Cold Air Assisted Radio Frequency Tempering Protocol For Frozen Chicken Breast

Frozen chicken breast needs tempering before further processing.Conventional tempering methods always take long time,which leading to quality losses.Since it has deep penetration depth,rapidly volumetric heating,and no significant quality loss,radio frequency(RF)heating has the potential for applying tempering.However,the heating non-uniformity is still a major obstacle for further industrial applications.So far,the methods to improve heating uniformity have drawbacks,such as limited improvement,unacceptable taste and complex operation of industrial process.This study took frozen chicken breast as the research object,determined the dielectric properties under different frequencies and temperatures by an open-ended coaxial probe system,and established the regression equations.Then used a free oscillating RF heating system with the power of 6 k W and the frequency of 27.12 MHz with a cold air system,to explore the effects of different end-point temperatures,different electrode gaps and cold air assisted on the heating rate and heating uniformity of frozen chicken breast.After that,the optimal end-point temperature and the electrode gap were selected,and the heating characteristics and product quality of the frozen chicken breast samples tempered by five methods were compared.Finally,the effects of cold air assisted RF tempering,RF tempering and water tempering on the heating characteristics and quality of chicken breast samples of two sizes were investigated,and their energy efficiency was calculated at last.The thesis provided a theoretical basis for the industrial application of cold air assisted RF tempering.The main research contents and conclusions are as follows:(1)By analyzing the effects dielectric properties of chicken breast samples with frequencies and temperatures,it was found that the dielectric constant and loss factor of chicken breast samples decreased with the increase of frequency,and it increased with the increase of temperature.Based on this,the predictive relationship between the dielectric properties and temperature at 13.56,27.12 and 40.68 MHz was established.After 30 min of precooling,a cold air system with a stable temperature of-5 ℃ and a speed of 1.5 m/s was built to explore the effects of different end-point temperatures,electrode gap and assisted cold air on heating characteristics.The results showed that the best heating uniformity was at the end-point temperature of-3 ℃,and the assisted cold air would slightly reduce the heating rate,but significantly improve the heating uniformity.In order to obtain relatively high heating rate and better heating uniformity,110 mm can be used as the electrode gap for cold air-assisted RF tempering and RF tempering for subsequent studies.(2)At the end-point temperature of-3 ℃,cold air-assisted RF tempering can obtain the higher heating rate and shorter processing time than air tempering,water tempering and refrigerator tempering,and provided the better heating uniformity than RF tempering,air tempering and water tempering.In terms of product quality,the chicken breast sample after cold air-assisted RF tempering had better color,drip loss(1.42%),p H(6.38)and volatile basic nitrogen content(10.37 mg/100g).(3)For both large and small volume samples,cold air-assisted RF tempering would slightly prolong the processing time of RF tempering,but its tempering rate and heating rate were better than those of water tempering;The heating uniformity and product quality of chicken breast samples after cold air-assisted RF tempering were better than those of water tempering and RF tempering.When used the same method,the tempering time of large volume samples was longer than that of small volume samples,and the heating uniformity and product quality of tempered large volume samples were worse than those of small volume samples.The energy efficiency of cold air assisted RF tempering was lower than that of RF tempering,and the energy efficiency of large volume samples was better than that of small volume samples.Therefore,the energy efficiency of cold air assisted RF tempering can be improved by increasing the product volume.