2. Universidad Cardenal Herrera-CEU

The use of human milk in milk banks requires thermal processing to eliminate microbiological hazards. An evaluation is made of the stability of overall human milk bactericidal capacity following 2 modalities of thermal pasteurization: 63°C/30 minutes and 75°C/15 seconds. Ten milk samples (mature milk) were analyzed. In each sample, the effect of both thermal treatments on bactericidal capacity against Escherichia coli was evaluated in relation to the capacity of fresh milk (control). All the samples analyzed possessed bactericidal capacity. Human milk pasteurization induced a significant loss of this capacity that was more pronounced after high-temperature treatment than after low-temperature processing. Untreated milk, low-pasteurized milk, and high-pasteurized milk yielded a reduction in E. coli growth of 70.10%, 52.27%, and 36.39%, respectively. In conclusion, human milk possesses antimicrobial activity that is lost in part as a result of thermal processing. Such bactericidal capacity is, moreover, better preserved by low-temperature, long-time pasteurization.

The population dynamic of constitutive biota on 84 samples belonging to two different types of French fermented dry sausages during the ripening process in a pilot-scale ripening chamber was investigated. Samples were analyzed in three steps of their production: fresh product, first drying stage, and finished product. In addition, 180 strains of lactic acid bacteria were identified using a miniaturized biochemical procedure of characterization. In general, the number of lactic acid bacteria that evolved during the ripening process of French dry sausages increased during the first days of the process after which the number of these organisms remained constant at approximately 8 log CFU/g. Lactobacillus sakei and Pediococcus pentosaceus, bacteria added as starter, were the dominant species. Pediococcus urinaeequi, Pediococcus acidilactici, and particularly Lactobacillus curvatus were also present. Finally, we have to take into account that the controlled conditions of the pilot plant generally contribute to the homogenization of the behavior of the starter biota.

The individual and combined antilisterial efficiency of nisin, lactic acid and modified atmosphere packaging (MAP) was investigated. Raw ground pork was inoculated with a strain of Listeria monocytogenes and samples were distributed into twelve lots. Half of the lots were stored aerobically and the other six lots were packaged using the MAP. A different combination of nisin (N) and/or lactic acid (LA) was added to each lot (300 ppm N, 500 ppm N; 2% LA; 300 ppm N and 2% LA; 500 ppm N and 2% LA). All samples were stored at 4 °C for 21 days (samples with MAP) or 7 days (samples stored aerobically). The inactivation of L. monocytogenes in samples stored aerobically was attained mainly with the combination of 500 ppm N + LA; however, in samples with MAP, the L. monocytogenes population decreased 3.45 log with the addition of LA, and the combination N + LA increased the inactivation other 0.5 log.

Restriction digestion analysis of the acyl transferase (AT) domain sequences of a polyketide synthase (PKS) gene was tested as a rapid method to identify isolates of Aspergillus tubingensis from grapes. Restriction endonuclease digestion of PKS products using the endonucleases BccI, HaeIII, HpaII, MboI and TaqI distinguished five types of restriction fragment length polymorphism (RFLP). Ochratoxigenic isolates were only identified within RFLP-types I and III. The RFLP assay is proposed as a rapid and easy method to identify A. tubingensis isolates from grapes. Amino acid sequences of AT domains from representative A. tubingensis isolates of the RFLP types obtained were aligned and analysed using phylogenetic methods. A comparison was also made with reference strains of Aspergillus section Nigri. Most of the A. tubingensis strains clustered into two distinct groups Gr1 and Gr2 with the exception of two isolates that remained unclustered. These results support the intraspeficific variability within A. tubingensis species reported using other techniques.

Samples from 240 carcasses were collected from four animal species (porcine, ovine, bovine and equine). Two samples were taken from each carcass, one using the excision method (EX) and the other the wet–dry swabbing method (SW). Eight areas from each carcass were sampled. Most of the samples obtained by SW revealed total aerobic viable counts (TVC) levels of between 3.1 and 4.0 log CFU cm−2, while most of the values corresponding to excision were located between 4.1 and 5.0 log CFU cm−2. Moreover, Enterobacteriaceae (EC) counts were only detected above 3.0 log CFU cm−2 in 0.85% of the carcasses when the samples were collected by swabbing, while the excision method revealed that 13.75% of the carcasses presented EC greater than 3.0 log CFU cm−2. TVC and EC by EX revealed statistically significant differences compared to SW, while no significant linear relationship was found between carcass surface bacterial counts obtained by SW and EX.

Fifty-five bovine, 50 equine, 60 ovine, and 50 porcine carcasses were sampled in a slaughterhouse in eastern Spain. Two samples were taken from each carcass, one using the excision method and the other using the swabbing method. Four different materials were used for swabbing: cellulose, polyurethane, or viscose sponges, and medical gauze. Samples were collected at the end of the process by four different people before the carcasses were taken to the cooler. The samples were examined for total viable bacteria counts (TVCs) and Enterobacteriaceae counts (ECs). The mean TVC for all species sampled by excision was 4.50 log CFU/cm(2), which was significantly higher than the 3.53 log CFU/cm(2) obtained by swabbing. The TVCs obtained using gauze and the cellulose and polyurethane sponges were significantly higher (P < 0.05) than the corresponding TVCs obtained using viscose sponges. Animal species, the person who collected the samples, and microbiological load also had a significant effect on TVC. ECs were obtained from 82.8% of excision samples, from larger percentages of samples obtained using cellulose or polyurethane sponges or gauze swabs, but from smaller percentages of samples obtained using viscose sponges. The Enterobacteriaceae load significantly influenced the EC. In contrast, animal species and the person who collected the samples had no significant effect. The cellulose sponge, polyurethane sponge, and gauze gave high mean log counts of aerobic bacteria and Enterobacteriaceae, which makes these swab types suitable for use in slaughterhouses for the purpose of assessing production process hygiene.

The sensitivity of different methods for the isolation and identification of Campylobacter, Listeria and Salmonella was compared, and their application in food safety control in a poultry slaughterhouse was evaluated. The VIDAS, SimPlate, Reveal and VIP systems were used, together with traditional microbiological methods. The study was carried out in a slaughterhouse and in the poultry carving room. One hundred and twenty samples (40 per microorganism) obtained from carcasses, viscera, different chicken parts, water and the environment were evaluated. For Campylobacter, the VIDAS system performed better than plate confirmation. The traditional method yielded results similar to those obtained with the SimPlate method. For Listeria, the plate count method proved less sensitive than the VIDAS, VIP and Reveal systems, which yielded similar results. For Salmonella, the VIDAS system displayed a detection rate comparable to that of traditional methods, while the Reveal system detected twice as many positive samples (16 in total). The Reveal method performed significantly better than either the plate count method or the VIDAS system. The alternative methods used here could be successfully applied in food safety control in poultry slaughterhouses, providing similar or better results and taking less time to perform. The VIDAS system, in general, and the Reveal system in the case of Listeria and Salmonella, appear to be effective alternatives to traditional methods.

The incidence of Listeria monocytogenes in refrigerated and frozen chicken parts was investigated, using the Mini-Vidas™ system (bioMérieux). Two hundred and eigthy chicken parts were tested: 40 skin samples from the breast and leg, 120 samples from refrigerated wings, breasts and legs and 120 samples from frozen wings, breasts and legs (40 of each). The 219 samples tested positive (78.21%). The parts with the highest incidence were frozen breasts (100%) and wings (95%). In frozen legs, the values were lower (60%). In refrigerated parts, the incidence was higher in breasts (85%) and in wings (80%). In legs samples, similarly to the frozen ones, the incidence was lower (50%). In the skin of the breasts and legs, the incidence was 77.50%. Statistical evaluation demonstrated that there are no differences between frozen breasts and wings but there are differences between similar refrigerated parts. The refrigerated and frozen legs are the only parts that are statistically equal. The percentages that were detected show the importance of requiring the absence of Listeria spp. in chickens.

During the processing of dry-cured meat products, sarcoplasmic and myofibrillar proteins undergo proteolysis, which has a marked effect on product flavor. Microbial proteolytic activity is due to the action of mostly lactic acid bacteria (LAB) and to a lesser extent micrococci. The proteolytic capacity of molds in various meat products is of interest to meat processors in the Mediterranean area. Eleven LAB and mold strains from different commercial origins were tested for proteolytic activity against pork myosin, with a view to possible use of these strains as starter cultures for Iberian dry-cured ham. Proteolytic activity was tested by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The LAB strains with the highest proteolytic activity were Lactobacillus plantarum (L115), Pediococcus pentosaceus (Saga P TM), and Lactobacillus acidophilus (FARGO 606 TM). The best fungal candidate was Penicillium nalgiovense LEM 50I followed by Penicillium digitatum, Debaryomyces hansenii, and Penicillium chrysogenum.

The study was carried out under field conditions in a commercial farm, and 1,440 as-hatched Ross-308 broilers were included. Broilers were randomly distributed into 24 experimental 4-m2 pens (60 broilers/pen). Pens were randomized to the 3 treatment groups: a) tylvalosin 10 mg/kg of live BW during 2 d, b) positive control (tylosin during 2 d), and c) negative control (no treatment). The drugs were provided in the water supply. Mortality, individual BW, and feed intake were assessed. Clostridium presence was assessed in fecal and cecal samples, coccidian oocyst counts were assessed in fecal samples, and bacterial diversity was assessed in ileal content. Live BW at 42 d old was significantly better in the tylvalosin group than in tylosin and no-treatment groups, with tylvalosin-treated broilers reaching 80 to 100 g higher final live weight. Average daily gain results mirrored BW findings. The improvement of feed conversion rate with tylvalosin amounted to 0.13 and to 0.10 versus tylosin and no-treatment, respectively, with mortality being similar in all groups. Significantly reduced sulfite-reducing Clostridium and Clostridium perfringens counts in tylvalosin and tylosin groups versus the no-treatment group were observed in cecum content samples. In conclusion, according to the present study results, tylvalosin, at doses substantially lower than registered for poultry in Europe, has proven effective in controlling the colonization of the cecum by Clostridium ssp. in broilers, improving some productive performances.