Study On Watermelon Juice Fermented By Two Kinds Of Lactobacillus

This paper discussed the changes of physical and chemical properties of the Black Beauty and Kylin watermelon juice fermented by Lactobacillus plantarum and Lactobacillus acidophilus during the fermentation, such as viable count, p H value, total acid, total sugar, reducing sugar and amion nitrogen. Moreover, with the static-headspace solid phase micro extraction(HS-SPME) method, the volatile flavor compounds of Black Beauty and Kylin watermelon raw juice, fermented juice for 10 hour, 24 hour and 48 hour were measured by gas chromatography-mass spectrometry(GC-MS). The results were as follows:(1) The growth and acid-producing ability of Lactobacillus acidophilus was better than Lactobacillus plantarum in whether fermented Heimeiren or Kylin watermelon juice, viable count of Lactobacillus acidophilus was about 109 cfu/m L. With the progress of fermentation, the content of reducing sugar and total sugar decreased fast firstly and then slowly reduced. However, the content of amino nitrogen was fluctuated and Lactobacillus plantarum have a higher content than Lactobacillus acidophilus. Adding carbon and nitrogen can promote two kinds of Lactobacillus to utilize watermelon juice during the fermentation, and the final viable count, acid-producing ability and reducing sugar utilization ratio increased, the stable period of Lactobacillus was extended effectively. But the flavor sensory of fermented juice was worse than raw juice.(2) For Heimeiren watermelon fermentation juice, there were a total of 124 kinds of volatile flavor compounds were isolated and identified, which consisted of 29 alcohols, 19 aldehydes, 13 ketones, 22 acids, 11 hydrocarbons, 17 esters and 13 other flavor compounds. Whether in watermelon raw juice or fermented juice, the alcohols were main volatile flavor compounds and their relative content up to 51%.(3) For Kylin watermelon fermentation juice, there were a total of 187 kinds of volatile flavor compounds were isolated and identified, which consisted of 36 alcohols, 27 aldehydes, 19 ketones, 22 acids, 28 hydrocarbons, 27 esters and 28 other flavor compounds.(E)-2-nonenal was the main volatile flavor compounds in Kylin watermelon raw juice, and cis-3-nonene-1-ol was major contributor of fermented juice’s aroma.(4) The changes of volatile flavor compounds between Heimeiren and Kylin watermelon juice fermented by the same Lactobacillus were analyzed. The results showed that Heimeiren and Kylin watermelon juice fermented by the same Lactobacillus had some same volatile flavor compounds, but the changes of relative content were different.(5) Sensory evaluation was conducted by professional panel. According to the results of sensory evaluation, the best fermentation time should be controlled in 24 h.