Study On The Preparation And Properties Of Celery Leaf Superfine Powder

China is a major celery(Apium graveolens L.)growing and consuming country,with celery leaves accounting for about 5-10% of the total weight of celery,and the nutritional and health value of celery leaves is much higher than that of celery stems.However,due to their pungent aroma and bitter and fibrous taste,celery leaves are usually discarded without being consumed during daily consumption and food processing,resulting in a great waste of celery leaf resources.In this project,in order to make full use of celery leaf resources,the drying method of celery leaves was firstly preferred,and then celery leaf superfine powder was prepared,its physicochemical,functional and in vivo metabolic properties were studied,and finally celery leaf superfine powder steamed bread were developed,with a view to providing technical support and theoretical support for the comprehensive use of celery leaf resources.The main results are as follows.(1)The drying methods of hot air drying(HA;50 ℃ for 4 h),intermittent hot air drying A(IHA-A;40 ℃ for 1 h,50 ℃ for 2 h,40 ℃ for 1 h),intermittent hot air drying B(IHA-B;35 ℃ for 2 h,45 ℃ for 3 h,35 ℃ for 3 h),vacuum hot air drying(VHA;50 ℃for 8 h)and vacuum freeze drying(VF;-60 ℃ for 8 h)were screened to evaluate their effects on the drying quality of celery.The results showed that the VF-treated samples best retained the morphology and quality of celery leaves,but the low temperature was not conducive to the production of volatile components.HA had the highest drying efficiency,but the high temperature led to browning of the leaves and a reduction in active ingredients.The drying temperature of VHA(50 ℃)was consistent with HA and better retained the phenolic and flavonoid compounds in the samples by avoiding oxidation reactions.However,the high temperature also led to an increase in bitter amino acids and the degradation and escape of volatile components.On the basis of HA,IHA preserved the nutritional and volatile components of the samples by reducing the drying temperature.The IHA-B treated samples had low cell fragmentation,high rehydration rate and maintained high levels of ascorbic acid,chlorophyll,antioxidant activity,total phenols and total flavonoids.In addition,it has a high content of volatile components and the highest content of sweet amino acids.Considering the production cost and product quality,IHA is a promising technology for drying celery leaves.(2)The dried celery leaves were subjected to superfine grinding(150 mesh and300 mesh)to investigate the effects of superfine grinding on the physicochemical properties(particle size distribution,colour parameters,hydration properties,fillability,flowability and microstructure)and functional properties(antioxidant activity and total phenol and flavonoid solubility)of the celery leaf powder.It was found that the higher the degree of grinding,the smaller the particle size of celery leaf powder and the brighter the color of the powder,which was also accompanied by a significant decrease in both water-holding capacity and swelling degree presented.The smaller the particle size of the superfine powder compared with the coarse powder,the higher the antioxidant activity and the dissolution of the main active substances.The total phenol and total flavonoid contents of the IHA-B treated samples increased from 12.13 mg/g and 122.39 mg/g to 13.97 mg/g and 129.16 mg/g,respectively.Therefore,the superfine grinding treatment improved the nutritional and functional values of celery leaves.(3)The metabolic pattern of the main flavonoids(quercetin,luteolin and apigenin)in the superfine powder of celery leaves in mouse plasma was studied by gavage.The results showed that 1 h after gavage,the superfine powders(150 and 300 mesh)had higher detectable concentrations of quercetin,lignan and apigenin in mouse serum than the coarsely ground powders.300 mesh superfine powders showed 3-4 h earlier detection peaks for quercetin and 4 h earlier for luteolin than the coarser powders.This indicates that the superfine powder was able to improve the metabolic efficiency of the dried celery leaves in mice.(4)The total phenols in celery leaves were extracted by ultrasonic-microwave combined extraction method,and the extraction process was optimized by the response surface method.The results showed that the extraction of total phenols from coarse ground celery leaves was influenced by ultrasonic time > material-liquid ratio >ultrasonic power.The optimized extraction conditions of total phenols were 6.84 min of ultrasonic time,580.83 W of ultrasonic power,and 1:72.75 g/m L of material-liquid ratio.Under these conditions,the total phenol extraction rate of coarse ground celery leaf powder was 16.15 mg/g.Compared with the total phenol content of celery leaf superfine powder,the experiment improved the extraction of total phenol from celery leaf in terms of optimization of extraction process,and provided a technical reference for the extraction and research development of total phenol.(5)Celery leaf superfine powder was added to steamed bread to study its effect on the quality of the bread.It was found that the smaller the particle size of the celery leaf powder,the lower the tenderness of the dough,which affected the colour of the bread and reduced the specific volume of the bread while the hardness,chewiness and hardening rate of the bread increased.The celery leaf steamed bread with 300 mesh superfine powder had significantly higher L* and b* values(P<0.05),a 7.73% decrease in specific volume and a 7.07% increase in hardness compared to the coarsely ground powder.The celery leaf powder steamed bread with the addition of 150 mesh superfine powder had a brighter colour and moderate hardness(5544.25 g)than the coarsely ground powder,with the fresh aroma of celery and the sweetness of steamed bread.In actual commercial and industrial processes,the addition of 150 mesh celery leaf powder can be considered.