Modeling and stability of polyphenol in spray-dried and freeze-dried fruit encapsulates

Several studies have investigated freeze-drying and spray-drying encapsulation to address the effect of operational parameters on the physicochemical properties and preservation of the polyphenol content in fruit encapsulates. Using a specific fruit or vegetable pulp or extract, most of these studies have examined the search for an appropriate wall. In this study, the effect of operational variables and the concentration of maltodextrin (MD) and gum arabic (AG) on the gallic acid (GA) content of spray- and freeze-dried encapsulates of a model fruit juice (MFJ) was evaluated. Three encapsulant ratios (100% MD, 100% AG, and 50% MD/AG) and three encapsulant concentration levels (10–20–30%) were used. MFJ was lyophilized at varying pressure (300 to 500mTorr) with a varied freezing rate (0.3°C/min to 0.7°C/min). The MFJ spray-drying conditions were feed flow (72–108–144mL/h) and air temperature (80–100–120°C). Second-order responses satisfactorily described the initial GA content as a function of independent variables to be determined. A higher initial GA content in the freeze-dried encapsulates was achieved with a wall blend ratio close to 100% AG and an encapsulant concentration was 10 to 20% or with an MD concentration in the range of 80 to 100% when the chamber pressure was greater than 400mTorr, and the freezing rates were higher than 0.65°C/min. For spray-drying, the best results were found with the following drying conditions: Air Inlet Temperature, 85 to 105°C; Feed Flow, 80 to 120mL/h; Encapsulant Concentration, 10 to 20%; and Encapsulant Ratio, 50 to 80%. The MFJ models were also suitable for the prediction of the initial polyphenol content in three encapsulated fruit pulps. The polyphenol in the spray- and freeze-dried MFJ encapsulates showed first-order kinetics during a 200day period of storage at 25°C with reaction rate coefficients fluctuating between 3×10⁻⁴ and 20×10⁻⁴days⁻¹ and between 7×10⁻⁴ and 50×10⁻⁴days⁻¹ respectively.