Dehulling of coriander fruit before oil extraction

Abstract

Coriander (Coriandrum sativum L.) is a summer annual traditionally grown for use as fresh green herb, spice or for its essential oil. The essential oil is obtained by steam distillation of crushed fruit and the residue is utilized as feed or processed further to recover the triglyceride. The triglyceride is obtained from the whole fruit by mechanical pressing or by solvent extraction. The coriander fruit has low density due to the void space between the mericarps and the high proportion of hulls in the fruit’s weight. Dehulling oilseeds before oil extraction is commonly employed whenever it is practical to do so, but this technique has not been applied to coriander seeds. This study evaluated the feasibility of dehulling coriander fruits as part of the seed preparation before oil extraction and developed a simple process of dehulling coriander. Coriander fruit with 17.6% oil and 10% moisture was dehulled by first splitting the fruit using an impact huller or a roller mill. Seeds still encased in the split hulls were loosened further using the impact huller. The hulls were removed by screening, aspirating, or using a gravity separator. Dehulled seed with purity >95% was attainable. Dehulling the coriander fruit reduced the weight by 50% and reduced the volume by 60%. Dehulling coriander also doubled the oil content, increased the crude protein by 70%, reduced the crude fiber by 28%, and reduced other carbohydrates by 65%. The coriander fruit and dehulled seeds with purity up to 95% were amenable to screw pressing. Prepressing and solvent extraction would be more appropriate for pure dehulled seeds due to their high oil content. Dehulled seeds must be oil extracted right away to minimize the increase in free fatty acid.