Spice Oil and Oleoresin from Fresh/Dry Spices
From time immemorial, people in many parts of the world have been using spices and herbs extensively to improve the flavour and aroma of food materials. Initially ground spices were used for this purpose. With the development of flavour industry the requirement for flavours have shifted from ground spices to Oils and Oleoresins. It is well known that flavours of all natural products are subject to a wide range variations. Even seasonal variations are not uncommon. When spices and herbs of the same species are grown in different geographical regions, there are variations in their flavour and aroma due to the compositional difference of the essential oil and flavouring compounds present in them. Oleoresins provide a uniform standardized flavour and its application is much more process friendly than application of ground flavors.
Currently the oils and Oleoresins are recovered from the spices by solvent extraction using solvents like hexane, acetone, methylene chloride, ethylene dichloride, supercritical carbon dioxide etc. The solvent extracted resins are carefully processed to remove the solvent and bring it down to 25 to 30 ppm residual solvent. Chlorinated solvents are widely used by the industry and due to strict regulations being imposed by the importing countries efforts are on to change over to other safer solvents.
India is the major producer of oils and oleoresins and about 95 per cent of the world demand is met by India. Currently dry spices are used for oleoresin manufacture and efforts were on for long time to develop a suitable technology which is commercially viable and can recover the active ingredients present in the spices economically. The spices when they are dried under the sun or by artificial means loose the major aroma imparting volatiles and the oleoresins produced from them do not have the pleasant aroma of the fresh spices. Since India is the major producer and consumer of spices, the fresh spices are available and in many places they are sold under distress conditions due to lack of processing and storage facilities. Thus it will be relevant in the social as well as from the marketing point of view to process the fresh spices to make value added products like oils and oleoresins from them. Thus oleoresins from fresh and dry spices can capture the international market and India has the unique opportunity to produce both the products because of the availability of the raw materials in fresh as well as dry form.
The north-eastern regions of India offer excellent raw material for oil and oleoresin industry. The agro climatic conditions existing in that part of the country prevents them from going for drying and material is available in plenty even during off seasons at competitive prices. The technology of processing fresh material without drying assumes significance in this context. If India is to make oleoresins and oil at a lower cost the potential of the north east have to be tapped. The selection of the raw material determines the end product quality. The active ingredients are analysed prior to purchase of the raw material to see that they meet the requirements for oleoresin manufacture. The ratio of active ingredient to volatile oil, the content of the active ingredient, the yield of oleoresin etc are ascertained before procurement. In certain cases the raw materials from different sources have to be blended to meet the customer requirements. The profitability of oleoresin manufacture depends to a great extent on the sourcing of the right raw material at the right price to meet the customer requirement. Processing the material at the appropriate time when the prices are low will reduce the inventory cost drastically. The pepper produced in India have a piperine content of five per cent compared to 9 to 10 per cent in Srilankan or Vietnamese pepper. Similarly the essential oil content in Srilankan pepper is as high as six to seven per cent compared to three or four per cent in Indian pepper. Thus it is obvious that selection of raw material plays a key role in the profitability.
Size reduction, reduction of the moisture, extraction and stripping off the solvent are the major operations involved in the manufacture of oils and oleoresins. In the case of fresh spices, the high initial moisture content necessitates the reduction of moisture levels by mechanical means to accomplish the high extraction efficiencies required by the industry. The dewatered fresh spices form two streams - one aqueous portion and another solid portion. The solid portion goes for extraction just like the dry spice where as the aqueous portion which has negligible amount of resinous matter but high percentage of essential oil goes for a simple distillation process. The distillation of the aqueous portion results in foaming and emulsion formation and proper design of the equipment and distillation conditions are to be ensured for the efficient recovery of the essential oil.
The extraction of the spices are done in stainless steel extractors provided with a jacket for passing hot water/ steam. The extractors are provided with a perforated bottom plate and jute cloth is spread over it to prevent the material going along with the miscella. The material from the size reduction unit are then fed into the extractors and each extractors are designed to hold 1.5-2 tonnes of ground spices. In the case of pepper and deseeded chillies it will hold more of the spice. The material after loading into the extractors are leveled properly so that no channeling take place.
Ethylene dichloride is the most commonly used solvent by the industry. But the restrictions imposed on the use of chlorinated solvents by the importing countries have made the industry to look for alternate solvents like hexane, ethyl acetate, alcohol, methyl alcohol, acetone and/or its mixtures. Research work is underway at the Regional Research Laboratory to go for eco friendly solvents other than supercritical carbon dioxide which will replace the conventional organic solvents. The oleoresin plants currently designed have provisions to go for any solvent system and are designed to switch from one solvent to another depending on the requirements.
Extractions are done in the batch extractors with sets of 4 or 3 extractors operating with different spices. After loading the extractors with the spices solvent is added to immerse the solids completely. The solvent is then raised to higher temperature and after a few hours the concentrated miscella is pumped for evaporation. Fresh solvent or lean solvent from other extractors are added for the second and subsequent washes. The extraction is repeated until the miscella becomes lean. In certain cases the spices are subjected to steam distillation prior to extraction for the recovery of the aroma imparting essential oils.
After the complete extraction, the solvent adhering to the bed has to be recovered. This is accomplished by steaming the bed and vaporizing the solvent from the bed. The vapours rising from the bed are condensed and collected for re distillation. To ensure complete removal of solvent from the bed, the steam rate have to bo maintained at half the weight of the charge.
The miscella from the extractor is concentrated in an evaporator provided with a distillation . Once the temperature in the evaporator starts raising above a certain temperature the concentrated miscella is pumped into the stripper or scraped surface heat exchanger for final de-solventisation. Scraped surface evaporator ensures short residence time and efficient solvent removal without affecting the product quality.
Final removal of the solvent is done in a stripper which is basically a reboiler provided with a rectification column. The concentrated miscella is evaporated in a re-boiler provided with a jacket steam heating and anchor type stirrer. The vapour is allowed to rise through a rectification column provided with structured packing or SS mesh packing and is condensed. Any remaining solvent will evaporate and the condensate is periodically tested for the presence of solvent. The stirring of the oleoresin and its recirculation are ensured so that proper mixing is effected. At the high vacuum and temperature maintained in the stripper, moisture and residual solvent if any, are removed. A sample of the oleoresin is then drawn for analysis. After the analysis if the oleoresin is free of solvent, it is pumped to the batching tank through the filter press. If any residual solvent is left, the oleoresin is aerated prior to pumping to achieve the permissible residual solvent level.
The products, to meet the international specifications, have to further processed to achieve the particle size and essential oil specifications. It has to be further blended with the essential oil and emulsifiers to meet the customer requirements. In the case of chilli oleoresin, the product has to either enriched or diluted to achieve the capsaicin and colour values. This is achieved by partitioning the colour and the capsaicin portion between two organic layers and separating them out. Turmeric oleoresin have to be processed further to isolate the curcumin. Crystallization of the curcumin from the oleoresin involve leaching out the resinous and essential oil fractions completely using organic solvents and steam stripping them to meet the bacterial and residual solvent limits.