Research On Radio Frequency Thawing Technology Of Mutton

Frozen meat of livestock plays an important role in the meat and meat processing industry,which is also an important chip for the state to reserve and regulate the meat market.It is also the main form in the import and export trade and regional circulation of meat products.Thawing is an important treatment in frozen meat processing and before eating.Radio frequency thawing technology utilizes the dielectric heating characteristics of food to make food be heated in radio frequency electric field,so as to achieve the purpose of thawing.It is a new thawing method.Compared with other thawing methods,the thawing rate is faster,the penetration depth larger,and the heating more uniformly of RF,which has great potential for application.In this paper,frozen mutton was used as the object of study.The dielectric properties of mutton,temperature distribution during the process of RF defrosting,heating uniformity and the quality of meat after thawing were studied.The specific contents are as follows:(1)Using the open end of a coaxial probe technique,from 1 MHz to 3 GHz frequency,determine the dielectric properties at 7 temperatures in the range of-20 to 10? for the lean meat and fat.Under 13.56,27.12,40.68 in 915,and 2450 MHz,the dielectric constant,dielectric loss factor and the penetration depth of the material are analyzed.(2)The internal temperature and surface temperature of the mutton during the process of RF thawing were monitored by hand thermocouple thermometer and infrared thermal imager,and the temperature distribution of the sample was obtained.(3)With the radio-frequency heating system with frequency 27.12 MHz and power 6 kW,3 kinds of shapes,4 kinds of packages and 6 different electoral gaps were selected for thawing test to determine the influence of various factors on the heating law and the uniformity during the thawing process.(4)The effects of RF thawing and air thawing on thawing efficiency and product quality were investigated.The conclusions are as follows:(1)The dielectric constant and dielectric loss factor of mutton decrease from 1 MHz to 3 GHz with the increase of frequency,and increase with the increase of temperature(-20 ~ 10 ?),and the dielectric constant and dielectric loss factor of the lean meat is much larger than that of fat.The penetration depth of electromagnetic wave for mutton decreases with the increase of frequency and temperature.Under the same conditions,the penetration depth of electromagnetic wave to fat is larger than that of the lean meat.The penetration of material by radio frequency is great,and the uniformity during heating of materials can be improved by using radio frequency.(2)The temperature distribution in the process of RF thawing is as follows: frozen mutton during thawing in the RF electric field appears the edge heating phenomenon.The internal material at the vertical section of temperature from the interior to the edge of the material increased gradually closer to the edge material temperature is higher;hot spots appear on the surface of the material,and cold spots always appear in the middle of the vertical direction of the meat pieces.(3)Three single factor experiments were carried out to investigate the influence of shape,package and distance of frozen mutton on thawing rate and heating uniformity.The thawing time of the ball material is long,and the thickness of frozen mutton should not be too large.The rate of thawing of flat material is faster.The using of PP boxes for frozen mutton can accelerate the thawing of meat pieces and increase the uniformity of heating,while the preservation film will cause local overheating of the meat surface.The electoral gap of 120 mm is the best for shortening the time of RF thawing and improving the heating uniformity of mutton.(4)The pH,L*,a*,b* value,protein solubility and thermal stability during thawing process of mutton have little effect,but compared with air thawing,RF thawing can greatly shorten the thawing time,reduce the drip loss and cooking loss rate during the thawing process,and reduce the production of volatile basic nitrogen.