Preliminary characterization of glucomannan– carrageenan edible films containing black cumin oil

Abstract

The growing demand for biodegradable food packaging has encouraged the development of edible films derived from natural biopolymers. This study presents a preliminary evaluation of eleven edible-film formulations prepared with systematically varied glucomannan–carrageenan ratios, while glycerol, olive oil, and black cumin ( Nigella sativa ) oil were maintained at constant levels. Films were produced by the solution-casting method and characterized for thickness, colour difference (ΔE), water activity (aw), solubility, moisture content, water vapour transmission rate (WVTR), and water vapour permeability (WVP). Film thickness ranged from 0.02 to 0.24 mm, water activity from 0.62 to 0.66, colour difference from 8.09 to 11.85, and solubility from 13% to 66%. Among formulations with valid barrier data, Sample 9 (0.2 g carrageenan/0.8 g glucomannan) showed the most favourable preliminary moisture-barrier profile, combining 0.03 mm thickness, 11% moisture content, the lowest valid WVTR (0.3889 g·m⁻²·day⁻¹), and the lowest valid WVP (0.0036 × 10⁻⁶ g·mm·m⁻²·day⁻¹·kPa⁻¹). Sample 10 was excluded because its negative WVTR is physically invalid and was not repeated. Since black cumin oil was fixed, its independent contribution was not assessed. These data provide a baseline for Mixture-RSM optimization and further mechanical, structural, and antibacterial characterization.