PubMed · 4235167
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J P Fields, A W Hoke, P C Cronce. 1968. Cheese mite dermatitis.. https://doi.org/10.1001/archderm.98.6.669
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A method is described for the determination of roquefortine C in (blue) cheese. After liquid liquid extraction with a mixture of hydrochloric acid and methanol, and filtration, an aliquot is analysed using column-switching reversed-phase liquid chromatography. The recovery of roquefortine C in Fetta cheese is about 85%, the calibration curve is linear from 10 to 2500 ng g(-1) (r2 = 0.998), and the detection limit is about 10 ng g(-1). In different batches of Danish Blue concentrations of 1000-2000 ng g(-1) of roquefortine C are found. As regards the stability of roquelfortine C its half-life in diffuse daylight is ca. 50 min, while after irradiation with ultraviolet light, it is about 10 min.
A practical study is described to characterise some problems encountered in the application of aqueous two-phase systems (ATPS) to protein recovery. These factors include practical design of extraction stages and the impact of ATPS compounding methods and biological suspension upon process performance. They were addressed using the recovery of whey proteins as a model. The known effects of system parameters (i.e. tie-line length, volume ratio and system pH) were exploited to define the specific operating conditions of a two-stage ATPS process for the recovery of whey proteins. The partition of whey proteins in ATPS assembled using different methods resulted in changes in the partition coefficient of the proteins. Such changes were associated with the initial location of the proteins in the polymer or salt-rich solutions of the ATPS. Cheese whey loaded into the ATPS caused the displacement of the binodal curve from the origin. Such behaviour was attributed to the residual fat present in the whey. These findings highlight those factors perceived as negative constraints on the wider adoption of ATPS processes for protein recovery from complex biological systems.
The yeasts present in Gouda cheese during processing were monitored in a single cheese factory during a 32 day ripening period. Despite the predominance of lactic acid bacteria during Gouda making, yeasts played a significant role in the ripening process in reaching counts as high as 10(5) cfu g(-1) at the later stages of ripening. The increase in the number of yeasts corresponded with the depletion in lactose content and the simultaneous stabilization of lactic acid bacteria numbers. The sources of yeast contamination which may lead to contamination of the curd were also determined. The brine and equipment surfaces were responsible for the highest yield of contaminating yeasts. A diverse variety of 23 yeast species representing 13 genera were present in the factory environment, during processing and ripening. Samples were taken at critical control points in the manufacturing process and analysed after incubation at 25 degrees C for 96 h. Although a broad spectrum of yeasts were found in Gouda cheese, Debaryomyces hansenii was the most abundant yeast isolated. Other species encountered were Saccharomyces cerevisiae and Yarrowia lipolytica, Kluyveromyces marxianus, Torulaspora delbrueckii, Rhodotorula glutinis, Cryptococcus albidus and Candida catenulata.