Proton nuclear magnetic resonance rapid and structure-specific determination ofω-3 polyunsaturated fatty acids in fish lipids

Based on proton nuclear magnetic resonance (¹H-NMR) spectroscopy, a rapid and structure-specific method for the determination of ω-3 polyunsaturated fatty acids (PUFAs) in fish lipids is presented. The different chemical shift observed for the methyl resonance of ω-3 PUFAs (δ=0.95 ppm) with respect to the methyl resonance of all other fatty acids (δ=0.86 ppm) has provided the possibility of proposing a new and rapid method for the determination of ω-3 PUFA content. Twenty-four fish lipid samples (raw, cooked and canned albacore tuna) produced results that showed good agreement between¹H-NMR analysis and gas chromatographic determination. Raw and cooked samples showed significantly higher levels of ω-3 PUFA than canned tuna.     

Dimensional stability of single‐site ethylene copolymers in rotational molding

The dimensional stability of ethylene copolymers in rotational molding was studied by comparing the warpage observed for a series of conventional and single‐site catalyzed ethylene copolymers. Bench‐scale molding trials were carried out under controlled molding conditions. The rapid cooling of the mold using a water spray resulted in greater warpage. Under such conditions, molded parts made using the single‐site resins showed less warpage compared to the Ziegler‐catalyzed copolymers with otherwise comparable densities. The Ziegler‐catalyzed copolymers were characterized by a faster crystallization rate, and were shown to generate larger crystallinity gradients through the part thickness during the cooling process. Second to temperature gradients, crystallinity gradients are a leading cause for the development of residual stresses and causing warpage. Differences in the crystallization rates between single‐site and Ziegler‐catalyzed copolymers are discussed based on their intermolecular comonomer distributions. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

Proteolysis of Hispanico cheese manufactured using lacticin 481-producing Lactococcus lactis ssp. lactis INIA 639

Hispánico cheese was manufactured using lacticin 481-producing Lactococcus lactis ssp. lactis INIA 639, bacteriocin-nonproducing L. lactis ssp. lactis INIA 437, or a combination of both strains, as starter cultures. Lactobacillus helveticus LH 92, a culture of high amino-peptidase activity sensitive to lacticin 481, was added to all vats. Milk inoculation with the bacteriocin producer promoted early lysis of Lb. helveticus cells in cheese. Cell-free aminopeptidase activity in cheese made with the 3 lactic cultures was 1.8 times the level reached in cheese made only with L. lactis strain INIA 437 and Lb. helveticus, after 15 d of ripening. Proteolysis (as estimated by the o-phthaldialdehyde method) in cheese made with the 3 lactic cultures was twice as high, and the level of total free amino acids 2.4 times the level found in cheese made only with L. lactis strain INIA 437 and Lb. helveticus, after 25 d of ripening. Hydrophobic and hydrophilic peptides and their ratio were at the lowest levels in cheese made with the 3 lactic cultures, which received the lowest scores for bitterness and the highest scores for taste quality.     

Uptake of Tritiated Liquids by Individual Breakfast Cereal Flakes

ABSTRACT: Surface liquid adhesion (SLA) and liquid absorption (LA) of tritiated liquids, including water and skim, low-fat, whole, and fat-enriched milks, by cornflakes (CF) and frosted flakes (FF) were determined by scintillation counting using water-[³H] at 0.5 μCi/mL. SLA or the liquid adhering to individual flakes after a short immersion period was the same for CF and FF in the case of water (approximately 0.011 μL mm⁻² of flake) but were always higher for CF than for FF and increased as the fat content in milks augmented. LA of individual flakes, followed for 300 s of soaking, increased with time and was always higher for CF than for FF (for the same liquid), however, data did not follow a regular pattern. Flakes showed quite compact outer surfaces and an internal porous matrix composed of air cells of various sizes separated by dense walls of different thicknesses. This heterogeneous microstructure of individual flakes may be the cause of the lack of a simple kinetics during the soaking process. Previous results obtained by soaking a mass of flakes overestimated the uptake of fluid by individual because they included the liquid occluded between the flakes.     

Characterization and Technological Properties of Lactic Acid Bacteria Isolated from Traditional Argentinean Goat’s Milk Products

A total of 286 lactic acid bacteria isolated from goat’s dairy products in northwest of Argentina were characterized. Lactobacilli (38%) and cocci (62%) were identified according to morphological, physiological, and relevant technological properties. L. plantarum (14%) and Enterococcus (34%) were the predominant species. S. thermophilus, Pediococcus and L. plantarum were the highest acid producers. Eight strains of L. fermentum produced bacteriocins or metabolites similar to bacteriocins. The API-ZYM test was applied to 39 isolates. Eight strains were selected from their both technological properties and enzymatic activities for use as starter or adjunct culture in the manufacture of artisanal goat cheeses.     

A transgenic mouse model for mammary carcinogenesis

Missense mutations in the p53 tumor suppressor occur frequently in human breast cancer and influence both the prognosis and response to chemotherapy. Amino acid 175 (equivalent to murine 172) is the second most common site of missense mutations in p53 in human breast cancer. Over 95% of these mutations are arginine-to-histidine (R-H) substitutions resulting in a gain-of-function, and not merely a dominant-negative phenotype. Transgenic mice expressing a p53 172(R-H) construct targeted to the mammary gland by means of a whey acidic protein (WAP) promoter were characterized as a model system in order to determine the specific effects of this mutation on mammary tumorigenesis. Although transgene expression alone had no apparent effect on normal mammary development, transgenic mice treated with the chemical carcinogen dimethylbenz(a)anthracene developed tumors with much shorter latency than did control littermates and had a greater tumor burden. Tumors arising in transgenic mice did not exhibit either decreased apoptosis or increased cell proliferation relative to tumors arising in nontransgenic littermates, but did display increased genomic instability. Large pleiomorphic nuclei were visible in many tumors from transgenic mice, and DNA flow analysis confirmed the presence of significant aneuploid cell populations. Since these transgenic mice develop very few spontaneous tumors, while accelerating carcinogen-and oncogene-mediated tumorigenesis, this mouse model will, therefore, be useful in the investigation of early events in mammary tumorigenesis. It may also be used as a preclinical model to test newly developed chemotherapeutic strategies.     

Model-based low-level control in flexible manufacturing systems

Low-level (supervisory) control of flexible manufacturing systems (FMS) assures conflict-free operation and enforces production requirements such as priorities. It forms a crucial link between medium and higher-level decision making, on the one hand, and the various machine-controllers and servomechanisms on the other. In the absence of a suitable control methodology, ad hoc development is the current practice and compromised results at high cost are far too common. Here we described a model-based framework for a new, systematic approach to supervisory control.     

Occurrence and behavior of Enterobacteriaceae and enterococci in mediterranean dry sausages during ripening in a Pilot-Scale chamber

The occurrence and evolution of Enterobacteriaceae, coliforms, Escherichia coli, and enterococci in 252 samples of six types of Mediterranean dry-ripened sausages during maturation was investigated. The changes of the pH values were also recorded. Samples were analyzed in three steps of the ripening process: fresh product, first drying stage, and finished product. In all six sausages, Enterobacteriaceae, coliforms, and E. coli counts were characterized by high initial concentrations that significantly decreased during ripening. However, the initial counts of enterococci remained stable throughout the experiments in all sausages types. The average pH values of finished sausages ranged from 4.54 to 5.31.