| Millet is one of the common grain of foodstuff in north China area.But the utilizable efficiency of human with the millet is not satisfactory because of the unbalanced proportion of millet amino acid.So the purpose of our study is to improve the utilization efficiency of millet protein,promote the innovation and development of mixed grain beverage industry.In this study,we selected high nutrient millet varieties and screened the complementary formula combination of grain protein using different varieties of millet and other grains such as quinoa as materials.And then the liquefaction,saccharification,sensory evaluation and system stability of millet-quinoa mixed grain thick pulp were explored and optimized.The results were as follows:1.It was found that the 'Qinzhouhuang' contained 12.20 g/100 g protein,5.39%fat and 3.15 g/100 g reducing sugar,which was higher than other varieties through measuring main nutritional components of three kinds of millet.Besides,gas chromatography analysis was adopted to find that'Qinzhouhuang' contained 73.81%total essential fatty acid,in which the contents of linoleic acid and linolenic acid were higher than other varieties.2.Using CS,AAS and EAAI as amino acids assessment indexes,we screened the best formula by determining amino acids contents.The results showed that the numerical values of amino acid assessment were 92.31,98.02 and 84.32 when the mass ratio of millet flour and quinoa flour was 1:2,which was the most ideal protein amino acids pattern in all experiment groups.Comparing with uncompounded millet,the numerical values of CS,AAS and EAAI increased by 175.14%,175.26%and 17.68%respectively,which improved significantly.3.Through single factor experiments and orthogonal test design,the best conditions of liguefaction and saccharificaiton were confirmed using DE as evaluation index.Results showed that the best conditions of liquefaction were 6 U/g for a-amylase,40 min for reaction time,70? for temperature and 7.0 for pH.The optimum conditions of saccharification were 120 U/g for ?-amylase,65? for enzymolysis temperature,60 min for time,6.5 for pH.Under above conditions,the DE value can reach to 45.46 indicating that the theoretical yield of maltose in millet-quinoa mixed grain thick pulp was as high as 90%,and soluble solid content of grain thick pulp was improved.4.The method of fuzzy mathematics and orthogonal test was adopted to evaluate the grain thick pulp's sensory quality.The result showed that the optimum seasoning adjuncts formula were 0.04%of citric acid,2%of sucrose and 1.5%of maltodextrin.Under this formula,the sensory evaluation score of the thick pulp was 83.73 and the quality was between superior and good grade level.The grain thick pulp had softer aroma,strong corn flavour,mellow taste,bright colors and better uniformity.5.Using centrifugal sedimentation rate as index,response surface methodology was adopted to explore the stability of millet-quinoa mixed grain thick pulp.The results indicated that it was beneficial to reduce centrifugal sedimentation rate of the thick pulp when mixing ratios of sucrose ester and monoglyceride was 1:1.The synergistic reaction of xanthan gum and sodium alginate had significant influence on decreasing centrifugal sedimentation rate.The optimized formula were 0.05%of glycerin monostearate,0.05%of sucrose ester of fatty acid,0.064%of xanthan gum,0.008%of sodium carboxymethyl cellulose and 0.036%of sodium alginate.Under this formula,the centrifugal sedimentation rate was 11.56%,which reduced by 45.80%comparing with before adding,and stability improved significantly. |
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