Kinetics of mould growth in the stored barley ecosystem contaminated with Aspergillus westerdijkiae, Penicillium viridicatum and Fusarium poae at 23-30 °C.

BACKGROUND: Owing to the lack of a rapid method for determining fungi on cereals, the best way to enhance the safety and nutritive value of stored grain is to develop prognostic tools based on the relationship between easily measurable online parameters, e.g. water activity (a(w)) and temperature (t) of grain, and fungal growth. This study examined the effect of unfavourable temperature (23 and 30 °C) and humidity (0.80-0.94 a(w)) storage conditions on mould growth in the stored barley ecosystem with its adverse microbiological state provided by contamination with Aspergillus westerdijkiae, Penicillium viridicatum and Fusarium poae. RESULTS: Among the applied storage parameters, a(w) turned out to be the main factor affecting mould development. The longest lag phase and period of fungal activation were observed for grain with 0.80 a(w), which was not threatened with fungal development for at least 30 days. However, in grain with 0.92 and 0.94 a(w), fungal activation occurred within 24-48 h. CONCLUSION: The obtained data and the identification of critical points in mould growth may be used to develop a control system for the postharvest preservation of barley based on a(w) and temperature of grain, which are easy to measure in practice.

Optimization of process parameters for microwave-vacuum puffing of black radish slices using the response surface method.

BACKGROUND: Due to the health-promoting value of black radish, authors decided to investigate the feasibility of forming - from its roots - chips, using the process of microwave-vacuum puffing. In order to produce desirable quality of chips, there is a need to determine the most advantageous values of process parameters. The main goal of the paper is to investigate the possibility of determining the best processing conditions for microwave-vacuum formation of black radish chips that can maximize the chips expansion ratio while maintaining consumer acceptability of sensory quality of chips. MATERIAL AND METHODS: The raw material for analyses comprised fresh roots of black radish {raphanns sativus linne varietas niger). A three-level, one-factor central composite experimental design (DOE) was applied. The response surface method (RSM) was used as a part of the Statistica software and the R computer program for optimization. Response surfaces were built using the second degree polynomial that includes principal effects of processing parameters values and their interactions. RESULTS: A regression model was derived, based on results of natural experiments, that give a satisfactory prediction level (R² = 0.96) of the expansion ratio of black radish chips as a function of processing conditions. Then, the best values of process parameters were found using the RSM. The best processing parameters values were determined to be 0.39 kg kg⁻¹ wb (wet basis) moisture content of pre-dehydrated radish slices, 14.5 kPa vacuum absolute pressure and 80 s of microwave heating time during puffing (for the 650 W power output of the microwave generator). CONCLUSION: Optimized process of puffing of black radish slices using the RSM provided a satisfactory high value of the sensory quality index of chips. In this paper we do not analyze the physical structure of chips. In the future more research needs to be done in this area.