Análise da secagem de cornichão (Lotus corniculatus L.) em leito fixo com escoamento de ar paralelo

Abstract

The growing necessity for the use of cool-season forage species in the southern region of the country has indicated a high demand for quality seeds. Among the legumes, the birdsfoot trefoil (Lotus corniculatus L.) is a forage legume which is originated in Europe and in the Mediterranean region. This versatility in the forage legume has its biggest advantage, since it presents forage production in the spring, summer and autumn, is resistant to drought and temporary waterlogging and shows good persistence of green mass. Furthermore, seeds of such kind can be mixed with winter species, which increases the yield of dry matter, gives a better distribution of the material throughout the year and adds an improvement in the quality of pastures. Despite these advantages, the seeds of birdsfoot marketed still have a poor quality. This fact is a result of an inefficient system of monitoring and difficulties associated to production and processing of the product. Another problem is that the seed producer of this species is facing cutaneous numbness, that is, the seed coat (tegument) is impermeable and does not allow the water, necessary for germination to reache the interior of the seed. In the literature, several studies have reported that there is an increasing demand for an increase in forage seed due to the improvement of native grassland and cultivated pastures. Faced with such a promising market, obtaining better quality seed still presents difficulties ranging from the production phase of the field, where the seeds are harvested early in relation to physiological maturation due to the natural loss process until its processing where the drying process is presented as a limiting step that requires particular attention to avoid losses in physiological final product. In general, drying is defined as the removal voluntary or not, full or partial, of a liquid or gaseous phase of any material by the transfer of heat and mass. Drying has its essence in order to ensure the preservation of a product through reduction of water content. In the case of organic materials, such as seeds, reduction in water content must be performed to the extent that the concentration of sugars, acids, salts and other components are sufficiently high to reduce the water activity and inhibit, therefore, the growth of microorganisms. In the production of high quality seeds the drying technology is seen with one of the most important steps, since it allows reducing the water content suitable for storage and marketing levels (12 to 15% moisture), preserves the seeds from physical changing and chemical induced excess moisture, makes it possible to maintain the initial quality during storage and enables the next harvest physiological maturity. However, the drying process, whatever it may be, should occurs in a controlled and uniform manner in order to avoid high temperature and humidity gradients within the material that could result in loss of quality of the final product. Towards to it, this paper aimed to conduct a study on the drying of seeds of birdsfoot trefoil (Lotus corniculatus L.) in a fixed bed dryer with parallel air flow. To accomplish this goal, this study was divided into the following steps: physical and physiological seed characterization, analysis of rewetting seed process, study of desorption isotherms of the rewetted seeds and evaluation the effects of temperature, air velocity and the height of the tray on the drying kinetics and physiological quality of the final product. The experimental data showed that the results for the dry seeds of UBU were in the range of 5 % to drying carried out at 60 ° C and about 8% to drying carried out at 40 ° C. With regard to seed germination, the values are found in a range of 44 to 59% for the drying carried out in this study. The drying condition whom presented the highest germination value about 59 % was performed on T = 40 ° C, v = 1,0 m/s and h = 1,0 cm.