Development of a Thin Tube Cultivation Method for Determining Coliform Counts in Milk
Authors: Kang, Dong-Hyun; Gray, Peter M.
Source: Journal of Food Protection®, Number 1, January 2002, pp. 5-237 , pp. 88-92(5)
Abstract:A new rapid coliform-monitoring method using thin tube cultivation (TTC) was developed. One hundred microliters of modified selective medium (1.5% agar) and 100 μl of sample were mixed in thin cultivation tubes, yielding a semisolid mixture of 0.75% agar. The tubes were incubated at 37°C and checked for a positive reaction (gas production from lactose fermentation and color changes from acid production) at 30-min intervals. The positive reaction times for TTC were compared with actual coliform numbers. The first experiment was performed to validate the TTC method using pure coliform cultures (the Escherichia coli group, the Enterobacter cloacae group, and the Klebsiella pneumoniae group). The results indicated that the TTC method saved about 10 to 14 h of incubation time compared with the conventional plating method. When coliforms were present in small numbers, such as 1 to 1.5 log10 CFU/ml, the TTC method detected their presence within 10 h. When highly contaminated samples were assayed (6 log10 CFU/ml), the TTC method detected the presence of coliforms within 4 to 5 h. In a food system experiment, pasteurized skim milk inoculated with a coliform mixture was assayed by the TTC method. The coliforms in the milk were quickly detected, resulting in a savings of 11 to 14 h compared with the conventional plating method. Cold-injured coliforms were studied to evaluate the TTC system. The recovery and estimation of injured coliforms by the TTC method strongly agree with those of the conventional plating method. The TTC system was also applied to ascertain the levels of natural coliforms in noninoculated milk. The TTC system reduced incubation times by about 11 to 14 h compared with the conventional plating method. According to these data, this method is a rapid, simple, accurate, and economical way to monitor and estimate total coliforms in milk.
Document Type: Research Article
Affiliations: Department of Food Science and Human Nutrition, Washington State University, Pullman, Washington 99164-6376, USA
Publication date: January 1, 2002
- IAFP members must first sign in on the right to access full text articles of JFP First published in 1937, the Journal of Food Protection®, is a refereed monthly publication. Each issue contains scientific research and authoritative review articles reporting on a variety of topics in food science pertaining to food safety and quality. The Journal is internationally recognized as the leading publication in the field of food microbiology with a readership exceeding 11,000 scientists from 70 countries. The Journal of Food Protection® is indexed in Index Medicus, Current Contents, BIOSIS, PubMed, Medline, and many others.
Print and online subscriptions are available to Members and Institutional subscribers. Online visitors who are not IAFP Members or journal subscribers will be charged on a pay-per-view basis. Information can be obtained by calling +1 800.369.6337; +1 515.276.3344; fax: +1 515.276.8655, E-mail: email@example.com or Web site: www.foodprotection.org
- Information for Authors
- Submit a Paper
- Subscribe to this Title
- Membership Information
- Information for Advertisers
- ingentaconnect is not responsible for the content or availability of external websites