Effects of Carrier Agents and Relative Humidity on the Physicochemical and Microstructural Characteristics of Hot Air-Dried Asian Pear (Pyrus pyrifolia Nakai cv. Niitaka) Powder

For improving the stability of Asian pear powder (APP), rice bran dietary fiber (RD) (used for the first time) and maltodextrin (MD) were employed as carrier agents; the physicochemical and microstructural characteristics of APP during room storage at various relative humidity (RH) levels for 25days were then evaluated. The RD-containing APP had a higher glass transition temperature, increased flowability, smaller particle size, and lower water adsorption capacity compared to the MD-containing APP. The comparison of the RD- and MD-containing APP samples revealed that the former had a higher total phenolic content and antioxidant activity, and showed fewer changes in color and agglomeration at the various RH levels. It was evident that the cracked appearance of APP samples was related to the higher degradation rate of the total phenols and higher antioxidant activity, especially at RH levels above 54%, during storage. FT-IR spectroscopy showed the chemical changes in APP caused by the carrier agents and RH. The results of the present study indicate that RD improved the functionality and storage stability of APP compared to MD; RD could be used as a potential carrier agent.