AGRE-0029 Improvement of Sunflower Dehulling Capacity

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ECLAIR Cluster I - Oils : Separation/Fractionation : Vegetable Oil/Fat

Prototype seed dehuller

SUMMARY

For many oil crops, the fibrous by-products left after oil extraction are marketed as animal feed. For several crops, the feed value for fowl and monogastrics is enhanced by the protein content of the residues. However, in the case of sunflower the use of the meal in animal feeding has been limited due to the high fibre content caused by residual seed hulls. Industrial dehulling is already performed in some countries (Argentina, France, Spain, USA), but the meal quality in terms of digestibility for poultry and monogastrics such as pigs, as well as protein content, is very variable. This reflects a large variations in the extent of dehulling. Experiments on technology for dehulling sunflowers carried out in France indicated that one of the most important factors affecting this is the properties of the seeds themselves. This ECLAIR project approached the problem over a broad front, aiming to obtain a better knowledge of the many different scientific, technical and economic areas (including plant physiology, agronomy, breeding and technology) for improving sunflower dehulling ability. A dehulling-sorting system has been established, as have factors (environmental, genetic and process related) which affect dehulling. As a result of this work a new process flowsheet has been designed.

INTRODUCTION

For many oil crops, the fibrous by-products left after oil extraction are marketed as animal feed, the value of which reflects both metabolisable energy (carbohydrate) and protein content. However, in the case of sunflower, the use of the meal in animal feed has been limited due to the high fibre content caused by residual seed hulls. Variability in the extent of hull removal results in a feed material which is also variable in terms of quality and value, giving poor digestibility for poultry and monogastrics such as pig.

Although consumption increased by a factor of three between 1981 and 1992, reaching nearly 4 million tonnes per annum, sunflower use is limited at present to low energy formulations. In the past, experimental work on technology for dehulling sunflowers carried out in France has suggested potential economic benefits of such technology which can increase the energy value by about 25%. This preliminary work suggested that the most important factors influencing the efficiency of dehulling are related to the seeds themselves. Hence, this research project adopted a broad approach, aiming to improve knowledge over a wide range of different scientific, technical and economic areas (including plant physiology, agronomy, breeding and technology) in order to improve the ability to dehull sunflower seeds prior to crushing to obtain vegetable oil.

OBJECTIVES

The objectives of the project included the development and evaluation of a laboratory dehulling system capable of accurately measuring dehulling using small samples of seeds and relating these to anatomical observations. In addition, they included aspects of plant breeding and the impact of environmental conditions on the extent and ease of dehulling of the seeds, as well as nutritional studies which were carried out using meals from dehulled sunflowers. The economics of the processes investigated were also studied. The work was led by CETIOM, the technical centre for French oilseed producers, and included, in addition to plant breeders from Universities and research, a French manufacturer of dehulling systems (TECMACHINE) and an oilseed crushing company (COMEXOL), which operates in sunflower in France and Spain.

ACTIVITIES

A small laboratory dehulling system was set up to measure the dehulling of batches of seeds. This was used both within the breeding programme, in order to rapidly compare different cultivars, and within the technology assessment, to forecast the ease of dehulling of commercial samples. Anatomical investigations were carried out in order to determine to what extent variations in dehullability can be explained by structure differences between seeds and to what extent these differences are under genetic control. A large variability of dehulling ability was observed in comparisons of more than 40 lines, cropped in 3 different environmental conditions, in 1992 and 1993. This enabled a breeding programme to be set up for genotypes which produced seeds with both a good dehulling ability and a high oil content. A comparison of parent lines and hybrids indicated high heritability (ratio 0.77 to 0.85). However, studies of environmental effects, in collaboration with breeders, indicated that there is a negative correlation between the moisture content of the seeds when harvested and dehull; the higher the moisture content, the lower the dehullability. Natural desiccation, taking place in good weather conditions, gives a crop that is easier to dehull. However, it has been found that the genetic effects are always predominant over environmental conditions. Even so, possibilities exist for improving dehulling of moist seeds by drying. Hence, various drying technologies were investigated as means of improving the dehullability of seeds. This included a comparison of the efficacy of traditional warm air drying with the feasibility and benefits of superheated steam drying. In fact such steam drying was found to significantly improve the process without damaging oil quality. However, protein solubility is lowered and the process generates much more kernel fines, picked up in the hull fraction, than dehulling without heat pretreatment.

COMMERCIALISATION

As a result of this work, a flowsheet for dehulling and sorting has been developed which has recommendations for the design of a new industrial dehulling system. At the same time, the nutritional value of several dehulled sunflower meals has been determined and the profitability of dehulling for both the crusher and the user of dehulled sunflower meal for animal feed has been studied. Profitability of dehulling depends for a large part on good technical control of the process, with maximum crude oil output which has improved reduction of loss of oil in hulls. Profitability also depends on hulls and crude oil prices, but in general it appears that dehulling can, under some conditions, increase the marketability of sunflower meal.

PARTICIPANTS

INRA, Station d'Amelioration des Plantes (Clermont-Ferrand, France), Istituto di Agronomia, Facolta di Agraria (Universita di Pisa, Italy), CIDA Junta Andalucia (Cordoba, Spain), Tecmachine (Andrezieux-Boutheon, France), Comexol (Bunge) (Boulogne-Billancourt, France), Istituto di Zootecnica Speciale (Pisa, Italy), INRA, Lab de Technologie Appliquee a la Nutrition (Nantes, France), Universite Paul Sabatier, Laboratoire Botanique et Forestier (Toulouse, France), CEREOPA, (Paris, France).