IL33451A - Process for the recovery of components from citrus fruit - Google Patents

Description

Process for the recovery of components from citrus fruit CENTRE FOR INDUSTRIAL RESEARCH 'THE NATIONAL COUNCIL FOR RSSEARCH AND DEVELOPMENT LTD.

C:-31042 This invention provides an improved process for preparing citrus fruit for peeling and/or for recovering' essential oil and/or other compOE.er.-ts of citrus fruit.

• The operation of peeling fresh citrus fruit, e.g. in preparation of the manufacture of fruit segment preserves, is time and labour consuming. It is ofte performed by hand. -With a view to making the peel easier to detach from the endocarp the fruit is as a rule first scalded in hot, nearly boiling water or even in steam, but this treatment adversely affects the quality of the segments.

As' regards the recovery o -oil from citrus fruit peel, which is preferably combined with the recovery of other components of the fruit such as the fruit juice or the fruit segments, this is known to be a difficult operation, and the percentage yield of oil, although varying with the various types of commercial recovery operations and with the citrus species concerned, is as a rule as low as 25 to 40$ of the total amount of oil present in the peel.

The oil is contained in the oil sacs or glands of the outer layer of the peel. In all processes for the recovery of the oil the walls of the oil sacs are ruptured and the oil is made to spurt out. In some processes, now abandoned, the oil was then collected from the surface of the peel by a sponge. In some processes the -oil is removed from dis- ' integrated peel by distillation or by solvent extraction. However, in the majority of the modem commercial processes the oil is carried from the peel surface during pressing b a flow of water,. 33451/2 3 tn the past, peels have sometimes been immersed in water for several hours 6r even days before being subjected to a squeezing process. This treatment Is too time-consuming for commercial operation. The rupture of the cell wall has been found to be easier, and spurting of the oil more forcible, In the presence of water. This may perhaps be partly explained as follows: the cells surrounding the oil sacs contain salts (and colloids) In aqueous solution, and In contact with water the higher osmotic pressure of the cell contents Induces diffusion of water into them, increasing the turgor pressure and subjecting tie oil sacs to stress from every side. Moreover, the flavedo In which the oil sacs He, and still more the adjacent albedo, are spongy and absorb liquids with great readiness. An average lemon weighs some 100 to 120 g., of which the peel forms about one-half, whereas the total oil content of the peel Is only some 0.5 to 0.7 g. The great volume of spongy tissue tends to absorb the oil as the sacs are broken, and it holds It with great tenacity, so that pressure yields first aqueous fluid and only later oil.

The situation is also unsatisfactory as regards the oil recovery from fruit that Is used for the production of fruit segments. For the production of segments the whole fruit Is usually treated with hot water or steam In order to soften the peel and to facilitate peeling. Most canneries do not further utilize for oil extraction the peel which has been removed from the fruit after the treatment with hot water or steam, because this process has made It very difficult to obtain a fair yield of oil by expression of the plumped and softened peel . 33451 /2 Other cttrus fruit components whose recovery Is desirable, are pectin and the bloflavanoids. fn the production of pectin, the peel Is heated for a long time with dilute acids. This operation Is expensive and tends to de-polymerize and to deester-tfy the product whereby the quality of the pectin is lowered.

In the production of bloflavanoids, the peel Is heated for a long time with water or the peel Is treated for a long time with alkali. This operation, too, Is expensive and tends to cause hydrolysis and chalconization of the product.

The Invention consists in a process for preparing citrus fruit for peeling and/or for recovering essential oil and/or other components from citrus fruit, wherein citrus fruit ■>;.·. : is Infused by Immersion with an aqueous liquid under sub-atmospheric pressure.

The immersion may be perfopined with separated peels obtained from the peeling of citrus fruit as well as citrus peel from any commercial fuice recovery or with whole citrus fruit or cut fruit comprising part of the peel or pulp of the nult. The temperature of the aqueous liquid used may vary within a wide range of which the upper limit Is given by the deteriorating effect of the heat on the quality of the recovered products such as the oil, the pectin and the blo lavan ids. For the recovery of the oil or the peeling of the fruit Immersion at room temperature is convenient. For the recovery of pectin or blo-flavanoids, immersion at higher temperature, even at the boll, may be preferatfe. The level of the vacuum and the time during which It Is applied may vary over a wide range but the penetration of the aqueous liquid into the peel is the better* the higher the vacuum and the longer the time during whic it is applied. Upon release of the vacuum, the aqueous liquid fills the inter-cellular voids. From the infused peel, the oil can be recovered by any conventional method, e.g. by means of a screw-press« Pectin can be recovered, for example, by heating the infused peel and subsequent squeeslng in any conventional manner.

When ifeole fruit is used as a starting materit-1 it is sometimes preferable to make a fev incisions, perforations, pinholes or abrasions in the peel, in order to facilitate the escape of the air upon application of the vacuum and the penetration of the aqueous liquid on release of the vacuum, but this should be done in such a manner that the membranes of the segments are not damaged. After the Infusing operation, the fruit can easily be peeled and the oil and/or other components be recovered from the peel* Conversely it is even possible to recover oil from the unpeeled fruit in any conventional manner and thereafter, if desired, to peel the fruit for further processing* The aqueous liquid used for the infusing operation may be water or an aqueous solution of salts, sugars or other substances. These solutes may serve various purposes. For example, an admixture of a calcium compound may serve to coagulate jellifiable matter which, in its colloidal state* tends to retain the peel Juice and requires the application of higher pressure for expressing the peel juice. Or it may be desirable to introduce hydrochloric acid into the peel for the subsequent recovery of pectin from the peel. If it is intended to recover bioflavaaoide the infusing liquid may he dilute aqueous alkali metal hydroxide.

The infusing liquid stay be recycled.possibly after the separation of the oil.

The method according to this invention faoilitatea the peeling of whole fruit and achieves higher oil yields and a higher reco ery of pool juice ectin and/or bioflavanoids, as compared with known citrus fruit processing methods. In particular where the infusing water contains calcium ions, the method of this invention coabiaee the desired effect of the vacuum infusing vita the desirable effect of the conventional "liming* of the peel, whereby two operations can be oombined int one. She peel juice contains fermentable or recoverable substances such as sugars, acide, bioflavanoids, gums, pectins, aiaino acids and the like, whose yield is increased by the higher yield of expressed peel liquor from the peel. At the sane time, sinoe the extraction of pectin from, the peel treated in accordance with the invention proceeds more qui#H¾y than in conventional processes, there is less danger of deterioration of the product. The SCUM applies to bioflavanoids union are thus leas liable to hydrolysis at the glucoside bond than in conventional processes.

Inasmuch as the process of the invention facilitates the peeling of citrus fruit, which is a costly factor in the production of citrus segments, the time required for this operation can be reduced.

Since in the method according to the invention the peel is saturated with the aqueous liquid in a very much shorter time than without the application of a vacuum, there is less danger that the oil undergoes spoilage and deterioration by chemical, enzymatic and microBiological processes than in previous soaking methods, and the oil recovery is much more rapid. The method of the invention yields an excellent quality of oil comparable to the beet-quality cold-presaed citrus oils currently obtained by other, less efficient processes* Also, because higher yields are obtained, the BB thod of the invention reduces the amount cf essential oil present in the byproducts, and it is possible to recover oil from waste peels which otherwise would not be used, such as the heat-treated peels from citrus segmenting lines.

She Invention is illustrated by the following Examples to which it is not limited. In the Examples the oil yield- as determined by titration with bromide-bromate (W.C. Scott & .K. Veldhuis, J.A.O.A.C.42 (3), 628, 1966). This measures the double bonds present in the oil,, from which the total quantity of oil is estimated by the application of an empirical factor.

EXAMPLE' 1 ' , (a) The peel of two Washington Navel oranges was removed from" the fruit in the form of longitudinal segments. 60 G-rams of peel was immersed in water and a vacuum corresponding to. a pressure of 6Q. mm Hg was applied for five minutes, then the vacuum was released.

A similar batch of peel from the same oranges, not immersed in water, served for comparison.

Prom both batches separately the oil was expressed by hand by bending the peel while it was being held over a vessel filled with water. The yield was: "^. water-infused peel: 0*20 ml not-infused peel:- 0.12 ml (b) A comparative experiment was run with grapefruit peel in the manner described in Example 1(a), except that the two batches consisted of peel from one and the same fruit. The yield was: water-infused peel: 0.42 ml not-infused peel: 0.10 ml \ EXAMPLE 2 The peels of two Shamouti oranges were removed from the fruit in" longitudinal segments. Lots of two longitudinal segments each, were immersed in water in a vacuum vessel under a pressure of 60 mm Hg for periods between 0 and 3 minutes, while one lot was not immersed in water. The oil was expressed as described in Example 1.

The' treatment of each lot and the results obtained are shown i the Table below y Weight of time of water oil yield oil yield peel in each ' infusion uptake (ml) (g) per lot (grams) (min) ( rams) (determined) kg peel - (calculated) 31.9 0 0 ■ .· 0.023 0.63 ,28.6 1/4 3 0.036 . 1.07 28.0 1/2 5 0.034 1.03 ' 29.4 ' 1 10 0.073 2.1 29.3 3 15 .0.088 2.6 EXAMPLE 3 , In each of four Valencia oranges, si longitudinal cuts were made in the peel from the top to the -stem end.

From each orange, half of the peel (three peel segments) was removed. The oranges with the remaining peel segments in place were immersed in water in a vacuum vessel. A vacuum corresponding to 60 mm Hg was applied for 15 minutes, then. the vacuum was released. The infused peel segments could be more, easily removed than the non-infused peel segments. The peel segments were expressed by bending the peel by hand and the essential oil was collected./ Th'e oil yields are shown in the Table below.

Oil water-infused peel 0.68 gram non-infused peel 0-32 gram.

EXAMPLE 4 In 252Ο grams of whole grapefruits six longitudinal incisions were made in the peel of each fruit from the top ' to the stem end. Then the grapefruits were infused with water for 15 minutes in a vacuum corresponding to 60 mm Hg, the vacuum was released and the fruits were peeled. The peeling of these grapefruits was easier than that of grapefruits from a "similar lot that had been heat-treated in open steam during five minutes. The peels were pressed in a screw-press fitted with a perforated cone with holes of 0.6 mm diameter;.- 1080 Grams of an emulsion containing 6.2 ml of oil was recovered, corresponding to 2.1 g. oil~per kg of fruit. In parallel experiments with not-infused fruit, as well as in commercial practice, the recovery J.s usually not higher than 1 - 1.5 g. oil per kg of fruit.

EXAMPLE .

A lot of 66.4 kg of grapefruit peels was obtained as waste product from a commercial grapefruit segmenting line. ' These peels were derived from the heat-treatment of whole fruit for three minutes in water at 95°C andj.s b- sequeht peeling. The peels were immersed in water for 15 minutes in a vacuum vessel at a pressure of 60 mm Hg, then the vacuum was released. The peels took up 31 kg of wate and were then expressed in a screw-press as in Example 4.

The emulsion recovered from the press amounted to 59 kg and contained 346 ml of oil. The emulsion was separated in a high-speed centrifuge whereby 254 ml of oil was recovered.

In a similar run, 47 kg of peels which had not been infused withwater, as pressed in the same screw-press with the addition of 36 kg of water sprayed over the surface of the « cone. ' 45 k of emulsion containing only '128 ml of oil was obtained.- In a high-speed centrifuge only 86 ml of oil separated from this emulsion.

The results of this experiment are remarkable since they show that by the method of this invention, a high oil yield can be. obtained even from peel of heat-treated fruit.

As is known,- and. as this Example also shows, such heat-treated peel gives normally a rather poor .oil yield.

EXAMPLE 6 .

Four lots of 100 g. of orange peel each, obtained by the hand-peeling of fresh oranges, were cut into- pieces , of about 1 x 1 cm and treated as follows.

• The first lot was intensively mixed during half an hour with a slurry of 0.5 g. of GaiOHjg in"*l 'ml of water, then the mixture was squeezed in a plunger type press.

■ The second lot was immersed in 20Q g. of water and kept for 5 minutes at a pressure of 50 mm Hg, then the peels were squeezed, as aforesaid. 1 A third lot was immersed in 200 g. of a saturated aqueous Ca(0H)2 solution containing about 0.2 g. of Ca(0H)2 per 100 g. Vacuum was applied for five minutes and the peels were Lot Peel treatamount of amount of recovered ment peel (g) '. vrater taken press - up b the liquor peel (g) (g) 1 liming 100 - 43 . 2 H20 100 96 108 infusion 3 Ca(OH) - 100 85 111 infusion 4. — 100 — · 2 Comparison between lots 1 and 3 shows that the ; total recovery of peel solids is substantially the same in both cases, which means that the same effect of liming as hitherto could be achieved with less time and, as it were, as a side-effect of an operation hich primarily serves another purpose.

EXAMPLE 7' ' A lot of 2530, g. lemons were halved and reamed to give 1447 ,g. peel. The peel was vacuum-infused as described in Example'!. This gave the peel a very hard consistency. 'The peels were squeezed in a screw-press as in Example 4. Because of the hardness of the peel, carebad to be taken that the press was operated under such conditions that it could handle the peel. Prom the press an oil emulsion containing 7*3 nil of oilms recovered. This corresponded to 2.9 ml/kg of fruit. In- a parallel run with not-infused peel, only 2.0 ml of oil per kg"bf fruit. ; was obtained..

EXAMPLE 8 ; ' 18 grapefruits were divided into three lots of 6. each.

The first lot was peeled after six longitudinal ' incisions had. been made in the peel of each fruit, care being taken not to disturb the segment membranes.

The second lot was scalded for five minutes in waterof 95°0,t then six longitudinal 'incisions were made in thespeel of eac fruit. * .

In- the peel of each of the fruits of the third lot, six longitudinal incisions were made, then the fruits were immersed in water for 5 minutes at a pressure of 50 mm Hg, and the pressure was released while the fruit were still immersed.

The fruits of the three lots were peeled as quickly as possible. .

The ease of peeling and the cleanness, of the surface of the peeled fruit were- compared. The ease of peeling is expressed as the time required to.- peel six fruit by hand. The cleanness of the surface is measured by the amount of albedo (as dry matter) that could be still removed by a careful further cleaning by. means of a knife.

The results are shown in the Table below. , treatment time (sec) dry weight (gram)- to peel 6 not removed albedo fruit Lot 1 _ 110 16.2 Lot 2·. ■ heat 100 ' . 14.4 Lot 3 infusion 70 13.9 EXAMPLE 9 Two lots of 10 g. each of peel taken from one orange by hand-peeling were cut into pieceseofiafeout 1 x 1 cm. The two lots were immersed each in 50 ml of 0.1,N HG1.

Then-one of the lots was put under a pressure of 50 mm Hg . for five minutes at room temperature. After boiling the lots for 8 minutes, and cooling* the peels were squeezed, the press-liquors were neutralized to pH 6 and their volumes were equalized with water. After filtration of fine particles from the liquors the viscosities were compared. The viscosity is expressed as the time needed for 2 ml of liquor to flow from a standard pipette. ½e amount of pectic matter in the two liquors was compared by precipitation with twice theVolume of ethanol « The precipitates were removed, freed from liquid by squeezing, washed with 95 ethanol and" dried for 3 hours at 80°C under 10 mm Hg* . . . .

The results are shown in the Table below* - EXAMPLE 10 g of grapefruit peel, recovered by hand-peeling from a. single fruit cut into pieces of about 1 x 1cm, were immersed in 250 ml of water, then the vessel was evacuated to a pressure, of '50 mm Hg and this sub-atmospheric pressure was maintained for 5 minutes at room temperature. Then the peeling was heated to 90°C and squeezed while warm; The press liquor contained 0.4 g of flavanoid, mainly naringine (determined according to W. Davis, Analytical Chemistry 19, page -476, .1947).

Example 11 One kilogram of whole lemon were cut into 1-2 cm segments. The segments were immersed in water in a vacuum vessel, A vacuum corresponding to 70 mm Hg was applied for 15 minutes then the vacuum was released. The infused segments were then pressed in a screw press fitted with a perforated cone with holes of 0.6 mm diameter. An amount of 680 grams of an emulsion containing 3.28 ml of oil was recovered. In parallel experiments with not-infused; fruit , the recovery was only 2.8 ml oil.

Claims (1)

1. CLAIMS lo A process for preparing citrus fruit for peeling and/or for recovering essential oils and/or other components from citrus fruit, wherein the peel is infused by immersio with an aqueous liquid under subatmosphe ic pressure* 2, A process according to Claim 1, wherein the infusion operation is performed on whole citrus fruitβ 3o A process according to Claim 1, wherein the infusion operation is performed on cut fruit comprising parts of the peel and pulp of the frui ....·■ ' . 4o A process according to Claim 1, wherein the infusion on operation is performed Aih peel by itself« . 5· ■ ■ A process according to Claim 2, wherein the peel is cut, punctured or abraded prior to the infus^ion operation. 6e A process according to any of Claims 1 to 5t wherein the infusion liquid is water or an aqueous solution of salts, sugara or other substances calculated to exert a physical or chemical influence on the peel or its components. 7. A process according to any of Claims 1 to 6, wherein an oil-containing aqueous liquor is recovered from the infused peel by pressing, and the oil, or at least the major part thereof, is separated from the liquor* 8. A process according to any of Claims 1 to 7, herein the infusion operation is carried out with an aqueous liquid possibly recycled font a previous operation,/ after the separation pf at • - 1 ' ! least the bulk of oil therefrom. ~~ ·. ''' . ' .■ ■ ■ " ■ v 9« A process according to Claims 7 or 8, wherein the aqueous liquor, possibly after the separation therefrom of all or part of the oil, and possibly after fermentation, is further processed for recoYering desired substances contained therein. 10· A process according to Claim 5, wherein the infusion liquid is a dilute aqueous add and pectin is subsequently recovered from the peel* 11. A process according to Claim 5, wherein the infusion liquid is a dilute aqueous alkali metal hydroxide and bio-flavanoidB are subsequently recovered from the peel. 12. A process for preparing citrus fruit for peeling and/or recovering essential oils and/or other components from citrus fruit, substantially as described herein with reference to the Examples. RC/ze