In situ Ca²⁺‑cross‑linking effects on pectin-tragacanth films for fresh raspberry preservation

In the present study, the effect of in situ cross-linking of Ca²⁺ of pectin-tragacanth gum active packaging films with succinic acid on the properties and storage of fresh Easy Rock raspberries was investigated. The introduction of CaCl₂ and Ca₃(C₆H₅O₇)₂ into the polysaccharide matrix at a concentration of 0.125 % (w/w) resulted in an increase (p < 0.05) in film strength. TS was 45.58 MPa (0.125CLF) and 44.66 MPa (0.125 F), respectively. CaCl₂ cross-linked films again showed significantly better barrier performance compared to films treated with calcium citrate. Oxygen permeance similarly declined with increasing cross-linker concentration, with the most substantial improvement occurring between 0.25 % and 0.5 % Ca²⁺. In unpackaged fruit, the amount of anthocyanins increased rapidly after 4 and 7 days. After 7 days of storage, the greatest colour stability and the smallest differences in brightness (L*) were observed in fruit packaged in CaCl₂ cross-linked films, suggesting that calcium more effectively protected the cellular structure of raspberries. Fruit packaged in film with added citrate retained its red colour intensity, but with slightly greater anthocyanin variability, which may be due to greater susceptibility to oxidation with pH changes.