Amado Isabel R, Vázquez Jose A, Guerra Nelson P, Pastrana Lorenzo
Departamento de Química Analítica y Alimentaria, Facultad de Ciencias de Ourense (Universidad de Vigo), Campus As Lagoas s/n, Ourense, Spain; Grupo de Reciclado y Valorización de Materiales Residuales (REVAL), Instituto de Investigaciones Marinas (IIM-CSIC), Eduardo Cabello, 6, Vigo (Pontevedra), Spain.
J Sci Food Agric. 2014 Aug;94(11):2274-81. doi: 10.1002/jsfa.6554. Epub 2014 Jan 31.
Cattle feed is at the beginning of the food chain in the 'farm-to-fork' model and might serve as a source of contamination with pathogenic bacteria. Heat treatment is one of the most effective methods utilized to ensure the microbial safety of feeds. In this work, the thermal resistance of Salmonella enterica, Escherichia coli and Staphylococcus aureus isolated from vegetable feed ingredients was investigated in phosphate-buffered saline (PBS) and in cattle feed.
Mean D values calculated in PBS ranged from 34.08 to 5.70 min at 55 °C, decreasing to 0.37 and 0.22 min at 65 °C for E. coli and S. enterica, respectively. No relationship was found between thermoresistance and source of isolation. D values in feed were calculated from the adjustment of two nonlinear models to the inactivation data. Thermal resistance of E. coli and S. enterica in cattle feed showed similar results to liquid medium; however, a fivefold increment of S. aureus thermoresistance in feed was observed. Our results also revealed an increase of microbial thermoresistance with the mean feed particle diameter.
These results provide relevant information for improvement in the safety of cattle feed regarding its process conditions (i.e. time, temperature and particle size).
在“从农场到餐桌”模式中，牛饲料处于食物链的起点，可能成为致病细菌污染的来源。热处理是确保饲料微生物安全最有效的方法之一。在本研究中，研究了从植物性饲料原料中分离出的肠炎沙门氏菌、大肠杆菌和金黄色葡萄球菌在磷酸盐缓冲盐水（PBS）和牛饲料中的热抗性。
在PBS中计算的平均D值在55℃下为34.08至5.70分钟，在65℃下大肠杆菌和肠炎沙门氏菌的平均D值分别降至0.37和0.22分钟。未发现热抗性与分离源之间存在关联。饲料中的D值是通过将两个非线性模型拟合到灭活数据来计算的。大肠杆菌和肠炎沙门氏菌在牛饲料中的热抗性结果与液体培养基相似；然而，观察到金黄色葡萄球菌在饲料中的热抗性增加了五倍。我们的结果还表明，随着饲料平均粒径的增加，微生物的热抗性增强。
这些结果为改善牛饲料加工条件（即时间、温度和粒径）的安全性提供了相关信息。
