Live or Dead

The detection of nucleic acids from pathogens has been recognized as a source of interpretative error in molecular investigations of food and environmental samples. Pathogens detected may not be alive and may present no risk to humans. The viable but nonculturable state into which some organisms such as Vibrio, Salmonella, and Campylobacter can enter further complicates interpretation. rRNA is an attractive target for detection because of its universal and constituent expression and its high...

Statistical Analysis of the Phylogenetic Tree

Once the phylogenetic tree has been generated, the next step is to statistically test its topology. One method that is commonly used to test phylogenetic tree topologies is the statistical method of bootstrapping (12). This method calculates the variability of the tree topology by resampling (with replacement) the original multiple sequence alignment a set number of times (i.e., a number between 100 and 2000) to generate a new set of artificial multiple alignments. This new data set is in turn...

False Negatives

False negatives resulting from reaction inhibition have been widely reported and reviewed (30-32). Inhibition may be total or partial and can become apparent as complete reaction failure or as reduced sensitivity of detection. In some cases, inhibition may be the cause of false-negative reactions because workers have not incorporated internal controls in each reaction tube. Early evidence of exquisite sensitivity using mammalian cells (33) involving detection of a single molecule of DNA from a...

Factors Affecting Detection Level

Cultural detection methods allow quantification of microorganisms with considerable precision. This may be of importance in clinical, food, and environmental investigations when distinguishing commensal organisms from those causing disease. Quantification of PCR product cannot necessarily be equated with number of organisms present in the original sample (16). The minimum number of cells containing a single-copy target gene theoretically detectable in a 10- L sample aliquot added to a 90- L...

Materials

Yeast identification system ID 32 C of BioMerieux (Marcy-l'Etoile, France or Hazelwood, MO, USA). 3. Growth media from Difco Laboratories (Detroit, MI) YM agar, yeast nitrogen base, yeast carbon base, yeast extract, potato dextrose agar, bacto vitamin-free yeast base. Names and Current Synonyms of the Yeast Species Treated 1 Arxula adeninivorans, synonym Trichosporon adeninovorans 2 Candida apicola, synonyms Torulopsis apicola, Torulopsis bacillaris 3 Candida boidinii, assimilates methanol 4...

Jose Manuel Bruno Barcena M Andrea Azcarate Peril and Faustino Sineriz

During the last few years we have seen a public debate, involving every social statement, concerning food products and ingredients (1). The appearance in the market of the first food products, or organisms, which have been improved by recombinant DNA technologies (rDNA), has been received by society in a negative manner. We are referring specifically to genetically modified (GM) food products. Several definitions can explain the concept of GM products or, in a general way, the imprecise word...

Total Nitrogen

Nitrogen compounds in grapes play important roles as nutrients for microorganisms involved in winemaking and wine spoilage and as aroma and aroma precursors (7). Nitrogen is taken up by the vine roots as nitrate and reduced by the nitrate reductases system to ammonia, transported and stored subsequently as amino acids (7). Compared with fermentable carbon generally present in grapes at > 20 (w v), total nitrogen levels range from 0.006 to 0.24 , of which only 0.0021-0.08 is biologically...

References On Food Microbiology

Giannessi, P., and Matta, M. (1978) Azoto amminico, in Trattato di Scienza e Technica Enologica, Vol. I. (Brescia, A. E. B., ed.) Analisi e Controllo dei mosti e dei Vini, Italy, pp. 87-88. 2. Henick-Kling, T., Edinger, W. D., and Larsson-Kovach, I.-M. (1996) Survey of available nitrogen for yeast growth in New York grape musts. Wein-Wissenschaft 51(3), 169-174. 3. Rapp, A., and Reuther, K. H. (1971) Der Gehalt von Aminosauren in gesunden und edelfaulen Beeren verschiedener Rebsorten. Vitis 10,...

PH Cascade Controller Design

Behaviourlism

System Analysis Using the Simulation Model A cascade controller of pH coupled with DO control developed here is shown in Fig. 3. Proportional and integral PI , and proportional, integral, and differential PID controllers were used as precompensators of DO and pH in the cascade controller, respectively. The dynamic response of boxes A and B can be analyzed using the simulation model. The analysis is useful for design of the controllers, especially selection of controllers and...