Study On Cooling And Refrigeration Technology Of Rice Dumplings

As the rhythm of modern life speeding up, people increasingly focused on food quality.This issue researched the methods of quick-frozen of rice dumplings and quality changesduring storage. Quick-frozen rice dumplings retain the nutrition and flavor of traditionalrice dumplings, and just heat them before eating, so they have advantages of convenient,security speedy, highly cost effective. Therefore, the study of quick-frozen rice dumplingshas very important significance, mainly includes the following four parts:1、The rice dumplings needed to cool after cooking. In order to find a suitable coolingmethod, the experimental used3ways to cooling after the cook process including vacuumcooling, cold air cooling, natural cooling, and determined the quality difference of ricedumplings. The results showed that comparing with conventional cooling methods, the rateof vacuum cooling was higher(p<0.05), cooling loss was higher(p<0.05), rigidity washigher(p<0.05). However, adhesion, viscosity, chewiness, and the recovery had nosignificant difference (p>0.05).The taste of vacuum cooling sample was better thanconventional cooling products, but still can be accepted. Chemical index analysis showedthat vacuum cooling can reduce the total number of bacterial colony. Electronic noseanalysis results showed that the volatile of vacuum cooling and conventional coolingproducts had significantly difference in red bean dumplings and meat rice dumplings, but inwhite rice dumplings it was non-significant. This study shows that vacuum cooling is a fastand safe cooling method.2、Quality changes of pork and non-filling quick-frozen rice dumplings made by rice andother materials were studied in4℃and-18℃storage. Indicators of measurementincluded moisture content, degree of gelatinization, the total number of colonies andelectronic nose. And texture analysis was determined in non-filling quick-frozen ricedumplings, determinations of TBA value and TVB-N value were determined in pork quick-frozen rice dumplings. The results showed that moisture content of both rice dumplingsdecreased as time went on, pork rice dumplings had significant difference（p＜0.05）indifferent temperatures. The total number of colonies increased. For non-filling ricedumplings, hardness increased to varying degrees, which had significant difference（p＜0.01）in different temperatures, adhesiveness and degree of gelatinization decreased, andthere were significant difference in adhesiveness（p＜0.05） and springiness（p＜0.01）.For meat rice dumplings, TVB-N and TBA value showed an upward trend. Electronic noseanalysis showed that dumpling flavor in two temperatures could be distinguished.3、In order to decrease the aging degree of rice dumplings, soaking temperature, soaking time and ratio of solid to liquid were studied by using single factor analysis method.Hardness was determined as respondent value, response surface methodology was using tooptimize three main, which were influence factors ratio of solid to liquid, soakingtemperature and soaking time. The result determined the most optimal process of the lowestaging degree were soaking time:50.23; soaking temperature:28.67; ratio of solid to liquid:0.74. On this condition, the hardness touched the bottom value473.781g.4、This study investigated the quality changes of rice dumplings quality under differentstorage temperature. Determination of indicators include moisture content, browningintensity, pH and color. As the storage time lasted, hardness and viscidity increased,elasticity and chewiness decreased,pH decreased, the value of L*, b*and a*increased.Regression analysis of several indicators determined that the viscidity, elasticity, chewinesscan be used as indicators to measure quality changes of rice dumplings during storage, andthe establishment of dynamic models of the three indicators were as follows: viscidity：t=2.31×10-4e3000/T；elasticity：t=-21.24×10-4e2367.234/T；chewiness：t=-25.95×10-5e2990/T. Finally, integrate the3indicators to determined the rice dumplings’ shelf life, andpredicted the shelf life of rice dumplings. As the error was smaller, they can well predictthe shelf life of rice dumplings in the storage, and can better control the quality of the ricedumplings during storage.