| Rice is one of the leading food corps in South East Asia including China. It can be ground into powder and utilized to produce many kinds of foods, including several types of cake. MiGao is one of the most widespread of these types of cake. It is famous for its soft and sticky texture and it is usually served as a dessert.The physical and chemical characters of Migao were studied during storage. The moisture content decreased after 2 days of storage and during the following days the crumb moisture content remained practically unchanged. The pH and a_w were fairly stable during storage. Water holding capacity, total water-solubles, soluble starch and Water holding capacity of MiGao decreased continuously throughout storage. Total plate counts in the products under study in the third day of storage were in the range <10~3 CFU/g and the shelf-life of the product was estimated to be only 2 or 3 days by the panelists. Firmness was developed mainly during the first day of storage, remained at a similar level from 2 to 3 day and increased slightly after the third day of storage. In view of the nutritional importance of starch, the major starch fractions viz, rapidly digestible starch, slowly digestible starch and resistant starch were measured by using controlled enzymic hydrolysis.Microbiological changes in MiGao were studied during storage at 25℃. Microorganisms examined for were: Enterobactericeae, lactic acid bacteria, Gram positive, catalase positive cocci, Staphylococcus aureus, Bacillus strains, yeasts and moulds. During the first 2 days, Gram-positive bacteria were dominant, mainly represented by S. epidermidis. Bacillus strains occurred by the third day, reaching a maximum level of 1×10~6 CFU/g after 5 days of storage. No Enterobactericeae or Lactic acid bacteria were detected in the processed products throughout the storage period. All the isolated strains from the mannitol salt agar belonged to the genus Staphylococcus. The predominant species were S. epidermidis and S. aureus. Most Bacillus strains, isolated from the tryptone soya agar, belonged to the species B. brevis. The count of yeasts and moulds increased slowly but remained low throughout the storage period and the isolated strains from the DG18 belonged to the species of Penicillium citreoviride and Penicillium citrinum.A numerical model was developed and validated to predict microbial growth during storage of Migao. For this the growth of the naturally occurring bacteria was studied at temperatures from 20℃to 30℃. Fitting of the model to the experimental data derived from Migao stored aerobically at 20℃, 25℃and 30℃successfully desc ribed the microbial growth kinetics in theMigao. Finally, the parameter values estimated by the fitting of the model on the data were used to predict microbial growth and shelf life in Migao at storage temperatures.Contamination by mold is serious problem of the steam-cooked rice cake, a traditional Chinese food. Growth responses to different temperatures and water activity values for Penicillium citreoviride and Penicillium citrinum, two of the most common molds, were investigated. Partial Least Square regression analysis showed that the growth of the two fungi did not differ in response to changes in water activity and temperature. Optimum a_w for growth was 0.90 a_w and optimum temperatures for growth were 30℃in most cases.Starch properties of MiGao were characterized during storage. Pasting viscosities of crumb-water slurries were measured with a Rapid Visco Analyser for evaluating the texture of MiGao. The most significant change in the pasting curve was the increase in peak viscosity over time. Differential scanning calorimetry was used to follow changes of starch retrogradation in MiGao crumb. Amylopectin recrystallisation in MiGao continued to increase during storage. FT-IR indicated changes in crystallinity of the MiGao crumb and the crystallinity of Migao stored at 25℃for up to 5 days was studied using X-Ray. The microstructure of Migao was studied by SEM.The effects of the addition of xantha, CMC,α- amylase andβ- amylase, in rice flour doughs, were studied in Migao. Thermal mechanical analysis techniques were used in order to evaluate the effect of additives on the retrogradation of starch in Migao. The type and extent of influence on Migao quality was dependent on the specific additives used and its supplementation level. Generally, the hardness of Migao decreased with addition of xantha, CMC andβ- amylase except forα- amylase. The Migao with good quality can be added with 0.2% xantha, 0.25% CMC和0.03%β- amylase.
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