Optimization of Lactic Acid Bacteria Fermentation Process and Volatile Component Analysis of Suli Pear Juice

Taking Jinding Xiehua Suli pear from Ningling County as the main raw material, lactic acid bacteria suitable for fermentation of pear juice were screened. The fermentation technology of Suli pear juice with lactic acid bacteria was optimized by orthogonal test based on single-factor experiments and the volatile component of the Suli pear juice with lactic acid bacteria after optimization were analyzed dynamically. The results showed that the best fermentation conditions were as follows: Rhamnose Lactobacillus:Lactobacillus acidophilus:Bifidum lactobacillus lactis=1:1:1 (V/V), the initial pH was 4.5, the amount of lactic acid bacteria addition was 4%, the amount of sugar addition was 10%, and the fermentation time was 50 h. Under this condition, the V_C content was 14.17 mg/100 mL, the total acid content was 7.66 g/L, the total phenol content was 3.68 mg/mL, the total flavonoids content was 6.25 mg/mL, the DPPH free radical scavenging rate was 90.05%, and the sensory score was 80.60. The volatile components of Suli pear juice after 0, 30, 40 and 50 h fermentation were analyzed by the gas chromatography-mass spectrometry (GC-MS). A total of 55 volatile substances were detected. With the prolongation of fermentation time, the types and contents of volatile substances increased. There were 7 kinds of volatile components in the raw Suli pear juice, the volatile components of pear juice after 30 and 40 h fermentation were 27 kinds, and increased to 46 kinds of volatile components after 50 h fermentation when higher alcohols, higher esters and higher acids were produced in large quantities, which brought lactic acid bacteria the sour and sweet taste and unique flavor of Suli pear juice.