title: The use of bacterial alkaline phosphatase assay for rapid monitoring of bacterial counts on spinach.
abstract: This study was undertaken to evaluate the applicability of bacterial alkaline phosphatase (ALP) activity for rapid monitoring of total mesophilic bacteria counts in spinach. A set of fresh and decayed spinach mixtures were tested to rapidly (10 min) monitor spinach bacterial counts. To assay ALP activity, Lumigen APS-5 was used as a substrate. Bovine ALP was reduced after heat treatment at 75 degrees C for 1 min; in contrast, bacterial ALP activity increased. To differentiate bacterial ALP from other ALP, heat treatment (75 degrees C, 1 min) was applied before measurement. As a result, a regression equation was established between the actual mesophilic aerobic bacteria count and ALP activity of spinach mixtures (r= 0.90). The predicted total mesophilic aerobic bacterial count calculated from the fitted regression line (predicted log(10) CFU/g = 0.00056 x ALP values + 1.4002) showed a high correlation with the actual observed total bacterial count (r= 0.93). The ALP assay is a simple and rapid method to utilize for estimation of existing or contaminating microorganism levels on spinach.
authors.affiliation: Department of Food Science and Human Nutrition, Washington State University, Pullman, WA 99164-6376, USA.
authors.forename: E-J
authors.initials: EJ
authors.lastname: Park
authors.forename: D-H
authors.initials: DH
authors.lastname: Kang
mesh_terms: D000469:Alkaline Phosphatase / Q000032:analysis / Q000378:metabolism*; D001419:Bacteria / Q000201:enzymology*; D015169:Colony Count, Microbial / Q000379:methods*; D003257:Consumer Product Safety; D005506:Food Contamination / Q000032:analysis*; D005516:Food Microbiology; D006801:Humans; D011786:Quality Control; D012044:Regression Analysis; D012680:Sensitivity and Specificity; D018724:Spinacia oleracea / Q000382:microbiology* / Q000592:standards; D013696:Temperature; D013997:Time Factors
chemical_list: D000469:Alkaline Phosphatase