Food freshness indicator

Details Food freshness indicator Food freshness indicator

2001-04-11

2004-04-20

Warden, Jill (Department: 1743)

Chemical apparatus and process disinfecting, deodorizing, preser

Analyzer, structured indicator, or manipulative laboratory...

Calorimeter

C436S021000, C436S022000, C436S023000, C436S024000, C422S051000, C422S050000, C422S067000

Reexamination Certificate

active

06723285

ABSTRACT:

FIELD AND BACKGROUND OF THE INVENTION
The present invention relates to indicators and, more particularly, to a system for visually indicating food spoilage in food containers.
There exist many known indicators of freshness of food products that indicate whether a certain food product may be spoiled. One of the prime indicators of food spoilage is microbial growth. On the other hand, some bacteria do not cause spoilage, but are actually added to milk or cream after pasteurization to make “cultured” products such as certain hard cheese. In those cases spoilage would be measured by looking for common pathogenic indicators such as salmonella or
E. coli
0157.
There are indicators of microbial growth that change color only after the microbe grows. Chemicals that change color when pH changes have been used to mark the presence or absence of bacterial growth. Commonly utilized pH indicators include phenol red, bromocresol blue, and neutral red. Attempts have been made to measure bacterial growth using other than pH indicators. Markers, such as electrical impedance, electrical conductivity, amount of ATP (adenosine triphosphate), turbidity (optical density), have been measured from microbes growing in a general medium with the addition of a chemical that is measured. Tests for the above mentioned markers can be accurate but not practical for store and home detection of bacterial growth. Turbidity is practical for clear liquids and mostly only consumers with trained eyes except of course for extreme contamination where the supposedly clear liquid is completely cloudy.
A popular indicator for product freshness which is popularly extrapolated to indicate product spoilage when it shows predetermined signs is Time and Temperatures Indicators. In U.S. Pat. No. 5,182,212, Jalinski teaches one of numerous Time and Temperature Indicators which are operable to signal the attainment of one or more preselected time-temperature integrals which monitor the temperature and time history of a product utilizing a dual system of specific reaction pairs which simultaneously generate acid and alkali from two neutral substrates. One of the substrates is present in excess of the other. The preferred dynamic indicator system generates a constant pH buffer in the alkali range that is maintained until one of the substrates is depleted. At that time, a rapid pH change in the indicator solution to the acid range occurs, resulting in a very sharp visual color change in a pH-sensitive dye. The specific reaction pairs are enzyme/substrate pairs, preferably urease/urea and yeast/triacetin. A preferred combination pH-sensitive dye package includes m-nitrophenol, p-nitrophenol and litmus to provide an indicator which changes from green to reddish pink upon the expiration of a given amount of time at constant temperature, or in a shorter period of time, upon exposure to elevated abuse temperatures. In especially preferred embodiments, one of the enzyme substrate pairs includes an enzyme component provided by a microorganism which has been shock treated prior to incorporation in the indicator to improve temperature sensitivity and provide extended half life. The new and improved integratin indicators are adapted for use with packaged foodstuffs intended for refrigerated and room temperature handling and storage at temperatures between about 20° F. to about 120° F.
A TTI that is commercially available is sold under the trademark “LIFELINES” by Lifelines Inc. of Morris Plains, N.J. The US Army uses a “Bull's Eye” TTI label manufactured by Lifelines at a cost of $0.03 a label that help in the management of rations.
Amongst the disadvantages of TTI labels are that labels do exactly what they are named for. They give a picture of the time and temperature without any actual knowledge of what has transpired to the food product within the package, as the TTI labels are attached to the package's exterior. There is also room for fraud by exchanging food wrappers together with the TTI labels by any one involved in the whole chain from the food packers until the food arrives home to the consumer. Certain food products such as meat products, the TTI label is within the container in contact with the food product. The same disadvantages apply here as well wherein the label offers no information about any changes transpiring to the stored food product itself and fraud is still relatively easy.
When the food within a sealed container starts to spoil, several by-products are given off. It is therefore theoretically possible to detect spoilage by detecting one or more of these by-products. Common to all such deterioration is the production of heat, acidity, pressure, and carbon dioxide. Heat evolved during spoilage is small. Thus the typical conditions of storage and transportation of many food containers would produce temperature conditions far in excess of those likely to result solely from the heat released during spoilage. Pressure is perhaps a slightly more workable indicator, but still not very practical. In the first place, due to temperature variations and the chance of mishandling before sale, such a detector would have to be unresponsive to nominal pressure changes. Also, many products are heat sterilized after the can is sealed, so such a pressure detector would have to be insensitive to the pressure increase developed when the can is sterilized and would not be applicable to softer packaging. However, the development of substantial pressure occurs rather late in the spoilage process, and therefore, to be effective, it would be necessary for such a detector to respond to slight pressure increases. These are obviously conflicting requirements which make pressure detection impractical. Additionally, it would be very difficult to gauge any pressure changes in a packaging softer than a can.
As far as carbon dioxide is concerned, U.S. Pat. No. 4,003,709 to Eaton et al teaches providing a liquid impermeable pouch in which a liquid carbon dioxide detecting solution is entrapped. The solution provides a visually observable change when the concentration of carbon dioxide rises substantially above that which is the normal ambient concentration for our atmosphere. A suitable opening is formed in the container and the pouch is sealed into and over the opening so that the inert plastic material seals the opening and the microporous plastic portion is inside the container in at least gaseous contact or communication with the food contents. Thus, if carbon dioxide gas is generated it will pass through the microporous plastic and react with the calcium hydroxide to precipitate calcium carbonate. This causes the solution to change from clear to milky white, and this change is readily observable from outside the container by looking through the window. Visibility may be further enhanced by providing a coloring on the pouch opposite the window, such as green or blue. Such coloring provides a colored field which is visible until the carbon dioxide gas is produced. When the gas is produced, the observer sees the color of the window change from the color of the field to white, indicating that the food is probably spoiled and should not be consumed. The abovementioned pouch is not really mixed with the food contents and only reacts after the carbon dioxide gas permeates the microporous plastic portion which can be in a very miniscule and undetectable quantities in many cases of spoilage. As a related example, donated blood within blood bags which are suspect to be spoiled must be vigorously shaken in the bag for carbon dioxide to be detected in sufficient quantities in a similar carbon dioxide detection system. Shaking a food product vigorously of course would not be practical for food products.
U.S. Pat. No. 4,285,697 to Neary teaches a food spoilage indicator comprising a liquid crystal disposed in a carrier of plastic tape, at least one portion of which is semi-permeable to gases generated in food spoilage. His invention depends on the discovery that: (1) the appearance or color of a liquid crystal can be significantly altered by absor

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