title: An investigation of the use of the MicroFoss as an indicator of the shelf life of pasteurized fluid milk.
abstract: The MicroFoss method was evaluated for its effectiveness as an indicator of fluid milk shelf life. Half-gallon, 2% fat fluid milk samples (n = 90) were obtained from a milk processing plant on 3 occasions postpasteurization and evaluated for shelf life. Sensory evaluation was performed by 3 judges experienced in the use of the American Dairy Science Association scorecard for milk. A score of 5 or less was considered to represent the end of the shelf life of the product. MicroFoss coupled with preliminary incubation (PI) was utilized to estimate the total viable (TVC) and gram-negative counts (GN) in the milk. The MicroFoss functions by using a pH indicator or CO2 production to detect changes in light reflection to estimate bacterial populations. Simple and multiple linear regression analyses were utilized to determine the relationship between MicroFoss (PI-GN and PI-TVC detection times) and product shelf life. It was concluded that using both PI-GN and PI-TVC in a combined algorithm is the optimal way of using MicroFoss as a shelf-life indicator. When PI-TVC was selected in the algorithm, a correlation coefficient of 0.89 existed between PI-TVC and shelf life; PI-GN was used in the algorithm in the place of PI-TVC when its detection time was within 6 h of the detection time of PI-TVC vials. The PI-GN detection times correlated well (r = 0.80) with shelf life, but more importantly, all but one PI-GN sample (n = 50) selected in the algorithm had a shelf life of less than 10 d. This indicates that the PI-GN measurement can be utilized along with PI-TVC detection time to indicate potential shelf-life problems.
authors.affiliation: Department of Food Science, Nutrition, and Health Promotion, Box 9805, Mississippi State University, Mississippi State 39762, USA. chwhite@ra.msstate.edu
authors.forename: C H
authors.initials: CH
authors.lastname: White
authors.forename: J
authors.initials: J
authors.lastname: Wilson
authors.forename: M W
authors.initials: MW
authors.lastname: Schilling
mesh_terms: D000465:Algorithms; D000818:Animals; D001962:Bromcresol Purple; D002245:Carbon Dioxide / Q000032:analysis; D015169:Colony Count, Microbial; D004866:Equipment Contamination; D005511:Food Handling / Q000295:instrumentation; D005519:Food Preservation / Q000379:methods*; D005947:Glucose; D006090:Gram-Negative Bacteria / Q000254:growth & development / Q000302:isolation & purification; D006863:Hydrogen-Ion Concentration; D007202:Indicators and Reagents; D016014:Linear Models; D008892:Milk / Q000737:chemistry / Q000382:microbiology*; D013649:Taste; D013997:Time Factors
chemical_list: D007202:Indicators and Reagents; D002245:Carbon Dioxide; D001962:Bromcresol Purple; D005947:Glucose