231 results match your criteria: "Southeast Dairy Foods Research Center[Affiliation]"
J Agric Food Chem
June 2002
Southeast Dairy Foods Research Center, Department of Food Science, North Carolina State University, Raleigh 27695, USA.
A method was developed for the production of a hydrolyzed/polymerized whey protein derivative with altered solution and gelation properties using a combination of recombinant DNA and immobilized enzyme technologies. The recombinant fusion proteins trypsin-streptavidin (TrypSA) and streptavidin-transglutaminase (cSAcTG) were produced in Escherichia coli, extracted, and then immobilized by selective adsorption on biotinylated controlled-pore glass. Recirculation through a TrypSA reactor induced limited proteolysis of whey proteins.
View Article and Find Full Text PDFAppl Environ Microbiol
June 2002
Department of Food Science, Southeast Dairy Foods Research Center, Raleigh, North Carolina 27695, USA.
Lactic acid bacterial strains were isolated from brines sampled after 7 days of an industrial sauerkraut fermentation, and six strains were selected on the basis of susceptibility to bacteriophages. Bacterial growth in cabbage juice was monitored, and the fermentation end products were identified, quantified, and compared to those of Leuconostoc mesenteroides. Identification by biochemical fingerprinting, endonuclease digestion of the 16S-23S intergenic transcribed spacer region, and sequencing of variable regions V1 and V2 of the 16S rRNA gene indicated that the six selected sauerkraut isolates were Leuconostoc fallax strains.
View Article and Find Full Text PDFAppl Environ Microbiol
February 2002
Departments of Food Science and Microbiology, Southeast Dairy Foods Research Center, North Carolina State University, Raleigh, NC 27695-7624, USA.
Antisense RNA complementary to a putative helicase gene (hel3.1) of a cos-type Streptococcus thermophilus bacteriophage was used to impede the proliferation of a number of cos-type S. thermophilus bacteriophages and one pac-type bacteriophage.
View Article and Find Full Text PDFJ Agric Food Chem
January 2002
Department of Food Science, Box 7624, Southeast Dairy Foods Research Center, North Carolina State University, Raleigh, North Carolina 27695, USA.
Nonfat dry milk (NDM) is widely used both as an ingredient in other preparations and for direct consumption. Flavor quality of NDM is a critical parameter because it can directly impact final product quality. Flavors can be formed in NDM during subsequent storage.
View Article and Find Full Text PDFAppl Environ Microbiol
September 2001
Department of Microbiology, Southeast Dairy Foods Research Center, North Carolina State University, Raleigh, North Carolina 27695, USA.
An efficient method is described for the generation of site-specific chromosomal integrations in Lactobacillus acidophilus and Lactobacillus gasseri. The strategy is an adaptation of the lactococcal pORI system (K. Leenhouts, G.
View Article and Find Full Text PDFJ Food Prot
July 2001
Department of Food Science and Technology, Southeast Dairy Foods Research Center, Mississippi State University, Mississippi State 39762-9805, USA.
The effects of acid shock, acid adaptation, starvation, and cold stress of Escherichia coli O157:H7 (ATCC 43895), an rpoS mutant (FRIK 816-3), and nonpathogenic E. coli (ATCC 25922) on poststress heat resistance and freeze-thaw resistance were investigated. Following stress, heat tolerance at 56 degrees C and freeze-thaw resistance at -20 to 21 degrees C were determined.
View Article and Find Full Text PDFJ Agric Food Chem
June 2001
Department of Food Science, Box 7624, Southeast Dairy Foods Research Center, North Carolina State University, Raleigh, NC 27695, USA.
Application of aroma extract dilution analysis (AEDA) on the volatile components of low-, medium-, and high-heat-treated nonfat dry milks (NDM) revealed aroma-active compounds in the log(3) flavor dilution (log(3) FD) factor range of 1 to 6. The following compounds contributed the highest log(3) FD factors to overall NDM flavor: 2,5-dimethyl-4-hydroxy-3(2H)-furanone [(Furaneol), burnt sugar-like]; butanoic acid (rancid); 3-(methylthio)propanal [(methional), boiled potato-like]; o-aminoacetophenone (grape-like); delta-decalactone (sweet); (E)-4,5-epoxy-(E)-2-decenal (metallic); pentanoic acid (sweaty); 4,5-dimethyl-3-hydroxy-2(5H)-furanone [(sotolon), curry]; 3-methoxy-4-hydroxybenzaldehyde [(vanillin), vanilla]; 2-acetyl-1-pyrroline and 2-acetyl-2-thiazoline (popcorn-like); hexanoic acid (vinegar-like); phenylacetic acid (rose-like); octanoic acid (waxy); nonanal (fatty); and 1-octen-3-one (mushroom-like). The odor intensities of Furaneol, butanoic acid, methional, o-aminoacetophenone, sotolon, vanillin, (E)-4,5-epoxy-(E)-2-decenal, and phenylacetic acid were higher in high-heat-treated samples than others.
View Article and Find Full Text PDFJ Food Prot
May 2001
Department of Food Science and Technology, Southeast Dairy Foods Research Center, Mississippi State University, Mississippi 39762-9805, USA.
A multiplex polymerase chain reaction (PCR) assay was developed for the detection and differentiation of enterotoxigenic Staphylococcus aureus in dairy products. A solvent extraction procedure was successfully modified for extraction of S. aureus DNA from 10 ml of artificially contaminated skim milk or 20 g cheddar cheese.
View Article and Find Full Text PDFJ Dairy Sci
March 2001
Department of Food Science and Technology, Mississippi Agricultural and Forestry Experiment Station, Southeast Dairy Foods Research Center, Mississippi State University, Mississippi State 39762, USA.
Carbonation, flavor, culture type, pH, and storage time were varied to investigate the effects of these variables and their interactions on the growth of both typical and nontypical yogurt cultures and some contaminating bacteria. Two types of yogurt cultures (YC-470 and YC-180) were used as the source of typical yogurt bacteria, Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus.
View Article and Find Full Text PDFEnzyme Microb Technol
April 2001
Southeast Dairy Foods Research Center, Department of Food Science, North Carolina State University, 27695-7624, Raleigh, NC, USA
A trypsin-streptavidin (TRYPSA) fusion protein was designed and its expression in Escherichia coli was evaluated. The streptavidin gene was PCR modified and cloned into the pET expression vector. The trypsin gene was subsequently inserted into this plasmid, thus generating a colinear fusion of trypsin and streptavidin genes (pTRYPSA).
View Article and Find Full Text PDFAppl Environ Microbiol
March 2001
Department of Microbiology, Southeast Dairy Foods Research Center, North Carolina State University, Raleigh, North Carolina 27695, USA.
The gusA gene, encoding a new beta-glucuronidase enzyme, has been cloned from Lactobacillus gasseri ADH. This is the first report of a beta-glucuronidase gene cloned from a bacterial source other than Escherichia coli. A plasmid library of L.
View Article and Find Full Text PDFJ Appl Microbiol
September 2000
Department of Food Science and Southeast Dairy Foods Research Center, North Carolina State University, Raleigh 27695, USA.
The Lactobacillus acidophilus complex includes Lact. acidophilus, Lactobacillus amylovorus, Lactobacillus crispatus, Lactobacillus gallinarum, Lactobacillus gasseri and Lactobacillus johnsonii. The objective of this work was to develop a rapid and definitive DNA sequence-based identification system for unknown isolates of the Lact.
View Article and Find Full Text PDFJ Appl Microbiol
July 2000
Department of Food Science and Technology, Southeast Dairy Foods Research Center, Mississippi State University, 39762, USA.
Rapid nucleic acid-based methods to detect human pathogens in foods are dependent on the reliability of the DNA or RNA extraction method used. Skim milk, non-fat dry milk, Cheddar and Brie cheese, and reconstituted whey powder were seeded with serially diluted (10(0)-10(7) cfu 10 ml(-1)) Escherichia coli O157:H7 and subjected to DNA extraction (i) directly from the food product using a solvent-based procedure and (ii) using a guanidinium isothiocyanate (GITC) procedure after previous bacterial concentration. Both the efficiency of DNA extraction and the overall PCR detection limits were evaluated.
View Article and Find Full Text PDFJ Food Prot
July 2000
Department of Food Science and Technology, Southeast Dairy Foods Research Center, Mississippi State University, Mississippi State 39762, USA.
A fluorescently labeled oligonucleotide probe (molecular beacon) was applied to detect Escherichia coli O157:H7 in artificially contaminated skim milk during polymerase chain reaction (PCR) amplification of extracted DNA. The probe was designed to hybridize with a region of the slt-II gene coding for the A subunit and to fluoresce when the hairpin-stem conformation was linearized upon hybridization to the target sequence. The molecular beacon was incorporated into PCR reactions containing DNA extracted from artificially contaminated skim milk.
View Article and Find Full Text PDFAppl Environ Microbiol
March 2000
Department of Food Science, Southeast Dairy Foods Research Center, College of Agriculture and Life Sciences, North Carolina State University, Raleigh, North Carolina 27695, USA.
Recombinant phages are generated when Lactococcus lactis subsp. lactis harboring plasmids encoding the abortive type (Abi) of phage resistance mechanisms is infected with small isometric phages belonging to the P335 species. These phage variants are likely to be an important source of virulent new phages that appear in dairy fermentations.
View Article and Find Full Text PDFMol Microbiol
September 1999
Department of Food Science, Southeast Dairy Foods Research Center, North Carolina State University, Raleigh, NC 27695-7624, USA.
The influence of low pH on inducible gene expression in Lactobacillus acidophilus was investigated by the use of differential display. Logarithmic phase cultures were exposed to pH 3.5 for various intervals, and RNA was isolated and reverse transcribed.
View Article and Find Full Text PDFInt J Food Microbiol
September 1999
Southeast Dairy Foods Research Center, Department of Food Science, North Carolina State University, Raleigh 27695-7624, USA.
Over the past 5 years the probiotic field has exploded with a number of new cultures, each purported to elicit a variety of benefits. Lists of functional characteristics and benefits, in vivo, are now commonplace to any presentation on probiotics. Scientifically established health claims remain among the highest priorities to companies who seek to establish solid health benefits that will promote their particular probiotic.
View Article and Find Full Text PDFJ Food Prot
August 1999
Department of Food Science and Technology, Southeast Dairy Foods Research Center, Mississippi State University, Mississippi 39762, USA.
Polymerase chain reaction (PCR) and reverse transcriptase (RT)-PCR using primers targeting 16S rRNA sequences in Escherichia coli O157:H7 were applied to monitor the stability of rDNA and rRNA in cells killed by mild heat treatment (60 degrees C) in skim milk. Serial dilutions of purified RNA and DNA from E. coli O157:H7 in skim milk were amplified by RT-PCR or PCR, respectively, before heat treatment and at time points 0, 6, 12, 24, and 48 h after heating.
View Article and Find Full Text PDFAppl Environ Microbiol
July 1999
Departments of Microbiology, Southeast Dairy Foods Research Center, North Carolina State University, Raleigh, North Carolina 27695-7624, USA.
The Lactobacillus johnsonii VPI 11088 groESL operon was localized on the chromosome near the insertion element IS1223. The operon was initially cloned as a series of three overlapping PCR fragments, which were sequenced and used to design primers to amplify the entire operon. The amplified fragment was used as a probe to recover the chromosomal copy of the groESL operon from a partial library of L.
View Article and Find Full Text PDFJ Dairy Sci
November 1998
Southeast Dairy Foods Research Center, Department of Food Science, North Carolina State University, Raleigh 27695-7624, USA.
Phosphopeptides that were derived from alpha s-CN or beta-CN were prepared with immobilized glutamic acid-specific endopeptidase, and their Ca2+ binding was characterized. alpha s-Casein or beta-CN was hydrolyzed in a fluidized bed bioreactor containing 2 ml of immobilized glutamic acid-specific endopeptidase by recirculating 20 ml of alpha s-CN or beta-CN solution (10 mg/ml in 50 mM Tris.HCl and 0.
View Article and Find Full Text PDFJ Dairy Sci
November 1998
Southeast Dairy Foods Research Center, Department of Food Science, North Carolina State University, Raleigh 27695-7624, USA.
Calcium binding to casein phosphopeptides that were derived from alpha s-CN or beta-CN was studied. Purified alpha s-CN or beta-CN was prepared from fresh skim milk using an anion-exchange column. Peptides were prepared by casein hydrolysis using a fluidized bed bioreactor containing 2 ml of immobilized trypsin (activity: 49.
View Article and Find Full Text PDFAppl Environ Microbiol
November 1998
Department of Food Science and Technology, Southeast Dairy Foods Research Center, Mississippi State University, Mississippi State, Mississippi 39762-9805, USA.
Differentiation of viable cells from nonviable cells is of considerable importance in the development of methods to detect foodborne pathogens. To study the suitability of 16S rRNA as an indicator of cell viability in nucleic acid-based detection assays, we examined rRNA stability in two representative foodborne pathogens, Escherichia coli O157:H7 and enterotoxigenic Staphylococcus aureus, which were inactivated by extreme heat, moderate heat, and UV irradiation. Cell death under all conditions was confirmed by a failure to grow in brain heart infusion broth after incubation for 48 h at 37 degrees C.
View Article and Find Full Text PDFGene
May 1998
Department of Food Science, Southeast Dairy Foods Research Center, North Carolina State University, Raleigh 27695, USA.
The abiA gene encodes an abortive bacteriophage infection mechanism that can protect Lactococcus species from infection by a variety of bacteriophages including three unrelated phage species. Five heptad leucine repeats suggestive of a leucine zipper motif were identified between residues 232 and 266 in the predicted amino acid sequence of the AbiA protein. The biological role of residues in the repeats was investigated by incorporating amino acid substitutions via site-directed mutagenesis.
View Article and Find Full Text PDFMol Microbiol
March 1998
Department of Food Science, Southeast Dairy Foods Research Center, North Carolina State University, Raleigh 27695-7624, USA.
The plasmid encoded LlaI R/M system from Lactococcus lactis ssp. lactis consists of a bidomain methylase, with close evolutionary ties to type IIS methylases, and a trisubunit restriction complex. Both the methylase and restriction subunits are encoded on a polycistronic 6.
View Article and Find Full Text PDFJ Bacteriol
February 1998
Department of Food Science, Southeast Dairy Foods Research Center, North Carolina State University, Raleigh 27695-7624, USA.
An inducible middle promoter from the lactococcal bacteriophage phi31 was isolated previously by shotgun cloning an 888-bp fragment (P15A10) upstream of the beta-galactosidase (beta-Gal) gene (lacZ.st) from Streptococcus thermophilus (D. J.
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