Development of pullulan/gellan gum films loaded with astaxanthin nanoemulsion for enhanced strawberry preservation.

Innovative packaging materials are essential for preserving food, serving as a substitute for petroleum-based options. In this study, biofilms consisting of pullulan and gellan gum which incorporates astaxanthin nanoemulsion were prepared to extend the shelf-life of strawberries. Hydrophobic deep eutectic solvents (DES) were used as solvents to extract natural astaxanthin from Haematococcus pluvialis. Water-in-oil emulsions were prepared with the DES (containing Ast of 95 μg/mL), tween 20, and water (containing chitosan of 0.3 % and sodium tripolyphosphate of 0.1 %) at a mass ratio of 7:8:85. The average diameter of the astaxanthin nanoemulsion ranged from 167.70 to 351.03 nm, and showed exceptional stability with a retention rate of 95.37 % at 25 °C on the seventh day. Moreover, the nanoemulsion exhibited high antioxidant activity, with an IC50 value of 14.87 μg/mL and high antibacterial effect to E. coli and S. aureus. In the process of preparing the pullulan and gellan gum biofilms, this antioxidant effect and antibacterial effect are maximally preserved. Furthermore, following 20 days of storage with the biofilm, the strawberry experienced a weight loss of 12.48 %, a soluble solid content of 7.4 %, an ascorbic acid content of 0.75 %, and a titrable acidity of 36.45 mg/100 g. The shelf-life of the strawberry was significantly prolonged using the biofilms loaded with astaxanthin nanoemulsion to a minimum of 18 days, surpassing the 12-day shelf-life of those stored with neatfilm. Therefore, the astaxanthin nanoemulsion combined with pullulan and gellan gum biofilms offers an innovative alternative for active food packaging.