Quality and Processing Characteristics of a Mixed Freeze-Dried Powder of Blueberry and Blue Honeysuckle Berries during Storage

The changes in the glass transition temperature (T_g), color, antioxidant components and antioxidant properties of a mixed freeze-dried powder of blueberry and blue honeysuckle berries were studied during at different temperatures (4, 25 and 37 ℃) and relative humidities (H_r, 43%, 75% and 95%) for up to 12 weeks. The behavior characteristics of the powder during storage were measured and analyzed as well. The results showed that compared with the other storage conditions, the basic physicochemical properties were better after 12 weeks of storage at 25 ℃ and 43% H_r (the T_g decreased by 4.62 ℃) or 4 ℃ and 75% H_r (the moisture content increased by 4.2%). In terms of the effect of antioxidant substance content and antioxidant capacity, with the prolongation of storage time, the contents of total phenols and total flavonoids and antioxidant capacity of different treatment groups decreased. The individual and total contents of six anthocyanins were least reduced at 25 ℃ and 43% H_r (the total anthocyanin content decreased by 23.92%), and the retention rate of total anthocyanins was higher at 4 ℃ and 75% H_r. The fluidity of the powder was maintained well after 12 weeks of storage at 25 ℃ and 43% H_r or 4 ℃ and 75% H_r. Therefore, both conditions were favorable for powder storage.