Time temperature indicator with distinct end point

An improved packaging for room temperature and refrigerated storage of a foodstuff including a label incorporating an indicator composition, said indicator composition being a time temperature integrating indicator comprising:

• a first specific reaction pair including an active reagent and a substrate specific to said active reagent, said first specific reaction pair being reactive to form a first reaction product, said first reaction product tending to cause the pH value to change in an acidic or a basic first direction away from neutrality;
• a second specific reaction pair including an active reagent and a substrate specific to said active reagent, said second specific reaction pair being reactive to form a second reaction product, said second reaction product tending to cause the pH value of the indicator to change in a second direction opposite said first direction and beyond neutrality;
• said first reaction product and said second reaction product in turn being reactive to form a third reaction product including a stable pH buffer which maintains the pH of the indicator at a stable value on the second direction side of neutrality until said second reaction product is no longer produced, said substrate in said first specific reaction pair being present in a stoichiometric excess amount over the amount of the substrate in said second specific reaction pair;
• and
• at least one pH-sensitive dye exhibiting one color for a pH in a basic pH range and a second different color in an acidic pH range, whereby said time-temperature integrating indicator exhibits a rapid and distinct color change from one to the other of said first and second colors after a pre-determined amount of time has elapsed upon exposure to relatively constant temperatures, or after a relatively shorter period of time has elapsed, upon exposure to elevated temperatures.

An indicator pouch for use in monitoring the time and temperature histories of an adjacent packaged food product to which said pouch is affixed, said pouch comprising a thermoplastic pouch envelope having an indicator solution-receiving cavity with a visually observable amount of a time temperature integrating indicator composition in said cavity, said indicator composition including:

• a first specific reaction pair including an active reagent and a substrate specific to said active reagent, said first specific reaction pair being reactive to form a first reaction product, said first reaction product tending to cause the pH value to change in an acidic or a basic first direction away from neutrality;
• a second specific reaction pair including an active reagent and a substrate specific to said active reagent, said second specific reaction pair being reactive to form a second reaction product, said second reaction product tending to cause the pH value of the indicator to change in a second direction opposite said first direction and beyond neutrality;
• said first reaction product and said second reaction product in turn being reactive to form a third reaction product including a stable pH buffer which maintains the pH of the indicator at a stable value on the second direction side of neutrality until said second reaction product is no longer produced, said substrate in said first specific reaction pair being present in a stoichiometric excess amount over the amount of the substrate in said second specific reaction pair;
• and
• at least one pH-sensitive dye exhibiting one color for a pH in a basic pH range and a second different color in an acidic pH range, whereby said time-temperature integrating indicator exhibits a rapid and distinct color change from one to the other of said first and second colors after a pre-determined amount of time has elapsed upon exposure to relatively constant temperatures, or after a relatively shorter period of time has elapsed, upon exposure to elevated temperatures.