| Soymilk is a kind of traditional plant beverage with high nutritional value in Asia.The desire of healthier life induces the fabrication and design of household soymilk machine.Whole-bean soymilk prepared by household soymilk machine has higher nutrient content,including protein content,soluble cellulose,thiamine,etc.This thesis studied the effect of blanching processing and the use of sugar alcohol on the anti-nutritional factors and the stability of soymilk in order to reduce the energy consumption of preparation of soymilk and improve the nutritional value of whole-bean soymilk.Firstly,we studied the effect of blanching temperature on the anti-nutritional factors and stability of soymilk.The results showed that the trypsin inhibitory activity(TIA)residual rate of soymilk significantly decreased after blanching(p < 0.05).The urease could not be completely inactivated after blanching,but the urease activity was negative after continuing to cook the pulp(600 W,5 min).The result of stability showed that the cooking process can improve the stability of soymilk.The processing method for rapid preparation of whole-bean soymilk was achieved: 50 g soybean was heated at 600 W with 500 m L water,and blanched when the temperature was up to 90? and kept for 30 s.Then it was ground and cooked for 5min at the same heating power.In this way,the activity of anti-nutritional factors of whole-bean soymilk was significantly inhibited compared to traditional soymilk.Its TIA residual rate was only 9.8% and the urease activity was inactivated.The processing time(16 min)was much lower than that of the soymilk machine on the market(40 min).Secondly,we studied the effect of blanching on thermal aggregation of soymilk and the inactivation mechanism of soybean trypsin inhibitor(STI).It was found that blanching changed the thermal aggregation mode of soy protein.There was obvious difference between blanched soymilk and traditional soymilk after ultracentrifugation(156000 g,30 min),including the protein composition in the precipitate and supernatant of soymilk and the interaction force between the subunits.The arrangement of interaction force through which protein of blanched soymilk aggregated into precipitate in order of importance is disulfide bond,hydrophobic interaction and hydrogen bond,while that of the traditional soymilk is disulfide bond,hydrogen bond and hydrophobic interaction.Blanching can promote more STI to aggregate into large particle aggregates.It was suggested that blanching could promote the interaction of some STI with soy storage protein and lost its activity.Some of STI was trapped by aggregates and can remain its activity.In the blanched soymilk,the aggregates encapsulating Bowman-birk inhibitor(BBI)included aggregates that were formed by ?,?' and ? subunit,acid subunits and basic subunits through non-covalent interaction,as well as aggregates that were formed by ?and ?' subunit,acidic subunits and basic subunits through disulfide bonds while ? subunit was in the core of aggregates since it lacked cysteine residues.In addition,part of BBI can form aggregates with acid subunits and basic subunits through hydrogen bond;some also can form aggregates with ? and ?' subunit,acidic subunits and basic subunits though disulfide bonds when ? subunit in the core of the aggregates,which decreased the BBI activity.Lastly,we studied the effect of the addition of sugar alcohol on the anti-nutritional factors and stability of soymilk.It showed that the urease activity was negative in the soymilk with sugar alcohol.However,the TIA residual rate of soymilk with sugar alcohol was higher than that of soymilk without sugar alcohol,which means that sugar alcohol can protect the activity of STI.The result of particle size and distribution as well as the stability of soymilk showed that the addition of sugar alcohol increased the volume percentage of soymilk at 4-30 ?m and30-400 ?m,and the stability of soymilk with sugar alcohol was significantly lower than that of soymilk without sugar alcohol. |
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