Cocoa and Chocolate Part 5

Fickendey says: "The object of fermentation is, in the main, to kill the germ of the bean in such a manner that the efficiency of the unorganised ferment is in no way impaired."

[2] _Philippine Journal of Science_, 1917.

From my own observations I believe that forastero beans are killed at 47 degrees C. (which is commonly reached when they have been fermenting 60 hours), for a remarkable change takes place at this temperature and time. Whilst the micro-organisms remain outside, the juice of the pulp appears to penetrate not only the skin, but the flesh of the bean, and the brilliant violet in the isolated pigment cells becomes diffused more or less evenly throughout the entire bean, including the "germ." It is certain that the bean absorbs liquid from the outside, for it becomes so plump that its skin is stretched to the utmost. The following changes occur:

(1) _Taste._ An astringent colourless substance (a tannin or a body possessing many properties of a tannin) changes to a tasteless brown substance. The bean begins to taste less astringent as the "tannin" is destroyed. With white (criollo) beans this change is sufficiently advanced in two days, but with purple (forastero) beans it may take seven days.

(2) _Colour._ The change in the tannin results in the white (criollo) beans becoming brown and the purple (forastero) beans becoming tinged with brown. The action resembles the browning of a freshly-cut apple, and has been shown to be due to oxygen (activated by an oxidase, a ferment encouraging combination with oxygen) acting on the astringent colourless substance, which, like the photographic developer, pyrogallic acid, becomes brown on oxidation.

(3) _Aroma._ A notable change is that substances are created within the bean, which _on roasting_ produce the fine aromatic odour characteristic of cocoa and chocolate, and which Messrs. Bainbridge and Davies have shown is due to a trace (0.001 per cent.) of an essential oil over half of which consists of linalool.[3]

(4) _Stimulating Effect._ It is commonly stated that during fermentation there is generated theobromine, the alkaloid which gives cacao its stimulating properties, but the estimation of theobromine in fermented and unfermented beans does not support this.

(5) _Consistency._ Fermented beans become crisp on drying.

This development may be due to the "tannins" encountering, in their dispersion through the bean, proteins, which are thus converted into bodies which are brittle solids on drying (compare tanning of hides). The "hide" of the bean may be similarly "tanned"--the sh.e.l.l certainly becomes leathery (unless washed)--but a far more probable explanation, in both cases, is that the gummy bodies in bean and sh.e.l.l set hard on drying.

[3] _Journal of the Chemical Society_, 1912.

We see, then, that although fermentation was probably originally followed as the best method of getting rid of the pulp, it has other effects which are entirely good. It enables the planter to produce a drier bean, and one which has, when roasted, a finer flavour, colour, and aroma, than the unfermented. Fermentation is generally considered to produce so many desirable results that M. Perrot's suggestion[4] of removing the pulp by treatment with alkali, and thus avoiding fermentation, has not been enthusiastically received.

[4] _Comptes Rendus_, 1913.

Beans which have been dried direct and those which have been fermented may be distinguished as follows:

CACAO BEANS

DRIED DIRECT. FERMENTED AND DRIED.

_Shape of bean_ Flat Plumper _Sh.e.l.l_ Soft and close fitting Crisp and more or less free.

_Interior: colour_ Slate-blue or mud-brown Bright browns and purples " _consistence_ Leather to cheese Crisp " _appearance_ Solid Open-grained " _taste_ More or less bitter Less astringent or astringent

Whilst several effects of fermentation have not been satisfactorily accounted for, I think all are agreed that to obtain one of the chief effects of fermentation, namely the brown colour, oxidation is necessary. All recognise that for this oxidation the presence of three substances is essential:

(1) The tannin to be oxidised.

(2) Oxygen.

(3) An enzyme which encourages the oxidation.

All these occur in the cacao bean as it comes from the pod, but why oxidation occurs so much better in a fermented bean than in a bean which is simply dried is not very clear. If you cut an apple it goes brown owing to the action of oxygen absorbed from the air, but as long as the apple is uncut and unbruised it remains white. If you take a cacao bean from the pod and cut it, the exposed surface goes brown, but if you ferment the bean the whole of it gradually goes brown without being cut.

My observations lead me to believe that the bean does not become oxidised until it is killed, that is, until it is no longer capable of germination. It can be killed by raising the temperature, by fermentation or otherwise, or as Dr. Fickendey has shown, by cooling to almost freezing temperatures. It may be that killing the bean makes its skin and cell walls more permeable to oxygen, but my theory is that when the bean is killed disintegration or weakening of the cell walls, etc., occurs, and, as a result, the enzyme and tannin, _hitherto separate_, become mixed, and hence able actively to absorb oxygen. The action of oxygen on the tannin also accounts for the loss of astringency on fermentation, and it may be well to point out that fermentation increases the internal surface of the bean exposed to air and oxygen.

The bean, during fermentation, actually sucks in liquid from the surrounding pulp and becomes plumper and fuller. On drying, however, the skin, which has been expanded to its utmost, wrinkles up as the interior contracts and no longer fits tightly to the bean, and the cotyledons having been thrust apart by the liquid, no longer hold together so closely. This accounts for the open appearance of a fermented bean. As on drying large inters.p.a.ces are produced, these allow the air to circulate more freely and expose a greater surface of the bean to the action of oxygen. Since the liquids in all living matter presumably contain some dissolved oxygen, the problem is to account for the fact that the tannin in the unfermented bean remains unoxidised, whilst that in the fermented bean is easily oxidised. The above affords a partial explanation, and seems fairly satisfactory when taken with my previous suggestion, namely, that during fermentation the bean is rendered pervious to water, which, on distributing itself throughout the bean, dissolves the isolated ma.s.ses of tannin and diffuses it evenly, so that it encounters and becomes mixed with the enzymes. From this it will be evident that the major part of the oxidation of the tannin occurs during drying, and hence the importance of this, both from the point of view of the keeping properties of the cacao, and its colour, taste and aroma.

It will be realised from the above that there is still a vast amount of work to be done before the chemist will be in a position to obtain the more desirable aromas and flavours. Having found the necessary conditions, scientifically trained overseers will be required to produce them, and for this they will need to have under their direction arrangements for fermentation designed on correct principles and allowing some degree of control. Whilst improvements are always possible in the approach to perfection, it must be admitted that, considering the means at their disposal, the planters produce a remarkably fine product.

[Ill.u.s.tration: FOR DRYING SMALL QUANt.i.tIES.

A simple tray-barrow, which can be run under the house when rain comes on.]

_Loss on Fermenting and Drying._

The fermented cacao is conveyed from the fermentary to the drying trays or floors. The planter often has some rough check-weighing system. Thus, for example, he notes the number of standard baskets of wet cacao put into the fermentary, and he measures the fermented cacao produced with the help of a bottomless barrel. By this means he finds that on fermentation the beans lose weight by the draining away of the "sweatings," according to the amount and juiciness of the pulp round them. The beans are still very wet, and on drying lose a high percentage of their moisture by evaporation before the cacao bean of commerce is obtained.

The average losses may be tabulated thus:

Weight of wet cacao from pod 100 Loss on fermentation 20 to 25 Loss on drying 40 -------- Cacao beans of commerce obtained 35 to 40

[Ill.u.s.tration: SPREADING THE CACAO BEANS ON MATS TO DRY IN THE SUN, CEYLON.]

The drying of cacao is an art. On the one hand it is necessary to get the beans quite dry (that is, in a condition in which they hold only their normal amount of water--5 to 7 per cent.) or they will be liable to go mouldy. On the other hand, the husk or sh.e.l.l of the bean must not be allowed to become burned or brittle. Brittle sh.e.l.ls produce waste in packing and handling, and broken sh.e.l.ls allow grubs and mould to enter the beans when the cacao is stored. The method of drying varies in different countries according to the climate. Jose says: "In the wet season when 'Father Sol' chooses to lie low behind the clouds for days and your cocoa house is full, your curing house full, your trees loaded, then is the time to put on his mettle the energetic and practical planter. In such tight corners, _amigo_, I have known a friend to set a fire under his cocoa house to keep the cocoa on the top somewhat warm. Another friend's plan (and he recommended it) was to address his patron saint on such occasions. He never addressed that saint at other times."

[Ill.u.s.tration: DRYING TRAYS, GRENADA.

The trays slide on rails. The corrugated iron roofs will slide over the whole to protect from rain.]

In most producing areas sun-drying is preferred, but in countries where much rain falls, artificial dryers are slowly but surely coming into vogue. These vary in pattern from simple heated rooms, with shelves, to vacuum stoves and revolving drums. The sellers of these machines will agree with me when I say that every progressive planter ought to have one of these artificial aids to use during those depressing periods when the rain continually streams from the sky. On fine days it is difficult to prevent mildew appearing on the cacao, but at such times it is impossible. However, whenever available, the sun's heat is preferable, for it encourages a slow and even drying, which lasts over a period of about three days. As Dr. Paul Preuss says: "II faut eviter une dessiccation trop rapide. Le cacao ne peut etre seche en moins de trois jours."[5] Further, most observers agree with Dr. Sack that the valuable changes, which occur during fermentation, continue during drying, especially those in which oxygen a.s.sists. The full advantage of these is lost if the temperature used is high enough to kill the enzymes, or if the drying is too rapid, both of which may occur with artificial drying.

[5] Dr. Paul Preuss, _Le cacao. Culture et Preparation_.

Sun-drying is done on cement or brick floors, on coir mats or trays, or on wooden platforms. In order to dry the cacao uniformly it is raked over and over in the sun. It must be tenderly treated, carefully "watched and caressed," until the interior becomes quite crisp and in colour a beautiful brown.

Sometimes the platforms are built on the top of the fermentaries, the cacao being conveyed through a hole in the roof of the fermentary to the drying platform.

[Ill.u.s.tration: "HAMEL-SMITH" ROTARY DRYER.

(Made by Messrs. David Bridge and Co., Manchester).

The receiving cylinders, six in number, are filled approximately three-quarters full with the cacao to be dried. These are then placed in position on the revolving framework, which is enclosed in the casing and slowly revolved. The cylinders are fitted with baffle plates, which gently turn over the cacao beans at each revolution so that even drying throughout is the result. The casing is heated to the requisite temperature by means of a special stove, the arrangement of which is such as to allow the air drawn from the outside to circulate around the stove and to pa.s.s into the interior of the casing containing the drying cylinders. The fumes from the fuel do not in any way come in contact with the material during drying.]

[Ill.u.s.tration: DRYING PLATFORMS, TRINIDAD, WITH SLIDING ROOFS.]

In Trinidad the platform always has a sliding roof, which can be pulled over the cacao in the blaze of noon or when a rainstorm comes on. In other places, sliding platforms are used which can be pushed under cover in wet weather.

_The Washing of Cacao._

In Java, Ceylon and Madagascar before the cacao is dried, it is first washed to remove all traces of pulp. This removal of pulp enables the beans to be more rapidly dried, and is considered almost a necessity in Ceylon, where sun-drying is difficult. The practice appears at first sight wholly good and sanitary, but although beans so treated have a very clean and bright appearance, looking not unlike almonds, the practice cannot be recommended. There is a loss of from 2 to 10 per cent. in weight, which is a disadvantage to the planter, whilst from the manufacturer's point of view, washing is objectionable because, according to Dr. Paul Preuss, the aroma suffers. Whilst this may be questioned, there is no doubt that washing renders the sh.e.l.ls more brittle and friable, and less able to bear carriage and handling; and when the sh.e.l.l is broken, the cacao is more liable to attack by grubs and mould. Therein lies the chief danger of washing.

[Ill.u.s.tration: CACAO DRYING PLATFORMS, SAN THOMe. Three tiers of trays on rails.

(Reproduced by permission from the Imperial Inst.i.tute series of Handbooks to the Commercial Resources of the Tropics).]

[Ill.u.s.tration: WASHING THE BEANS IN A VAT TO CLEAN OFF THE PULP, CEYLON.]

_Claying, Colouring, and Polishing Cacao._

[Ill.u.s.tration: CLAYING CACAO BEANS IN TRINIDAD.]