| In this paper,the passion fruit skin as the main raw material,supplemented juice,spray drying and vacuum freeze-dried method to prepare passion fruit peel powder,the use of orthogonal test to optimize the drying agent and drying process parameters.The two-step fermentation method was used to ferment yeast and Lactobacillus composite strains in the passion fruit pulp slurry,and the fermentation process parameters were optimized,and the passiflora pericarp enzyme powder containing active probiotics was prepared by vacuum freeze-drying method.The simulated digestion test and storage test were conducted to explore the biochemical characteristics and storage characteristics of enzyme powders.The specific findings are as follows:(1)The influences of the amount of auxiliary drying agent,spray drying air inlet temperature and feed flow rate on the rate of powder drying,moisture content,etc.of spray-dried peel were studied.The proportion of auxiliary drying agent was determined by single-factor test and orthogonal test(The amount of auxiliary drying agent was calculated as the solid content of passion fruit pulp and spray drying process parameters.The preferred parameters were: soluble starch content 90.0%,CMC additive content 6.0%,inlet air temperature 170°C,feed flow rate 600 mL/ h.The obtained powdered fly-dried powder had a powder collection rate of 34.7%,a moisture content of 3.5%,a solubility of 82.17%,and a dissolution time of 4.4 min.The amount of compounding drying aids was studied for the moisture content and solubility of the vacuum freeze-dried peel powder.Influence,single-factor test and orthogonal test to determine the amount of compound auxiliary drying agent,the preferred parameters are 50.0% malt dextrin,6.0% CMC addition amount,9.0%addition of β-cyclodextrin,obtained vacuum freezing The moisture content of dried peel powder was 4.2%,the solubility was 85.6%,and the dissolution time was 3.8 minutes.(2)Using the coefficient of variation method to compare the difference in the bulk density,hygroscopicity,powder fluidity and other indicators of the two peel powders obtained by the above-mentioned process spray drying and vacuum freeze-drying conditions,and the overall score size,indicating that different drying The fruit peel powder prepared by themethod has advantages and disadvantages.The peel powder prepared by the spray drying method is superior to freeze-drying in freezing density,hygroscopicity,and rehydration in the bulk density,but the fruit powder prepared in the vacuum freeze-drying method is in the powder.The liquidity,color,and sensory scores are superior to the former,and have better protection effect on live bacteria.Therefore,different drying methods can be selected for powders with different needs.(3)The two-step fermentation process of yeast and lactic acid bacteria in the passion fruit pulp slurry was studied.Firstly,using the number of viable yeast cells and ethanol production as indexes,the optimized technological parameters of yeast fermentation by the single factor and orthogonal test were: yeast inoculum 1.5%,fermentation temperature29°C,fermentation time 16.0h Secondly,the single factor experiment was used to determine the technological parameters of Lactobacillus complexus fermented pulp.The inoculation volume was 2.0%,the fermentation temperature was 39°C,and the fermentation time was 24.0 hours.Finally,the Lactobacillus sp.After fermentation and fermentation,changes in the acid content,viable count,and total phenol content of the fermentation broth,the process parameters for the two-step fermentation of passion fruit pulp were determined as follows: total fermentation time 40.0 h,initial inoculation of yeast After fermentation for 16.0 h at 29° C.,2.5% of Lactobacillus paracasei(Lactobacillus casei: Lactobacillus plantarum=1:1)was added at 1.5% for 24.0 h at 39° C.to obtain a Passion fruit peel fermentation broth.The number of live Lactobacillus species was 8.9lgcfu/mL,the total phenol content was 24.0 μg/mL,and the total acid content was 4.4mg/mL.The two-step fermentation method not only avoided the nutrient competition between different strains of the mixed bacteria fermentation and led to difficult control of the fermentation process,but also exerted the advantages of producing aromas by the yeasts,inhibiting the production of ethanol,increasing the acidity of the bacteria and lactic acid bacteria,and retaining the polyphenol substances.(4)Passion fruit enzyme powder was prepared by vacuum freeze-drying method.The difference of physicochemical characteristics of freeze-dried enzyme powder prepared by adding different lyoprotectants was compared.The enzyme added with freeze-dried protective agent was slightly yellowish,and the powder was more delicate and uniform.The combination of trehalose and skim milk powder had a better protection effect.Compared with the blank group without the freeze-dried protective agent,the survival rate of probiotics increased.34.9%,and trehalose can also be used as a prebiotic to improve the probiotic properties of probiotic powder.It was determined that the conventional indicatorssuch as sodium chloride and ethanol in the two-step fermentation lyophilized enzyme powder meet the requirements of the standard.In terms of characteristics,the total phenol content is 16 μg/mL,and the total acid content is 0.66 mg/mL.The number is 8.08 lgcfu/g,which is higher than the TCBFIA 08001-2016 Guidelines for Classification of Enzyme Product ≥ Standards,and the fruit of passion fruit is rich;(5)The biochemical characteristics and storage characteristics of Passiflora enzyme powder were studied.The test showed that the probiotics in the enzyme powder were well tolerated in simulated human digestive tests.The number of viable cells after digestion for simulated gastric juice after 3.0 hours was 7.0 lgcfu/g,and the survival rate was 77.0%;in simulated intestinal fluid 3.0 The number of viable cells after h was 8.0 lgcfu/g,and the survival rate was also 88.0%;the survival rate was lower than 6.0 lgcfu/g in low-concentration bile salt mimic bile,while the simulated bile was at high concentration of bile salt After 3.0 hours,the live probiotic bacteria was 5.7 lgcfu/g,indicating that the enzyme powders prepared by the fermentation and freeze-drying methods studied here have good biochemical characteristics.At different storage temperatures,the survival rate of probiotics in the enzyme powder was different.The rate of decline at room temperature was faster than the rate of decline at low temperatures.After 60 days of monitoring,the probiotic survival rate of enzyme powder at room temperature was 70.0%.The survival rate at low temperatures can be maintained at more than 80.0%.Refrigerated or frozen storage is beneficial to maintain the quality of enzyme powder,indicating that the enzyme powder prepared by the fermentation and freeze-drying method studied here has good biochemical characteristics. |
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