In Situ Stability of Anthocyanins in Lycium ruthenicum Murray.

In this research, the effects of drying method, storage temperature, and color protector glucose on anthocyanin preservation in the Lycium ruthenicum Murr. fruit were studied. Compared with hot-air drying, vacuum freeze-drying preserved about 5.8-fold more anthocyanins. The half-life of anthocyanins in the freeze-dried fruit samples with glucose was 3.6 days, 1.8 days, and 1.7 days at 4 °C, 20 °C, and 37 °C, respectively. On the other hand, the half-life values without glucose addition were 2.2 days, 2.3 days, and 2.1 days at each temperature, respectively, indicating that glucose protected anthocyanins at low temperature. The composition and contents of anthocyanins and anthocyanidins in the freeze-dried Lycium ruthenicum Murr., stored for 20 days, were investigated with a HPLC-MS/MS setup. It was found that most anthocyanidins in Lycium ruthenicum Murr. are linked with coumaroyl glucose to form anthocyanins, while glycosylated and acetyl-glycosylated anthocyanins were also detected. Five anthocyanidins were detected: delphinidin, cyanidin, petunidin, malvidin, and peonidin, and delphinidin accounts for about half of the total amount of anthocyanidins. It is much more economic to conserve anthocyanins in situ with freeze-drying methods and to store the fruits at low temperatures with glucose.