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Practical Food Microbiology 3rd Edition - Part 8

The following methods are recommended for the examination of shell eggs for salmonellae on the basis of their successful use. Whenever possible an attempt should be made to quantify the numbers of organisms present | 8 Eggs and egg products 8.1 Shell eggs 8.2 Bulk liquid egg 8.1 Shell eggs The following methods are recommended for the examination of shell eggs for salmonellae on the basis of their successful use. Whenever possible an attempt should be made to quantify the numbers of organisms present. Disposable gloves should be worn during the examination of shell eggs. Documentation Record the following The source of the eggs i.e. shop supermarket farm gate etc. . The type and size of the eggs i.e. battery or free-range small medium large etc. . The name of the packer or producer. The packing and sell-by dates. The presence of visible cracks and or faecal material adhering to the shell. Equipment Incubator set at 37 1 C Incubator set at 41.5 1 C. Media Buffered peptone water BPW Rappaport Vassiliadis soya peptone broth RVS Selective agars xylose lysine desoxycholate agar XLD and a second medium of choice e.g. modified brilliant green agar BGA manitol lysine crystal violet bile agar MLCB a chromogenic agar etc. Eggs and egg products 219 Method 1 Individual eggs examination without shell disinfection Fig. 8.1 Procedure a Crack the egg against the top of a sterile screw-capped jar or disposable plastic 250 mL container holding 180 mL BPW and drop the contents into it. b Homogenize the mixture by shaking the container. The use of BPW is optional as homogenized egg is a good culture medium. BPW prevents coagulation of the egg during incubation. c Drop the shell into a further 180 mL BPW contained in a separate screw-capped jar. d Incubate the BPW cultures at 37 C for 18 2h. e Subculture the BPW containing egg contents to XLD and a second medium of choice and proceed with isolation of salmonellae as described in steps c - f of Section 6.12 method 1. f Subculture 0.1 mL of BPW containing the shells to 10mL of RVS broth. Incubate at 41.5 C for 20-24 h and proceed with the isolation of salmonellae as described in steps c - f of Section 6.12 method 1. A modified procedure to separate .