VEGETABLE MATERIAL

TECHNICAL FIELD

The present invention relates to a process for the recovery of volatile aroma compounds from vegetable material. It particularly relates to the process of recovery of volatile aroma compounds from tea. BACKGROUND

Recovering volatile aroma compounds during processing of vegetable materials is known. JP2005087122 A2 (SHOWA NOUGEI KK, published in 2005) discloses a production method for the coffee flavor comprising a process of bringing roasted coffee beans into contact with water vapor to extract in water vapor flavor components of the coffee beans, a process of obtaining condensate containing the flavor components through condensing the water vapor by cooling, and a process of re-extracting the obtained condensate with fatty acid ester of glycerol, preferably triacetin (glyceryl triacetate). Such methods require a further separate subsequent step of drying the vegetable material leading to additional energy consumption and complexity of process. Even when the vegetable material is further dried, the dried vegetable material lacks usual aroma/taste and visual characteristics.

US3615665 A (WH ITE WI LLIAM V, published in 1971 ) also discloses a process for stripping and recovering volatile compounds from roasted coffee wherein coffee beans are contacted with steam. US2007/003683 A1 (INOUE TAKASHI et al, published in 2007) discloses a method of extracting volatile compounds from food such as tea, coffee by contacting food material with steam and recovering the liberated volatile compounds by cooling. It is known to contact aroma-laden air obtained during drying of vegetable materials with water or some other aroma d issolution liqu id . JP2005021040 A2 (RIKEN PERFUMERY KK, published in 2005) discloses a method for producing a tea extract comprising : leading roasting aroma generated via roasting to the outside of a hermetically sealed heating vessel, and capturing the aroma into water to efficiently collect the aroma, and using the aroma solution as a whole amount or a part of an extract solvent, or adding the solution to extracted liquid separately extracted using water to obtain the tea extract rich

in roasting aroma.

US4335150 A (HOSAKA HI DEKAI et al, published in 1982) discloses a process for drying food by using a drying gas such as air or nitrogen . The used gas may be further applied in process such as being used a purge as which is contacted with adsorbed water. There is no disclosure of contacting the purge gas with water vapour or steam.

US5214998 A (NAGAOKA PERFU MERY CO LTD, published in 1993) discloses a process wherein a food material which is hermetically accommodated in a heating unit is heated and a generated aroma component is delivered by a carrier gas supply unit together with a carrier gas through connection pipe to an aroma component dissolving and capturing unit including a hermetically sealed container in which an aroma dissolving solution is stored. In such a process, the recovery of aroma per unit mass of dried material is relatively low. Furthermore, the concentration of aroma compounds obtained in dissolving solution is relatively low.

WO2007/039018 (Unilever) describes a process of manufacturing a leaf tea product comprising the steps of recovering aroma from the tea leaf followed by drying the tea leaf, characterized in that aroma recovery is whilst at least partially drying the fresh leaf in a low convection dryer. Such a process requires special equipment and can not be used in conventional drying processes. One of the objects of the present invention is to overcome or ameliorate at least one of the disadvantages of the prior art, or to provide a useful alternative.

Another object of the present invention is to provide a process of recovering volatile aroma compounds from vegetable material without compromising the quality of the dried vegetable material. Yet another object of the present invention is to provide a process of recovering volatile aroma compounds from vegetable material that provides relatively higher recovery of volatile aroma compounds per unit mass of vegetable material on dry basis. Yet another object of the present invention is to provide a process of recovering volatile aroma compounds from vegetable material with the concentration of volatile aroma compounds in the condensate being relatively high

Yet another object of the present invention is to provide a process of recovering volatile compounds from vegetable material with relatively low energy consumption.

Present inventors have surprisingly found that injecting steam into the dryer exhaust gases emerging from a vegetable dryer before condensation provides relatively high recovery of aroma

SUMMARY OF THE INVENTTION

According to the present invention there is provided a process for the recovery of volatile aroma compounds from a vegetable material comprising the steps of:

a. Contacting the vegetable material with a gas in a dryer wherein the amount of moisture in the gas entering the dryer is less than 15 g/kg dry gas; b. Contacting the dryer exhaust gas stream with water vapour or steam to obtain a gaseous mixture, and;

c. Condensing the gaseous mixture to recover a condensate comprising volatile aroma compounds.

DETAILED DESCRIPTION OF THE INVENTION

The vegetable material

The term vegetable material as used herein means material obtained from plants. Vegetable material may be obtained from root, stem, leaf, seed, flower or any other part of th e plant. Preferably the vegeta ble material i nclu des volati le aroma compounds.

Vegetable material is preferably obtained from the group of plants including medicinal plants, spices, horticulture crops including fruits and vegetables, flower crops, plantation crops, aromatic crops, root, tuber and blulbous crops.

Preferred spice plants include Alpinia galangal, Amomum sublatum, Capsicum annum, Capsicum fruitenscens, Cinnamomum aromaticum, Cinnamomum tamala, Cinnamomum zeylancium, Curcuma longa, Elettaria cardamomum, Garcinia cambogia, Garcinia indica, Murraya koenigi, Myristica fragrans, Pimenta diocia, Piper nigrum, Sysygium aromaticum, Tamarindus indica, Vanilla planfolia, Vanilla fragrans, Zinziber officinalis, Coraindrum sativum, Cuminum cyminum, Cuminium odorum, Foenciulum vulgare, Carum copticum, Anetheum graveolens, Tigonella foenum- graecum, Nigella sativa, Pimipnella anisum, and Apium graveolens. Particularly preferred spices include Capsicum annum, Capsicum fruitenscens, Cinnamomum aromaticum, Cinnamomum tamala, Cinnamomum zeylancium, Curcuma longa, Elettaria cardamomum, Vanilla fragrans, Zinziber officinalis, Coraindrum sativum, and Cuminum cyminum., Preferred fruits include Fragaria vesca, Mangifera indica, Carica papaya, Vitis vinifera, Punica gargantum, Psidium guajava, Citrus limon, Citrus, aurantifolia, Citrus latifolia, Mnilakara zapota, Achras sapota, Persea Americana, Passiflora edulis, Litchi chinensis, Annona reticulate, Artocarpus heterophyllus, Ziziphus mauritiana, Emblica officinalis, Phyllanthus emblica, Ficus carica, Carissa carandas, Aegle marmelos, Artocarpus incise, Averrhoa carambola, Prunus avium, Phoneix dactylifera, Syzygium cuminiim Eriobotrya japonica, Vassila latifolia, Garcinia mangostana, Grewia subinequalis, Nephelium lappaceeum, Ananas comosus, Syzigium jambos, Feronia limonia, Malus domestica, Pyrus communis, Prunus persica, Prunus amygdalus, Prunus armeniaca, Juglans regia, and Actinidia chinensi. Particularly preferred fruits include Citrus limon, Citrus, aurantifolia, Citrus latifolia, Fragaria vesca, and Ananas comosus

Preferred vegetables include cucurbits, crucifers and temperate vegetables, leguminous and leafy vegetables.

Preferred cucurbits include Momordica charantia, Cucurbita moschata, Cucurbita pepo, Lagenaria siceraria, Cucumis melo, Citrulus lanatus, Benincasa hispida, Cucumis sativus, Cucumis melo var. utilissimus, Coccinia indica, Luffa acutangula, Luffa cylindricale, Praecitrullus fistulosus, Trichosanthes cucurmerina, Cucurmis melo var. momordica, Cucumis callosus.

Preferred crucifers and temperate vegetable plants include Brassica oleracea subsp. Capitata, Brassica oleracea L. var botrytis, Brassica oleracea var. Italica, Brasssica oleracea var. gongylodes, Daucus carota, Beta vulgaris, Raphanus sativus, Brassica oleracea var. bengalensis, Lactuca sativa, Beta vulgaris var. bengalensis, Petroselinum hortense, Lycopersicon esculentum, Solanum melongena, Abelmoschus esculentus, and Spinaceae oleracea. Particularly preferred crucifers and temperate vegetable plants include Brassica oleracea subsp. Capitata, Brassica oleracea L. var botrytis, Brassica oleracea var. Italica, Brasssica oleracea var. gongylodes, and Daucus carota. Preferred leguminous and leafy vegetables include Phaseolus vugarsis, Vigna unguiculata, Dolichos lablab, Pisum sativum, Cyamopsis tetragonolobus, Moringa oleifera, Sesbania grandiflora, and Petroselinum crispum. Particularly preferred leafy vegetable is Petroselinum crispum.

Preferred tuber and bulbous crops include Solarium tuberosum, Manihot esculenta, Ipomoea batatas, Dioscorea alata, Dioscorea esculenta, Dioscorea rotundata, Amorphophallus paeoniifolius, Pachyrrhizus erosus, Allium cepa, Allium sativum, and Maranta arundinaceae. Particularly preferred tuber and bulbous crops include Allium cepa and Allium sativum.

Preferred flower crops include Polianthes tuberose, Dianthus cayophyllus, Callistepheus chinensis, and Cymbidicum dendrobium.

Preferred plantation crops include Cocos nucifera, Areca catechu, Theobroma cacao, Anacardium occidentale, Camelia sinensis, Coffea Arabica, Coffea robusta, Hevia brasilensis, Elacis guineensis, Cichorium intybus, and Borassus flabellifer. Particularly preferred plantation crops include Cocos nucifera, Camelia sinensis, Coffea Arabica, and Coffea robusta. Camelia sinensis is the most preferred plantation crop.

Preferred aromatic crops include Cymbologon flexuosus, Cymbopogon martini var. motia, Mentha spicata, Pelargonium graveolens, Valeriana jatamansi, Artemisia pallens, Cympopogon winterianus, Mentha arvensis, Pogostemon patchouli, and Vetiveria zizanioides.

Preferred medicinal plants include Papaver sominferum, Chlorophytum borivilianum, Dioscoria floribunda, Digitalis lanata, Glaucium flavum, Glycyrrhiza glabra, Rauvolfia serpentine, Solanum laciantum, Solanum viarum, Piper betle, Hyoscyamus muticus, Ahelmoschus moschatus, Acorus calamus, Adhatoda zeylanica, Aloe barbadensis, Alpinia calcarata, Azardichta indica, Caesalpinia sappan, Cassia angustifolia, Curcuma zerumbet, Catharanthus roseus, Croton tiglium, Curcuma angustifolia, Ficus benghalensis, Ficus religiosa, Gloriosa superba, Indigofera tinctoria, Inula racemosa, Jatropha curcas, Kemfaria galangal, Lawsonia inermis, Lepidium sativum, Ocimum basilicum, Ocimum sanctum, Ocimum tenuiflorum, Piper longum, Plantago ovata, Plechtranthus barbatus, Pongamia pinata, Sylibum marianum, simmondsia chinensis, Trachyspermum ammi, Vitex negundo, Withania somnifera and Zizyphus jujube. Particularly preferred medicinal plants include Ocimum basilicum, Ocimum sanctum, and Ocimum tenuiflorum. It is particularly further preferred that the vegetable material is derived from the the group of plants consisting of tea (Camellia sinensis), basil (Ocimum basilicum, Ocimum sanctum, Ocimum tenuiflorum), parsley (Petroselinum crispum), capsicum and chillies (Capsicum annum, Capsicum fruitenscens), carrot (Daucus carota), asparagus (Asparagus Racemosus), broccoli (Brassica oleracea var. Italica), cinnamom (Cinnamomum aromaticum, Cinnamomum tamala, Cinnamomum zeylancium) Curcumin (Curcuma longa), Cardamomd (Elettaria cardamomum), Vanilla (Vanilla fragrans), ginger (Zinziber officinalis), Coriander (Coraindrum sativum), strawberry (Fragaria vesca), Allium cepa (on\on),Allium sativum (garlic) and Cuminum cyminum.

Com minuted or uncommi nuted vegetable material may be used . Comminuted vegetable material is preferred.

According to one aspect of the invention , vegetable material from a tea plant is preferred. Vegetable material from a tea plant may be fresh tea leaf, green tea, black tea, oolong tea. Any fermented or unfermented or partially fermented tea material may be used. However, it is particularly preferred that the tea material is at least partially fermented tea leaf. The vegetable material comprises from about 0.1 to 10 kg, more preferably from 0.5 to 5 kg, and most preferably from 1 to 4 kg moistu re per kg dry weight of the vegetable material. The term "volatile aroma compounds" as used herein means the organic compounds in the vegetable material that are separated from the vegetable material when the vegetable material is heated to temperature greater than 30 °C at normal atmospheric pressure. Total volatile organic carbon content of the vegetable material is typically indicative of the amount of volatile aroma compounds in a vegetable material, and such total volatile organic carbon content of the vegetable material may be determined by any suitable method known in the art. Preferably, the total volatile organic carbon content is measured by exposing the vegetable material to temperature of 90 °C at vacuum of less than or equal to 200 mm Hg, and condensing the vapours generated to obtain a condensate which include a mixture of volatile aroma compounds and water. The condensate is then analyzed for total organic carbon content. It is preferred that the total volatile organic carbon content of the vegetable material is at least 100 mg per kg of the dry weight of the vegetable material. The total volatile organic carbon content of the vegetable material is preferably greater than 150 mg per kg of the dry weight of the vegetable material, more preferably greater than 200 mg per kg of the dry weight of the vegetable material. The total volatile organic carbon content of the vegetable material is preferably less than 10000 mg per kg of the dry weight of the vegetable material.

The step (a)

The step (a) is the step of contacting the vegetable material with a gas in a dryer. Vegetable material may be contacted with any gas.

The gas is preferably air or nitrogen or carbon dioxide, or a mixture thereof. It is preferred that the temperature of the gas in the step (a) is greater than 30 C. The temperature of gas is preferably at least 40 C, more preferably at least 75 C, and most preferably at least 100 C. The temperature of gas is preferably less than 300 C, more preferably less than 200 C, and most preferably less than 150 C.

The step (a) is carried out at absolute pressure of preferably from 0.5 to 5 atm , more preferably from 0.9 to 3 atm and most preferably from 0.95 to 1 .2 atm. The step (a) is carried out at absolute pressure of preferably from 0.051 to 0.51 M Pa , more preferably from 0.091 to 0.31 MPa and most preferably from 0.096 to 0.12 MPa. Pressure close to atmospheric pressure (about 0.1 MPa) is particularly preferred.

The d ryer is any equipment that has a chamber for contacting the gas with the vegetable material and an outlet for dryer exhaust gases. Preferably the dryer has an inlet for bringing the gas into the dryer. Any suitably drying equipment can be used. Preferred dryer includes air dyrer such as tray dryers and fluidized bed dryers.

Dryer may be a batch dryer or a continuous dryer.

The temperature of the gas entering the dryer is preferably from 30 °C to 300 °C more preferably from 40 °C to 250 °C and most preferably from 100 °C to 160 ^° C.

The amount of the moisture in the gas entering the dryer is less than 15 g/kg dry gas, more preferably less than 10 g/kg dry gas, and most preferably less than 5 g/kg dry gas. The amount of the moisture in the gas entering the dryer is preferably greater than 0.01 g/kg dry gas.

Preferably the quantity of the gas contacted with the vegetable material in the step (a) is from 10 to 1200, more preferably from 25 to 800 and most preferably from 40 to 500 kg/kg dry weight of the vegetable material.

The step (b) The step (b) is the step of contacting the dryer exhaust gas stream with water vapour or steam to obtain a gaseous mixture.

The term "steam or water vapou r" as used herein means a gaseous substance comprising at least 50% evaporated water by mass, more preferably at least 90% evaporated water by mass and most preferably at least 95% evaporated water by mass. It is particularly preferred that "water vapour or steam" is a gaseous substance substantially comprising evaporated water.

The step (b) is preferably carried out outside the dryer.

The temperature of the water vapour or steam is preferably from 70 C to 170 C, , more preferably from 80 ^° C to 150 ^° C and most preferably from 95 °C to 120 ^° C. The absolute pressure of the water vapour or stream is preferably from 0.3 to 7 atm , more preferably from 0.5 to 2 atm and most preferably from 0.8 to 1 atm. The absolute pressure of the water vapour or stream is preferably from 0.0304 MPa to 0.71 MPa, more preferably from 0.051 MPa to 0.202 MPa atm and most preferably from 0.081 MPa to 0.101 MPa.

The amount of the water vapour or steam added per kg of the gaseous mixture is preferably from 1 g to 500 g, more preferably from 5 to 200 g and most preferably from 10 to 100 g. The step (c)

The step (c) is the step of condensing the gaseous mixture to recover a condensate comprising volatile aroma compounds. The step (c) may be carried out by using any condenser.

Suitable condenser that can be used includes, for example, shell and tube type, coiled type, tubular type, spiral type and finned tube type condenser. The temperature of the cooling water is preferably below 40 C, more preferably below 10 °C and most preferably below -5 C.

The condensation may be single stage or m u ltistage. However single stage condensation is preferred. Without wishing to be limited by theory, it is believed that recovery of aroma volatiles in single stage condensation is higher than that obtained in multistage condensation.

The condensate comprises recovered volatile aroma compounds and water. The amount of volatile aroma compounds is typically from 0.02 to 5 g per kg dry weight of the vegetable material, however this depends upon the choice of vegetable material and the amount of moisture removed.

The concentration of aroma volatile compounds in the condensate is preferably from 1 to 500 ppm of water, more preferably from 5 to 400 ppm of water, and most preferably from 12 to 200 ppm of water.

The condensate may be further concentrated by various methods known to a person skilled in the art in order to increase the concentration of volatile aroma condensate. The preferred methods of further concentration of aroma condensate i nclude distillation, phase separation, adsorption, desorption and membrane separation.

The aroma condensates obtained from the above mentioned process may be used directly or preferably in concentrated form or in encapsulated form by adding to any product for imparting/enhancing flavour and aroma.

The dried vegetable material

The term dried vegetable material as used herein means the vegetable material left at the end of the step (c). The dried vegetable material has moisture content that is less than the vegetable material in the step (a). The dried vegetable material comprises less than 3 kg, more preferably less than kg, and most preferably from less than 1 kg moisture per kg dry weight of th vegetable material. EXAMPLES

The invention will now be demonstrated with examples. The examples are for the purpose of illustration only and do not limit the scope of the invention in any manner

Effect of steam injection

The experiments were conducted by contacting the 180 g of black tea leaf (sourced from Kenya) as a vegetable material with air. The air entering the dryer was at temperature of 1 10 °C and the moisture content of 1 1 g/kg dry air. The vegetable material contained 2.33 kg moisture/ kg of dry weight of vegetable material. The flow rate of air entering the dryer was 3.2 kg/hr. Total amount of air contacted was 40 kg/kg of dry weight of vegetable material. The dryer exhaust consisted of air stream with carryover of aroma volatiles and moisture released from the vegetable material during drying. Steam at a temperature of 100 °C and at a rate of 96 g/hour was injected in the dryer exhaust air stream to generate the gaseous mixture. The amount of added steam was 30 g per kg of the gaseous mixture. The gaseous mixture was fed into a spiral condenser supplied with chilled water at 2 °C. The air flow and steam injection were stopped after 40 minutes. The condensate was analysed using TOC meter (Shimadzu Model 5000A ) to obtain TOC values which was taken to be the amount of volatile aroma compounds. From this the amount of aroma (expressed as mg/kg dry weight vegetable material as well as concentration of volatile aroma compounds in condensate (ppm water) were calculated. The dried vegetable material contained 0.72 kg moistu re per kg d ry weight of vegetable material . Another experiment was conducted in a manner identical to the one described above except that there was no steam injection. The results of the experiments are reported below

Table 1 a: Effect of steam injection (Tea)

From the results, it is clear that the process of the present invention (with steam injection) provides relatively higher recovery of volatile aroma compounds without significantly decreasing the concentration of the volatile aroma compounds in the condensate,

Aroma recovery from Basil

Similar Experiments were carried out with Basil. Experimental details are given below: Total amount of vegetable material: 160 g

Amount of moisture in vegetable material: 9 kg/kg dry weight of the vegetable material Amount of moisture in the dried vegetable material: 1 .63 kg per kg of dry weight of the vegetable material.

Air flow rate entering the dryer: 3.2 kg/hr

Steam injection rate: 180 g/hr

Steam temperature: 100 °C

The amount of added steam was 56 g per kg of the gaseous mixture.

Air flow and Steam Injection was stopped after 60 minutes.

The results of the experiments (with and without steam injection) are reported below Table 1b: Effect of steam injection (Basil)

From the results, it is clear that the process of the present invention (with steam injection) provides relatively higher recovery of volatile aroma compounds. Concentration of the volatile aroma compounds in the condensate in slightly low, but acceptable.

Effect of temperature

All experiments below were run for 60 minutes. The experiment was carried out with basil. Experimental conditions are given below.

Air Flow rate entering the dryer: 4.5 kg/hr

Steam injection rate: 180 g/hr.

The inlet air temperature into the dryer bed was varied as tabulated below along with the results.

Table 2: Effect of temperature

Temperature of air at inlet Amount of volatile aroma Concentration of Volatile of dryer compounds recovered aroma compounds in

(mg/kg dry condensate (ppm ) weight material)

110 801 56

60 407 33 32 341 31

From the results, it is clear that the recovery of aroma compounds increases with the increase in the drying temperature of inlet air into the dryer. Effect of the amount of steam added per kg of the gaseous mixture

All experiments below were run for 60 minutes. The experiments were carried out with basil. Experimental conditions are given below.

Air Flow rate entering the dryer: 4.5 kg/hr

The inlet air temperature into the bed: 1 10 °C.

Amount of steam added was varied as tabulated below along with the results.

Table 3: Effect of the amount of steam added per kg of the gaseous mixture

From the results, it is clear that the recovery of aroma compounds increases with the amount of steam added per kg of gaseous mixture. Although this is accompanied by some reduction in the concentration of volatile aroma compounds in the condensate, it is preferred that the amount of steam added per kg of gaseous mixture is relatively higher.

Comparartive data when dryer exhaust is contacted with water Following experiment was conducted under similar conditions as those in Table 1 b except that the dryer exhaust was bubbled through liquid water instead of injecting steam. Table 4: Comparartive data when dryer exhaust is directly contacted with water

^* Not possible to collect volatile aroma compounds due to splashing and loss of water. It was found that when the amount of water used is relatively low, the recovery of volatile compounds was very low, and when higher amount of water was used the concentration of volatile aroma compounds in water was relatively too low. This indicates that the process of the present invention of steam injection provides significantly better results as compared to the prior art processes wherein dryer exhaust is directly contacted with liquid water.