Study The Compound Preservative Of Convenient Rice Cake

Convenient rice cake is a unique flavor food. Because of its high water content, water activity and rich nutrition, it can easily lead to microbial growth and reproduction. In addition, due to high content of rice starch, convenient rice cake is prone to retrogradation. In this paper, the study on the convenient rice cake were summarized on the key indicators during storage; the effects of temperature on starch retrogradation; isolation and identification the advantages of microbial; study a compound preservative.First, by studying the charge of convenient rice cake in the physical, chemical and microbial indicators during storage, to determine the key factor of convenient rice cake is microbial and starch retrogradation. The fresh convenient rice cake Aw is 0.93, water content is 44.5%, pH value is 6.7, these conditions can easily cause microbial growth and reproduction. Storage temperature has significant influence to the total number of microbial, pH, moisture content, the hardness (P <0.05). The shelf life stored under 30℃is shorter than 20℃.Second, the texture characteristics and thermodynamic properties of convenient rice cake in different temperature was studied during storage. It find that storage temperature has significant influence to hardness, chewiness, adhesiveness, cohesiveness and resilience (p<0.05). The texture parameters of convenient rice cake charged at the previous seven days. Avrami model was used to study the retrogradation of starch in convenient rice cake. The n value in Avrami model was less than 1, it show that starch recrystallization is nucleation model for once. Effect of temperature on crystal growth rate is 4℃>20℃>30℃。Third, after isolation, purification and disproof of the microbes in the convenient rice cake, two strains of bacteria, three strains of yeast and one strain of mold were obtained as the spoliage microbes. Morpha character, physiological and biochemical characteristics, and microbial identification system reveal that two strains of bacteria are Bacillus subtilis and Acinetobacter sp. ,three strains of yeast are Candida spp., one strain of mold is Aspergillus nidulans.Finally, single factor design was applied in the experiment and three preservatives were selected from five preservatives. The concentration of the optimum compound preservative constituted with sodium diacetate, nipagin complex ester and sodium dehydroacetate were decided by three factors quadratic totating design. The comparison concludes that the effects order of three factors on the number of microbe is as follows: sodium diacetate, nipagin complex ester, sodium dehydroacetate.The result reveals that sodium diacetate (0.238%)+nipagin complex ester (0.0262%) + sodium dehydroacetate (0.0244%) could constitute the optimun compound preservative.