Preparation of a Microbial Time-temperature Indicator by Using the Vegetative Form of Bacillus amyloliquefaciens for Monitoring the Quality of Chilled Food Products

Abstract

Background and Objective: Time-temperature indicators are used in smart packaging, and described as intelligent tools attached to the label of food products to monitor their timetemperature history. Since the previous studies on microbial time-temperature indicators were only based on pH-dependent changes, and they were long-time response indicators, in the present work, a new microbial time-temperature indicator was designed by using the alpha amylase activity of Bacillus amyloliquefaciens vegetative cells.Material and Methods: The designed time-temperature indicator system consists of Bacillus amyloliquefaciens, specific substrate medium and iodine reagent. The relation of the timetemperatureindicator’ response to the growth and metabolic activity (starch consumption and production of reduced sugars) of Bacillus amyloliquefaciens was studied. In addition, the temperature dependence of the time-temperature indicator was considered at 8 and 28˚C. Finally, in order to adjust time-temperature indicator endpoint, the effect of the inoculum level was investigated at 8oC.Results and Conclusion: In the designed system, a color change of an iodine reagent to yellow progressively occurs due to the starch hydrolysis. The effect of the inoculum level showed the negative linear relationship between the levels of Bacillus amyloliquefaciens inoculated in the medium and the endpoints of the time-temperature indicators. The endpoints were adjusted to 156, 72 and 36 hours at the inoculum levels of 102, 104 and 106 CFU ml-1, respectively. The main advantages of the time-temperature indicator is low cost and application for monitoring the quality of chilled food products.Conflict of interest: The authors declare no conflict of interest.