Document Type : Research Paper
Authors
1 Graduated M.Sc. student, Department of Biosystems Engineering, Faculty of Agriculture, Shahid Chamran University of Ahvaz, Ahvaz, Iran.
2 Assistant Professor, Department of Biosystems Engineering, Faculty of Agriculture, Shahid Chamran University of Ahvaz, Ahvaz, Iran.
3 Associate Professor, Department of Biosystems Engineering, Faculty of Agriculture, Shahid Chamran University of Ahvaz, Ahvaz, Iran.
Abstract
Introduction Drying is one of the most economical ways to preserve food and is used to increase its shelf- life. Microencapsulation protects sensitive foods from adverse environmental conditions (such as the effect of moisture and oxygen) and reduces food quality fluctuations. The principle of microencapsulation via spray drying is to prepare an emulsion or suspension and spray it in the hot air of the drying chamber. Plant pigments, such as anthocyanins, have been considered, but they are unstable under processing conditions. Hibiscus sabdariffa (sour tea) is a resistant herbaceous shrub and annual or perennial plant that contains anthocyanins. More than 300 types of sour tea are found in tropical and subtropical regions worldwide. Gum Arabic and maltodextrin are used as carrier materials to maintain the stability and functional characteristics of the powder prepared by spraying. Owing to its high solubility, low viscosity, and suitable emulsifying properties, gum Arabic is a carrier of interest in the spray drying process. Maltodextrin is a partial hydrolysis product of starch and oligosaccharides and has become one of the most important and widely used carrier compounds in spray drying because of its high solubility and low viscosity. Because anthocyanins are soluble in water, they are compatible with formulations containing maltodextrin, gum arabic, and starch. The main goal of this research was to investigate the microencapsulation of sour tea extract using a spray drying method for the development of stable anthocyanin formulations because this method is scalable.
Materials and Methods Sour tea was prepared from the gardens of Khuzestan province, Karun city, in 2023. To prepare the sour tea plant, the sepals were first washed with distilled water and dried in an oven for 15 h at a temperature of 40º C. The sepals were then powdered using a hand mill. After passing through a sieve with a mesh size of 150 micrometers, the prepared powder was extracted using 50% ethanol. The extract was passed through a paper filter and centrifuged in a refrigerated centrifuge (10 minutes, 3780 g). Extraction was performed from sour tea, and after the concentration stage, it was combined with gum arabic and maltodextrin as carriers. The carrier material including the binary solution of gum arabic and maltodextrin in a specific ratio dissolved in 1000 ml of warm distilled water (at a temperature of about 70 º C) and stirred overnight on a magnetic stirrer at 4º C were kept. The ratio of the extract to the wall material was varied (1, 2, and 3% by weight). In this study, the inlet air temperature, inlet air flow, and inlet feed temperature to the dryer were considered constant, and the inlet air was sent to the dryer at a constant temperature of 160º C. The feed and air flow rate were 70% (respectively equivalent to 3 L/min and 25 m3 /h), and the nozzle opening and closing time intervals were 3 and 1 s, respectively. In order to optimize the preparation of the powder, the response surface methodology (RMS) with a central composite design (CCD) was used to obtain a mathematical model to predict the process behavior. The effects of independent variables, including the amount of wall material (4, 7 and 10%) and sour tea extract (1, 2 and 3%), on dependent variables, such as total anthocyanin (TAC), surface anthocyanin (SAC), and encapsulation efficiency (EE), were investigated. Moisture content, solubility index, bulk density, tapped and particle density, flowability, porosity, and morphology were also investigated in the powder samples.
Conclusion The obtained data were modeled using the Design Expert software11. The data analysis showed that the best model for estimating the surface anthocyanin and anthocyanin encapsulation rate was the third-order model with coefficients of explanation of 0.8853 and 9205. After final optimization, the SAC value was 0.49, TAC was 4.371 mg/liter, EE was 42.27%, moisture content was 3.92, solubility index was 45.47%, bulk density was 0.98, tapped density was 1.03, and particle density was 2.28 g/cm3. Hausner and carr index confirmed the excellent flowability of the powders. The optimal wall and core materials were 66.6% and 1.63%, respectively. Scanning electron microscopy images showed that the powder particles were micrometer in size and almost spherical. Powders containing a high percentage of gum Arabic showed relatively greater shrinkage and indentation than powders containing high maltodextrin content.
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