Moisture Sorption Isotherms and Storage Stability of Spray-Dried Yogurt Powder

Abstract

Moisture adsorption isotherms of spray-dried yogurt powder were determined at 10, 25, and 40°C using the standard, static-gravimetric method. Experimental data were fitted to five mathematical models (Guggenheim-Anderson-de Boer [GAB], Brunauer-Emmett-Teller [BET], Halsey, modified Oswin, and modified Henderson). A nonlinear regression analysis method was used to evaluate the constants of the sorption equations. The shelf-life of yogurt powder was predicted based on the relationship between permeability coefficient of the packaging material and moisture adsorbed by the powder determined by the GAB equation. Furthermore, the storage stability of spray-dried yogurt powder in terms of quality parameters including moisture content, water activity, color change, and thiobarbituric acid (TBA) value was studied in aluminum laminated polyethylene (ALPE) pouches under storage conditions of 25°C and 50% relative humidity (RH).

Keywords:

• Moisture adsorption isotherm
• Sorption model
• Spray drying
• Storage stability
• Yogurt powder

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Corrigendum

ACKNOWLEDGMENTS

The authors acknowledge the financial support of TUBITAK-TOVAG (Project No. 107 O 090) and Pinar Dairy Products Company, Izmir, Turkey.

Notes

Adapted from Greenspan.^{[ 22 ]}

^a a _w Range for BET equation was 0.11–0.5; only the first four data points are used.