Abstract:To realize the high-value utilization of Rosa roxburghii juice processing by-products，a coupled technology of compound microbial fermentation and enzymatic hydrolysis was adopted to prepare bioactive peptides from these by-product，and a novel Rosa roxburghii polypeptide oral liquid was further developed. In this study，single-factor and orthogonal experiments were performed to optimize the key parameters of fermentation，protein extraction，enzymatic hydrolysis，and oral liquid formulation. The results indicated that the optimal fermentation conditions were established using a four-strain compound probiotic system （Lacticaseibacillus rhamnosus，Lactobacillus acidophilus，Bifidobacterium adolescentis，and Lactiplantibacillus plantarum with an equal volume ratio of 1∶1∶1∶1，a fermentation temperature of36 ℃，and a fermentation duration of20d. After fermentation，the crude protein content of Rosa roxburghii juice processing by-product increased from 10.61 g/100 g to 13.54 g/100 g，representing a 27.6% elevation，while the contents of anti-nutritional factors including total sugar and tannin were markedly reduced. Protein isolates were extracted from the by-products via the alkali solution and acid precipitation method with ultrasonic assisted under the conditions of pH10，51 ℃，and 49 min of ultrasonic treatment，achieving a protein extraction rate of 17.35%. The optimal enzymatic hydrolysis conditions were as follows：bromelain to neutral protease=1∶1（volume ratio），hydrolysis temperature of 55 ℃，hydrolysis pH value of 7.5，and hydrolysis time of 1.0 h. Under these optimal conditions，the peptide yield reached 29.45%，which was 48.06% higher than that of the single bromelain hydrolysis group. The optimal formulation of the polypeptide oral liquid was determined as 10% arabinose，0.10% mogroside，5% Rosa roxburghii polypeptide，and 0.10% carboxymethylcellulose sodium （CMC-Na） as the stabilizer. The finished oral liquid prepared with this optimal formula achieved a sensory evaluation score of 85.2 and a centrifugal precipitation rate of3.92%.