![]() Lanska, in Encyclopedia of the Neurological Sciences (Second Edition), 2014 Computed Tomography If no suitable automated system can be found, appropriate colour charts to enhance the RN scoring system could be considered to allow reproducible results between partners.ĭ.J. Further work is required on the quantification of the level of β-carotene remaining in margarine on the surfaces of large pieces of equipment after cleaning. Visual comparison of results does, however, suggest that similar results can be obtained. As test results are thus recorded on an arbitrary (RN) scale, statistical analysis of repeatability studies by the RN scale is difficult. In addition, techniques based on absorbance spectrophotometry after extraction of the β-carotene into hexane have also proved less sensitive. The detection of β-carotene in margarine soils is dependent on visual observation, since automated colour recognition systems have been found to be less sensitive than the human eye. The method is also cheap and suitable as a means of reducing the number of the more expensive microbiological tests required during the development of new food processing equipment. This method is easier to apply and gives results faster, but is less sensitive than the microbiological method. One difference from the EHEDG microbiological method is that instead of a bacterial spore, a colorant ( β-carotene) is used as soil residue indicator ( EHEDG, 1997). The relative amount of residual soil is recorded on a relative number (RN) scale from 0 to 4 where 0 represents no visible yellow soil and 4 indicates soil being highly visible. All product contact surfaces of the test item can then be examined for the presence of residual soil by visual inspection and by swabbing the surface with a cotton wool tipped swab. After cleaning, the test item is removed from the test rig and dismantled. In this method a test item is filled with a commercially available soft margarine, containing 80% fat with a viscosity of less than 60 mPa s at room temperature, and pressurised to 5 bar. Rugh, in Hygiene in Food Processing (Second Edition), 2014 6.3.1 EHEDG β-carotene residues test for closed equipment More sophisticated techniques can be used to measure the intensity distribution (beam shape). The power output of the transducer is measured by ‘weighing’ the sound pressure with a force balance, or by measuring the heating effect using a calorimeter. ![]() Greyscale performance and Doppler function, which need more complex objects, usually based on phantoms with tissue-equivalent properties, based on gelatine loaded with different reflecting materials often called tissue-mimicking phantoms. Because sound travels faster in Perspex than in tissue, each 7 mm of Perspex is equivalent to 4 mm of tissue. Sensitivity, dynamic range and accuracy of the A-scan calliper: using a Perspex block machined with a number of equally spaced vertical rods, some others of different diameters, and of decreasing depth. Resolution: tested by imaging a test rig composed of parallel wires mounted on a frame and immersed in a Perspex bath containing a fluid in which sound travels at 1540 m s −1. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |