Quantitative survival of native Salmonella serovars during storage of frozen raw pork

The quantitative survival of material contaminants of Salmonella serovars was studied in raw pork during frozen storage. Raw pork samples were obtained from public markets in Guadalajara, Mexico, and tested for Salmonella. Three positive samples were selected for survival studies in three different trials. Populations of Salmonella were determined by the most probable number (MPN) method, with isolation on bismuth sulfite agar plates. One typical colony was selected from each plate and subjected to serovar identification. Approximately 20 colonies were serotyped for each portion of frozen pork at each sampling time during storage. During frozen storage, numbers of Salmonella were reduced from 7-11 to 1.6 MPN g(-1) over a period of 22 weeks in Trial 1, from 1500 9000 to 2.5 MPN g(-1) over 42 weeks in Trial 2, and from 2000-20,000 to 20 MPN g(-1) over 78 weeks in Trial 3. The number of different Salmonella serovars identified was 10, 14 and 29 for Trials 1, 2 and 3, respectively. In Trial 3, S. agona, S. newbrunswick, S. drypool and S. anatum predominated over the other 25 serovars identified. S. agona was not only the most prevalent, but also the most abundant. At 15 weeks of storage, estimated MPNs of this serovar were 700 g(-1) of pork. Most serovars were detected sporadically; nine were isolated only once, and nine only twice. Serovars such as S. derby and S. newlands appeared only at the first sampling time, while others such as S. schwarzengrund, S. dublin and S. newport appeared only at the last sampling time. Most serovars identified in this study are commonly isolated from human clinical sources and from raw or processed foods in Mexico.     

In situ transesterification of fatty acids from Iberian pig subcutaneous adipose tissue

The purpose of this study was to optimize a rapid method for fatty acid analysis in Iberian pig subcutaneous adipose tissue. An in situ transesterification method was used to avoid the lengthy lipid extraction step. Samples were in situ transesterified with 5% HCl/methanol at 70°C, and toluene was used to help dissolve lipids. The method had advantages over other in situ methods since only 45 min were required to completely transesterify the fatty acids, and 10 min to obtain the fatty acid profile. A sample size of 25 mg of adipose tissue was suitable. The in situ transesterification gave higher fatty acid concentrations than conventional lipid extraction and transesterification, the differences being significant for all the fatty acids. Relative fatty acid contents were similar to those found by the conventional method.     

Content of biogenic amines in table olives

Content of biogenic amines in flesh and brines of table olives was determined by high-pressure liquid chromatography analysis of their benzoyl derivatives. No biogenic amines were found in the flesh of fresh fruits at any stage of ripeness. Contents of biogenic amines in Spanish-style green or stored olives increased throughout the brining period but were always higher in the former. Putrescine was the amine found in the highest concentration. Small quantities of cadaverine were found in the samples taken after 3 months of brining. This compound and histamine, tyramine, and tryptamine were also found in samples taken after 12 months. Gordal cultivar showed the highest contents, followed by Manzanilla and Hojiblanca. No relationship was found between contents of biogenic amines and lactic acid production or table olive spoilages, although zapatera olives had considerably higher amounts than those brines that had undergone a normal process. Concentrations in directly brined olives were markedly lower than contents in Spanish-style olives. With respect to partition between flesh and brine, there was equilibrium between both media in the case of Spanish-style olives, whereas the contents in directly brined olives were higher in flesh than brine.     

纳米厚度牺牲层腐蚀速率研究

通过大量的实验研究,建立了一套纳米量级牺牲层腐蚀行为的实验研究方法.对牺牲层厚度对腐蚀速率的影响进行了详细地研究,并得到了如下结论:当牺牲层厚度达到微米量级时,其腐蚀速率随着牺牲层厚度的增大而加快,但当其达到纳米量级时,由于固体表面存在的静电荷而产生双电层效应,这种效应对腐蚀速率的影响超过了牺牲层厚度的影响,最终使得腐蚀速率和牺牲层厚度无关.     

Strain Relief Analysis of InN Quantum Dots Grown on GaN

We present a study by transmission electron microscopy (TEM) of the strain state of individual InN quantum dots (QDs) grown on GaN substrates. Moiré fringe and high resolution TEM analyses showed that the QDs are almost fully relaxed due to the generation of a 60° misfit dislocation network at the InN/GaN interface. By applying the Geometric Phase Algorithm to plan-view high-resolution micrographs, we show that this network consists of three essentially non-interacting sets of misfit dislocations lying along the directions. Close to the edge of the QD, the dislocations curve to meet the surface and form a network of threading dislocations surrounding the system.     

Influence of estrus of dairy goats on somatic cell count, milk traits, and sex steroid receptors in the mammary gland

Two experiments were conducted to study the effect of the stage of a spontaneous estrus cycle on milk yield and constituents [somatic cell count (SCC), fat, protein, caseins, lactose, and urea content] and on estrogen receptor-α (ERα) and progesterone receptor (PR) immunostaining in the mammary gland. In experiment I, the major components of milk and SCC were monitored weekly in 80 lactating Saanen goats for 6 wk, whereas detection of estrus was daily. In experiment II, milk samples were collected daily for SCC determination during 1 spontaneous estrus (d 0) until the second spontaneous estrus in 14 Saanen goats. The day of the estrous cycle was confirmed by plasma progesterone and 17β-estradiol levels. Immunoreactivity of ERα and PR was analyzed in mammary gland samples of 8 Saanen goats (d 0, n = 4; d 10, n = 4) and the number of positive nuclei and intensity of the staining were evaluated in 1,000 cells. In experiment I, milk casein and protein percentages were significantly affected by the stage of estrous cycle; during proestrus and estrus, these variables were higher (3.32 ± 0.06 and 4.44 ± 0.08) than during metestrus (3.03 ± 0.07 and 4.07 ± 0.10), but not higher than during diestrus (3.23 ± 0.06 and 4.35 ± 0.09, respectively). In experiment II, daily measurement of SCC revealed higher levels at estrus (7,195 ± 672 × 10³ cells/mL) and a decline toward the luteal phase (1,694 ± 672 ± 10³ cells/mL). Estrogen receptor-α and PR immunostaining were exclusively detected on epithelial cells. The percentage of positive nuclei to ERα was higher on d 0 than on d 10 (75.4 ± 8.8 vs. 68.3 ± 8.8%), but no change was observed for PR (4.0 ± 0.3 vs. 3.5 ± 0.4%). The average immunostaining intensity for both receptors was greater on d 0 than on d 10 (ERα : 1.44 ± 0.02 vs. 1.35 ± 0.02; PR: 0.079 ± 0.008 vs. 0.057 ± 0.008). The high SCC at estrus in experiment II was associated with high plasma estradiol and low progesterone, suggesting that the increased SCC could be brought about by the estrogen-induced proliferation and exfoliation of epithelial cells. In addition, this action may be supported by the higher sensitivity to estrogens (ERα content) found at d 0.     

Extensive feeding versus oleic acid and tocopherol enriched mixed diets for the production of Iberian dry-cured hams: Effect on chemical composition, oxidative status and sensory traits

The present study aimed to analyse the chemical composition and oxidative status of Iberian dry-cured hams from pigs fed different finishing diets: extensive feeding on acorns and pasture in a "Montanera" traditional system (MON), fed in confinement with a mixed diet containing high-oleic sunflower oil (115g/kg of diet) and supplemented with 250mg/kg α-tocopherol (HOVE), and fed in confinement control mixed diet (CON) without added tocopherol and oleic acid fat. Muscles from MON dry-cured hams contained significantly (p<0.05) higher amounts of intramuscular fat (IMF) than those from HOVE and CON hams. The feeding background affected the tocopherol levels in dry-cured hams as those from MON and HOVE pigs had significantly higher levels of α-tocopherol than those from CON pigs whereas the extensive feeding provided muscles from MON pigs with significantly higher levels of γ-tocopherol than the experimental diets did to CON and HOVE pigs. The HOVE diet significantly increased the levels of oleic acid in Iberian dry-cured hams with these levels being similar to the oleic acid levels found in MON hams and significantly higher than those in CON hams. Compared to dry-cured hams from CON pigs, those from MON and HOVE pigs exhibited a higher oxidative stability as a likely result of a most favourable fatty acid composition and the presence of higher tocopherol levels. The principal component analysis (PCA) successfully discriminated between dry-cured hams from pigs fed different finishing diets.     

Identification of meats from red deer (Cervus elaphus), fallow deer (Dama dama), and roe deer (Capreolus capreolus) using polymerase chain reaction targeting specific sequences from the mitochondrial 12S rRNA gene

Polymerase chain reaction (PCR) based on oligonucleotide primers targeting the mitochondrial 12S rRNA gene was applied to the specific identification of meats from red deer (Cervus elaphus), fallow deer (Dama dama), and roe deer (Capreolus capreolus). The use of a common reverse primer, together with forward specific primers for red deer, fallow deer, and roe deer, allowed the selective amplification of the desired cervid sequences. The specificity of each primer pair was verified by PCR analysis of DNA from various game and domestic meats. The assay can be useful for the accurate identification of meats from cervid species, avoiding mislabeling or fraudulent species substitution in meat products.     

The GPI-anchored Gas and Crh families are fungal antigens

The cell wall is the first interface between a fungus and its extracellular environment. Glycosyltransferases involved in the formation and dynamic remodelling of the polysaccharide network of the cell wall have recently been identified. The best characterized ones belong to the Gas family, which elongates beta(1,3)-glucans, and to the Crh family, which are involved in the cross-linking of chitin to beta(1,6)-glucan. All these proteins carry a glycosylphosphatidylinositol (GPI) anchor. In this work, we show that recombinant soluble forms of Gas1-5 and Crh1p from Saccharomyces cerevisiae and their orthologous proteins Gel1-Gel2 and Crf1 from Aspergillus fumigatus are specifically recognized by antibodies present in the sera of patients with Aspergillus or Candida infections. Quantification of the antibody titres against recombinant Gas/Gel and Crh/Crf proteins separated aspergilloma and candidiasis patients from non-infected individuals. Cross-reactivity was seen between the antibody response of patients with aspergillosis and candidiasis towards the Gas/Gel and Crh/Crf proteins. These results suggest that GPI-anchored cross-linking enzymes are relevant immunologically reactive constituents of the cell wall that may play a role during human fungal infections.