Abstract
In the thesis presented the use of colorimetry for objective determination of discolorations of fat tissue in pig slaughter carcasses was tested. The result was the development of a secure, fast and cost saving method for diagnosis of jaundice in pig slaughtering.
The analysis of official meat inspection statistics from one slaughterhouse covering the years from 1994 to 2000 showed that 4.45 % of all condemned pig slaughter carcasses were classified as not suitable for human consumption due to the diagnosis of jaundice. In the visual inspection directly after slaughtering 11.57 % were judged as false positive results. After confiscation for 24 hours this judgement was corrected in a repeated inspection of the carcasses. The analysis showed, that jaundice presents an important proportion of the condemnations, these justifying the development and testing of an objective method for jaundice diagnosis.
Spectrophotometry and colorimetry by tristumulus measurement are the present objective methods for colorimetry. Both methods were tested for use in the diagnosis of jaundice. The spectrophotometrical investigations were carried out using the Shimadzu Spectrophotometer CM 100. The colorimetrical measurements were made with the Minolta Chromameter CR 300.
In pre-tests for spectrophotometry the samples of pigments to be investigated were prepared following the General Administrative Order for Meat Hygiene (AVVFlH) using the alcohol-ether-test-kit. Spectrophotometry allows to differentiate the two-peak-spectra of carotins from the one-peak-spectra of bile-pigments. As the preparation of samples involves costs and time the spectrophotometry is not suitable for the development of a fast test. However it is possible to objectify the official method by exact measurement of solutions in alcohol-ether-tests.
In pre-tests with the Minolta Chromameter CR 300 was found that it is possible to differentiate the pigments by colorimetry very fast and without laboratory peparation. In fat tissues of 54 fattened sows, 54 fattened castrated males and 54 breeding sows, wich were suitable for human consumption, different color-parameters (L*a*b* and L*C*H°) in these diffent groups could be demonstated.
From parameters of fattened sows and castrated males a color standard of pig fat tissue (mean ± standarddeviation) was calculated:
L* = 67,81 ± 2,55; a* = 2,43 ± 0,66;
b* = 2,93 ± 0,69; C* = 3,85 ± 0,76;
H* = 50,18 ± 8,78
In subsequent investigations the fat tissues of 54 uncastrated males, including cryptorchids and hermaphrodites were measured. These fat tissues with a brightness parameter of L* = 78,85 were brighter than suitable fat tissue. There a differentiation is possible.
The colorimetrical investigation of 54 slaughter carcasses with jaundice showed, that icteric pig fat is different from suitable pig fat in all color-parameters (mean ± standarddeviation):
L* = 77,24 ± 3,05; a* = 0,92 ± 1,14;
b* = 8,48 ± 3,00; C* = 8,64 ± 3,00;
H° = 82,83 ± 9,36
Only the fat of uncastrated males is similar in brightness L*.
By using the colorimetry as fast test for the diagnosis of jaundice limits for brightness L* = 72,3 and yellowness b1* = 4.6 (with identification of uncastrated males) or b2* = 5 (without identification of males) were calculated.
It showed that jaundice is present when the color parameters are higher than both limits.
The colorimetry using the Minolta Chromameter CR 300 in combination with the calculated limits is useful as fast test in pig fat for the diagnosis of jaundice in fresh slaughtered carcasses.
Further investigations showed the influences of technological factors such as time, cooling and residues of slaugtering on fat color.
|
