ABSTRACT
This paper researches two volatility transmission phenomena that take place within ('heat wave') and between ('meteor shower') spot and futures markets of four precious metals-gold, silver, platinum and palladium. We create conditional volatilities by considering three types of Markov switching GARCH models in combination with three different distribution functions. Conditional volatilities are subsequently embedded in Markov switching mean model. We find that 'heat wave' effect is more intense than 'meteor shower' effect, and this applies for both spot and futures markets of all precious metals. The results indicate that 'heat wave' effect is more intense in high than in low volatility periods, and also this effect is stronger in futures markets than in spot markets. 'Meteor shower' effect is stronger in low volatility regime than in high volatility regime, which is particularly true for the futures markets. Rolling regression results are in line with switching parameters. In addition, we find that 'meteor shower' effect, from futures to spot market, is stronger when short-term futures are analysed vis-à-vis long-term futures.
ABSTRACT
Raspberries are one of Serbia's best-known and most widely exported fruits. Due to market fluctuation, producers are looking for ways to preserve this fresh product. Drying is a widely accepted method for preserving berries, as is the case with freeze-drying. Hence, the aim was to evaluate convective drying as an alternative to freeze-drying due to better accessibility, simplicity, and cost-effectiveness of Polana raspberries and compare it to a freeze-drying. Three factors were in experimental design: air temperature (60, 70, and 80 °C), air velocity (0,5 and 1,5 m · s-1), and state of a product (fresh and frozen). Success of drying was evaluated with several quality criteria: shrinkage (change of volume), color change, shape, content of L-ascorbic acid, total phenolic content, flavonoid content, anthocyanin content, and antioxidant activity. A considerable influence of convective drying on color changes was not observed, as ΔE was low for all samples. It was obvious that fresh raspberries had less physical changes than frozen ones. On average, convective drying reduced L-ascorbic acid content by 80.00-99.99%, but less than 60% for other biologically active compounds as compared to fresh raspberries. Convective dried Polana raspberry may be considered as a viable replacement for freeze-dried raspberries.
ABSTRACT
BACKGROUND: Two hard wheat varieties and one soft variety grown under the same agroecological conditions were analyzed for their physical and uniaxial stress-strain compression properties. RESULTS: The physical properties of wheat kernel were determined at a moisture content of 0.13 kg kg(-1) (wet basis), whereas the stress-strain compression test was conducted at a kernel moisture content from 0.082 to 0.433 kg kg(-1) . Mean kernel lengths were 5.46 (5.37 and 5.38) mm, widths were 2.56 (2.47 and 2.62) mm and thicknesses were 2.12 (2.18 and 2.43) mm for Simonida, Dragana and NS 40S cultivars, respectively. Bulk densities were 791.34 (Simonida), 788.51 (Dragana) and 731.77 kg m(-3) (NS 40S). The force at the yield point was 241.46 N for Dragana (moisture content 0.133 kg kg(-1) ), 244.30 N for Simonida (0.136 kg kg(-1) ) and 164.90 N for NS 40S (0.433 kg kg(-1) ). CONCLUSION: The width and thickness of the analyzed kernels were small compared with the length, and bulk densities were also moderate. The yield point force values of the two hard varieties were 2.2 times higher than the values of the soft variety, at a moisture content of 0.136 kg kg(-1) for Simonida, 0.133 kg kg(-1) for Dragana and 0.141 kg kg(-1) for NS 40S.
