2. Universidad Cardenal Herrera-CEU

Nonthermal methods are more efficient at preserving various biological properties of human milk, as compared with holder pasteurization (HoP), which is the most common preservation method. This study was performed to assess the effects of nonthermal processing on bactericidal activity against Escherichia coli in human milk. Milk samples obtained from the Regional Human Milk Bank in Warsaw at Holy Family Hospital were processed by HoP, irradiated with ultraviolet-C (UV-C) for 5, 10, and 15 minutes (6720 J/L each minute), subjected to 2 variations of high-pressure processing (HPP): 450 MPa for 15 minutes and 200 MPa for 10 minutes + 400 MPa for 10 min, with a 10-minutes break. The samples were then evaluated by a bactericidal assay (raw untreated human milk was used as a control). The bactericidal capacity after HoP was preserved in 12.1% of samples, showing a significant reduction in bactericidal properties compared with in raw milk (P < 0.05). The differences between samples preserved by nonthermal methods and raw milk were not significant (P > 0.05). Nonthermal methods of human milk treatment better preserve the bactericidal capacity compared with holder pasteurisation. Those alternative technologies to HoP can be proposed after further investigation for milk processing for Human Milk Banks facilities.

Background: Neonatal infections with Cronobacter sakazakii have recently been associated with the consumption of expressed human milk. Study Aims: (1) To evaluate whether human milk has antimicrobial capacity against C. sakazakii and (2) to determine the stability of its capacity when it is subjected to various treatments. Methods: The antimicrobial capacity of human milk against C. sakazakii was evaluated using an observational, cross-sectional, comparative design. Mature human milk samples (N = 29) were subjected to different treatments. After incubation at 37°C for 72 hr, samples were compared with fresh milk on the stability of their antimicrobial capacity. Two-way analysis of variance (ANOVA) was performed. Results: In fresh milk, counts of C. sakazakii were reduced by 47.26% (SD = 6.74) compared to controls. In treated milk, reductions were: refrigeration at 4°C for 72 hr (M = 33.84, SD = 13.84), freezing at –20°C for 1, 2, and 3 months (M = 40.31, SD = 9.10; M = 35.96, SD = 9.39; M = 26.20, SD = 13.55, respectively), Holder pasteurization (M = 23.56, SD = 15.61), and human milk bank treatment with (M = 14.37, SD = 18.02) and without bovine fortifier (M = 3.70, SD = 23.83). There were significant differences (p < .05) between fresh and treated milk. Conclusions: Human milk has antimicrobial capacity against C. sakazakii. However, its capacity is negatively influenced by common preservation and hygienization methods. Milk should be stored refrigerated for a maximum of 72 hr or frozen for a short period of time.

Milk supplied to neonates in neonatal units is kept at room temperature for some time, which could influence microbial growth. This study aims to evaluate the growth of Escherichia coli in HM and PIF under various treatments and conditions, as well as to determine the influence of different thawing methods on microbial growth in HM. The number of E. coli generations appearing over a 4 h period at 22 °C in HM (frozen; frozen and pasteurized; and frozen, pasteurized, and fortified) and in PIF (four brands) was determined. E. coli counts in HM inoculated and thawed using different methods were also compared. In frozen HM and in pasteurized and frozen HM, significant differences were found after 2.5 h and 1.5 h, respectively. In PIF, differences were found between 1.5 and 3 h. With regard to the thawing process, the lowest microorganism counts were obtained at 4 °C overnight; thus, it seems advisable to store milk at room temperature for a maximum of 1 h during administration in neonatal units. Thawing HM at 4 °C overnight should be the method of choice.

Listeria monocytogenes, a contaminant of raw milk, includes hypervirulent clonal complexes (CC) like CC1, CC4, and CC6, highly overrepresented in dairy products when compared to other food types. Whether their higher prevalence in dairy products is the consequence of a growth advantage in this food remains unknown. We examined growth kinetics of five L. monocytogenes isolates (CC1, CC4, CC6, CC9, and CC121) at 37 and 4 °C in ultra-high temperature (UHT) milk and raw milk. At 4 °C, hypovirulent CC9 and CC121 isolates exhibit better growth parameters in UHT milk compared to the hypervirulent CC1, CC4, and CC6 isolates. CC9 isolate in raw milk at 4 °C exhibited the fastest growth and the highest final concentrations. In contrast, hypervirulent isolates (CC1, CC4, and CC6) displayed better growth rates in UHT milk at 37 °C, the mammalian host temperature. Proteomic analysis of representative hyper- (CC1) and hypovirulent (CC9) isolates showed that they respond to milk cues differently with CC-specific traits. Proteins related to metabolism (such as LysA or different phosphotransferase systems), and stress response were upregulated in both isolates during growth in UHT milk. Our results show that there is a Listeria CC-specific and a Listeria CC-common response to the milk environment. These findings shed light on the overrepresentation of hypervirulent L. monocytogenes isolates in dairy products, suggesting that CC1 and CC4 overrepresentation in dairy products made of raw milk may arise from contamination during or after milking at the farm and discard an advantage of hypervirulent isolates in milk products when stored at refrigeration temperatures.

In this study, the possible influence of the food matrix and the interfering population of microorganisms on the detection and count of Listeria monocytogenes in three common foods of the Spanish diet (Spanish omelette, fresh cheese and vegetable salad) was determined. Four groups were assayed: one control, two groups with interfering microorganisms (Salmonella Enteritidis, Staphylococcus aureus and Proteus mirabilis) with different levels of L. monocytogenes and a final group only contaminated with L. monocytogenes. The samples were analyzed with the normalized method (UNE-EN ISO 11290:2018) and with an alternative technique (VIDAS). The results show that the presence of interfering microorganisms did not seem to interfere with the determination of L. monocytogenes. Furthermore, the type of food did not seem to influence the determination of L. monocytogenes, but the culture media used showed differences. In fact, regardless of the type of food, the ALOA medium showed higher sensitivity than the other media, with higher recovery in 100% of samples (only for the Spanish omelette in Group B was the result the same as that for PALCAM, 􀀀8.11 log cfu/g). The results obtained using the VIDAS were not influenced by any of the factors or conditions used and show 100% efficiency.

Two experiments were carried out; one with female pigs and the other with male pigs destined for Teruel dry-cured ham production, to evaluate the effect of immunocastration (entire gilts-EG vs. immunocastrated gilts-IG and surgically castrated males vs. immunocastrated males-IM) and diet (control vs. high energy vs. low crude protein and amino acids) on meat quality and fat composition. Fifteen meat samples and eight fat samples of each treatment were analyzed in both experiments. In the case of males, six fat samples per treatment were analyzed to determine boar taint. Immunocastration is a good strategy in gilts intended for dry-cured ham production because improves meat composition; however, in males, immunocastration impairs the results of pork chemical composition compared with surgical castration. The IG presented a lower polyunsaturated/saturated fatty acids ratio than EG, improving fat technological quality. Diets had little effect on pork or fat quality in gilts, but a high-energy level using oilseeds and a low-crude-protein and -amino-acids diet from 80 to 137 kg of body weight could be interesting in IM to maintain or increase fat consistency, respectively. Moreover, in general, immunocastration is effective in avoiding boar taint in males.