Research On Characteristics Of Ohmic Heating Of Hydrocolloids Containing Fruit Particulates

Ohmic heating is an important method for heat processing .In the procedure of conventional cooking ,sterilizing and processing ,food heating may increase food nutrient losing ,and overheating liquid around these granules will also boil out solid surface, destroy the integrity of granules and even degrade food quality as well as commercial value. During ohmic heating technology ,food was heated by alternating current, food materials all have some resistance to electricity ,which are essential to ohmic heating .When electricity is applied, food liquid phase and solid phase are all working as electric resistance and heated rapidly and uniformly . The integrity of food granules is maintained. This technology has advantages such as supplies intensify fast ,heating even, high utilization ratio and good processing food . Ohmic heating is one of the most prospecting techniques for liquid food with granules processing. So in this paper characteristics of ohmic heating of hydrocolloids containing fruit particulates is studied.A great of references about ohmic heating were studied in the thesis. The properties of hydrophilic colloids and characteristics of hydrophilic colloids containing fruit particulates were studied. The main conclusions are as following:1.Properties of different hydrophilic colloids during ohmic heating1)The electric conductivity and heating temperature of hydrophilic colloids demonstrate a kind linear relation ,that is ,the electric conductivity increases linearly along with the promotion of heating temperature .2)The electric conductivity of potato starch rises along with the descending of concentration and the ascending of citric acid content in colloid solution. Heating rate increases along with the ascending of electric conductivity. The electric conductivity of sodium alginate and CMC-Na hydrophilic colloid rises along with the ascending of concentration and the critic acid content in colloid solutions, but heating rates increase along with the critic acid content in colloid solutions.2.Properties of mixture of hydrophilic colloids during ohmic heating1)When it concerned about the mixture of potato starch and sodium alginate, The electric conductivity rises along with the descending of the concentration of potato starch and the ascending of the concentration of sodium alginate . The electric conductivity changing regularities vary with the critic content in mixture with different concentration and proportion of potato starch and sodium alginate, but ohmic heating rates rises along with the ascending of the critic content.2)When it concerned about the mixture of potato starch and CMC-Na hydrophilic colloid, The electric conductivity rises along with the descending of the concentration of potato starch and the ascending of the concentration of CMC-Na hydrophilic colloid . The electric conductivity changing regularities vary with the critic content in mixture with different concentration and proportion of potato starch and CMC-Na hydrophilic colloid, but ohmic heating rates rises along with the ascending of the critic content.3)When it concerned about the mixture of sodium alginate and CMC-Na hydrophilic colloid ,if the concentration of sodium alginate is aptotic, the electric conductivity rises along with the ascending the concentration of CMC-Na hydrophilic colloid and the descending of the critic acid content ,but the ohmic heating rate increases along with critic acid content; if the concentration of CMC-Na hydrophilic colloid is aptotic, the electric conductivity rises along with the ascending the concentration of sodium alginate and the descending of the critic acid content ,but the ohmic heating rate increases along with critic acid content.3.Single-factor effect on characteristics of ohmic heating of hydrocolloids containing pear particulates1)If pear particles are small in size, the temperature distinction presents uniformity ,that is to say , the pear particles and hydrocolloids can be heated at the same time, the slope of the electric conductivities curves of hydrocolloids and pear particles are great ,the time used to heat it until 99 degrees Centigrade is little, and the heating curve presents large slope, that is to say ,the ohmic heating rate is great.2)If the concentration of pear particles is low, the time used to heat it until 99 degrees Centigrade is little, the slope of the electric conductivities of hydrocolloids and pear particles are great , and temperature curve steepenes , that is to say ,the ohmic heating rate accelerates. Both of the slope of the electric conductivities curves of hydrocolloids and pear particles decrease along with the increasing of the concentration of pear particles.3)When it concerned about the mixing proportion of CMC-Na hydrophilic colloid, if the proportion of CMC-Na hydrophilic colloid is below 30 percent and above 50 percent, the temperature distinction of the materials isn't uniform, that is to say , the pear particles and hydrocolloids can't be heated at the same time. If the proportion of CMC-Na hydrophilic colloid is between 30 percent and 50 percent, the temperature distinction presents uniformity, that is to say, the pear particles and hydrocolloids can be heated at the same time. The slope of the electric conductivities curves of hydrocolloids and pear particles increase along with the ascending of the proportion of CMC-Na hydrophilic colloid, and the heating curve presents large slope, the time used to heat it until 99 degrees Centigrade is little, that is to say, the ohmic heating rate is great.4)When it concerned about the concentration of the mixture of hydrophilic colloid(the mixing proportion of CMC-Na hydrophilic colloid is aptopic),if the concentration of hydrophilic colloid is below 1 percent and above 5 percent, the temperature distinction of the materials isn't uniform, that is to say , the pear particles and hydrocolloids can't be heated at the same time. If the concentration of hydrophilic colloid is between 1 percent and 5 percent, the temperature distinction presents uniformity, that is to say, the pear particles and hydrocolloids can be heated at the same time. The slope of the electric conductivities curves of hydrocolloids and pear particles increase along with the ascending of the concentration of the mixture of hydrophilic colloid , and the heating curve steepenes, the time used to heat it until 99 degrees Centigrade is little, that is to say, the ohmic heating rate is great.5)When it concerned about the critic acid content of the mixture of the materials,if the critic acid content is over low or over high , the temperature distinction of the materials isn't uniform, that is to say , the pear particles and hydrocolloids can't be heated at the same time. If the critic acid content is between 0 percent and 1 percent, the slope of the electric conductivities curves of hydrocolloids and pear particles increase along with the increasing of the critic acid content, and the heating curve steepenes, the time used to heat it until 99 degrees Centigrade is little, that is to say, the ohmic heating rate is great.6)The electric conductivity and heating temperature of the pear particles and hydrophilic colloids demonstrate a kind linear relation ,that is to say,the electric conductivity increases linearly along with the promotion of heating temperature in the procedure of Ohmic heating .7)Ohmic heating is suitable to the processing of hydrocolloids containing fruit particulates, the pear particles and hydrocolloids can be heated at the same time. with appropriate control of every factor that effects the procedure of ohmic heating ,and the fruit particulates can't be heated excessively. The ohmic heating result to the hydrocolloids containing big particles is better .4.Results of researching on the ohmic heating of hydrocolloids containing pear particulates by five-factor quadratic orthogonal revolving compounding design are drawn out.1)Mathematic regression model is founded and optimized to reflect the relationship between heating time(heating rate ) and affecting factors :particulate size,particulates content,the proportion of CMC-Na hydrophilic colloid,the concentration of the mixture of hydrophilic colloid and the critic acid content of the mixture of the materials. In the model, coding values of the above five factors are used as independent variables ,as following:By statistical check, the equation plans to share well. Its significance level is 0.01. Namely confidence degree of the equation is 99%.2)The ranking of the effect of each factor to the value of heating time is: the concentration of the mixture of hydrophilic colloid.> the proportion of CMC-Na hydrophilic colloid> the critic acid content of the mixture of the materials> particulate size> particulates content.3)According to the mathematical model, the optimal scheme is that the particulate size is 1.0 centimeter, the particulates content is 30 percent, the proportion of CMC-Na hydrophilic colloid is 50 percent, the concentration of the mixture of hydrophilic colloid. is 4 percent and the critic acid content of the mixture of the materials is 0.25 percent. The shortest heating time is 167seconds.4)Mathematic regression model is founded to reflect the relationship between nature variable and the ohmic heating ,as following :5.Impact of ohmic heating on the viscosities of hydrocolloids The changing regularities of viscosities of potato starch, sodium alginate and CMC-Na hydrophilic colloid in the procedure of Ohmic heating .are tested. The viscosities of hydrophilic colloids decrease along with the increasing of temperature and the descending of the concentration. and the viscosities also decrease along with lower initial values. When it concerned about the hydrophilic colloids with aptopic concentration. the viscosities decrease along with the increasing of the critic acid content of the hydrophilic colloids.6.Impact of ohmic heating on the physical-chemical properties of hydrocolloids containing fruit particulates.The total sugar,total acid and Vc content of the fruit particulate decrease though traditional heating and ohmic heating,but The total sugar,total acid and Vc content of the fruit particulate though ohmic heating decrease less than the ones though traditional heating.,the compression strength of fruit particles all reduce, and the reduced degree varies with fruit. The percentage of the compression strength of Ohmic heating reduces less than that of traditional heating.The innovative research results of this paper are:1)Properties of different hydrophilic colloids and mixture of hydrophilic colloids during ohmic heating was studied, the changing regularoties of the viscosities of different hydrophilic colloids and the mixture of hydrophilic colloids along with the concentration.,temperature and pH values was studied.2)Mathematic regression model that reflect the relationship between heating time(heating rate) and affecting factors is founded by quadratic orthogonal revolving compounding design, the ranking of the effect of each factor to the value of heating time and the optimal scheme of the technics parameters were obtained.