Mathematical Modelling, Moisture Transport, Shrinkage and Nutrient Content Properties in Drying Selected African Leafy Vegetables

HighlightsPage model best described their drying pattern at moisture content above 0.5 w.b.Shrinkage linearly correlates to moisture loss.Activation energy correlates to air temperature.Vitamins A, C, and E are preserved by drying and storage. ABSTRACT. The study investigated physical, thermodynamic, and nutritional properties with drying and storage of selected African green leafy vegetables. The vegetables studied were: (Jute Mallow), (Slender Leaf), (Cowpea), (Nightshade), and (Amaranthus). Drying experiment was done at 30°C, 40°C, and 50°C in a convective laboratory dryer and drying was pattern fitted to existing models, moisture diffusivity, and activation energy trends were determined, shrinkage was determined from change in leaf thickness, and vitamins A, C, and E were analyzed using spectroscopy and high-pressure liquid chromatography as freshly harvested and after drying at 40°C and storage for 60 days. Results showed that drying occurred in the falling rate period and Page model could simulate the drying pattern of the vegetables with a ˜97% correlation between the empirical and predicted values with the model prediction being precise above 0.5 moisture content on wet basis (w.b.). Shrinkage was found to be a function of moisture loss at a range of 89% to 98% linear correlation. The rate of moisture loss and activation energy correlated with air temperature. The trend in the drying characteristics and moisture transport of the vegetables was unique with each vegetable. Drying at 40°C and storage for 60 days realized a retention in the scale range of 50% to 75% for vitamins A, C, and E. The study showed that drying is an effective way to preserve the vegetables. Keywords: Mathematical modeling, Mass transfer, Nutrient preservation, Shrinkage, Thermodynamic properties.

Effects of drying pattern on aflatoxin in stored paddy rice

This study was done to evaluate the impact of drying pattern on the accumulation of aflatoxin in paddy rice during storage. Two drying pattern includes, 1) single step drying to reduced the moisture content of paddy rice 11-12 % within 6 hours and stored for long time; and 2) two steps drying to reduce the moisture up to 18%, in its first step and stored for short term (2 weeks) and in the second step, dried again to reduce the moisture content up to 11-12% and stored for longer time, with twenty five different paddy rice samples having moisture content ranging from 24-22 % were evaluated for the accumulation of aflatoxins in paddy rice during storage. In addition, this study also evaluated the best drying method that can control the accumulation of aflatoxin during prolong storage. The study results revealed that one step drying is safer than that of two steps drying in accumulating aflatoxins in paddy rice during 210 days of storage. The maximum total aflatoxins (B1, B2, G1,G2) was recorded as 27 ppb in paddy rice sample in two steps drying process, on the other hand, non-detectable level or <10 ppb level of aflatoxins was recorded in all the 25 paddy rice s amples analyzed.Bangladesh J. Sci. Ind. Res.53(4), 253-258, 2018

Mathematical Modeling of Drying Pattern of Ogi Produced From Two Types of Maize Grain

<p>This paper presents thin layer modeling of <em>ogi</em> produced from yellow and white maize at varying soaking period and dried in the cabinet and oven at 50 ºC. The moisture decrease for cabinet dried o<em>gi</em> produced from white maize from 49.0 11.5%, 49.5 to 11.32%, 46.5 to 12.33% and 46.12.29%. The drying rate for both oven and cabinet dried <em>ogi</em> produced from yellow maize decreased from 4.6 to 0.0525 kg/min, 4.5 to 0.0513 kg/min, 4.35 to 0.049 kg/min and 4.4 to 0.047 kg/min while for oven dried <em>ogi</em> followed a similar trend. The experimental data obtained were fitted to five thin layer models: Newton, Page, Herderson and Pabis, Two term and Wingh and Singh models. The values obtained for <em>ogi</em> produced from white maize and dried in the cabinet and oven at 50 ºC for Newton model gave a lower R², ?², RMSE compared with respective values obtained from Page, Herderson and Pabis, two term, Wing and Singh models. The two terms model appear to be the best model among the five models used in this work and had higher R², lower ?², and RMSE. The <em>ogi</em> produced from yellow maize at varying soaking period of 24, 48, 72 and 96 hours and dried in cabinet dryer and fitted with two term showed model constants a, K_0, b, K₁ 0.04315, 0.0388995, 0.919, 2.2 × 10^-3 while the R², ?²RMSE were 0.9933, 5.85 × 10^-4 and 4.85 × 10⁵for <em>ogi</em> produced for 24 hours soaking, respectively. The soaking period does not seem to affect the moisture ratio and the thin layer drying model. However, the initial moisture and equipment seems to affect significantly.</p>