Drying of Soybean Seeds in a Concurrent Moving Bed: Heat and Mass Transfer and Quality Analysis

The purpose of the present work is to study the simultaneous heat and mass transfer between air and soybean seeds in a concurrent moving bed dryer, based on the application of a two-phase model to the drying process. The numerical solution of the model is obtained by using a computational code based on BDF methods (Backwards Differentials Formulas). The experimental data of air humidity and temperature and of seed moisture content and temperature at the dryer outlet are compared to the simulated values, showing a good agreement. This work also analyzes the effect of the main process variables (drying air temperature, air relative humidity, air velocity and solids flow rate) on the soybean seeds quality during drying. Empirical equations fitted to the experimental data are proposed for predicting the soybean seed quality (germination, vigor and fissures) as a function of the investigated variables.     

Air-Drying of Seeds: A Review

Beginning with harvesting, seeds are usually subjected to a series of processes which include drying for immediate or future use. Seed quality can be influenced by several factors during drying. This article presents a review of the seed air-drying process, including mathematical models based on differential equations derived from mass and energy balances for seeds and air in fixed and moving bed dryers. The article concludes with an overview of several potential drying technologies that can be applied to seeds.     

Quality of Soybean Seeds Undergoing Moving Bed Drying: Countercurrent and Crosscurrent Flows

The present work describes and analyzes Brazilian research related to the quality of soybean seeds dried in moving bed dryers. The main process variables were drying air temperature, relative humidity and velocity, and solid flow rate. The statistical methodology used allowed the achievement of empirical equations for predicting the quality of soybean seeds (germination, vigor, and fissures) in two classical configurations of the moving bed: countercurrent and crosscurrent. The results show that the increase of the seed coat cracking is associated to conditions that lead to a high drying rate. Germination and vigor reduction is also associated to the overdrying conditions.     

Analysis of Seed Quality and Drying Performance of a Multistage Countercurrent Sliding‐Bed Dryer

The effect exerted by the number of stages (one, two, three, and four stages) of a countercurrent sliding‐bed dryer on the quality indices and drying performance of soybean seeds is evaluated by simulation. The two‐phase model is used to describe heat and mass transfer between air and soybean seeds. The constitutive model equations are taken from specific studies. The seed quality is determined based on germination and nonfissured seed indices obtained by empirical functions reported in the literature. The simulated results show that dividing the air mass flux and air velocity can produce a lower seed outlet temperature which may yield higher quality indices and better drying performance in multistage configurations.     

Controlling Argan Seed Quality by NIR

The suitability of using visible/near infrared spectroscopy (Vis/NIR), as a rapid and non‐destructive technique for monitoring the quality of argan seeds (Argania spinosa Skeels) was studied. The analyzed parameters were the fatty acid composition of argan seed oil, seed moisture content, seed oil content and oil stability index (OSI). The ratio between major unsaturated and saturated fatty acids (U/S) during the oxidation assay at constant temperature was studied. Values from infrared drying were used as a laboratory reference for the moisture. Argan seed oil content was determined by Soxhlet extraction. A fatty acid analysis was carried out by gas chromatography and the OSI was determined by the Rancimat test. Predictive models of argan seed moisture, ratio U/S and OSI showed good accuracy. Therefore, Vis/NIR measurements can be used for controlling several argan seed quality parameters. This procedure might be of interest to the argan oil industry, which is currently in the process of modernization and expansion.     

Dehulling of canola by hydrothermal treatments

Hydrothermal pretreatments for loosening the hull of Westar canola (Brassica napus L.) to promote dehulling of the seeds were investigated. The samples tested had on average 14.5% hull on a mass basis. Conditioning treatments involved soaking the seeds in distilled water or exposing the seeds to saturated steam. The moistened seed was treated with one of the following drying methods: unheated-air drying, infrared drying, and fluidized-bed drying. The dried grain was milled in an abrasive dehuller to break the hulls loose. The hulls were removed from the mix by aspiration. The treated seeds yielded a minimum of 11.4% to a maximum of 14.9% of the seed mass as the hull fraction. Nontreated seeds yielded 9.4% of the seed mass in hull fraction after abrasive dehulling and aspiration. Among treatments, raising the moisture content of the whole seed from 6 to 15% by exposure to steam, followed by drying in a fluidized bed, resulted in the maximum percent dehulling efficiency. The hull fraction contained about 24% crude fiber, 18% oil, and 18% protein on a dry-mass basis.     

Effect of air temperature and velocity on moisture diffusivity in relation to physical and sensory quality of dried pumpkin seeds

Understanding the effect of drying process parameters on food quality is helpful in process optimization and control. The objective of this work is to understand the effect of mild and harsh effective moisture diffusivity (D_eff), varied by air temperature and velocity, of drying processes on the physical and sensory quality of flat food products. Pumpkin seeds were selected as a food representative. It was found that increments of air temperature and velocity resulted in increased D_eff and brown color on seed hull surfaces and embryos, but decreased hardness of seed embryos. Changes in taste and aroma of seed embryos were able to be sensed. Indicating that D_eff is related to seed physical quality. Similar phenomena occurred with both tray and fluidized bed drying. Air temperature, velocity, and D_eff should be controlled to ensure the best dried flat food products. Mild drying conditions are potentially preferred for good physical and sensory quality.     

Single Seed Selection for Low Phytate Lines

Most seed phosphorus (P) is bound in phytate which is unavailable to monogastric animals depriving them of P and causing eutrophication from P in animal waste. It is valuable to reduce the phytate levels of seeds used for food and feed. Low phytate mutant seeds such as soybean [Glycine max (L.) Merr.] MIPS (D‐myo‐inositol 3‐phosphate synthase) mutants have correspondingly increased inorganic phosphate (Pi). Measurement of seed Pi levels is an established technique for screening for low phytate mutants but to date it has not been performed non‐destructively from single seed samples. A protocol was developed greatly reducing the sample size thereby reducing the cost and time and saving a generation in the selection of low phytate mutant seeds based on the high Pi phenotype. Pi was extracted using 12.5 % trichloroacetic acid. Pi reacts with ammonium molybdate in acidic solution to form phosphomolybdic acid, which upon reduction with ascorbic acid produces an intensive blue color. This new technique was tested using 1–2 mg samples, 96‐well plates with 8 MIPS mutants (GM‐lpa‐TW1), 8 wild‐type and 8 seeds segregating for the MIPS mutation. Selection of low phytate mutant seeds based on the high Pi level measured via a colorimetric assay based on a reaction of extracted Pi with ammonium molybdate forming a blue color. This was confirmed by DNA analysis of seed chips. This protocol is applicable to many other crop seeds including corn, wheat, rice and sorghum.     

DRYING OF OILSEEDS

Drying of oilseeds is a post harvest operation required for safe storage of harvested seeds. Oilseeds have gained importance in India over the last few years. Fluidized bed (FB) drying and Spouted Bed (SB) drying of oilseeds were studied as potential dryers for these seeds. Experimental pilot fluidized bed dryers were developed and a 2 TPH capacity (mustard seed) FB dryer plant was designed and installed in the lab. Experimental units and a pilot spouted bed dryer were also developed. The dryer units and the plant have been extensively tested and satisfactory drying performance has been achieved. Drying data and drying characteristics have been generated for different oilseeds such as mustard, sunflower, soybean and groundnut etc. The drying rates in different regimes of drying characterized by constant rate and falling rate periods have been evaluated. The salient results of the work are briefly outlined.     

BIXIN POWDER PRODUCTION IN CONICAL SPOUTED BED UNITS

ABSTRACT

Recent work has demonstrated that the red carotenoid bixin is easily extracted from Bixa orellana seeds by particle attrition and impact rather than by solvent extraction. This technique may require a previous step for drying seeds at a safe temperature to preserve pigment quality. A spouted bed (SB) with a draft tube is the most appropriate equipment to process both seed drying and bixin extraction at low operational costs. Operational parameters of the SB unit are optimized as a function of the powder production rate. The maximum air inlet temperature for drying the seeds is also specified. A high performance liquid chromatography method has been developed for the semi-quantitative determination of bixin content in the powder produced. Results show that this SB unit can be more competitive than ball mill equipment.     

Fruit oils of four plant species of Turkish origin

The characteristics of fatty oils recovered from seeds of four plant species of Turkish origin have been investigated. Seed oils ofRhus coriaria L. andEcballium elaterium (L.) A. Rich. showed a close resemblance to those of previously published reports. Oil extracted from the seed ofCeltis australis L. andGundelia tournefortii L. show characteristics similar to fruit oils of the plant families to which they belong. In the focus of their technological evaluation,Ecballium elaterium seed oil can be regarded as a typical drying oil, while the others show characteristics of semidrying oils.     

Analysis of the Drying Kinetics of Brachiaria brizantha (Hochst. Stapf) Grass Seeds at Different Drying Modes

Forage grass seeds have a high economical importance in the Brazilian bovine cattle breeding and seed drying is a fundamental stage of processing to guarantee their stability and allow their storage for long periods. In this context, the objective of this work was to develop a pilot-scale belt dryer, which operates also as a fixed and fluidized bed. Brachiaria brizantha seeds dehydration was analyzed under different air velocities and temperatures. Experimental data of moisture content variation along the drying time was successfully fit to a one-term exponential model. The experimental drying rate points were calculated by approximating the derivatives to finite differences. Its behavior was accomplished fitting curves of the drying rate versus water content and time. Finally, fissure, germination, and vigor rates were analyzed as a function of the drying conditions so that the experimental conditions combine the best process efficiency with the best physiological quality maintenance.     

Improved Estimation of Oil,Linoleic and Oleic Acid and Seed Hull Fractions in Safflower by NIRS

Near-infrared reflectance spectroscopy (NIRS) of intact seeds allows the non-destructive estimation of seed quality parameters which is highly desirable in plant breeding. Together with yield, oil content and quality, a main aim in safflower (Carthamus tinctorius L.) breeding is the selection of genotypes with a low percentage of empty seeds even under cooler climates. We developed NIRS calibrations for seed oil content, oleic and linoleic acid content, the seed hull fraction and the percentage of empty seeds using seed meal and intact seeds. For the different calibrations 108–534 samples from a safflower breeding program with lines adapted to German conditions, were analyzed with reference analyses (Soxhlet, gas chromatography), and scanned by NIRS as intact seeds and seed meal. Calibration equations were developed and tested through cross validation. The coefficient of determination of the calibration (R ²) for intact seeds ranged from 0.91(oil content), 0.90 (seed hull fraction), 0.84 (empty seeds), 0.73 (linoleic acid) to 0.68 (oleic acid). The coefficient of determination of the cross validation was higher for seed meal than for intact seeds except for the parameter seed hull fraction. The results show that NIRS calibrations are applicable in safflower breeding programs for a fast screening.     

SORPTION DRYING OF SOYBEAN SEEDS WITH SILICA GEL. I. HYDRODYNAMICS OF A FLUIDIZED BED DRYER

ABSTRACT

Fluidization technology has been employed to mix soybean seeds and silica gel particles in aim of sorption drying of particulate agricultural products. The characteristic fluidization velocities, mixing mechanisms and fluidization quality have been studied in a 180 mm I.D. fluidized bed. Two sizes of silica gel particles (SG2 and SG3) were selected, with the mass fractions in the range of 0.33–0.75 to form a static bed with height from 100 to 280 mm (H/D = 0.56–1.56). The results show that the dispersion rate of soybean seeds is increased with addition of either SG2 or SG3, and that the frequency and the span of pressure fluctuations within the bed are increased. It is inferred that the gas–solids contacting is improved with addition of small particles in the bed of large particles. In addition, for practical design and operation of such a fluidized bed of binary mixtures, empirical correlations for characteristic fluidization velocities were developed with a wide application.     

The effects of intercepted solar radiation on sunflower (<Emphasis Type="Italic">Helianthus annuus</Emphasis> L.) seed composition from different head positions

The effect of intercepted solar radiation during fruit filling on seed weight and oil content from seeds of three sectors of the head in two sunflower (Helianthus annuus L.) hybrids of low and high potential oil percentage was investigated. Seed weight in each sector depended on both the level of radiation intercepted (modified by shading and thinning plants) and the genotype grown. A higher level of intercepted solar radiation increased seed weight in each sector. Central seeds of shaded plants showed the lowest weight. The seed and kernel oil content hierarchy among the three sectors was modified only in the hybrid with high potential oil content. For each head sector, variations in seed oil content associated with changes in the level of intercepted radiation could be accounted for by changes in the kernel oil content, not in the kernel/seed ratio. Significant relationships were found between seed oil and kernel oil contents when analyses between treatments (R>0.86) and sectors (R>0.92) were carried out. These relationships together with the growing conditions of plants during seed filling, the genotype, and the seed position on the head are essential factors that should be taken into account when selecting seeds in sunflower breeding programs since they affect the commercial/industrial quality of seeds.     

Seed oils fromCitrus sinensis

Comparative analyses of seed oils from the four most important orange varieties at different stages of maturity have shown remarkably similar fatty acid content by GLC. Percentage distribution of fatty acids, refractive index, and iodine number could probably be used to differentiate or help confirmCitrus species since there is enough variation between species to make a valid comparison. Seed content was noted as being related to fruit maturity, as was moisture content of seeds. The oil content of pineappleorange seeds was found to be variable, correlated to moisture content of seeds, and it reached a maximum when seed moisture had decreased to approximately 49%. Journal Series No. 1662. University of Florida Agricultural Experiment Stations.     

Phospholipids of environmentally stressed soybean seeds

Protein and oil content of the soybean [Glycine max (L.) Merr.] seed and the fatty acid composition of the oil can be altered by environmental stress. The objective of this study was to characterize the composition of the phospholipid (PL) from soybean seeds after exposure to drought and high temperature during seed fill. Drought stress was imposed on greenhouse-grown soybean plants at temperatures of 28 and 33‡C after the beginning of seed fill and was maintained throughout the seed-fill period. The fatty acid composition of each PL class was altered by drought and high temperature. With phosphatidylcholine and phosphatidylethanolamine, which composed 89% of the separated PL, greater proportions of 16:0 and 18:0 and lesser proportions of 18:2 and 18:3 were present in soybean seeds exposed to high temperature and severe drought. More linolenic acid and less palmitic acid were present in phosphatidylinositol. The changes were comparable to those of the triglyceride because of high temperature. The elevated temperature increased the proportion of phosphatidylcholine and phosphatidylinositol and decreased that of phosphatidylethanolamine. The effect of drought and high temperature stress on PL class and fatty acid composition has important implications on the quality of soybean seed oil and lecithin and on the ability of the seed to maintain optimum rates of metabolism in the development and germination environment.     

Corn,Rice, and Wheat Seed Drying by Two-Stage Concept

Corn, rice, and wheat seeds with an initial moisture content (IMC) of 20–25% wb were dried to moisture content below 18% wb at 40–80°C in a fluidized bed dryer (FBD) and spouted bed dryer (SBD) and the seeds with IMC 18% wb were dried to below 14% wb at air temperatures 18–30°C and relative humidity 60–70% by an in-store dryer (ISD). As a result, it appears that a two-stage drying concept is feasible in drying high-moisture-content seeds due to the high germination rate of dried seeds. Nonetheless, the drying temperature must be carefully selected. A drying temperature of 40°C was clearly safe for all samples, whereas more than 90% of wheat seeds still germinated after drying at 60°C in FBD. Furthermore, drying seeds with IMC 18% wb by ISD was safe under specified drying conditions.     

Microwave vacuum drying of lotus seeds: Effect of a single-stage tempering treatment on drying characteristics,moisture distribution,and product quality

This study evaluated the effects of a single-stage tempering treatment during microwave vacuum drying (MVD) on drying characteristics and quality of lotus (Nelumbo nucifera Gaertn.) seeds using two parameters: intermediate moisture content (IMC) and tempering temperature (4 and 25°C). Magnetic resonance imaging (MRI) was used to examine moisture migration and distribution in individual lotus seed during tempering. Results from MRI showed tempering could reduce the moisture gradient in lotus seeds during MVD. The tempering treatments led to increased moisture diffusivity (3.96–43.56%) and a shortened drying time (6.25–31.25%) when compared with continuous MVD. Furthermore, tempered samples exhibited a greater rehydration capacity, a limited overall color change, and increased amounts of taste-active amino acids when compared with nontempered lotus seeds. High IMC improved rehydration ratios of dried samples. Low tempering temperature provided favorable free amino acid content and desirable product color.     

Comparison of Different Possible Technologies for Epoxidation of Cynara cardunculus Seed Oil

The world production of epoxidized vegetable oil, mainly epoxidized soybean oil, is continuously increasing because this product can have a wide range of applications. Non‐edible vegetable oils, recovered by the plants growing on marginal and polluted lands, represent a possible answer to industry versus food chain debate. Cardoon (Cynara cardunculus L.) seed oil can be considered as an interesting and sustainable alternative to edible soybean oil to make plasticizers. In this work, a comparison between different epoxidation methods of cardoon oil is depicted and argued, focusing on strong points and weaknesses for each of them. It is found that cardoon seed oil can be successfully epoxidized through feasible existing technologies, by peracids and hydrogen peroxide equally. Moreover, it is demonstrated that a “greener” cardoon oil epoxidation process is possible, by using hydrogen peroxide in the presence of commercial γ‐alumina as heterogeneous solid catalyst. Practical Applications: The paper analyzes the advantages and the problems of different epoxidation methods in order to obtain a final product with high quality and answer the environmental, social, and economic sustainability requirements.