| The freeze-thaw solid-liquid separation method can shorten the drying time of potato granules and save the energy consumption.As the only by-product,potato juice separated by centrifugation is rich in nutrients,which is a kind of beverage and food resources with strong processing and utilization potential.However,the flavor acceptance of the separated juice is not high,which greatly limits the development and transformation of related products.In this paper,the main nutrients of the juice of six different potato varieties were analyzed and compared,and the juice was treated by pectinase pre hydrolysis,α-amylase and glucoamylase simultaneous hydrolysis.The flavor changes of the juice before and after enzymolysis were analyzed by sensory quantitative description combined with electronic nose.The composition and content of volatile flavor compounds in the juice before and after enzymolysis were analyzed by GC-MS.The amino acid composition and content of the juice were compared by amino acid analyzer,and the mechanism of Maillard reaction intensity and flavor contribution was discussed.The effect of enzymatic treatment on the stability of potato juice emulsion was investigated.Taking the stability of beverage as the index,single factor and orthogonal test were used to optimize the fermentation conditions.The main results are as follows:(1)There were significant differences in juice yield,reducing sugar,starch,pectin,soluble protein and mineral elements in different varieties of potato.Among them,the Black King Kong potato has the highest juice yield(325.0 m L/kg),the Favorita potato reducing sugar and starch content(2.75 mg/m L and 9.9 mg/m L respectively),the highest pectin content the No.7 Long shu potato(21.16 g/kg),soluble protein content(4.42 mg/m L)and the highest Cu,Fe,Zn and K content(8.02mg/L,27.81 mg/L,3.89 mg/L and 1103.47 mg/L respectively),the highest Ca content of the No.7 Long shu potato(25.47 mg/L),and the highest Mg content of the Favorita potato(4.43 mg/L).(2)The physicochemical and flavor characteristics of potato juice were changed by the treatment of α-high temperature amylase and glucoamylase.After enzymolysis,the a and b values of color difference increased,the content of soluble solids and light transmittance increased,and the viscosity decreased.Sensory evaluation results showed that α-amylase combined with glucoamylase treatment weakened the fishy value of potato juice,improved the sensory flavor acceptance,and the No.9 Qing shu potato enzyme hydrolysate had the lowest fishy value.The results of electronic nose analysis showed that the flavor differences of different varieties of potato juice were obvious,and the flavor similarity of the juice after enzymatic hydrolysis was improved.The analysis of volatile flavor compounds in the juice showed that enzymolysis reduced the content of 1-octene-3-ol,which was the key fishy substance in the juice of potato,and generated aldehyde,ketone,ester,pyrazine and other flavor compounds,among which phenylethanol,geranyl acetone,ester,pyrazine and thiazole were the key flavor modifying components.(3)The analysis of the intensity of Maillard reaction in the process of enzymatic hydrolysis showed that the intermediate products of Maillard reaction accumulated gradually,the concentration increased,and the juice browning was obvious,among which the No.9 Qing shu potato was the most obvious and Maillard reaction was the strongest.The composition and content of total amino acids and free amino acids in potato juice before and after enzymolysis were compared.It was found that the contents of total amino acids and free amino acids in potato juice after enzymolysis were significantly reduced,among which the contents of aspartic acid,glycine,alanine,phenylalanine and lysine were the most significantly decreased.Through the correlation analysis of the main flavor substances and free amino acids in the enzymatic hydrolysis of the juice processed with potato powder,it can be obtained that alanine,arginine,methionine and lysine are the main amino acids involved in the accompanying maillard reaction in the enzymatic hydrolysis process,which have important contributions to the improvement of the flavor of the juice processed with potato powder.(4)The stability analysis of the emulsion prepared from different varieties of potato juice showed that the centrifugal sedimentation rate was the lowest and the stability was the best,followed by the No.9 Qing shu potato and Black King Kong.The results of correlation analysis show that the decrease of starch content is an important factor affecting the stability of the emulsion.The optimum fermentation conditions for the production of potato juice lactobacillus beverage were as follows:0.8% trisodium citrate,0.5% sucrose,2% skimmed milk powder,7 hours fermentation time and 1% lactobacillus. |
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