Gravure-printed colour indicators for monitoring kimchi fermentation as a novel intelligent packaging

Gravure-printed colour indicators on common nylon/polyethylene (Ny/PE) films were newly developed for kimchi (fermented vegetable products in Korea) packaging to examine the degree of fermentation of such products non-destructively during distribution and sale. A printing ink consisting of Ca(OH)(2) as a CO2 absorbent, bromocresol purple (BP) or methyl red (MR) as a chemical dye, and a mixture of polyurethane and polyester dissolved in organic solvents as a binding medium, was applied on Ny films by the gravure process and then laminated with PE films to form the printed indicator. During storage at 0, 10, 20degreesC, kimchi fermentation was assessed for titratable acidity (TA), and the colour of the indicators was determined as Hunter values and expressed as total colour difference (TCD). Although TCD value of the BP type indicator was slightly less than that Of the MR type, colour changes in both the types of indicator correlated well to TA values of kimchi. The results suggest that gravure-printed colour indicators have great potential as an intelligent packaging system for monitoring the ripeness of commercial kimchi products. Copyright (C) 2002 John Wiley Sons, Ltd.