ARCHIVED RESEARCH BITES

2000

The casein macropeptide, also known as the glycomacropetide (GMP) is produced when rennet acts on milk during the manufacture of cheese.  The peptide, with a molecular weight of approximately 6800 Daltons, has no aromatic amino acids. Thus it may have utility for people with PKU or liver function difficulties.  GMP was prepared from sodium caseinate and calcium caseinate.   The yield was better from calcium caseinate, so that further studies were made with GMP from calcium caseinate by three different methods.  GMP obtained from rennet action of calcium caseinate, followed by 20 hours of dialysis was the most homogenous.   MALDI mass spectrometry analysis showed that it had only two peptides, with the peptide having a molecular weight of approximately 6800 Daltons making up about 99% of the product.  It did have a high ash content, which affected its functionality.  In comparison a commercial GMP product from cheese whey was much more heteregeneous, with more than 8 components. The 6800 Dalton material made up 66% of the total peptide product.

SWISS CHEESE CONSORTIUM
May 12/2000
A new project, supported by the Swiss cheese consortium, has been
initiated under the direction of the Parker Chair in Dairy Food with Polly Courtney and W. James Harper as Co-Principal Investigators. IAttention will given first to the interrelationships between the three starter organisms used in the manufactor of Swiss cheese (Lactocci, Lactobacilli and propionibacter).   A new methods for follwing the growth of the three types of oganisms will be developed using a sterile slurry system. 

OXIDIZED MILK
May 12/2000
Feeding soybeans to cows has been shown to increase unsatuated fatty acids and the suceptibility to oxidized flavor.  Earlier results had shown no relationship between hexanal, a common indicator of lipid oxidation, and the intensity of the oxidized flavor in the milk.  The new Agilent Technology Chem Sensor 4400 has been used to see if it could provide answers as to the chemical nature of the flavor.   The instrument was operated in three modes: (a) normal inization, (b) positive chemical ionization with methane and (c) negative chemical ionization with methane.  The chem sensor only differentiated oxized and non-oxidzed milk when operated in the negative ionization mode.  Compounds tentatively identified in elevated concentrations in the oxidzed milk were hexanal, hexenal, heptanal, octanal, nonental and decanal.  Research is continuing.

MPC IN FETA CHEESE
May 12/2000
Cast Feta cheese made with MPC containing 56, 70 or 85% proteins have been used in the manufacture of Feta cheese.  As the protein content increases, the texture of the cheese becomes softer.  The use of environmental scanning electon miscroscopy has shown differences in the structure of the cheese made with MPCs of different protein content.  The differences made be related to differences in the hydration of the different MPCs.

1999

This page provides a means for reporting the latest results of research in the Parker Chair Laboratory. The findings will often be incomplete and preliminary in nature.

5/17/99  We now have a Hewlett Packard headspace/mass detector "electornic nose", in which the masses detected become the sensors.  At the present time, we are on a steep "learning curve" with the instrument.   Last week we showed that a WPC with an oxidized flavor could be differentiated from a WPC with no oxidized aroma off flavor and that the masses that differentiated the two products were 55,56 and 57 and in the ratio typical of octanal -- which is the major aldehyde formed from the oxidation of oleic acid.

5/18/99  The HP/MS system has succesfully differentiated three varieties of beer, which could not be differentiated with an electronic nose using metal oxide sensors.  Differences were noted both qualitatively and quantitatively for more that 15 differnt masses.  Work in is progress to determine the specific compounds contributing to the differentiation.

5/17/99 Heating beta-lactoglobulin or lactoferrin in the presence of lactose results in the formation of a glyco-protein (lactosylated berta-lactoglobulin) which is reported to have modified functional properties.  Work this past week with an electrospray mass spectrometer has shown the ability to identify the lactosylated proteins.  Commercial beta-lactoglobulin has been shown to have a small amount of lactosylated beta lactoglobuline for both the A and B genetic variants.

ELECTRONIC NOSE RESEARCH
4/3/00
A updated combination electronic nose (EN) and GC/MS instrument was commissions on March 27, 2000. In the EN mode a dynamic head space sampler transfers sample to a MS instrument, where each mass number becomes a sensor. The masses that differentiate the samples are then noted. The instrument in then converted to the GC/MS modes and chromatograms examined only for the masses that differentiate the products.
Preliminary results suggest that an order of magnitude great sensitivity is achieved with the new model , and that aromas in samples that were not previously differentiated can now be separated from each other.
FUNCTIONAL FOODS
4/3./00
A small clean room has been installed in Vivian Hall room 215 to assist in the maintenance of cancer cell lines without contamination. Preliminary work indicate the room now permits growth of cells without contamination. Results are expected over the next several months
CHEDDAR CHEESE FLAVOR
4/3/00
A new sulfur detectors has been added to the Parker Chair GC. Work is in progress to investigate sulfur compounds in sharp Cheddar cheeses. Because of the small quantities of most higher molecular weight sulfur compounds in Cheddar cheese, pre-concentration is necessary and the final touches are be place on the methodology. Preliminary research suggests up to 25 sulfur compounds may be present in aged cheddar cheese, most of them in ppt concentrations.

04/29/04
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