No abstract

Dried turmeric is used as a spice and traditional medicine. The common drying methods for turmeric (Curcuma longa L.) are sun drying and solar drying. In this study, turmeric slices with a thickness of 2 mm were dried at 40, 50, 60, and 70 °C in a laboratory hot-air dryer with a simulated solar radiation applied through transparent polycarbonate cover (UV impermeable) and PMMA cover (UV permeable). Air velocity and relative humidity of drying air were fixed at 1.0 M·s−1 and 25 g H2O kg−1 dry air, respectively. Light significantly increased the sample temperature under both covers. Page was the best model to predict the drying characteristics of turmeric slices. Drying rate correlated with the effective moisture diffusivity, which increased at higher temperature. The hue angle (h°) of turmeric was distinctly lower at 70 °C under both covers. The dried products were of intensive orange color. Curcumin, demethoxycurcumin, and total curcuminoids were affected by the cumulated thermal load (CTL). The lowest curcumin content was found at 40 °C under PMMA (highest CTL). The optimum drying condition was 70 °C under polycarbonate cover due to shorter drying time and better preservation of color and curcuminoids in the dried product.

To reduce the energy consumption during the drying of agricultural and food products, the optimization of the drying process with regard to the drying behavior and the quality of the end products is necessary. Therefore, much effort is spent designing and developing dryers to study the drying behavior of a wide range of products. This often results in a trade-off between measurement accuracy and the sufficient production of dried material required for the product quality analysis. Therefore, a laboratory dryer was developed consisting of three high-precision drying columns, each able to process 600 g of sample mass, and a flatbed dryer that can be loaded with 20 kg of fresh product. Drying curves could be recorded simultaneously by electronic balances in the three precision dryers and the flatbed dryer. The high-precision laboratory dryer HPD TF3+ proved to be suitable for establishing drying curves for a defined temperature, rel. humidity and velocity of the drying air.

No abstract

The process of nutrient recovery from biogas digestate and the extraction of lactic acid from silages is technically feasible, but so far no investigations are available on the environmental sustainability of these technologies in the context of the biogas production chain. The aim of the present study is to show whether the recovery of nutrients from digestate (NR) and the extraction of lactic acid from silages (LA) can be integrated in the biogas production process system in an environmentally sustainable way. The modelling in the present study is based on the standards DIN ISO 14040 and DIN ISO 14044 and the results are evaluated with respect to the 100-year global warming potential, the primary energy demand and the eutrophication potential. Results show that the recovery of nutrients from digestate can be a sustainable solution to the problem of surplus nutrients in biogas regions. Furthermore, lactic acid, which is extracted from silages can provide an environmentally sustainable source of income for biogas plant operators. The urgency of the nutrient surplus problem in these regions calls for increased research and the support of policy makers to foster development activities.