Preparation Of Calcium-tolerant Soy Protein And Its Application To Clinical Nutriment

Soy protein is an important plant protein with high nutritional value and excellentfunctional properties. It has high value in use and further development. Calcium is animportant inorganic nutrient needed by our body, which plays an important role on humanhealth. However, if soy protein foods are rich in calcium, it can easily lead to aggregation andformate insoluble aggregates, thus affecting the stability of product and the intake andabsorption of calcium. So soy protein isolate is subject to certain restrictions on theapplication to clinical nutriment which are generally rich in minerals. Phytase and proteasetreatment were mostly used to inhibit protein aggregation, but these methods have somelimitations, so it’s difficult to achieve industrial application.This study aims to prepare calcium-tolerant soy protein and apply it to clinicalnutriment. After analyzing the influencing factors of soy protein aggregation induced bycalcium, we found a new method of preparing calcium-tolerant soy protein by jet cookingtreatment. Structural and functional properties of the obtained protein were analyzed, andinitial explore were made on the mechanism of the new method improving soyprotein tolerance to calcium. The soy protein was used as a substitute to replace the sodiumcaseinate applied to clinical nutriment. The results were showed as follows:(1) Factors affecting calcium-induced aggregation of soy protein were analyzed. It wasfound that the maximum calcium tolerance of SPI was about60mg/100g protein. The7S soyprotein fraction had much higher tolerance than the11S fraction. High pH was good to inhibitthe aggregation. Adding sodium citrate or other chelating agents could protect the protein. Thestudy found that heat treatment could improve the calcium tolerance of soy protein and theeffect would be better with the heat treatment temperature increasing.(2) A new method of protein preparation by the pre-jet cooking (FHTC) was found byanalyzing the effects of jet cooking treatment on soy protein tolerance of calcium. The resultsshowed that: heat treatment could improve the protein tolerance of calcium, and hydrothermaltreatment (120℃and140℃) was more effective than heat treatment (80℃and100℃).Protein with140℃jet cooking treatment had the highest tolerance. We also found that theheat treatment sequence would affect the effect; the pre-jet cooking was superior to thepost-processing. Not only the tolerance of calcium was improved, but the protein yield andrecovery increased by using the pre-jet cooking treatment. The optimized conditions werechoosed as follows: the temperature was140℃, the duration was90s. And the calcium tolerance of the protein was up to100mg/100g protein.(3) The structure and functional properties of soy protein obtained by FHTC werestudied systematically. The results showed that: compared with SPI, sugar content of FHTCsoy protein increased, and the phytate content reduced. The solubity and emulsifying activitywas lower than SPI, but the emulsion stability was greatly improved, and the calciumtolerance of the protein emulsion was enhanced. The results of GPC and SDS-PAGE showedthat the protein had larger of molecular and size, and the surface hydrophobicity index washigher than SPI. The soluble macromolecular aggregates mostly formed by11S proteinfraction through disulfide bonds and hydrophobic interactions.(4) The FHTC soy protein was applied to clinical nutriment replacing the sodiumcaseinate. It was found that of the FHTC soy protein nutrition with1.0%(wt) calcium hadfew precipitations after heat sterilization at121℃for20min. The product was creamy white,and had low viscosity and high stability, which made it have industrial application prospects.