Drying of plums to prunes is an important postharvest processing step, as it results in a product with higher nutrient density, increased shelf life, and significantly greater antioxidant and fiber content. However, due to the waxy layer present on the plums surface having low permeability toward moisture, plum dries very slowly which is an energy-demanding process. Therefore, to breakdown waxy layer on the surface and enhancement of skin moisture diffusivity, two genotypes (V91074 and V95141) of Yellow European Plums (YEPs) were dipped in 1% (w/ v) of Ascorbic Acid (AA), Citric Acid (CA), and Potassium Metabisulfite (KMS) solution for 1 min at 40°C. The pretreated YEPs were dried at three different temperatures (50°C, 60°C, and 70°C) until a final moisture content of approximately 30% (wet basis) was reached. It was observed that treated samples (AA and KMS) dried faster as compared to untreated samples, except for CA treatment where no significant difference in drying time was observed. One model cannot be selected for describing the thin layer drying characteristics of YEPs. Five out of 11 models used were found to be a perfect fit for genotype V91074 and genotype V95141, respectively. Pretreatment had a significant effect on effective moisture diffusivity (D eff ). D eff for untreated and treated plum samples ranged between 4.6 × 10 −11 to 8.6 × 10 −11 (m 2 /s) and 4.9 × 10 −11 to 9.1 × 10 −11 (m 2 /s). The drying temperature had a significant effect on phenolic content and antioxidant activity, whereas no significant effect of pretreatment was observed.
Rice bran, which is one of the major by products of paddy contain high quality proteins and edible oil apart from fibre, ash and NFE (nitrogen free extract). The existing solvent extraction method employs n-hexane as the most viable solvent for the extraction of oil from rice bran. But the high cost and scarce availability of n-hexane resulted in uneconomical extraction of rice bran oil. In this study, rice bran was ohmically heated for different time periods(1, 2 and 3 min) with different current values (5, 15 and 20 A) and with different concentration of sodium chloride (1 M, 0.1 M and 0.01 M) as conducting medium. The ohmically heated rice bran was subjected to extraction studies. Ohmic heating of rice bran of paddy varieties Red Triveni and Basmati reduced the extraction time by nearly 75 % and 70 % respectively and gave a maximum quantity of oil extracted when compared to bran, which was not ohmically heated. From the experiments with varying concentrations, residence time of ohmic heating and currents, it was found that ohmically heating the rice bran with 1 M sodium chloride solution and with a current value of 20 A for 3 min gave maximum oil extraction with minimum extraction time.
Microwave drying of corn (Zea mays L. ssp.) was conducted in this study and its germination was tested after drying. The objective of the test was to determine an optimum microwave drying method for corn seeds to achieve maximum germination and minimum drying time, as well as to obtain the maximum temperature that can achieve the best results without reducing the viability. The different methods used for drying included constant temperature drying at 30, 40, and 50 C; intermittent power microwave drying; and fixed power microwave drying at 2, 3, 3.5, and 4 W/g. The drying was started with an initial moisture content of 33% (wb) and ended with a final moisture content of 16% (wb). In the constant temperature method, the microwave power was automatically controlled to keep the temperature constant throughout the drying period. A control cycle of 20 s was used for intermittent drying in which the microwave generator was on for 12 s and off for 8 s throughout the drying process. In fixed power microwave drying, the power was constant throughout the process. The germination tests were conducted on all samples with the rolled blotting paper method. The minimum drying time was reached with 4 W/g fixed power where 0% germination resulted. The optimum method for drying of corn seeds for maintaining a high germination rate was 4 W/g intermittent power microwave drying, which took 110 min to dry from 33% moisture content to 16% (wb). The germination percentage of 4 W/g intermittent power was 93.3%. The maximum permissible temperature of corn seeds when subjected to intermittent microwave power resulting in maximum germination was 67 C.
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