2. Universidad Cardenal Herrera-CEU

Background: Listeria monocytogenes is a foodborne bacterial pathogen that causes listeriosis, an infectious disease in animals and people, with pigs acting as asymptomatic reservoirs. In August 2019 an outbreak associated with the consumption of pork meat caused 222 human cases of listeriosis in Spain. Determining the diversity as well as the virulence potential of strains from pigs is important to public health. Methods: The behaviour of 23 L monocytogenes strains recovered from pig tonsils, meat and skin was compared by studying (1) internalin A, internalin B, listeriolysin O, actin assembly-inducing protein and PrfA expression levels, and (2) their invasion and intracellular growth in eukaryotic cells. Results: Marked differences were found in the expression of the selected virulence factors and the invasion and intracellular replication phenotypes of L monocytogenes strains. Strains obtained from meat samples and belonging to serotype 1/2a did not have internalin A anchored to the peptidoglycan. Some strains expressed higher levels of the studied virulence factors and invaded and replicated intracellularly more efficiently than an epidemic L monocytogenes reference strain (F2365). Conclusion: This study demonstrates the presence of virulent L monocytogenes strains with virulent potential in pigs, with valuable implications in veterinary medicine and food safety.

This study assessed carcass characteristics and meat quality of bulls finished in individual pens and fed with different diets. A completely randomized design determined how to feed 24 crossbred bulls (European × Nellore) with four diets over 84 days: CONT) without additives; MONE) inclusion of 30 mg of monensin/kg DM; MO + VI) inclusion of 30 mg of monensin + 30 mg of virginiamycin/kg DM; and MO+AD) inclusion of 30 mg of monensin/kg DM + 1.57 g of a blend of organic trace minerals, live yeast, beta-glucan, and mannans per kg DM (Advantage-Confinamento). MO+VI resulted in lower pH (P < 0.05) and lighter meat (P < 0.05) compared with other treatments. Cooking loss was less (P < 0.05) with MO+AD at 14 days of aging time. At 14 days, Warner-Bratzler shear force was higher for meat from bulls fed with CONT and MONE diets and slower (P < 0.05) for meat from bulls fed with MO+VI and MO+AD diets. In conclusion, including monensin combined with virginiamycin and monensin combined with a blend of organic trace minerals and yeast in the diets of bulls finished in individual pens can improve the color, Warner-Bratzler shear force of meat, and lower cooking losses.

Este trabalho substitui o cloreto de sódio (NaCl) por cloreto de potássio (KCl) em níveis crescentes, com a adição de óleos essenciais de orégano e tomilho para mitigar o efeito do cloreto de potássio na avaliação sensorial dos consumidores de hambúrgueres bovinos. Foram testados três níveis de substituição de sódio por potássio (KC20, KC40 e KC60 com 20%, 40% e 60% de substituição, respectivamente) e comparados com o controle (CONT, 100% cloreto de sódio), quanto às características microbiológicas iniciais e avaliação sensorial por 112 consumidores. A substituição de NaCl por KCl não alterou (P > 0,05) a população microbiana inicial. Da mesma forma, os níveis de substituição de NaCl por KCl não alteraram (P > 0,05) a aceitabilidade de cor, odor e textura dos hambúrgueres bovinos. As substituições de 20% e 40% de NaCl por KCl melhoraram (P < 0,05) o sabor e a aceitabilidade geral dos hambúrgueres bovinos. Ainda, para níveis de substituição de 60%, não foi observada diferença (P > 0,05) quando comparado ao grupo CONT. Diferentes grupos de consumidores foram observados para sabor e aceitabilidade geral (P < 0,050). Em conclusão, é possível substituir até 60% de NaCl por KCl em hambúrgueres bovinos, com inclusão de óleos essenciais de orégano e tomilho, na avaliação sensorial pelos consumidores, sendo 20% o nível de substituição mais recomendado.

Background: Forty crossbred steers were supplemented with different doses (from 0 control to 6000 mg/animal/day) of natural additive blend containing clove essential oil, cashew oil, castor oil, and a microencapsulated blend of eugenol, thymol, and vanillin for 80 days. Carcass characteristics, drip loss, and antioxidant activity were evaluated 24 h post mortem on longissimus thoracis, and the effects of aging (until 14 days) were evaluated for water losses (thawing/aging and cooking), texture, color, and lipid oxidation. Results: The use of the natural additive blend did not modify (P > 0.05) carcass characteristics but did, however, modify body composition (P < 0.05). Drip losses were unaffected by the treatments tested (P > 0.05). There was an observed quadratic effect (P < 0.05) on losses from thawing/aging on the first day of storage. Regarding the effects of natural additives on cooking losses, there was a quadratic effect (P < 0.05) among the treatments on day 7 of aging. Differences between days of aging were only observed with control treatment. Shear force was similar among treatments on days 1 and 7 of aging. On day 14 a linear effect (P < 0.05) was observed. Also, a linear effect (P < 0.05) appeared on meat lightness, meat from the control group being clearer on day 1. No changes were observed in redness among treatments or days of storage (P > 0.05). Yellowness was not modified by the treatments (P > 0.05)but only by the days of storage in control and the lowest dosage used. Conclusion: The blend of natural additives has potential use in pasture feeding and could improve meat quality. However, doses should be adjusted.