| Provolone Cheese is an Italian semi-solid cheese, which is one of the "Pasta Filata" Cheese. The taste of Provolone is mild, so that is relatively easy to become popular in China. In the same time, radialization, as an effective and safety technology for sterilization without heating, is widely utilized in almost every field of food industry. In this paper, Provolone Cheeses made by our own were radialized by Co-y of different doses, and they were stored. The impact of microbe in the cheese after radialization was studied, and the value of D10and D of total number were measured. Furthermore, the main physical, chemical, and sensory indexes of radialized cheeses were also detected in their storage. The peculiar smells resulted from radialization were analized, and the mechanisms and the preventing methods of their forming were discussed. Main conclusions are as follow:1. After radialization, the number of microorganisms was decreased remarkably. And more the dose of radialization was, the less the number of microorganisms was. In the same time, the effects of sterilization on bacteria for fermentation were small, while the effects on coliform were prominent. According to the total number of bacteria of cheese after different dose of radialization, the value of D10was2.44kGy, and the value of D was2.69kGy. From the value of D, taking the original quantity of microbes and economical factors into account, the dose of radialization was determined as lower than3kGy.2. During the storage, with the increase of the dose of radialization, the value of AV, POV and TBA were all improved evidently. This indicated that the process of fat oxidation was accelerated by radialization in some extent. In addition, the content of total free fat acid (FFA) was reduced by half, and the quantity of unsaturated FFA was lowered prominently. This suggested that radialization affected fat greatly, so the dose of radialization should be controlled well for a good quality of the nutrition of cheese.3. In storage, the content of pH4.6SN and12%TCA SN were both reduced with the increase of the dose of radialization; The TPA rigidity, flexibility and coagulation of radialized cheese were lowered, too. From the electrophoretic results, radialization worked on the proteolysis of as-casein and β-casein weakly, but strongly on the peptides and micromolecules from them. In the same time, the microstructure of cheese was changed, that is the smooth and uniform three-dimensional net structure became unconspicuous, and the protein bind became obvious.4. The water activity was decreased with the increase of the dose of radialization in storage. The reason of this phenomenon was that water was ionizated by radialization directly, and then ions and radicals made redox with protein and fat. Finally, that is proved that there was a large difference between the sensory data of the cheeses which were under radialization or not.5. Volatile flavors of Provolone cheeses of different doses of radialization were detected by HS-SPME-GC-MS. The result showed that the variety and quantity of volatile flavors were changed obviously after radialization. Main volatile flavor in Povolone cheese which had not been radialized were alcohol, aldehyde, ketone, ester, benzene, alkene, volatile organic acid, etc. While main volatile flavor in radicalized Povolone cheese were hexanal, ethyloctanonate, phenyl-acetaldehyde etc. it is proved that hydroxybenzene and ester were reduced remarkly, so the characteristic flavors of Provolone cheese were weakened. In the same time, the variety and quantity of aldehyde, ketone, alkyl, alkene were decreased notably, and the content of sulfide were increased. In addition, the synthetical results of many volatile substances may lead to abnormal smells of radialized cheese, and the mechanisms and the preventing methods of their forming were waiting to be studied. Abnormal smells could be reduced by lowering the dose of radialization, so the dose should be controlled well for assurance the good quality of cheese. |
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