Heating by focused microwaves in the continuous thermal processing of fluid foods is an emerging technology that is under study because it has the advantage of providing a rapid temperature increase, without overheating of the tube wall, thus reducing loss of quality attributes. The aim of this research project is to study the heat transfer and the temperature history in the continuous thermal processing in a pilot processing unit with focused microwave heating on apple juice pasteurization. The unit UHT/HTST Lab-25 EHVH (Micro Thermics, USA) comprises a positive displacement pump (30 L/h), pre-heating heat exchanger, microwave applicator, holding tube, cooling heat exchanger, magneton (6 kW, 2450 MHz) and heating (18 kW) and cooling systems. The unit allows to operate conventionally without using the microwave applicator. There is temperature record throughout the product line, as well as pressure and power use in the magnetron. Initial tests will be carried out with water for evaluation of flow regimes, heat loss to the environment and energy balances. Estimation of internal volumes and residence times allow obtaining the temperature history and the consequent evaluation of integrated lethality. The methodology will be applied to the processing of cloudy apple juice, extracted by fragmentation and compression of fruits of the variety Fuji Suprema, considering the conventional processing and by microwave. The results will be assessed for the reliability, consistency and applicability. The scientific dissemination will occur through scientific events in the fields of chemical and food engineering. It is estimated that this work will bring an important contribution to the ongoing projects at the Research Center for Food that evaluates processing in this unit.
News published in Agência FAPESP Newsletter about the scholarship: