- 作者: 李根永; 黃啟仲
- 作者服務機構: 東海大學食品科學研究所
- 中文摘要: 本研究從Food MicroModel (方程式無法摘錄) Database中擷取Brochothrix thermosphacta、Listeria monocytogenes、Yersiniaenterocolitica、Bacillus cereus、Escherichia coli O157:H7、Salmonella spp.、Staphylococcus aureus及Clostridium perfringens八株菌不同溫度下之比生長速率,將溫度與其相對的比生長速率契合入乘冪模式(r=a (方程式無法摘錄);r=比生長速率;T=溫度;a,d=迴歸參數),並以此模式探討溫度對微生物生長速率的影響。模式中指數d-值在次最適(suboptimum)生長溫度範圍內可以反映溫度對生長速率變化的影響力,d-值愈大溫度上升時生長速率增加愈多。由數據顯示d-值與微生物生長溫度範圍有關。生長溫度範圍狹窄者,d-值小,如耐冷菌B. thermosphacta與Y. enterocolitica,其d-值均趨近1。中溫菌B. cereus,S. aureus,Salmonella sp. , E. coli O157:H7,d-值在2.31~2.90間。高溫菌C. perfringens d-值是3.29。乘冪模式中的係數α值會因限制因子的存在而減小,表示在不良環境下溫度對菌體生長的影響力變弱。在不良環境下不同菌株的d-值,有的會增加,有的會減少。因此d-值與菌株本身克服生長障礙的能力,以及培養基的營養組成份和限制因子有關。環境影響d-值的現象亦可在中式香腸中觀察到。Enterococcus sp.生長在冷藏香腸的d-值是0.833,而在MRS的d-值是2.36。冷藏食品通常含有多種添加物,因此於其中的耐冷腐敗菌,d-值會接近1,所以預測在此環境下耐冷腐敗菌的增殖,線型模式是合理的選擇。
- 英文摘要: The specific growth rates of Brochothrix thermosphacta, Listeria monocytogenes, Yersmia enterocolitica,Bacillus cereus, Escherichia coli 0157:H7, Salmonella spp., Staphylococcus aureus and Clostridium perfringensat various temperatures were taken from the Food MicroModel (方程式無法摘錄) database, and the data sets of specificgrowth rate versus temperature were fitted using the multiplicative model (r = a (方程式無法摘錄), r = specific growth rate;T = temperature; a, d = regression parameters). The exponential d-value derived from microbial growth atsuboptimum temperatures reflected the effectiveness of temperature in enhancing growth. A microorganismwith a large d-value exhibited a large increment of growth rate as temperature increased. The d-value of amicroorganism was related to the temperature range for growth. The temperature range for the growth ofpsychrotrophs was usually narrow for B. thermosphacta and Y. enterocolitica; hence the d-values of these twopsychrotrophs were close to 1 whereas d-values of mesophiles, such as B. cereus, E. coli O157:H7, Salmonellaspp., and S. aureus, were 2.31~2.90, and the d-value of C. perfringens, a thermophile, was 3.29. The values ofparameter a of the model were affected by extra salt added into cultures. For all the strains mentioned above,the a-values decreased when the cultures contained higher levels of salt. The lowering of the a-value impliedthat the influence of temperature on the growth rate in the model was reduced. The change of the d-value wasdependent on the capability of the microorganism to overcome the obstacle to growth and was affected by thecomposition of the nutrients and by inhibitory factors in the culture. The influence of environmental factorson the d-value was also found in Chinese sausages. The d-value of a dominant spoilage strain of Enterococcussp. derived from sausages was 0.833 whereas the d-value derived from MRS cultures was 2.36. In refrigeratedfoods which usually contained some preservatives and were stored at low temperature, the d-value ofpsychrotrophic spoilage bacteria was around 1, In this case, the linear model could be a reasonable choice forpredicting the proliferation of spoilage bacteria.
- 中文關鍵字: specific growth rate; model; predict.,
- 英文關鍵字: --