A method for the assessment of volatile compounds in dairy products
was developed using solvent desorption dynamic headspace sampling. The
method was first applied to assay for diacetyl and acetoin in buttermilk.
Major buttermilk volatiles recovered included diacetyl, acetic acid, and
acetoin. Normalized detector responses were linear over the range...
Heat resistant sporeforming psychrotrophic bacteria were
isolated from raw milk samples from 59 Grade A farms in Oregon.
Forty-nine of the 59 (83%) raw milk samples in this survey
contained sporeforming psychrotrophic bacteria; isolates from
twenty-four (40%) of the samples exhibited proteolytic properties. Populations of sporeforming psychrotrophic bacteria ranged
from...
A casein agar diffusion method was developed to detect and quantify pertinent
levels of proteinases produced in raw milk supplies by heat resistant Bacillus
sporeformers. In order to optimize the required heat treatment conditions of raw milk
samples, trials that involved a combination of different temperatures and times were
evaluated....
Several methods for estimation of the potential
shelf-life of pasteurized fluid milk products were evaluated
for their efficacy in this investigation. These methods
were evaluated and compared to sensory, biochemical and
bacteriological indices through a series of experiments
conducted on different brands of commercially pasteurized
fluid milk. The methods evaluated...
Phage-insensitive Streptococcus cremoris starter strains were
selected by assaying cheese whey against potential starter
strains. Six strains were selected and characterized for continual
use in cheesemaking. Upon phage-infection, strains were removed
from the blend. Cheesemaking continued with remaining strains. A
phage-insensitive, fast-acid-producing mutant of the infected
strain was isolated and...
The effect of reducing sodium chloride in Cheddar cheese was
studied. Milled curd from a split-lot was salted at selected NaCl
concentrations and analyzed through aging by sensory and rheological
tests. Estimation of differences in compositional analysis, lactic
acid populations, degree of proteolysis, water activity, and pH were
also determined....
A consumer and a trained descriptive panel was utilized to
determine liking ratings and flavor profiles, respectively, for
commercial brands of pre-stirred yogurt. Once the consumer and
descriptive panel data was collected, the data was combined to
determine the interrelationship of these two sets of data and to
determine the...
Microgard, a commercially-available pasteurized
fermented milk, was found inhibitory to gram negative
bacteria such as Pseudomonas putida, some well-known foodborne
pathogens (e.g. Salmonella, Yersinia and Aeromonas)
and some fungi as revealed by an agar incorporation assay
method. Gram positive bacteria, however, were not
inhibited. Rather, some bacteria in this group...
Published June 1975. Facts and recommendations in this publication may no longer be valid. Please look for up-to-date information in the OSU Extension Catalog: http://extension.oregonstate.edu/catalog
Published October 1980. Facts and recommendations in this publication may no longer be valid. Please look for up-to-date information in the OSU Extension Catalog: http://extension.oregonstate.edu/catalog
Published December 1975. Facts and recommendations in this publication may no longer be valid. Please look for up-to-date information in the OSU Extension Catalog: http://extension.oregonstate.edu/catalog
Organoleptically, flavored yogurts appear to contain lower
levels of acetaldehyde than plain yogurt. This study was undertaken
to seek the reasons for this phenomenon by focusing on the analyses
of acetaldehyde production by yogurt culture bacteria in yogurt base
containing added sucrose and by performing other analyses such as
the...
A sample of 243 Willamette Valley households participated in
personal interviews and kept 7-day records of all foods brought into
the household but not consumed by human household members. Their
reason for discarding the foods, the amounts of discard, and their
assessment of the safety of the foods were compared...
Eight foodborne pathogenic and spoilage Gram-positive bacteria were
evaluated for their spontaneous resistance frequencies to the peptide
antimicrobial nisin. In brain heart infusion (BHI) medium, nisin resistance
frequencies were in the range of l06 to l08 when exposed to nisin at
concentrations 2 to 4 times the minimal inhibitory concentrations....
Several lactic acid bacteria (LAB) of the Lactococcus, Lactobacillus,
Leuconostoc and Pediococcus genera were screened for inhibition of
food-borne pathogens and spoilage microorganisms in raw milk and
dairy products. Listeria monocytogenes was killed by Lactococcus
lactis subsp. lactis and Pediococcus pentosaceus due to their
production of bacteriocin-type inhibitors. Staphylococcus aureus...
Lysozyme is a natural antimicrobial agent that is effective against many
food spoilage and pathogenic microorganisms by disintegrating their cell walls.
Immobilization of lysozyme has attractive applications for use in the food
industry: (1) The enzyme could be readily separated from treated foods and
beverages and re-used while the foods...
The purpose of this study was to identify antimutagens in yogurt active against the
experimental colon carcinogen, N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). Our
initial experiments showed that acetone extracts of yogurt, or milk fermented by various
lactic acid bacteria were antimutagenic against MNNG and 3,2'-dimethyl-4-aminobiphenyl
(DMAB) in the Ames test (Salmonella typhimurium TA...