A high-hygroscopic, porous pH-colorimetric label based on κ-Carrageenan and carboxymethyl cellulose composite cryogel for monitoring pork freshness

In this paper, κ-Carrageenan/carboxymethyl cellulose/Ca 2+ (κC/CMC/Ca 2+ ) composite cryogels with high porosity, low density, and excellent hygroscopicity were obtained via cross-linking effect. The porosity and density of the cryogel (κC: CMC (w/w) of 7:3, 5.0 wt% Ca 2+ ) were 94.85%, and 0.067 g/cm 3 , respectively, and the moisture absorption reached 39.84% at 75% relative humidity (RH). Moreover, Clitoria ternatea anthocyanins (CTA) were introduced into κC/CMC/Ca 2+ cryogel to fabricate a porous pH-colorimetric label (κC/CMC/Ca 2+ /CTA cryogel) whose maximum moisture absorption of the cryogel was increased to 42.50%. κC/CMC/Ca 2+ /CTA cryogel (κCCCC) possessed excellent pH-color development and a quick response because it turned from blue to green within 7 s after injecting 7.50 mmol/L ammonia at 53% RH. The label with diameter of 0.75 cm could be used to declare the quality of 200 g pork due to obvious color change as the total volatile basic nitrogen (TVB-N) increased to 14.57 mg/100 g. The results showed that κCCCC would play an important role in the practical application for food quality indication.