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

Area of Science:

• Food Science
• Materials Science
• Polymer Science

Background:

• Active packaging films are crucial for extending the shelf life of fresh produce.
• Pectin and tragacanth gum are natural polysaccharides with potential for film formation.
• Calcium cross-linking can modify the physical and barrier properties of polysaccharide films.

Purpose of the Study:

• To investigate the impact of in situ cross-linking of pectin-tragacanth gum films with calcium ions on the properties of the films.
• To evaluate the effect of these active packaging films on the storage quality of fresh raspberries.
• To compare the efficacy of different calcium sources (CaCl₂ and calcium citrate) as cross-linking agents.

Main Methods:

• Pectin-tragacanth gum films were prepared with varying concentrations of CaCl₂ and calcium citrate.
• Film properties, including tensile strength (TS) and oxygen permeance, were measured.
• Easy Rock raspberries were stored in the developed active packaging films for 7 days.
• Raspberry quality attributes, such as color stability and anthocyanin content, were assessed.

Main Results:

• Calcium cross-linking (0.125% w/w) significantly increased film strength (TS: 45.58 MPa for CaCl₂).
• CaCl₂-cross-linked films exhibited superior barrier performance, reducing oxygen permeance.
• Raspberries packaged in CaCl₂ films showed the best color stability and minimal brightness changes after 7 days of storage.
• Calcium citrate films maintained red color intensity but had higher anthocyanin variability.

Conclusions:

• In situ cross-linking of pectin-tragacanth gum with CaCl₂ effectively enhances active packaging film properties.
• CaCl₂-based active packaging significantly improves the storage quality and color stability of Easy Rock raspberries.
• Calcium cross-linking protects the cellular structure of raspberries, extending their shelf life.