Gingerbread with Fruit Filling: Preservation Factor Assessment

The ratio of ‘bound' and ‘free' water plays an important role in the studies of staling of various baked confectionery products. Gingerbread with fruit filling is a traditional flour confectionery product with intermediate moisture, which causes transfer processes during storage. Temperature, relative humidity, light exposure, mechanical stress, and pressure affect the staling speed of such confectionery products. The shelf life of raw gingerbread was increased from 10–20 days to more than two months, which caused microbiological deterioration during storage. Moisture transfer between the filling and the crumb increases water activity and ruins the capillary structure of gingerbread during storage, thus significantly increasing the risk of microbiological damage. The present research featured the changes in the mass fraction of moisture and water activity of individual parts of raw gingerbread with fruit filling during storage at different temperatures and relative air humidity. The samples were packed in a 40-micron polypropylene film. During storage, the mass fraction of moisture and water activity may change in various parts of the product, which can lead to their molding. In this case, starch degradation processes led to the destruction of the structure and a decrease in the content of mechanically-bound moisture, as well as to the release of ‘free' water and an increase in water activity. As a result, the risk of molding increased significantly. The water activity increased from 0.71 to 0.79 on the sample surface after six weeks of storage at 30°C and a 40% of equilibrium relative humidity. A set of experiments in microbiological indicators revealed no signs of molding in the freshly prepared samples. After one month of storage, the amount of mold reached 10 CFU/g. The quantity of mesophilic aerobic and facultative anaerobic microorganisms in different parts of the crumb increased from 3×10 to 9×102 CFU/g and in the filling – from 1×10 to 2.3×103 CFU/g. After two months of storage, the amount of mold reached more than 103 COE/g, which greatly exceeds safety norms. As the relative air humidity increased from 30% to 40%, the moisture transfer rate between the products and the environment was reduced by half. As a result, the shelf life decreased by 1–2 weeks. The research also studied the patterns of moisture transfer processes in summer and winter conditions. The research results contribute to the development of technology and shelf life forecasting for complex flour confectionery products with intermediate moisture.