Pasteurizing the milk with the induction heating energy and evaluating its organoleptic properties

Heating of milk for the purpose of removing the bacterial pathogens should be done for the shortest time, and sufficient pasteurization must be ensured. The limitation of the classical methods of pasteurization is due to the high sensitivity of the milk to coagulation by the application of high temperature, which sometimes prevents the proper process and causes problems such as milk clotting and the formation of non-washable layers (milk stones) on the interior surface of the pasteurization tubes. These layers prevent the sufficient heat transfer and the adequacy of the pasteurization of the next inlet milk, and as a result, the mentioned milk contains high levels of microbial contamination that will be hazardous to consumers. Therefore, the aim is to find a suitable pasteurization method that does not have the above-mentioned disadvantages and also the milk obtained from the pasteurization process will have a higher quality. Therefore, in this research, the inductive electromagnetic flow heat was used for pasteurization of the milk. In this method, the milk container acts as the second coil of the electromagnetic current (transformer) and allows direct flow of electricity in the milk. In the preparatory steps of the project (stages 1 to 3), whose results are not mentioned in this article, milk pasteurized was done by induction heating in an attempt to modify, revise, and refine the usual classical process. In order to obtain the best conditions for milk pasteurization by the induction method, the effect of four different factors were investigated, namely three diameters of the test vessel (23, 17 and 12 cm), three electrical conductivities (350, 1000 and 1600 watts), three temperatures (72, 75 And 84 ° C), three storage periods at pasteurization stage (15, 20 and 30 seconds) and three replications; Where 243 samples were selected in a completely randomized factorial experiment design. And the tested samples were categorized based on 1) the lowest percentage of residual microbial load, 2) the minimum time spent for pasteurization, and (3) the least Energy consumption for pasteurization. Three selected samples in the third stage of the previous project were prepared using the standard method in this study with the correct mixing at a certain temperature and used for the organoleptic test by the taste Group during the following steps. 1) Selection of 10 panelists. 2) Explaining the method and providing relevant questionnaires; 3) Checking and assuring the qualification of the panelists for evaluation (no smoking, medication, etc.); 4) explaining the evaluation method to the testers. Then, the physical and organoleptic characteristics of the produced samples were determined by the panelist group using a grading method based on the color, aroma, taste, texture, consistency and concentration of the samples. In the samples pasteurized using the induction pasteurization method with 1600 W power transmission intensity, 30 seconds holding time, temperature of 84 ° C and 23 cm cross section of the container, desirable organoleptic and physical properties were obtained compared to the other samples and the control (pasteurized under conventional conditions). So, there was a significant difference between consistency, concentration, and aroma and customer
satisfaction in two treatments at the level of 5% confidence and for the color attribute at 1% level due to the high speed of heat transfer in milk. The induction method of pasteurization is superior to the HTST method in favor of the production of desirable organoleptic properties, and is a very good substitute for the classic method of the factory under the same conditions.