Stability Testing of Spray- and Spouted Bed–Dried Extracts of Passiflora alata

Abstract

The aim of this research was to perform a stability testing of spray- and spouted bed–dried extracts of Passiflora alata Dryander (Passion flower) under stress storage conditions. Spouted bed– and spray-dried extracts were characterized by determination of the average particle diameter (d _P ), apparent moisture content (X _P ), total flavonoid content (T _F ), and vitexin content. Smaller and more irregular particles were generated by the spouted bed system due to a higher attrition rate (surface erosion) inside the dryer. The SB dryer resulted in an end product with higher concentration of flavonoids (≈10%) and lower moisture content (1.6%, dry basis) than the spray dryer, even with both dryers working at similar inlet drying air temperature and ratio between the extract feed flow rate to drying air flow rate (W _s /W _g ). Samples of the spouted bed– and spray-dried extracts were stored at two different temperatures (34 and 45°C) and two different relative humidities (52 and 63% RH for 34°C; 52 and 60% RH for 45°C) in order to perform the stability testing. The dried extracts were stored for 28 days and were analyzed every 4 days. The flavonoid vitexin served as the marker compound, which was assayed during the storage period. Results revealed shelf lives ranging from 9 to 184 days, depending on the drying process and storage conditions.

Keywords:

• Dried extract
• Passiflora alata
• Spouted bed
• Spray drying
• Stability testing

ACKNOWLEDGMENTS

The authors acknowledge Dr. Joaquim Adelino de Azevedo Filho (IAC) for supplying the authenticated plant material, Dr. J. Zhang and Dr. Peng Zhou (Department of Food Science and Nutrition, University of Minnesota) for the technical assistance, the Department of Food Science and Nutrition for the facilities, CAPES (Coordenação de Aperfeiçoamento de Pessoal de Nível Superior) for the Sandwich fellowship for the first author, and FAPESP (The State of São Paulo Research Foundation) for the financial support.

Notes

H ₀ = static bed height; W _s /W _max = mass feed flow rate of extract relative to the dryer evaporation capacity; W _g  = drying gas flow rate; Q/Q _jm  = spouting gas flow rate relative to gas flow at minimum spouting; T _gi  = inlet gas temperature; γ = conical base angle.

^a High-molecular-weight carbohydrate (HMWC) and low-molecular-weight carbohydrates (LMWC).

d _P  = particle size; X _P  = apparent moisture content; T _F  = flavonoid content; D =flavonoid degradation.

m ₀ = monolayer moisture content (% dry basis); C and K = parameters of the GAB model; R ² = determination coefficient; MAE = mean absolute error.

RH = relative humidity; CL = confidence level.

RH = relative humidity.

RH = relative humidity.