ABSTRACT
Grape extract is reportedly rich in phenolic compounds that possess strong antioxidant activities. Encapsulation of such extracts in nanoparticles (NPs) is an effective way to preserve various food products. In the present study, grapes were first extracted, and the amount of total phenolic content and different types of phenolic acids was determined. The extracts at different chitosan/extract weight ratios (1:0.25, 1:0.5, 1:0.75, and 1:1) were then encapsulated in chitosan nanoparticles (NPs) using the ionic gelation method. The extract-loaded chitosan nanoparticles were characterized by their physicochemical properties using the dynamic light scattering (DLS) technique, chemical properties using Fourier-transform infrared (FTIR) spectroscopy, and X-ray powder diffraction technique (XRD), the morphological properties using scanning electron microscopy (SEM), and the antioxidant activity using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) test. The encapsulation efficiency (EE) and loading capacity (LC) were also assessed. Our findings showed that the free radical inhibition effect of NPs significantly increased with an increase in extract concentration. Chitosan NPs presented acceptable encapsulation efficiency and loading capacity (LC), and the encapsulation process enhanced the antioxidant activity of the free grape extracts. At the weight ratio of 1:0.5, the particle size and zeta potential of the NPs were 177.5 ± 2.12 nm and 32.95 ± 0.49 mV, respectively. FTIR and XRD analyses verified the credibility of the encapsulated grape extract in chitosan NPs. These NPs can be an efficient way to increase the shelf-life of food products.
ABSTRACT
The present study aimed to investigate the impact of polylactic acid (PLA) integrated with nanochitosan (NC) composite film and Ziziphora Clinopodioides essential oil (ZCEO) on oxidative spoilage of rainbow trout fillets during a 9-day refrigeration period. For this purpose, first, six degradable films including T1: PLA, T2: PLA + NC, T3: PLA + NC + 1% ZCEO, T4: PLA + NC + 1.5% ZCEO, T5: PLA + 1% ZCEO, and T6: PLA + 1.5% ZCEO were prepared. Next, the properties of the films were investigated. The results of the mechanical tests showed that ZCEO decreased the tensile strength and increased the elongation at the break of the PLA films. However, adding NC improved the mechanical characteristics of the PLA film. The outcomes of physical tests including moisture content (14.02%), solubility (17.41%), water vapor permeability (1.14 × 10-7 g s-1 m-1 Pa-1), and oxygen transmission rate (21.54 cm3.mm/m2.24 hr) showed that adding 1% ZCEO improved the film physical characteristics. Nevertheless, by adding 1.5% concentration EO to the PLA film, the values of water vapor permeability, porosity (according to the scanning electron microscopy), and turbidity increased and cross-sectional pores were observed. Moreover, the films had high antioxidant properties (84.33%). In the next step, the effects of the mentioned films on the oxidative spoilage of rainbow trout fillets were investigated. The results of the chemical analysis in PLA film with the EO compared with the control treatment revealed the increasing trend of oxidation indices, in general. Moreover, increasing the concentration yielded better results such that all treatments containing EO showed satisfactory results up until the storage period ends. In most cases, adding NC affected the mentioned characteristics positively, and the best results were observed in T4 and then in T3. However, based on economics and the better mechanical and physical properties of T3, the film can be applied as an active packaging in fishery products.
