamine in Gln-His-ProNH(2) or Gln-Leu-ProNH(2) is significantly accelerated during the application of heat and even more strongly when elevated temperature and pressure combinations are used. The reaction rate depended on the intensity of the pressure treatment, the pH, and the nature of the amino acids adjacent to glutamine. The products of the reaction were identified as thyrotropin-releasing hormone (TRH) and [Leu(2)]TRH. The reported reactions could affect the naturally balanced concentration of short-chain peptides in foods and therefore induce unpredictable biological effects.


Subject(s)
Hot Temperature , Peptide Hormones/chemistry , Protein Precursors/chemistry , Pyrrolidonecarboxylic Acid/analysis , Cyclization , Glutamine/chemistry , Hydrogen-Ion Concentration , Pressure , Solutions , Thyrotropin-Releasing Hormone/chemistry
9.
Biotechnol Prog ; 18(5): 1076-81, 2002.
Article in English | MEDLINE | ID: mdl-12363360

ABSTRACT

The effects of high-pressure treatment on the reaction rates of horseradish peroxidase (HRP) with guaethol or guaiacol as a hydrogen donor were evaluated from direct transmission measurements in a high-pressure optical cell at 435 nm. Peroxidases are known to be very barostable and insensitive to heat. With guaethol the reaction velocity was independent of pressure up to 500 MPa, but with guaiacol the cytochrome c oxidase underwent a mechanism-based irreversible inhibition of catalytic activity when subjected to pressure; in the resting states (fully oxidized or reduced), it was insensitive to pressure. The enzyme inactivation took place with an inactivation rate constant of 5.15 x 10(-1) min(-1) at 500 MPa, 25 degrees C and pH 7. The degree of inactivation was correlated to the concentration of guaiacol. This is the first report on a mechanism-based pressure inactivation of HRP triggered at moderate pressure and temperature and mediated by the hydrogen donor.


Subject(s)
Enzyme Activation , Guaiacol/chemistry , Horseradish Peroxidase/chemistry , Phenols/chemistry , Hydrogen Peroxide/chemistry , Oxidation-Reduction , Pressure , Sensitivity and Specificity , Spectrophotometry/instrumentation , Spectrophotometry/methods , Temperature
10.
Appl Environ Microbiol ; 68(5): 2550-4, 2002 May.
Article in English | MEDLINE | ID: mdl-11976133

ABSTRACT

The structural genes for the two-peptide bacteriocin enterocin 1071 (Ent1071) in Enterococcus faecalis FAIR-E 309 were cloned. DNA sequence analysis showed that the enterocin 1071A (Ent1071A) peptide of strain FAIR-E 309 differed by two amino acids from the Ent1071A reported for E. faecalis BFE 1071 (E. Balla, L. M. T. Dicks, M. Du Toit, M. J. van der Merwe, and W. H. Holzapfel, Appl. Environ. Microbiol. 66:1298-1304, 2000), while the Ent1071B gene encoded identical peptides in these strains. However, resequencing of ent1071A from E. faecalis BFE 1071 showed that the Ent1071A peptide sequence reported previously was incorrect in two amino acids. Also, ent1071B in E. faecalis FAIR-E 309 encoded a prepeptide that was three amino acids shorter than that previously reported for E. faecalis BFE 1071 Ent1071B. A presumptive immunity gene (eni1071) was located downstream of the bacteriocin structural genes. This gene was cloned into the heterologous host E. faecalis ATCC 19433 and was shown to confer immunity. A truncated ABC transporter gene was located upstream of the Ent1071 structural genes.


Subject(s)
Bacteriocins/genetics , Enterococcus faecalis/genetics , Amino Acid Sequence , Bacteriocins/metabolism , Base Sequence , Cloning, Molecular , DNA, Bacterial/analysis , Enterococcus faecalis/metabolism , Molecular Sequence Data , Sequence Homology, Amino Acid
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