Evaluation of the microbiological safety and sensory quality of a sliced cured-smoked pork product with protective cultures addition and modified atmosphere packaging.

The aim of this study was to evaluate the effect of two protective lactic acid bacteria cultures combined with modified atmosphere packaging on the survival/growth of Listeria innocua 2030c (as a surrogate for Listeria monocytogenes) and on sensory attributes of ready-to-eat 'lombo' over storage time. Sliced 'lombo', a traditional cured-smoked pork loin, was inoculated with L. innocua 2030c, Lactobacillus sakei ST153 (isolated from 'salpicão') and BLC35 culture (with Lactobacillus curvatus, Staphylococcus xylosus and Pediococcus acidilactici; CHR Hansen) as protective cultures. Samples were packed in two modified atmosphere packaging conditions (20% CO2/80% N2 and 40% CO2/60% N2) and stored at 5 ℃ for 124 days. Both cultures led to a reduction of 1-2 log CFU/g of L. innocua 2030c after 12 h; however, at the end of storage only Lb. sakei ST153 maintained this antilisterial effect, which was more evident at 40% CO2/60% N2. The influence of cultures addition and modified atmosphere packaging conditions on the sensory characteristics of the product were not significant. Thus, Lb. sakei ST153 combined with modified atmosphere packaging is a strong candidate to be used in a biopreservation strategy maintaining the traditional sensory quality of cured-smoked pork products and increasing their safety with respect to Listeria spp.

Effects of microbial inoculants on corn silage fermentation, microbial contents, aerobic stability, and milk production under field conditions.

The present study aimed to investigate the effects of 2 corn silage inoculation strategies (homofermentative vs. heterofermentative inoculation) under field conditions and to monitor responses in silage variables over the feeding season from January to August. Thirty-nine commercial dairy farms participated in the study. Farms were randomly assigned to 1 of 3 treatments: control (nonactive carrier; Chr. Hansen A/S, Hørsholm, Denmark), Lactisil (inoculation with 1 x 10(5)Lactobacillus pentosus and 2.5 x 10(4)Pediococcus pentosaceus per gram of fresh matter; Chr. Hansen A/S), and Lalsil Fresh (inoculation with 3 x 10(5)Lactobacillus buchneri NCIMB 40788 per gram of fresh matter; Lallemand Animal Nutrition, Blagnac, France). Inoculation with Lactisil had no effects on fermentation variables and aerobic stability. On the contrary, inoculation with Lalsil Fresh doubled the aerobic stability: 37, 38, and 80+/-8h for control, Lactisil, and Lalsil Fresh, respectively. The effect of Lalsil Fresh on aerobic stability tended to differ between sampling times, indicating a reduced difference between treatments in samples collected in April. Lalsil Fresh inoculation increased silage pH and contents of acetic acid, propionic acid, propanol, propyl acetate, 2-butanol, propylene glycol, ammonia, and free AA. The contents and ratios of DL-lactic acid, L-lactic acid relative to DL-lactic acid, free glucose, and DL-lactic acid relative to acetic acid decreased with Lalsil Fresh inoculation. Lalsil Fresh inoculation increased the silage counts of total lactic acid bacteria and reduced yeast counts. The Fusarium toxins deoxynivalenol, nivalenol, and zearalenone were detected in all silages at all collections, but the contents were not affected by ensiling time or by inoculation treatment. The effect of inoculation treatments on milk production was assessed by collecting test-day results from the involved farms and comparing the actual milk production with predicted milk production within farm based on test-day results from 2007 and 2008. The average milk production of lactating cows at test days during the study (January to September 2009) was 30.7+/-0.5 kg of energy-corrected milk/d. Milk production was 104.6+/-0.7% of the predicted yield and did not differ among treatments. In conclusion, the present study showed that homofermentative inoculants might not compete efficiently or might not deviate sufficiently from the epiphytic flora on whole-crop corn to affect fermentation in standard qualities of corn silage. Heterofermentative inoculation increased aerobic stability and numerous fermentation variables. None of the treatments affected milk production, and more-stable corn silage seemed to have a similar production value as compared with less-stable homofermented silage. Heterofermented silage can be evaluated for its properties to limit aerobic silage deterioration in the feed chain.

Modelling the effect of the starter culture on the growth of Staphylococcus aureus in milk.

The competitive growth of a starter culture of lactic acid bacteria (Fresco 1010, Chr. Hansen, Hørsholm, Denmark) and Staphylococcus aureus was studied in milk. The lactic bacteria (LAB) were able to induce an early stationary state in S. aureus. The developed model highlights that the growth of S. aureus is inhibited when the LAB have reached a critical density. The model was tested in different conditions of temperature (from 12 degrees to 25 degrees C), for various inoculum sizes of LAB and S. aureus. The results show that the model accurately quantifies the kinetics of S. aureus as a function of the starter culture.