Six experiments were done with a total of 73 veal calves. Two pilot experiments were concerned to determine the maximal concentrations of lactic acid sprays that were acceptable in terms of fat cover color score and flavor score of lean Longissimus muscle. These pilot experiments indicated that concentrations up to 1.25% (vol/vol) of L-lactic acid did not produce unacceptable discoloration, and concentrations up to 2.00% (vol/vol) were not significantly different from controls in terms of flavor. In four additional experiments, the bactericidal properties of 1.25% L-lactic acid sprays were quantified. When measured 24 h postmortem, aerobic colony counts (3 d, 30°C) were reduced by 0.8 and 1.3 log10 CFU/cm2 on breast and perineum, respectively. Enterobacteriaceae counts, that were approximately 1.8 log10 CFU/cm2 initially, were reduced below their limit of detection (<1.3 log10 CFU/cm2) as a result of lactic acid treatment. All tests for Salmonella were negative. Few, if any, Lactobacillaceae were isolated both in treatment and control groups.

Three experiments involving a total of 114 calves were done. The first two experiments, conducted under simulated export conditions, monitored the immediate and delayed microbiological effects of decontamination with 1.25% (vol/vol) L-lactic acid on calf carcasses as well as the effects of an additional treatment with 2.00% (vol/vol) L-lactic acid and vacuum-packaging on hot-boned veal cuts. In a third experiment, data from these investigations were tested under actual export conditions and were found to be similar. As a result of 1.25% (vol/vol) L-lactic acid treatment, aerobic colony counts (3 d at 30°C and 5 d at 17°C) were reduced by 0.8 log10 CFU as compared with initial counts of approximately 3.0 log10 CFU/cm2 on control carcasses. However, the reduction increased to 1.3 log10 CFU at 14 d postmortem, indicating some delayed effect of lactic acid. The percentage of samples positive for Enterobacteriaceae was reduced from 50% to approximately 10% which corresponded with a mean reduction of 0.3 log10 CFU/cm2. Vacuum-packaging virtually completely inhibited growth of bacteria, yeasts and molds on hot-boned cuts, but 1 wk after breaking the counts reached values similar to controls. When measured 7 d postmortem, lactic acid treatment combined with vacuum-packaging was significantly more effective in reducing aerobic colony counts than vacuum-packaging alone. At 14 d postmortem, this was still the case for cuts that had been subjected to an additional decontamination with 2.00% (vol/vol) L-lactic acid immediately before vacuum-packaging. The Enterobacteriaceae colony count of hot-boned vacuum-packaged cuts remained under its limit of detection of 1.3 log10 CFU as a result of lactic acid decontamination. Lactobacillaceae colony counts were extremely low in all treatment groups. No salmonellae were isolated from any sample, indicating that marked progress has been made in controlling Salmonella contamination of veal in The Netherlands. This was accomplished by having separate fattening and slaughter lines and markedly improving slaughter house practices.

Because current hygienic practices did not appear to result in bacteriologically fully acceptable porcine livers, the combined effects of decontamination and vacuum packaging on their bacteriological condition were investigated. Livers were taken from freshly slaughtered carcasses, immersed either in a 0.20% (v/v) lactic acid solution for 5 min or in hot water at 65°C for 15 s and subsequently vacuum packed and stored at 3 ± 1°C for 1 or 5 d. As compared with controls, both treatments resulted in significant reductions of total colony counts (TCC at 32°C), Enterobacteriaceae CFU-counts (EC at 37°C) and Lactobacillaceae CFU-counts (LC at 30°C) both after 1 d and, with the exception of LC in the hot water group, after 5 d of cold storage. Treatment with lactic acid was significantly more effective in reducing TCC and LC on liver surfaces than treatment with hot water. Moreover, lactic acid, but not hot water, improved the bacteriological condition of the inner parts of liver, resulting, after 5 d of storage at 3 ± 1°C, in a significant decrease of TCC and EC; a similar tendency was found for LC. Decontamination resulted in a reduction of the number of genera of Enterobacteriaceae as compared with controls. The genus Escherichia was isolated most frequently both in control and in treated groups. Slight discoloration of the liver surface was effected by both treatments. It disappeared, however, within 2 h after opening of vacuum packs.

In two experiments involving two groups of 20 calves each, the microbiological condition of veal produced in an alternative (Electrical Stimulation/Hot Boning) and a conventional (No Stimulation/Cold Boning) slaughtering/boning sequence was investigated. Two levels of hygiene were practiced, i.e. (a) “strictly hygienic” by using surgical gloves and disinfected knives, and (b) “hygienic” by using no gloves and only one (visually) clean knife at the start of incision. All hot-boned cuts were sprayed with a 1% v/v L-lactic acid solution, vacuum packed and immersed in icewater. Hot- and cold-boned cuts were stored at 2°C, as vacuum packs during 6 d and exposed to air for an additional week. Using a destructive method, samples for microbiological examination were taken from the 8–10th rib section of the dorsal carcass surface at the end of the slaughterline as well as before boning, and from the epimysium of longissimus cuts immediately after boning, 7 d post mortem (p.m.) upon opening vacuum packs and 14 d p.m. As compared with “hygienic” boning, “strictly hygienic” boning resulted in a significant decrease in aerobic colony count on longissimus cuts from 1.9 to 1.4 log/cm2 and from 2.4 to 1.4 log/cm2 for alternative and conventional procedures, respectively. An effect of lactic acid decontamination could not be demonstrated earlier than 7 d after opening of vacuum packs (14 d p.m.). Counts of Enterobacteriaceae and yeasts and molds were extremely low under all experimental conditions. No salmonellae could be isolated from any sample.

Sixty calves of the Dutch Friesian (FH) breed were stunned mechanically. Without previously having been stunned, another 30 calves were stuck according to the Jewish rite. Upon opening of the skulls (1-2 h post mortem) brains of mechanically stunned calves were collected either conventionally ( n = 30) or 'hygienically" (n = 30), i.e. using a fresh pair of surgical gloves during each removal to avoid cross contamination. For ritually slaughtered animals only the hygienic procedure was followed. Samples of 10 g were excised from undamaged hemispheres and in the mechanically stunned treatment group also from the site of impact of the captive bolt. After storage in polystyrene trays at 3 + I°C for 7 days sampling was repeated. Bacteriological examination included the assessment of aerobic colony counts at 30°C for 3 days (ACC-30) and 4°C for 14 days (ACC-4) and Enterobacteriaceae colony counts at 37°C for 20 h (ECC). In conventionally collected samples the ACC-30 and ACC-4 were 3.8 and 3.0 log10 cfu g-1 at day 1 and 6.2 and 6.4 loglo cfu g-1 at day 8. With hygienic collection these counts were reduced by approximately 1 log unit. Whilst by conventional practice the ECCs, at day 1 and 8 were 2.6 and 4.8 log10 cfu g-I these counts were 1.8 and 2.6 log10 cfu g-I for hygienic practice. In samples excised from the site of impact of the captive bolt the hygienic procedure had similar, though less marked effects. On day 1 brains from ritually slaughtered animals had a bacteriological contamination similar to that found in the hemispheres of mechanically stunned calves. However, whilst at day 8 their mean ECCs were 3.4 and 3.5 log10 cfu g-1 the percentages of plates 'positive' for Enterobacteriaceae were only 10% in the ritually vs. 53% in the mechanically stunned group. The Enterobacteriaceae in this case were composed of psychrotrophic non-pathogenic genera of environmental origin. Salmonella was not isolated from any sample.