Development of a Microbial Time/Temperature Indicator Prototype for Monitoring the Microbiological Quality of Chilled Foods

Abstract

A time/temperature indicator (TTI) system based on the growth and metabolic activity of a Lactobacillus sakei strain was developed for monitoring food quality throughout the chilled-food chain. In the designed system, an irreversible color change of a chemical chromatic indicator (from red to yellow) progressively occurs due to the pH decline that results from microbial growth and metabolism in a selected medium. The relation of the TTI response (color change) to the growth and metabolic activity (glucose consumption, lactic acid production, pH decrease) of L. sakei was studied. In addition, the temperature dependence of the TTI kinetics was investigated isothermally in the range of 0 to 16°C and modeled with a system of differential equations. At all temperatures tested, the pH and color changes of the TTI system followed closely the growth of L. sakei, with the endpoint (the time at which a distinct visual color change to the final yellow was observed) of the TTI coinciding with a population level of 10 7 to 10 8 CFU/ml. The endpoint decreased from 27 days at 0°C to 2.5 days at 16°C, yielding an activation energy of 97.7 kJ/mol, which was very close to the activation energy of the L. sakei growth rate in the TTI substrate (103.2 kJ/mol). Furthermore, experiments conducted on the effect of the inoculum level showed a negative linear relationship between the level of L. sakei inoculated in the system medium and the endpoint of the TTI. For example, the endpoint at 8°C ranged from 6 to 2 days for inoculum levels of 10 1 and 10 6 CFU/ml, respectively. This relationship allows the easy adjustment of the TTI endpoint at a certain temperature according to the shelf life of the food product of concern by using an appropriate inoculum level of L. sakei. The microbial TTI prototype developed in the present study could be used as an effective tool for monitoring shelf life during the distribution and storage of food products that are spoiled primarily by lactic acid bacteria or other bacteria exhibiting similar kinetic responses and spoilage potentials. Apart from the low cost, the main advantage of the proposed TTI is that its response closely matches the loss of the quality of a food product by simulating the microbial spoilage process in particular environments.A modern quality and safety assurance system should prevent contamination through the monitoring, recording, and controlling of critical parameters during a product's entire life cycle, which includes the postprocessing phase and extends over the time of use by the final consumer (20). Since temperature is the parameter that predominantly determines the shelf life and final quality and safety of food products after their processing according to Good Manufacturing Practices and Good Hygiene Practices, monitoring and recording the temperature conditions during distribution and storage are of crucial importance (40,41). Time/temperature indicators or integrators (TTIs) are used as cost-effective and user-friendly devices to monitor, record, and translate the overa...

Application of a Prototype of Microbial Time Temperature Indicator (TTI) to the Prediction of Ground Beef Qualities during Storage

“…Therefore, the use of LAB makes it possible to reflect the microbial degradation kinetics of foods on which the microbial TTIs are affixed (Ellouze et al, 2008). For good example, Vaikousi et al (2008) used Lactobacillus sakei to develop a prototype microbial TTI. In the present research, we manufactured microbial TTI using Weissella cibaria which had been classified as Lactobacillus spp.…”

Packaging Technologies for Dates and Date Products

“…Time-temperature indicators can be used in monitoring temperature variation in dates supply chain. Several new time-temperature devices have recently been described in literatures based on various principles, for instance, the growth of metabolic activity of Lactobacillus sakei (Vaikousi et al 2008), the reaction between amylase and starch solution (Yan et al 2008) the development of microorganisms (Ellouze and Augustin 2010) and the incorporation of anthocyanin into chitosan matrix (Maciel et al 2012).…”

New Blue Pigment Produced by Pantoea agglomerans and Its Production Characteristics at Various Temperatures

“…A digital thermorecorder is an electronic TTI, and the temperature data need to be transformed to microbial growth data with a mathematical model. The mechanisms of chemical and biological TTIs have to be based on irreversible changes and reactions; most of the changes are expressed as color changes or the movement of a boundary (2,3,11,15,21). Among these TTIs, the main advantage of a microbial TTI is that test microorganisms that have growth characteristics similar to those of food or clinical product contaminants can be selected.…”

“…Among these TTIs, the main advantage of a microbial TTI is that test microorganisms that have growth characteristics similar to those of food or clinical product contaminants can be selected. The mechanism in most microbial TTIs is an irreversible color change of a chemical chromatic indicator which follows a pH decline due to microbial growth in a medium (2,21).…”

“…Thus, monitoring and recording the temperature history of these products during the period from manufacturing to consumption is very important. Devices capable of assessing the temperature history of food and clinical products, known as time-temperature integrators or indicators (TTIs), have been developed (2,3,11,15,21). TTIs are categorized as electronic, chemical, and biological (microbial).…”