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This study aims to investigate the drying kinetics, energy analysis and milling performance of two common rice varieties namely BRRI-28 and BR-16 by two stage drying. Parboiled paddy samples were dried employing two schemes of two stage drying. First scheme is first stage by fluidized bed drying at temperature profile of (150–170 °C) with fixed bed thickness of 10 cm, tempering (30 min) and followed by fluidized bed drying again using lower temperature 80±2 °C and second scheme is first stage fluidized bed drying (150–170 °C) and tempering and followed by sun drying method. In addition, sun drying method as complete single stage drying was considered as control drying. Drying results indicated that total drying time required in first scheme, second scheme and control drying are 1.4, 4.75 and 11–12 h, respectively. Energy analysis showed that for both paddy varieties, first scheme yielded the highest specific electrical (12.6 MJ/kg H2O evaporated) and thermal energy consumption (10.5–11.6 MJ/kg H2O evaporated) compare to second scheme (0.58–1.6 MJ/kg H2O evaporated) of drying. Milling quality as head rice yield (HRY) was significantly varied among the drying schemes. For BR-16 variety, first scheme yielded the highest HRY (66 ± 0.706%) compare to BRRI-28 variety that yielded the lowest HRY (43.9 ± 0.571%). Better milling recovery (75 ± 0.64%) was obtained in first scheme compare with control dried sample (71 ± 0.56%). Therefore, parboiled paddy is suggested to be dried by any scheme of two stage drying for achieving quality dried grain with minimum energy consumption.

Abstract A prototype refrigerated unit with a capacity of 30 to 60 kg depending on bulk density was designed and developed to preserve fresh fruits and vegetables. The performance of the device was evaluated in terms of cooling time, cooling efficiency, specific energy consumption, unit device cost, and quality of stored products. Guava and cauliflower were stored in the device at 5 ± 1 °C and 6 ± 1 °C, respectively at 95 ± 2% relative humidity (RH) to evaluate the storing performance of the device. The cooling time was 2.08 ± 0.05 h at 5 °C and the device showed little fluctuation in relative humidity under load conditions compared to empty conditions at set temperatures of 5 °C and 6 °C. Notably, the cooling efficiency of the device was 93 ± 2% with specific energy consumption of 0.0524 and 0.1104 kWh/kg day for preserving guava and cauliflower, respectively. The overall preservation cost was $0.116 and $0.242 per kg per month for guava and cauliflower, respectively. The results revealed that the shelf life of guava extended for 18 days in this refrigerated device with minimal quality degradation and a weight loss of 3.78%, compared with freshly harvested guava. On the contrary, the weight loss, firmness, pH, and whiteness index for cauliflower at 18 days were 7.17%, 7.17 kg/cm2, 6.59, and 64.19, respectively. Meanwhile, the fresh cauliflower exhibited a firmness of 9.85 kg/cm2, a pH of 5.74, and a whiteness index (L*) of 65.58. The results demonstrated that the freshness of stored fruits and vegetables was preserved, meeting physiological and chemical quality standards. Therefore, the inexpensive refrigeration system, effectively maintains necessary temperature and humidity levels, offering a profitable solution for minimizing post-harvest losses at the greengrocer level. Additionally, the scientific methodology outlined can be readily applied to develop commercial-scale refrigeration units for preserving high-moisture produce.

Drying vegetables in a suitable dryer is an imperative concern in the food-processing sector. To address this issue, a cabinet-type tray dryer has been developed by modifying its design, employing a comprehensive approach ensuring uniform air velocity and temperature in all the trays, and naming it a modified tray dryer (MTD). A comparative analysis of drying performance, physical characteristics, functional attributes, and antioxidant capacity of mallow (Malva verticillata) vegetables dried in MTD and existing three drying methods such as sun, shade, and traditional cabinet drying was accomplished. The performance evaluation study revealed that MTD demonstrated a faster moisture removal capacity and required less drying time compared to other drying methods. Statistical analysis revealed that drying methods had a significant (p < 0.05) impact on the physical properties, functional qualities, and bioactive functions of the dried mallow powder (MP). The higher chlorophyll content (27.41 ± 0.84 mg/100 gm of dry matter, DM), total phenol content (15.71 ± 0.95 mg GAE/g DM), and DPPH activity (8.82 ± 0.81 mg TEAC/g DM) were noticed in the mallow vegetable powder dried in MTD than shade, sun and traditional cabinet drying methods. A slightly lower value (statistically insignificant) of ascorbic acid content (9.64 ± 0.78 mg/100 gm DM) and total flavonoid (1.44 ± 0.05 mg QE/g DM) was achieved in contrast to other drying methods. The antioxidant capacity of the analyzed data was lowest for shade drying compared to other drying methods, while MTD exhibited the highest capacity. Therefore, this study might assist in selecting a suitable dryer for drying vegetables. The findings suggest that MTD can be an alternative drying technique as a quicker drying technique and for obtaining better-quality dried products in terms of antioxidant and functional properties than the traditional and existing process of vegetable drying.

This research aimed to evaluate the effect of two-stage drying techniques on drying characteristics and selected physical parameters, colour, and nutritional qualities of dried maize. To execute this study, the maize sample was dried by (i) fluidized bed drying at 120–160 °C temperatures followed by sun drying at 32 °C (Technique 1), (ii) fluidized bed drying using higher temperatures (120, 140, and 160 °C) at first stage followed by lower temperature (65±2 °C) at the second-stage (Technique 2), and (iii) sun drying method (∼32 °C) (control). Results signposted that lower drying time was attained in the second approach (1.5 h) compared to the drying Technique 1 (4.5 h) while the sun drying method took 10 h for plummeting high moisture (25.43%, wb) to a safe level (

A straw chopper is a mechanical device used to uniformly chop fodder into small pieces to mix it together with other grass and then feed it to livestock. The objective of this research was to design and develop an animal fodder chopping machine to be utilised by dairy farmers within their purchase range. The drawing of these machine parts was undertaken in AutoCAD software and the construction was performed in a local workshop. After development of this machine, performance tests were carried out on a farm. The chopping machine tests were carried out with commonly grown fodder (namely: straw, grass, and maize) in Bangladesh. The performance evaluation of the developed machine was carried out in terms of the chopping efficiency, machine productivity, and energy consumption. The economic analysis of the straw chopping machine was assessed by indicating the cost effectiveness to the poor farmers. Analysis of the data in regard to chopping efficiency and machine productivity varied from 93 to 96% and from 192 to 600 kg×h-1, respectively. The energy consumption during the chopping process ranged between 0.0025 and 0.01 kWh for the different types of fodder. The break-even point of the fodder chopping machine was 3 793 kg of cut straw and the payback period was within one year depending on the use.

Effects of drying temperature (60, 70, and 80 °C) and air velocity (3.0, 6.0, and 9.0 m/s) on thin layer and color kinetics of maize grain during mixed flow dryer (MFD) were investigated for the present study. Five thin layer grain drying models (Henderson and Pabis, Page, Lewis, Midilli et al. and Wang and Singh) as well as Zero order reaction rate were applied with the experimental data to predict the drying and color kinetics of maize, respectively. Increased drying temperature had significant leverage on drying time whereas proliferation of air velocity (>6.0 m/s) is scarcely imperative. Model fitting analysis revealed that Lewis and Page model is aptly applied in evaluating drying kinetics for mixed flow drying of maize as coefficient of determination (R2) is higher. Effective moisture diffusivity (4.92 × 10−7 to 8.38 × 10−7 m2/s) was maximum both for higher temperature and air flow whereas specific energy consumption was lowest (2.75 MJ/kg) for lower temperature and air flow. Regression analysis of color attributes (L*, a*, and b*) designates that color kinetics of maize grain occurred according to the zero order reaction. L* and b* indices of color decreases while a* and color difference (ΔE) increases with drying temperature and time. Thin layer and kinetic constant (k) is proportionate with drying temperature while adverse results were noticed for color attributes. Drying and color degradation kinetics of maize can readily be described by Lewis and Page model and zero order reaction, respectively for mixed flow drying.