This section is from the book "Experimental Cookery From The Chemical And Physical Standpoint", by Belle Lowe. Also available from Amazon: Experimental cookery.
Fig. 9. - Crystals from divinity which was beaten until a piece dropped from a spoon would hold its shape, yet still appear glossy. Magnification approximately x 200.
Fig. 10. - Crystals from divinity. Some of the same divinity as that shown in Fig. 9. But these pieces were not beaten as long as those in Fig. 9. They flattened out when dropped from a spoon. These crystals and those shown in Fig. 2 emphasize the importance of beating candy sufficiently. Magnification approximately x 200.
Fig. 11. - Crystals from divinity. Same as those shown in Fig. 9, but after 40 days' storage. Compare with crystals in Fig. 7 and Fig. 8. Magnification approximately x 200.
Fig. 12. - Corn sirup, sucrose and water cooked to 119°C. and beaten while hot until the mass was stiff. Corn sirup retards crystal growth, see Fig. 1, but not to the same extent that both corn sirup and egg white do. See Fig. 9. Magnification approximately x 200. remembered that evaporation is greater from a small quantity of fondant, while it is being stirred, than from a large quantity. On rainy or damp days, when the humidity is high, moisture may be absorbed from the air by the sirup, so that it is preferable to cook the sirup to the higher temperature. Cooking the sirup to a temperature above 116°C. gives a fondant that is too dry and crumbly. Jordan states that commercially the amount of moisture in fondant is controlled carefully and according to the use for which it is intended, as a difference of 1 per cent of moisture results in a fondant too soft to handle or too dry to knead.
The growth of crystals in fondant. Freundlich states that "surface tension is also the cause of recrystallization, in which small crystals unite to larger ones. Probably this phenomenon is similar to the union of minute droplets to larger ones, when in direct contact, for it is unlikely that the formation of larger crystals could be due to the increased vapor pressure of the smaller ones bringing about a distillation; the process takes place far too rapidly to allow of the latter explanation." Water in fondant is a saturated sucrose solution. The crystals are in contact with this saturated solution. Owing to the higher surface energy of small crystals, as discussed in Chapter I (The Relation Of Cookery To Colloid Chemistry), the smaller crystals dissolve, and the larger crystals increase in size.
Crystals in fondant may grow in size during storage. Halliday and Noble have reported the growth of crystals in fondant stored for 17 days. Figs. 3 to 8 show crystals from fondant. Fig. 7 shows the growth of crystals in fondant after 40 days' storage. Compare these crystals with those shown in Fig. 3.
The addition of egg white to fondant. Egg white may be added to fondant. Paine states that the clumping together of air particles into larger particles lessens the intensity of the white and that the addition of a small quantity of egg white to fondant prevents the aggregation of the air particles, thus aiding in keeping the fondant white. The beaten egg also incorporates additional air.
The addition of beaten egg white to fondant also retards the rate of crystal growth during storage. Figs. 4, 6, and 8 show crystals from fondant to which egg white has been added. Since the egg white is adsorbed by the crystals, the effectiveness of the egg white in preventing crystal growth may partially depend upon how the egg white is distributed throughout the fondant. Swanson found that not much more than 6 per cent of beaten egg white could be added to the fondant, without the fondant becoming too fluid. She found 3 per cent of added egg white to be as effective as 6 in preventing growth of crystals during storage.
The addition of dextrose, levulose, or invert sugar to fondant. Dextrose, levulose, or invert sirup may be added directly to sucrose solutions to aid in regulating the size of the crystals. Or, invert sugar may be formed during cooking of the sucrose sirup by adding citric, tartaric, or acetic acids. Often cream of tartar is used for inverting sucrose in fondant.
It is difficult to regulate conditions, such as the time of cooking, to obtain a definite percentage of invert sugar for sucrose is inverted more rapidly with higher temperatures and greater acidity. Hence, it is sometimes preferable to add a definite quantity of dextrose, levulose, or invert sugar. Woodruff and van Gilder found that cream of tartar inverted the sucrose more slowly than citric, tartaric, or hydrochloric acids at the same pH. Cream of tartar can be added in sufficient quantity to produce enough invert sugar to give small crystals and to add to the smoothness of the fondant. If added in too large a quantity, too much invert sugar is formed, so that the fondant is too fluid. The flavor of the fondant is quite acid when a large proportion of cream of tartar is used.
The larger the quantity of dextrose or levulose added in making fondant the longer the time required to beat the sirup to bring about crystallization. With too large a proportion of these sugars the fondant is soft. When fluid centers of confections are desired, it is necessary to add substances that bring about inversion of the sucrose after the fondant is dipped in chocolate or treated in some way to give a firm outer coating.
Woodruff and van Gilder state that sirups with concentrations of 43 per cent or more invert sugar would not crystallize; those containing 16 to 23 per cent formed a semi-fluid mass of crystals; and those containing 6 to 15 per cent gave a plastic, moldable product. With 11.1 per cent or more of invert sugar the crystals of maximum size measured 10 to 13.2 microns and the grain was exceedingly fine to tongue and roof of the mouth. Fondants containing 7 per cent reducing sugars of either kind (glucose or levulose) were of agreeably fine texture, with their largest crystals measuring 15 to 19 microns. Crystals in candies of observed coarse texture measured 45 or more microns. Differences in crystal size of 6 to 10 microns, which was the difference of crystal measurements of fondants rated very fine and slightly coarse, could be detected by the tactile sense.
Halliday and Noble have reported that the addition of corn sirup, which contains dextrose and dextrin, tends to prevent the growth of crystals during storage of fondant. They also found that fondant made with cream of tartar retarded crystal growth during storage.
Color of fondant. Fondant crystallizing without stirring is not snowy white but more transparent. The snow-white appearance of the stirred fondant is due to the small air particles. When the water contains alkaline salts the fondant without cream of tartar added has a yellow or gray tinge; that with cream of tartar or acids is white.
Fondant made with hard water, pH 7.2 to 7.8, has a creamy tint. This may be caused by slight traces of flavones in the sugar, but it is probable that it is due to caramelization or some other cause. If, to some of the same sugar and water, a little cream of tartar is added, a snowy white fondant is always obtained. If, however, corn sirup is added to the sugar to make fondant with the above water a gray color develops. The color is so pronounced that the fondant is not attractive looking. If distilled water is used with the corn sirup and sucrose, the gray color does not develop.
Ripening. When fondant stands 12 to 24 hours it seems more moist and is more plastic and kneads more easily than when it was first made. In the candy trade this is known as "ripening." Fondants that contain substances that cause slow hydrolysis of the sucrose become softer on account of the formation of invert sugar, but "ripening" is an additional process and occurs in fondant containing only sucrose. Carrick suggests that the reason for this "ripening" is that the small crystals in the mass are dissolved, thus letting the large crystals move more easily, and they are thus more plastic.
Honey fondant. Candies made from pure honey, on account of their high levulose content and the moisture-absorbing property of honey, usually become very sticky in a few hours after they are made. Phillips reports the combination of honey, whole milk, and lactose sugar to make fondant. Stratton combined honey and lactose in fondant. Fondant usually contains some crystals of each of the sugars that enters into its composition, but in Stratton's combination the crystal phase was entirely lactose, the crystals being particularly minute. But the lactose crystals have a tendency to grow so that fondants smooth at first became somewhat grainy. It was found that the honey fondant would absorb a relatively high percentage of whole milk by mechanical mixing, and that this milk tended to prevent the growth of the lactose crystals. It was also found that the honey has an unusual preservative action, for the milk in the mixture remained sweet as long as the candy was kept.