Effect of drying methods on chemical composition, color and antioxidant properties of Thai red curry powder.Kasetsart

ABSTRACT Thai red curry pastes were transformed into powder by two different drying methods: microwave and hot-air drying. The microwave drying was carried out in a microwave oven with output powers of 180, 360 and 540 W and the hot-air drying was carried out at air temperatures of 60, 70 and 80°C. The quality attributes of Thai red curry powder were evaluated for proximate composition, color (Hunter L, a and b) and antioxidant properties (total phenolic content and antioxidant activities). The Folin-Ciocalteu method was used to determine total phenolic content, while 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging and ferric reducing antioxidative power (FRAP) assays were used to elucidate antioxidant activities. The drying methods showed no significant effects on the chemical compositions of the red curry powder, whereas color and antioxidant properties were all affected by the two methods to different extents. Microwave drying resulted in darker and less yellow color than the hot-air drying. Almost all red curry powder in the microwave-dried samples had a greater phenolic content and antioxidant activity than hot-air dried samples

Hawkes processes and their applications

Hawkes processes are a special class of inhomogenous Poisson processes used to model events exhibiting interdependencies. Initially introduced in Hawkes [1971], Hawkes processes have since found applications in various fields such as seismology, finance, and criminology. The defining feature of Hawkes processes lies in their ability to capture self-exciting behaviour, where the occurrence of an event increases the risk of experiencing subsequent events. This effect is quantified in their conditional intensity function which takes into account the history of the process in the kernel. This thesis focuses on the modeling of event histories using Hawkes processes. We define both the univariate and multivariate forms of Hawkes processes and discuss the selection of kernels, which determine whether the process is a jump or a non-jump process. In a jump Hawkes process, the conditional intensity spikes at an occurrence of an event and the risk of experiencing new events is the highest immediately after an event. For non-jump processes, the risk increases more gradually and can be more flexible. Additionally, we explore the choice of baseline intensity and the inclusion of covariates in the conditional intensity of the process. For parameter estimation, we derive the log-likelihood functions and discuss goodness of fit methods. We show that by employing the time-rescaling theorem to transform event times, assessing the fit of a Hawkes process reduces to that of an unit rate Poisson process. Finally, we illustrate the application of Hawkes processes by exploring whether an exponential Hawkes process can be used to model occurrences of diabetes-related comorbidities using data from the Diabetes Register of the Finnish Institute for Health and Welfare (THL). Based on our analysis, the process did not adequately describe our data, however, exploring alternative kernel functions and incorporating time-varying baseline intensities hold potential for improving the compatibility

Moisture sorption of Thai red curry powder

Moisture sorption study was conducted on Thai red curry powder prepared by two different drying methods, viz. microwave and hot-air drying. Moisture sorption isotherms of the red curry powder at 30 C and water activity in the range of 0.113-0.970 were determined by a static gravimetric method. The isotherms exhibited Type III behaviour. The moisture sorption data were fitted to several sorption models and a non-linear regression analysis method was used to evaluate the constants of the sorption equations. The fit was evaluated using the coefficient of determination (R2), the reduced chi-square (2) and the root mean square error (RMSE). The GAB model followed by the Lewiski-3 model gave the best fit to the experimental data. The monolayer moisture content, taken as the safe minimum moisture level in the red curry powder, was determined using the BET equation and was found to range between 0.080 - 0.085 gram water per gram dry matter

Enhanced Quick-Cooking Red Beans: An Energy-Efficient Drying Method with Hot Air and Stepwise Microwave Techniques

This research introduced an energy-efficient drying method combining hot-air drying with stepwise microwave heating for producing quick-cooking red beans. Crucial parameters such as the effective diffusivity coefficient (De), and specific energy consumption (SEC) were examined across varying conditions with the aim of optimizing the drying condition. The results showed that De and SEC varied in a range of 0.53 × 10−9–3.18 × 10−9 m2·s−1 and 16.58–68.06 MJ·(kg·h−1)−1, respectively. The findings from the response surface methodology indicated that optimal drying conditions for cooked red beans are achieved at a hot air temperature of 90 °C, a microwave power of 450 W (corresponding to an initial intensity of 2.25 W·g−1), and a rotational speed of 0.2 Hz. These conditions lead to the maximum effective diffusivity coefficient and the lowest specific energy consumption. Further investigations into step-up (150–300 W to 300–450 W) and step-down (300–450 W to 150–300 W) microwave heating modes were conducted to refine the drying process for enhanced energy efficiency. The synthetic evaluation index revealed that step-down microwave heating strategies of 450 W-to-150 W and 300 W-to-150 W, applied at a temperature of 90 °C and a rotational speed of 0.2 Hz, were notably effective. These methods successfully minimized energy use while preserving the quality attributes of the final product, which were comparable to those of traditionally cooked and freeze-dried red beans. The combined approach of hot-air drying with step-down microwave heating presents a promising, energy-saving technique for producing quick-cooking beans that retain their rehydration qualities and texture

Effects of stepwise microwave heating and expanded bed height control on the performance of combined fluidized bed/microwave drying for preparing instant brown rice

Drying is the most energy-intensive operation in instant brown rice production. The effects of stepwise microwave heating on energy consumption and product qualities were investigated for combined fluidized bed microwave (FDBMW) drying. Red jasmine rice (RJR) was used as the test sample and was dried to the desired level with a variation of microwave power ranging in 0-450 W, while fluidizing air temperature was kept constant at 98 degrees C. Two drying periods in stepwise modes were predicted using the Page drying equation. An image processing technique was applied to capture the bed kinetics during convective fluidized bed drying and further used to control bed stability in the FDBMW drying process. Energy consumption was reduced by 7 to 23% when the expanded bed height was controlled as a dense fluidization regime in the heat transfer zone. Based on energy saving concerns, FDBMW drying operating with a step-down mode from 300 to 150 W and control of bed stability was the optimal condition to produce instant good-quality brown rice

Production and physicochemical properties of carboxymethyl cellulose films enriched with spent coffee grounds polysaccharides

Extracts rich in polysaccharides were obtained by alkali pretreatment (PA) or autohydrolysis (PB) of spent coffee grounds, and incorporated into a carboxymethyl cellulose (CMC)-based film aiming at the development of bio-based films with new functionalities. Different concentrations of PA or PB (up to 0.20% w/v) were added to the CMC-based film and the physicochemical properties of the final films were determined. Scanning electron microscopy, Fourier-transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, as well as determinations of optical and mechanical properties, moisture content, solubility in water, water vapor permeability, contact angle and sorption isotherms were performed. The addition of PA or PB resulted in important changes in the properties of the CMC-based film, mainly in color and opacity. The polysaccharides incorporation significantly improved the light barrier of the film and provided an enhancement or at least a preservation in the physicochemical properties.This work was supported by the Science and Technology Foundation of Portugal (FCT − grant SFRH/BD/80948/2011); the Strategic Project of UID/BIO/04469/2013 unit; and the Project BioInd − Biotechnology and Bioengineering for improved Industrial and Agro-Food processes (REF. NORTE-07-0124-FEDER-000028), Co-funded by the Programa Operacional Regional do Norte (ON.2–O Novo Norte), QREN, FEDER.info:eu-repo/semantics/publishedVersio