Anthocyanins lipid microparticles obtained by spray chilling grape peel extract

Abstract

This study used spray chilling microencapsulation of grape peel extract, rich in coloring and antioxidant compounds aimed at using discarded grape peels. Besides the sensory properties for use in food, these compounds are valuable for human health, as they act in the prevention of several diseases. However, they are sensitive to heat, light, and humidity, losing their properties in food processing and storage stages, which makes their replacement necessary for a healthy diet. Microencapsulation by spray chilling is performed at mild temperatures, minimizing thermal damage and using lipid compounds as encapsulating materials. First, the polyglycerol polyricinoleate (PGPR) emulsifier content, and the ultrasound-assisted homogenization (160 and 200 W; 4 and 6 min) were studied to prepare stable emulsions

containing the grape peel extract (40%) using fully hydrogenated trans-free palm oil (FHPO- 80%) and palm oil (PO-20%) as encapsulating agents. An emulsion produced with the aid of a

magnetic stirrer (750 rpm/4 min) was used as a control. The emulsions were evaluated for kinetic stability, droplet size and distribution, rheological behavior, optical microscopy, FTIR, retention of bioactive compounds, and oxidative stability. The effect of the homogenization process on the formation of microparticles by spray chilling was also investigated, as well as the anthocyanins and color stability. PGPR proved to be an effective emulsifier at a concentration of 4%. Ultrasound-assisted technique allowed the formation of more stable emulsions, mainly for the process conditions of 200 W and 4 minutes. FTIR spectra confirmed the presence of the bioactive compounds and the absence of lipid oxidation in all emulsions. The phenolic compounds content, antioxidant activity, degradation kinetics of anthocyanins, and storage stability were improved in the US-treated emulsions. The microparticles made with the US-treated emulsion (200 W and 4 min) showed improved visual appearance, flowability, and stability of the anthocyanin pigment when compared to the microparticles made with the control emulsion. After optimizing the emulsion formulation, the effect of different FHPO to Po ratios (90:10; 80:20; 70:30; 60:40, and 50:50) was evaluated concerning the physicochemical properties, storage stability (-18°C, 4°C, and 25°C/90 days) and the resistance to the gastrointestinal tract of spray-chilled microstructured lipid microparticles (MLMs) containing grape peel extract. Increasing the proportion of FHPO improved the thermal resistance of MLMs, although all treatments led to the production of MLMs with β' and β' crystalline behavior. The anthocyanins retention in the MLMs ranged from 81.5 - 61.2% and the treatment MLM_90:10 showed the best result. Similar behavior was observed for the phenolic compounds content (1443.1 - 1247.2 mg GAE/100 g) and antioxidant activity (92.6- 86.8%). During the storage, MLMs containing FHPO to PO ratios of 80:20, 70:30, and 60:40 exhibited better retention of anthocyanins and lower color changes for all temperatures studied. In vitro gastrointestinal simulation revealed that all treatments protected anthocyanins from the gastric phase and maintained a maximum and controlled release of this compound in the intestinal phase. The present results suggest a promising application of MLM in food systems for coloring, flavoring, and antioxidant purposes.