| Probiotic beverages have been very popular in recent years.Fermented dairy products are the most common,but they are not conducive to the health of people with chronic diseases such as hypertension and hyperlipidemia due to their high fat and high cholesterol.As a non-dairy probiotic beverage,fermented fruit and vegetable juice has received widespread attention.Lactobacillus plantarum is widely used in the field of fruit and vegetable fermentation because of its good vigor and strong acid resistance in fruits and vegetables.Its fermented products have the functions of regulating the intestinal flora and enhancing immunity.As one of the most common vegetables in life,tomato has the characteristics of high nutritional value and unique flavor.my country is the world’s largest tomato producer.The development of a fermented tomato juice product is of great significance for improving the flavor and quality of tomatoes and deepening the processing and utilization of tomatoes.In this paper,the "Provence" tomato in Weifang,Shandong Province is used as the research object,and Lactobacillus plantarum BNCC337796 is used as the fermentation strain to study the optimal fermentation process parameters of fermented tomato juice,the types and proportions of compound stabilizers,and the concentration of color preservatives.On this basis,the changes in nutritional quality and antioxidant properties of tomato juice before and after fermentation and the changes in flavor substances before and after fermentation were studied.The main findings are as follows:(1)During the fermentation process,the initial bacterial inoculum,fermentation temperature and fermentation time will all affect the quality of fermented tomato juice.Through single-factor experiments,it is determined that the fermentation temperature is34～38 ℃,the inoculation amount is 1～3%,and the fermentation time is 24～32 h as a good level.Based on this,the Box-Behnken combination design is used to optimize the fermentation process of tomato juice.Response surface analysis and optimization prediction obtained the best process parameters as fermentation temperature 37 ℃,strain inoculation amount 2%,and fermentation time 30 h.At this time,the sensory score of fermented tomato juice was 87.69 points.Single factor and orthogonal experiment determined the type and concentration of compound stabilizer as carrageenan addition amount 0.15%,xanthan gum addition amount 0.15%,CMC-Na addition amount 0.2%;the fermented tomato juice was affected by the addition amount of different ascorbic acid For the effect of color,add 0.15% ascorbic acid as a color protectant.(2)The changes in nutrients,active substances,and antioxidant properties of tomato juice before and after fermentation were studied.During the fermentation process,the p H of tomato juice decreased,and the number of viable bacteria increased first,and then stabilized after 30 h,at 30 h and 48 h The sugar-acid ratio is 11.4 and 6.13 respectively.Excessive fermentation will affect the taste of the product.The viable cell count and total acid of fermented tomato juice changed significantly after being stored at room temperature for 21 days.When stored at 4 ℃,the quality could be guaranteed within 21 days.After fresh tomato juice is made into tomato juice and subjected to high temperature sterilization,the content of lycopene and β-carotene is affected by processing,sterilization and fermentation,and the content decreases.The content of total phenols and total flavonoids increased from 1.26 g/L and 1.07 g/L to 2.81 g/L and 1.35 g/L,respectively,and the content of Vc decreased from 0.75 g/L to 0.35 g/L.Fermentation consumes sucrose,fructose and glucose,of which glucose consumes the most.The most important organic acid in tomato juice before fermentation is malic acid,followed by citric acid.At the end of fermentation,the content of malic acid and citric acid is significantly reduced,of which citric acid The content of pyruvate and pyruvate increased first and then decreased,and lactic acid increased from 0 mg/L at the start of fermentation to 3697.12 mg/L.After juicing and sterilizing fresh tomatoes,the ABTS free radical scavenging ability and DPPH free radical scavenging ability decreased from 52.34% and 84.38% to 27.62% and 47.69%,respectively,but significantly increased to 34.77% and 77.06% after fermentation.The scavenging ability of superoxide free radicals is the opposite,which increases from 51.18% to 86.39%after juice sterilization,and then drops to 45.67% after fermentation.The scavenging ability of hydroxyl free radicals does not change significantly during the whole process.Fermentation enhances the antioxidant capacity of tomato juice,reduces the sugar content,and generates a large amount of lactic acid,but at the same time some nutrients are also lost.(3)The changes of flavor quality before and after fermentation of tomato juice were studied,and the changes of flavor quality before and after fermentation were analyzed using GC-MS and electronic sensory technology.The tomato juice fermented by Lactobacillus plantarum added 11 new volatile flavor substances and Most of the added volatile flavor substances have good flavor attributes;the electronic nose and electronic tongue test found that the flavor changes significantly before and after fermentation,and the flavor changes little after 21 d storage at 4 ℃.Through the automatic amino acid analyzer,the changes of free amino acids before and after fermentation were studied,and16 free amino acids were preliminarily identified,of which the content of 12 kinds of amino acids increased.The total amount of free amino acids before fermentation was520.94 mg/100 m L,which increased to 569.01 after fermentation.mg/100 m L,the content of sweet amino acids and aromatic amino acids increased.The content of essential amino acids in tomato juice after fermentation is also higher than that in unfermented tomato juice.QDA sensory analysis was used to evaluate the flavor quality at different stages of the fermentation process,and it was found that fermentation at 30 hours of fermentation made the tomato flavor of tomato juice more mellow and mellow.At this time,it has the highest sensory score for floral and fruity aromas.At this time,fermented tomato juice has the most Good flavor.On the whole,after fermentation,the four senses of sweetness,grassy taste,steaming taste and freshness decreased,while the five senses of sourness,tomato taste,fermented taste,floral and fruity aroma increased,and the astringency changed little,so It can be concluded that fermentation will bring better sensory attributes.After fermentation,it was stored at 4 °C for 21 days and then tested for sensory,hygienic and microbiological indicators in accordance with my country’s light industry industry standard QB/T5356-2018.The final product is qualified and meets the edible safety requirements of fermented fruit and vegetable juice. |
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