Search

A time-temperature integrator (TTI) based on laccase@Cu3(PO4)2 nanoflowers (laccase@NFs) was created to monitor the freshness of pasteurized milk during storage. To address the challenges of easy inactivation, poor stability, and high use-cost of laccase in the application of TTI, laccase@NFs were synthesized by ultrasonic-assisted biomineralization. The laccase@NFs-based TTI was created through the enzymatic reaction between laccase and 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonic acid ammonium salt), and the effects of laccase@NFs addition amount on the reaction rate, discoloration lifetime and activation energy (Ea) were discussed. Furthermore, the spoilage pattern and kinetic properties of pasteurized milk were explored based on titratable acidity. The measurement of the Ea was determined as 49.98 kJ/mol, and an investigation was conducted to assess the suitability of the TTI with pasteurized milk under both constant and variable temperature conditions. This research aims to contribute valuable insights into the application of enzymatic TTI in monitoring the shelf life of pasteurized milk.

The temperature abuse encountered by food products during storage due to deviations from the recommended storage conditions often leads to a considerable loss, especially for frozen and refrigerated foods. From a consumer perspective, the real history of time–temperature data is of interest so that the customer can get an idea about the remaining shelf-life. The time–temperature indicator or integrator (TTI), a small and inexpensive device, is attached to the packaging material and provides the time–temperature history of a food product during storage, thus estimating remaining shelf-life in a non-destructive manner. The enzymatic TTI is based on a thermo-sensitive reaction between enzyme and substrate. A suitable dye is mixed into this medium as an indicator, which changes its color depending on the variation in the pH of the reaction medium. In the recent past, several TTIs have been developed based on different enzymes, including lipase, amylase, phospholipase, urease, laccase, and others. The corresponding applied food matrices were fruits, vegetables, milk products, seafood, poultry, and meat products. Developing a new enzymatic TTI requires a systematic approach to correlate the response-TTI dependency. Such development needs a thorough understanding of the kinetics of food quality attributes and the activation energy. This review provides an overview of enzymatic TTI, theoretical considerations, and the systematic approach required to develop any enzymatic TTI. The integration of such information will simplify the design of novel enzymatic TTIs for a wide array of food products during frozen storage. [ABSTRACT FROM AUTHOR]

Time-temperature integrator/indicator (TTI) is a temperature monitoring tool that visually presents the temperature history of foods to easily and cost-effectively manage the temperature of food products in cold chain system. However, few TTIs exhibit suitable performance under chilled conditions over a long period, such as beyond 100 days, as in the storage and distribution of chilled beef across the world. This study aimed to visualize the temperature history of chilled vacuum-packed beef, during international distribution, using Maillard reaction–based TTIs to record the accumulated temperature under chilled conditions, for more than 100 days. The developed Maillard reaction–based TTI comprised of double-sealed large and small plastic pouches. While the small pouch contained 500 μL D-xylose solution, the large pouch contained 1000 μL glycine solution with disodium hydrogen phosphate solution. Both the solutions were mixed by breaking the small pouch into the large pouch, following which the Maillard reaction started, depending on the ambient temperature. We examined two different combinations of the solution concentrations of TTI that turned brown and yellow at − 0.5 °C after approximately 77 days and 100 days, respectively. The developed TTIs, along with Tasmanian chilled beef, were transported from Australia to Japan through commercial supply chains and stored at a constant temperature of − 0.5 °C. One of the TTIs (TTI-brown) turned pale brown after 77 days which is the current shelf life of Australian chilled beef in Japan. The color of TTI-yellow changed to clear yellow after 150 days, when the chilled beef developed an off-odor, as judged by sensory evaluation. The TTI-brown was functional until day 77 which is the current shelf life of Australian beef in Japan, while the TTI-yellow was functional until day 150 to indicate remaining shelf life of beef. The results collectively indicated the Maillard reaction–based TTIs to realize visualization of temperature history during long-term storage and distribution of chilled beef. [ABSTRACT FROM AUTHOR]

Research was undertaken to develop an enzyme-substrate-based time-temperature integrator (TTI) for monitoring higher temperature thawing of frozen buffalo meat. Alpha-amylase and iodine-starch complex were standardized for enzyme-substrate combinations and process optimization and packed in 2 × 2 cm LDPE bags. The meat samples were packed in polystyrene trays with cling film overwrap and frozen at -18 ± 1 °C. Each sample had a sticker-type TTI attached to the surface of the package. The frozen samples were subjected to temperature abuse at 25 ± 1 °C and 37 ± 1 °C, keeping a control at 4 ± 1 °C. On higher temperature thawing at 25 ± 1 °C, the TTI remained bluish black for 6 h, changed to brown at 12 h, and then changed to yellow at 18 h. At 37 ± 1 °C, color change was not observed in the TTI up to 4 h, then it turned brown at 8 h and to yellow at 12 h. In the control group of frozen meat thawed at 4 ± 1 °C (normal thawing), no color change was observed. From this observation, a color chart was developed to compare TTI color variation with the acceptability of thawed meat. Results have shown that during high temperature thawing of meat, the response of the TTI corroborated well with changes in various meat quality parameters like pH, extract release volume, free amino acids, fluorescein diacetate hydrolysis, total volatile basic nitrogen, D-glucose concentration, shear force, tintometer color units, microbial counts, and sensory scores. It is concluded that a TTI based on the starch-iodine-amylase complex can be successfully used to evaluate the history of high temperature thawing of frozen buffalo meat. [ABSTRACT FROM AUTHOR]

Food sterilisation, i.e. heating to above 120 °C for several min, still remains a primary method of food preservation. Current time-temperature integrators (TTIs), used to assess the thermal impact, only work at pasteurisation temperatures (below 100 °C). The aim of this work was to develop and validate a sterilisation TTI using an α-amylase from the hyperthermophile Pyrococcus furiosus. Previous experiments have found that this α-amylase has a z value similar to that of Clostridium botulinum spores and the enzyme is sufficiently heat resistant to show a measurable residual activity after 30 min at 121 °C. Analysis found a D value of 24 min and a slightly variable z value of around 11 °C. The decrease in enzymatic activity from thermal processing was found after a F process of 5 min to be 67 %, and for a F of 30 min it was 12 %, thus making P. furiosus α-amylase a strong and relevant candidate for a sterilisation TTI. Trials with canned water and mango chutney as test materials have confirmed the potential application of the enzyme within an industrially relevant setting of a model reel and spiral retort. The thermal data showed that at low or marginal F values, of less than 15 min, the correlation between the TTI and thermocouple data was closely comparable ( R = 0.96). The applicability of these TTIs over the range of industrial processes is also shown. [ABSTRACT FROM AUTHOR]