Dynamic Flavor Changes of Rosa roxburghii Juice during Frozen Storage

To evaluate the effects of long-term frozen storage on the flavor quality of Rosa roxburghii juice, sensory evaluation, electronic nose, and headspace solid phase microextraction gas chromatography-mass spectrometry (HS-SPME-GC-MS) were utilized to analyze the dynamic changes of sensory and aroma characteristics of Rosa roxburghii juice at −20 ℃ for various storage times(0, 2, 4, 6, 8 M). The results revealed the identification of a total of 127 volatile compounds, the majority of which were alcohols (31), hydrocarbons (34), and esters (24). The contents of 1-hexanol, (Z)-3-hexen-1-ol, 1-octene-3-ol, linalool, 1-octanol, α-copaene, ethyl hexanoate, ethyl octanoate, and methyl eugenol decreased over time, indicating that the fragrance of green grass, fruit, and flowers may diminish over time. The concentration of nonanal increased substantially (P<0.05) from 3.65 μg/100 g before storage to 10.87 μg/100 g after storage, resulting in an accumulation of a disagreeable odor. The aroma of Rosa roxburghii juice was more prominent before storage, while the aroma diminished or disappeared as storage progressed, particularly the pine and irritating odors. Fresh Rosa roxburghii juice contains 12 essential aroma components with a relative odor activity value (ROAV) greater than 1. The concentration of thoes essential aroma components decreased about 60%~90% after storage. Based on the partial least squares discriminant (PLS-DA) and variable importance in the projection (VIP), it was the maximum rate of change of volatile compounds of Rosa roxburghii juice after 8 months of storage. Ten volatile compounds were screened out as important markers to distinguish Rosa roxburghii juice under specific frozen storage conditions for different times. The results of the present study could serve as a basis for monitoring the quality and optimizing the storage conditions of frozen Rosa roxburghii juice.