Proximate composition and selected phytochemical component of Dawrach (Raphanus raphanistrum L.) as affected by blanching temperature.

Dawrach (Raphanus raphanistrum L.) is an underutilized wild edible plant belonging to the Brassicaceae family. Dawrach is widely regarded as a weed, and there is a lack of information about its nutritional profile such as, proximate, antioxidant properties, health-promoting vitamins, minerals and significant phytochemicals. The plant also contains anti-nutrients which need a pretreatment to be minimized and deteriorating enzymes that should be inactivated to make shelf stable products. Blanching temperature is the most critical factor that needs great attention during the blanching process to minimize the anti-nutrients and minimize the loss of desirable components of Dawrach such as, proximate and phytochemical contents and antioxidant activity. Thus, this study aimed to investigate the influence of blanching temperatures on the proximate, phytochemicals and antioxidant activity of Dawrach leaves. The parameters were evaluated following standard analytical methods and procedures. Dawrach leaves were blanched at 50, 60, 70, 80, and 90 °C temperature for 3 min, and raw or unblanched Dawrach was used as a control. Blanching temperature significantly affected the proximate, phytochemicals, antioxidant activity and anti-nutrients of the Dawrach. As a result, the moisture content of raw and blanched at 90 °C was 10.77 and 7.69 g/100g, respectively. Thus, blanching decreases the moisture content of Dawrach to the recommended safe moisture level for the products. Moreover, there was a significant decrease in the values of antioxidants activities, beta carotene, and l-ascorbic acid as the blanching temperature increased from 50 to 90 °C. Besides, as blanching temperature increased, there was a reduction in oxalate and tannin of the Dawrach leaf.

Harmonizing Drying Time, Layer Thickness, and Drier Zones for Drying Kinetics: Quality and Safety of Solar Tunnel-Dried Wet-Processed Parchment Coffee (Coffea arabica L.).

Tunnel solar dryer is the recently used drying method for better quality and safety of parchment coffee. However, the higher variation of drying temperature and RH along the long tunnel solar dryer results in a heterogeneous environment in the tunnel, which could make parchment coffee dried at different times or with different moisture contents. This study is aimed at investigating the effect of solar tunnel dryer zones at different zones of the dryer, divided into three zones from the inlet to the exit side of the drier and drying layer thicknesses on the drying time, drying kinetics, physicochemical, sensory, and fungal growth loads of parchment coffee. Furthermore, seven mathematical models were evaluated to select the best-fitting model for a specific zone to predict drying time. Results showed that dryer zones significantly (p < 0.05) interacted with layer thickness for most of the measured parameters except titratable acidity and sensory properties. The dryer zone, coupled with the reduction in drying layer thickness, caused an increase in effective diffusivity and moisture removal rate and reduced drying time. The drying time to reach constant moisture content varied from 14 to 17 hours. Overall raw bean, cup, and total quality varied from 36.3 to 37, 48 to 51, and 84.3 to 87.3%, respectively. Values for physicochemical parameters ranged from 5.3 to 6.9 (pH), 2.1 to 2.6% (titratable acidity), 2.3 to 4.3°Brix TSS, 10.9 to 15.2% (ether extract), 39.2 to 53.5GAE/g (total phenolic content), and 38.5 to 59.2 (DPPH scavenging capacity). The fungal infection percentage at the end of drying varied from 4 to 93.3%, which could be associated with potential mycotoxin formation if recommended conditions were not maintained. In general, for better quality, similar drying times, and a lesser fungal load, it is recommended to use 4, 5, and 6 cm layer thickness in zones one, two, and three, respectively. The drying kinetics of parchment coffee in different dryer zones with different drying layer thicknesses showed variation. Zone one at 2 and 4 cm layer thicknesses is best described by the Verma model. Four- and six-centimetre layer thicknesses in zones 2 and 3 are best described by the modified Midilli model.

Effect of Pretreatments and Solar Tunnel Dryer Zone on Drying Characteristics and Stability of Pumpkin (Cucurbita maxima) Slices.

Drying fruits and vegetables can be achieved using different drying methods based on the crop's economic value and the technology's affordability. However, in Sub-Saharan Africa, where sunlight intensity and duration are high, it is recommended to use solar drying methods. A solar tunnel dryer is one of the methods commonly used to produce dried fruits and vegetables. It is necessary to determine the drying kinetics at different dryer zones and select a suitable drying kinetics model to overcome the limitation. In addition, pretreatment methods are commonly recommended to improve the quality of the dried product. This work aimed to determine the drying kinetics of pumpkin slices at different zones of drier and pretreatment effect on product quality. Three zones of drier and four pretreatments were employed in the two-factor factorial experiment. Seven thin layer kinetic models were evaluated. pH, TSS, TA, moisture content (MC), and water activity (a w) were determined for quality evaluation. Recorded data showed that the temperature in the tunnel increased from zone I to III with a decrease in RH. Results showed a higher drying constant (K) and effective diffusivity (D eff); drier zone III > II > I. Pretreatments also showed a significant effect on K and D eff. Regardless of pretreatment types, two-term exponential and diffusion models are better fitted for zones I and II/III, respectively. With pretreatments and drier zones, the TSS value increases from zones I to III but with a decrease in titratable acidity, moisture content, and water activity. From the result, it can be concluded that different drying rates are observed in different zones. However, a better quality of pumpkin powder was observed in drier zone II for pumpkin slices pretreated with a 2% salt solution. It is recommended to create a drying medium that resembles zone II or better to use the recommended kinetic models to predict the drying time for each zone for a better quality product by avoiding under- or over-drying of slices.

Effect of pretreatments and solar tunnel dryer zones on functional properties, proximate composition, and bioactive components of pumpkin (Cucurbita maxima) pulp powder.

Pumpkin fruits are large in size and need to be cut into pieces for use. The quality and storage life of cuts rapidly deteriorated. Big size fruits can be converted to shelf stable product to minimize postharvest loss using solar driers. However, drying temperature and RH in long solar tunnel drier not uniform and may affects quality of dried products. Therefore this research work aimed to investigate the effects of pre-drying treatments and solar tunnel dryer zones on the functional properties, proximate composition, and bioactive components of pumpkin pulp powder. Three groups of pumpkin slices were pre-treated in 1% citric acid (20 min), 2% salt (20 min) solutions, and the other group blanched at 65 °C in 1% salt solution (2 min), untreated sample used as a control. Pre-treated samples then dried in three zones of tunnel solar drier (zone I, zone II and zone III). Treatment combinations were laid down in factorial RCBD replicated 3 times. Results showed that pulp powder from salt pre-treated slice and dried at zone III results in the highest values of shrinkage, rehydration ratio, water holding capacity, and bulk density. Moisture content decreased from zone I to III, and with salt blanching in range of 8.2 to 6.4%, no effect in crude fat content, slices pre-treated in 2% salt solution results is better crude protein and fiber contents in zones. Better retention of total polyphones, beta-carotene, ascorbic acid, with high DPPH scavenging activity and lowest IC50 values were observed for salt pre-treated sample but dried in zone II of the drier. In general relatively better functional properties, proximate composition and bioactive compounds of the powder can be preserved when slices pre-treated in 2% salt solution and dried in zone II of solar tunnel drier characterized by 54.9 ± 3.7 °C, RH value of 31.4 ± 3.4% and air velocity of 0.45 m/s.