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Litmus Based Packaging Material for Milk & Orange Juice Disclosure Number: IPCOM000004561D
Publication Date: 2001-Feb-02

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The Prior Art Database


An indicator, a natural or synthetic substance that changes color in response to the nature of its chemical environment can be incorporated into milk containers as part of its packaging. Indicators are used to provide information about the degree of acidity of a substance pH or the state of some chemical reaction within a solution being tested or analyzed. One of the oldest indicators is litmus, a vegetable dye that turns red in acid solutions and blue in basic ones. Other indicators include alizarin, methyl red, and phenolphthalein, each one being useful for a particular range of acidity or a certain type of chemical reaction. Litmus, vegetable dye obtained from lichens, usually of the genus Variolaria, and used in chemistry to determine the presence of acids and bases in a solution. Strips of paper impregnated with a blue or red litmus solution, or small quantities of the solution itself, are used to indicate the presence of an acid or a base; acids turn blue litmus red, and bases turn red litmus blue. Milk and other pasteurized liquids consumed by the people have a shelf life ranging from1 week for fresh milk to 1 month for orange juice. This is why most fresh food packaging is dated so to allow the user to know its freshness. But the expiration date is an estimated time. As an added precautionary measure, material used for packaging milk and orange juice can be litmus based. As with strips of litmus paper, milk and orange juice cartons cartons and pH meter can be used to determine how far into the shelf life is the container of milk. Change in acidity can be a good parameter of the milks freshness. A slight change in acid level, undetectable by the consumer is detectable by the pH meter. Normal pH is 7.4. A lower pH level would indicate a more acidic change is occurring in the milk. A higher pH level would indicate a more basic change to the milk. The pH is color coded for easy interpretation. In Figure 1, a strip of paper impregnated with litmus solution acts as a pH indicator 120. The pH indicator 120 is located on the side panel of milk carton 110 and changes color when solution in milk carton becomes more acidic or basic over time. If pH indicator 120 is a shade of red, then milk in milk carton 110 has become more acidic. If pH indicator 120 changes to a shade of blue, the milk has become more basic over time.