An investigation on the effect of polyphenolic extracts of Nigella sativa seedcake on physicochemical properties of chitosan-based films

Nigella sativa seedcake phenolic extract (NSE), as compared to tannic acid (TA), was evaluated for its effect on film-forming ability of chitosan. These films were evaluated for their tensile strength, elongation, water vapor permeability (WVP), type of bonding, color, surface morphology, polyphenol and in vitro antioxidant activity release profile. At 7.5% (v/v of film-forming solution), NSE led to 42% decrease in tensile strength but improved the elongation by 66%, contradicting the effect of TA in chitosan films. WVP and crystallinity decreased with increasing NSE concentration. Changes in absorbance intensity by FTIR indicated structural modification. The calorimetric analysis showed changes in melting point and degree of crystallinity due to NSE. The release of total polyphenols and subsequent antioxidant activity in the water, 50% ethanol, and 95% ethanol media indicated potential application in active-packaging. This study shall help valorization of N. sativa seedcake after oil extraction for packaging, pharmaceutical, and allied applications.