| Liquid infant formula milk is a kind of liquid dairy based infant formula.Compared with other infant formulas, it is safety,convenient and comprehensively nutritional.On the domestic market at present, main dairy based infant formulas are infant formula milk powder, and quite a number of products’cow milk proteins are not modified and processed, so part of infants can develop dyspepsia and allergy symptoms. A very small amount of liquid infant formulas on the domestic market are mainly designed for older infants.So, in the projects,we utilize enzymic hydrolysis method to process cow milk proteins and combination technology to put soybean protein and other materials to products for developing a kind of new type of liquid infant formula milk which is hypoallergenic. quickly digested, full of immune modulatory effect, nutritive closely to breast milk and stable. Main conclusions were drawn:Skimmed milk proteins were desensitized by sigle enzyme and double enzyme, the result showed that during the process of sigle enzyme hydrolysis, when the degree of hydrolysis was 13-14%, the antigenicity reduction of as-casein,α-lactalbumin,p-lactoglobulin in hydrolysates made by flavor protease, trypsin or alcalase was the maximum, they were 90.13%,91.00%, 50.08%; 79.00%,85.11%,11.02%; 96.24%,99.04%,58.45% respectively,bitter value was all lower. The color and status was best.During the process of double enzyme hydrolysis, when the degree of hydrolysis was 13-14%, the desensitization effect made by any two enzymes of flavor protease, trypsin or alcalase in two stage hydrolysis was better than which made by any one enzyme of flavor protease, trypsin or alcalase in one stage hydrolysis and any two mixed enzymes in one stage hydrolysis.When 0.3% alcalase was used to hydrolyze skimmed milk for 30min, then flavor protease was used to hydrolyze skimmed milk for 10min,the antigenicit-y reduction of as-casein.α-lactalbumin,β-lactoglobulin in hydrolysate was the maximum, they were 98.83%.98.17%,68.50% respectively.SDS-PAGE and fast protein liquidchromatography were used to analyze the hydrolysate made by 0.3% alcalase and 0.5% flavor protease in two stage hydrolysis, the result showed that the hydrolysate contained 94.73% peptides whose molecular weights were lower than 6500Da, few peptides whose molecular weights were larger than 12.3KDa, compared with hydrolysate made by one enzyme in one stage, more peptides whose moleculaer were lower than 1040Da,which occupied 19.96%.Skimmed milk hydrolysate made by 0.3% acalase and 0.5% flavor protease in two stage hydrolysis and other materials were mixed to prepare liquid infant formula milk by compound technolyge.In the process of research and development,we refered to food safety standards of the state-standard for infant formula.Excel and matlab7.0 softeares were used to design the best informula of liquid infant informula milk,the informula was as follws,31.35g milk hydrolysate,7.26g demineralized whey powder.0.104g soy protein isolate,2.32g mixed oil (20% soy oil,50% palm oil.17% sunflower oil,17% perilla seed oil,8% camellia oil),0.8g mixture of oilgofructose and oligogalactose(1:8),5mg taurine,2.8mg nucleotide,1.5mg L-carnitine,30mgDHA,40mg AA.0.05g vitamin compounds,0.3g composite mineral,0.07g sucrose ester of fatty acid,0.06g monoglycerides,0.37g lecithin,0.04g kappa-carrageenan. 0.02g PGA, (the additive proportions of sucrose fatty acid ester, monoglycerides,lecithin, kappaca-rrageenan, propylene glycol alginate were determined in the subsequent experiments ), water was added to 100ml. The fatty acid model, amimo acid model and micronutrient levels of this formula can meet food safety standards of the state-standard for infant formula, and close to breast milk.The additive proportions of sucrose fatty acid ester, monoglycerides, lecithin, kappaca-rrageenan, propylene glycol alginate were determined by single factor experiment.The results showed the optimal additive proportions were 0.07%.0.06%,0.37%,0.04%,0.02% respectively.The results were obtained by measuring emulsifying activity index, centrifugal sedimentation rate, viscosity, average particle size, surface tension, zeta-potential measureme-ent and observing with transmission electron microscope.On this basis, four factors and four levels experiment was designed by the response surface experimental design to further optimize the emulsifying activity index, the centrifugal sedimentation rate, the viscosity, the average particle size, the surface tension, the zeta-potential measurement respectively. The best additive proportions of fatty acid ester, monoglycerides, lectithin, kappa-carrageenan, propylene glycol alginate were determined by optimization above.The result showed when the best additive proportions of mixture of monoglycerides and sucrose fatty acid ester, lecithin, kappa-carrageenan, propylene glycol alginate were 0.14%,0.38%,0.04%,0.02% respectively, the emulsifying activity index was max, emulsifying activity index was 0.97. When the best additive proportions of them were 0.13%,0.37%,0.05%,0.02% respectively, the minimal centrifugal sedimentation rate was 1.69%. When the best additive proportions of them were 0.14%,0.37%,0.04%,0.02% respectively, max viscosity was 2.77 mPa·S. When the best additive proportions of mixture of them were 0.15%,0.38%,0.04%,0.03% respectively, the minimal average particle size of was 0.5μm. When the best additive proportions of them were 0.15%,0.37%,0.04%,0.02%, the minimal surface tension was 41.58 mN/m. When the best additive proportions of them were 0.14%,0.37%,0.04%,0.02% respectively, the minimal zeta -potential was-30.41mv. Emulsifying activity index, centrifugal sedimentation rate, viscosity, average particle size, surface tension.zeta-potential were opitimized stimultan-ously,the optimal results showed when the best additive proportions of mixture of monglycer-ides and sucrose fatty acid ester, lecithin, kappa-carrageenan. propylene glycol alginate was 0.14%,0.37%,0.04%,0.02% respectively, they were 0.97.1.70%,0.60μm,2.77 mPa·S,41.68 mN/m,-30.37 mv respectively.Sucrose fatty acid ester, monoglycerides, lecithin,kappa-carra-geenan, propylene glycol alginate were added respectively to final products according to the above additive proportions, which was verified to be fairly stable for the products placed for six months.Fating floating and sediment weren’t found. The stability of liqud infant formula milk was best when the homogeneous pressure and temperature were 25 MPa and 60℃ respectively,the ultra high temperature was used for products.Toxicology evaluation of liquid infant formula milk was carried out.The result of acute toxicity test showed that the rats were fed with LD50>10 g/kg bw of liquid infant formula, no rats died and other abnormalities happened during feeding, which belonged to actually non-toxic. Ames test, mice bone marrow cells micronucleus test and sperm teratogenic test were studied, the result showed each dose group of liquid infant formula milk had no mutagenesis on almonella typhimurium, bone marrow cells and reproductive cells.After ninty days feeding experiment,the body weight, food utilization, routine blood indexes, blood biochemical indexes, main viscera weight had no significant difference compared with the corresponding blank control group (p> 0.05), the main organ pathology inspection was normal.Animal experiments were done to research on digestibility,growth and development effe-ct, immune regulation effect, sensitization of liquid infant formula milk. Protein digestibility developed were higher than which of other sample groups in stomach and intestines of rats. Protein digestion rate developed in intestines of rats could be as high as 94%. Liquid infant formula milk could effectively promote growth and development of body, main organs and bone of rats during gavage for eight weeks. Liquid infant formula milk could increase the liver and thymus index of mices. increase spleen lymphocyte stimulation indices and enchance the delayed-type allergy of mices, increase the antibody cell formation and the level of serum hemolysin of rats, and also increase phagocytic index a, abdominal macrophage phagocytosis rate and NK cell activity of mices. Liquid infant formula milk had certain allergenic, passive skin allergy test showed the blue spot diameter was 5.03 mm, 1gE, LgG1 and histamine content of the rat serum were 550 mu g/ml,55.12 mu g/ml,45.53 ng/ml respectively.But compared with cow milk and two kinds of liquid infant formula milks seld, they reduced significantly, the sensitization of liquid infant formula milk developed reduced significantly.By studying on the change of each indexes of infant formula milk during storage at low temperature and room temperature for 180 days, we monitored the quality of the product. The result showed that the acidity change was little, no significant change in pH, peroxide value, hexanal, amyl aldehyde, malondialdehyde content gradually increased. Storage at 4-6℃ for 180 days, the acidity. pH value,peroxide value, hexanal, amyl aldehyde,malondialdehyde content of products were 17.04° T.6.9,1.88 meq/kg,0.24mg/kg,0.37 mg/kg,8.14 p.g/100g.Stor-age at 24-26℃ for 180 days, the acidity, pH value, peroxide value, hexanal,amyl aldchyde, malondialdehyde content of products were 17.4° T,6.55,2.89 meq/kg,0.36 mg/kg,0.71 mg/kg,15.2μg/100g, therfore. Compared with storage at 24-26℃, the acidity, pH value, peroxide value, hexanal. amyl aldehyde, malondialdehyde content of products increased more slowly.Furfurals detected were mainly HMF and F.Compared with same products commercial-ly available, the product were more stable. Using the principal component analysis to analyse detected 37 kinds of volatile substances, which could be substituted for two principal compon-ents.The main volatile components were aldehydes, ketones, alcohols, acids, furan, furfural, thioether compounds. Compared with storage at 24-26℃, the total volatile matter content of infant formula milk was lower. In the process of storage,total sugar, protein, fat content of infant formula milk reduced gradually, except vitamin B1, vitamin B2, vitamin C content were significantly reduced, vitamin D. vitamin k. vitamin E content declined little, other vitamins and minerals were stable.Staphylococcus aureus,e.coli,salmonella, mononuclear cell hyperpla-sia liszt fungus, aflatoxin B1, aflatoxin M1, coliform group had not been checked out. The total number of bacteria was less than 10 cfu/mL, which met the food safety standards. Stability of infant formula milk decreased gradually in the process of storage,no obvious stratification was found. |
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