Sugar in Confectionery

Sugar in Confectionery L. F. MARTIN

Downloaded by UNIV OF NEW SOUTH WALES on September 9, 2015 | http://pubs.acs.org Publication Date: June 1, 1955 | doi: 10.1021/ba-1955-0012.ch007

Sugarcane Products Division, Southern Regional Research Laboratory, New Orleans, La.

Problems in the use of sugars in confectionery have not re-ceived attention commensurate with their importance and the volume of sugars used. Review of recent advances in ex-plaining the reactions of sugars in candymaking emphasizes the need for applying the methods and results of this research to the candymaker's art. Highly concentrated solutions of sugars at elevated temperatures undergo complex transformations, some initial products of which have been identified. The equally important reactions of sugars with proteins have been the subject of extensive recent research. The accumulated re-sults of this work can be used to improve the quality of con-fectionery products. Formation of sugar anhydrides and cara-melization products can account for many production difficul-ties and shortcomings of improperly processed hard candies. Determination of the extent to which these reactions proceed in practical hard candy manufacture, or can be controlled by variables in processing conditions, offers an opportunity for profitable research. Caramels are an example of candies in which it is desirable to accelerate as well as control the com-plex degradation reactions of sugars with proteins. They have been perfected as far as possible by rule of thumb methods, and any improvement must be based upon facts disclosed by fundamental research.

T h e confectionery industry uses approximately a billion and a half pounds of sugar and three quarters of a billion pounds of corn sirup and dextrose annually to produce candies and chocolate goods. I n volume, i t is the second largest industrial customer of the industries producing these sugars. A wide variety of other ingredients are combined w i t h the sugars to produce 85 or 90 different items, but the chemistry of candy is p r i m a r i l y sugar chemistry. The reactions of sugars i n various processes of confectionery manufacture largely determine the quality of the products, either by changes produced i n the sugars themselves or by their reactions w i t h the other i n gredients. Recent research on the mechanism and products of these reactions applicable to candy problems has not received attention commensurate w i t h i t s i m portance; therefore a review of pertinent results and their applications should serve a useful purpose. This review deals largely w i t h progress i n the chemistry of sugars rather than studies of the candymaking processes themselves. It is i n tended to point out opportunities f o r research and possibilities f o r using sugar more efficiently i n candy production. A basis for systematic review of this subject is provided by Table I , which shows the large total percentages of sugars entering into the composition of the more important types of candy, and the wide range of v a r i a t i o n i n the proportions used. I t is evident that the chemistry of these p r i m a r y ingredients of the candies must have the greatest importance i n their formulation and processing. The table also gives the approximate range of cooking temperatures and final moisture contents f o r each type of candy. The most important reactions to be considered are those of sugars subjected to relatively high temperatures i n extremely concentrated solutions, p a r t i c u l a r l y h a r d candies, caramel, fudge, and " s h o r t " or grained 64 In USE OF SUGARS AND OTHER CARBOHYDRATES IN THE FOOD INDUSTRY; Advances in Chemistry; American Chemical Society: Washington, DC, 1955.

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M A R T I N — S U G A R IN CONFECTIONERY

marshmallows. I n a l l but plain h a r d candy and brittle, reactions of the sugars w i t h other ingredients under these conditions are also important. Jellies a n d soft marshmallows are made w i t h less drastic modification of the sugars, as their consistency or "body" is provided by starch, pectin, or gelatin.


Action of Hear upon Sugars

The reactions of sugars i n solution at high concentrations have received less attention, but useful deductions can be made by interpolating between observations made i n the extensive research on dilute solutions and the d r y sugars. Caramelization of sucrose has been studied by numerous investigators (25). The stepwise dehydration of d r y sucrose to "caramelan," "caramelen," and " c a r a m e l i n " proposed b y Gélis (8) has been supplanted by later work establishing the mechanism a n d products of at least the i n i t i a l stages of reaction. Pictet and his coworkers (19, 21) identified the i n i t i a l decomposition products, glucose and levulosan, formation of which precedes elimination of water i n the reactions. Evidence f o r this reaction was obtained by Gélis (7), but he was unable to separate and identify the products. C12H22O11

Sucrose

^

CeHisOe

Glucose

-f- ΟβΗιοΟδ

Levulosan

The glucose formed is subsequently converted to glucosan, w i t h evolution of the first molecule of water. CeH^Oe

— >

Glucose

CeHxoOs

+

H 0 2

Glucosan

E v e n i f the water is rapidly removed by vacuum, at this stage the reactions w i l l inevitably tend to follow the course of those occurring i n very concentrated solution. The sugar anhydrides readily form dimers, levulosan i n particular being converted into diheterolevulosans. I t is now known that similar products are formed by refluxing fructose i n 8 0 % solution (24). The reactions of caramelization cannot be limited to the i n i t i a l stages without simultaneous further dehydration and polymerization, as well as extensive degradation to produce hydroxymethylfurfural (13). Table I.

Candy Hard Plain Butterscotch Brittle Creams Fondant Cast Butter

Range of Cooking Temperatures, Moisture Contents, and Proportions of Sugars of Principal Types of Candy Final Cooking Temp. Range, F. 0

Final Moisture Content Range,

%

Sugar

Ingredients Range, %

11

Sucrose

Invert

Corn sirup solids

Principal Other Ingredients Ingredient Range, a

%

275-338 240-265 290-295

1.0-1.5 1.5-2.0 1.0-1.5

40-100 40-65 25-55

0-10

235-244 235-245 235-247

10.0-11.5 9.5-10.6 9.5-11.0

85-100 65-75 50-66

5-10

0-10 25-40 25-40

Fudge

240-250

8.0-10.5

80-70

0-17

12-40

Caramel

240-265

8.0-11.6

0-50

0-15

0-50

8.0-8.5

20-50

0-15

30-60

Starch E g g albumen Butter Milk solids Fat Milk solids Fat Fat

12.0-14.0 15.0-18.0

50-78 26-64

0-5 0-10

15-40 40-60

Gelatin Gelatin

1.5-3 2-6

14.5-18.0 18.0-22.0

25-60 40-65

0-10

28-65 30-48

Starch Pectin

7-12 1.6-4

255-270 Nougat Marshmallow Grained 240-245 Soft 225-230 Jellies Starch 230-235 Pectin 220-230 Adapted from (12). Honey is often used.

0-60 35-60 20-50

5

Butter

1-7

0-1 0-0.05 1-16 5-15 1-5 15-25 0-10 0-5

β

6

A key to the i n i t i a l reactions of sugars i n solution over a wide range of con ditions is provided b y the L o b r y d e B r u y n - v a n Ekenstein transformation (16). Solutions of pure sucrose r a p i d l y become acid upon heating, and i n candymaking In USE OF SUGARS AND OTHER CARBOHYDRATES IN THE FOOD INDUSTRY; Advances in Chemistry; American Chemical Society: Washington, DC, 1955.


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A D V A N C E S IN

CHEMISTRY SERIES

the inversion thus produced is usually accelerated by addition of acid, or of invert sugar and glucose. Whatever candy formula is used, a system is established i n which glucose and fructose are present, and they tend toward equilibrium w i t h each other and w i t h mannose. This interconvertibility of the three simple sugars, first discovered by L o b r y d e B r u y n and v a n Ekenstein, proceeds to a n extent governed by the concentration, p H , temperature, and ionic catalysts present. It is catalyzed p a r t i c u l a r l y by alkalies, but takes place over a wide p H range. M a x i m u m stability prevails for both glucose (23) and fructose (17) at a p H of approximately 3.0 to 3.3; i n more strongly acid solutions the p r i n c i p a l reaction is anhydride formation at the expense of the sugars (17, 2U). Glucose can be transformed into fructose at p H 6.4 to 6.6 i n the presence of phosphates and certain other salts (6). U n d e r a l l conditions of p H , concentration, and temperature that have been studied, the transformation of the reducing sugars by the rearrangement is accompanied by the formation of sugar anhydrides, p a r t i c u l a r l y f r o m fructose, which is the least stable of these hexoses. Gottfried and Benjamin (9) investigated the kinetics of this reaction under widely v a r y i n g conditions and showed that the m a x i mum yield of fructose obtainable from glucose is 2 1 % , w i t h the simultaneous f o r m a tion of 8.5% of anhydrides and other unfermentable derivatives, and 3% of sugar acids. A t extremely high concentrations or w i t h only traces of water present, these reactions approach the changes associated w i t h caramelization. Colored polymers are invariably formed, becoming the predominant products at the maximum concentrations i n the presence of acids or salts. Applications to Hard Candy Production Problems

P l a i n hard candies are regarded as the simplest type, as they are made entirely of sugars w i t h added flavor, color, and sufficient acid to cause some inversion. They provide the best example of the importance of the chemistry of sugars i n candymaking i n the absence of complex reactions w i t h other ingredients. Their production requires cooking temperatures above 300° F . , or 270° F . w i t h application of vacuum, to reduce the moisture content to approximately 1.5%. Substantial amounts of corn sirup, which is a complex mixture of glucose w i t h v a r y i n g proportions of maltose and dextrin, are generally added. Consideration of the reactions at high concentrations and temperatures described i n the previous section makes it evident that the final chemical composition of hard candy may be as complex as that of any other type. Controlling color formation, preventing c r y s t a l l i z a tion or g r a i n i n g , and minimizing the hygroscopicity or stickiness of the finished product are the p r i n c i p a l problems i n practical manufacture of hard candies. Desirable properties i n finished hard candy are known to depend upon the quality of the sugar used i n its production. The "candy test" has been used by candymakers for control of sugar quality (2,3). A hard candy is made f r o m definite weights of sugar and pure water, cooked under carefully controlled conditions, and poured on a polished sheet of copper. The candy disk is observed to determine color and time of crystallization, as well as its tendency to become sticky. It serves to determine the " s t r e n g t h " of the sugar, which can be defined best as its resistance to inversion and further decomposition. Differences i n quality and strength of sugars determined by this empirical test are attributable to the presence of very small traces of impurities (2). A d d i t i o n of as little as 0.001% soda is known to have a strengthening effect i n shortening the time required for crystallization. W a t e r quality is p a r t i c u l a r l y important i n h a r d candy production for this reason, as traces of minerals i n water may offset the advantage of using strong, or high quality, sugar. The caramelization test of Pucherna (22) is another empirical test of sugar quality that has been modified recently by Kalyanasundaram and Rao (i-4). The latter workers improved the test by heating the sugar i n glycerol, which permitted them to study the effect of additions of 0.1% of various salts and acids. Sodium chloride had the least effect i n f o r m i n g color, without measurable destruction of sugars, although it produced extensive inversion. Potassium chloride destroyed or transformed 4.2% of the total sugars without producing any color or causing measurable inversion. A s would be expected, ammonium salts at this concentration caused the inversion of nearly a l l of the sucrose and destruction of a major proportion of the invert sugars formed, w i t h maximum coloration. In USE OF SUGARS AND OTHER CARBOHYDRATES IN THE FOOD INDUSTRY; Advances in Chemistry; American Chemical Society: Washington, DC, 1955.


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67

Although the candy test is applied and interpreted as a measure of resistance to inversion, the strongest sugars being those which crystallize i n the shortest time after cooling, crystallization is not desirable i n h a r d candies. Corn sirup is usually added i n sufficient amounts, or organic acids are usecLin pure sugar h a r d candies to produce enough inversion, so that crystallization is prevented almost indefinitely under proper packaging and storage conditions. It is unlikely that these measures would suffice for the purpose, were i t not for the further decomposition of sucrose and its inversion products to f o r m an extremely complex mixture. Sucrose, g l u cose, and fructose or their mixtures are not extremely hygroscopic, but the a n hydrides of these sugars are very much so. Small percentages w i l l account f o r the excessive tendency of h a r d candy to become sticky upon exposure to humid atmospheres. The maltose present i n corn sirup also yields an anhydride on heating (20), the properties of which have not been investigated as thoroughly as those of glucosan and fructosan. Methods are now available (24) by which these complex sugar decomposition products may be separated quantitatively f r o m mixtures w i t h unchanged sugars. T h e i r application to the analysis of hard candies produced under different conditions should make i t possible to determine the extent to which such substances are formed and affect the quality of the product, thus providing the information necessary for rational improvement of processing methods and composition of the finished candies. Production of h a r d candy w i t h desirable color has been greatly facilitated by the wide adoption of vacuum cooking equipment w i t h steam jacket heating. T h i s makes possible more uniform heating and a reduction of about 30° F . i n maximum cooking temperatures. Recent experimental development of h i g h speed, continuous cooking equipment promises f u r t h e r improvement by shortening the time of heating necessary. Such improvements also make i t possible to control inversion and decomposition of sugars to the anhydrides and degradation products which polymerize to f o r m the colored substances associated w i t h caramelization. In order to take f u l l advantage of the precise control of process conditions permitted by this modern equipment, i t w i l l be necessary to determine the exact nature and extent of the chemical changes t a k i n g place and the precise conditions favorable to the formation of desirable final reaction products. Reactions of Sugars with Other Ingredients

The chemical transformations of sugars are less important i n candy which does not require cooking to temperatures and final concentrations as high as those necessary to produce h a r d candies. I n most of the other candies listed i n Table I, reactions of the other ingredients w i t h the sugars assume greater importance. I n i t i a l products of sugar transformation are diverted to reactions involving these other compounds. The chemistry of certain side reactions has been studied extensively i n recent years w i t h some success i n a r r i v i n g at an understanding of the i n i t i a l changes involved. M u c h of this research is directly applicable to the production of fudge, caramel, and other types of candies made w i t h fats, proteins, starch, and other nonsugars. W h i l e details of these more complex chemical transformations are beyond the scope of this review, some of the obvious applications of recently acquired knowledge of the subject to improvements i n candy production are worth noting. The most important reactions i n the production of candies made w i t h m i l k are those of the sugars w i t h the m i l k protein. I n addition to the casein, m i l k i n t r o duces another sugar, lactose, which may enter into reactions similar to those of s u crose, increasing the number and complexity of the reaction products. Research up to 1951, and conclusions drawn f r o m its results regarding the mechanism of the sugar-protein reaction, are summarized by Danehy and P i g m a n (4)» I n this case also, only the i n i t i a l reaction steps have been investigated w i t h any success; because these reactions are more complex, their mechanism and i n i t i a l products have not been established w i t h as much certainty as those of the decomposition of the sugars alone. More progress has been made i n determining the course of the reaction of simple sugars such as glucose w i t h individual amino acids instead of complex proteins (5). In the presence of amino compounds, transformation of the sugars is directed along a different path as a result of condensation of sugar-aldehyde and amino groups, followed by a rearrangement first described by A m a d o r i (1), but only In USE OF SUGARS AND OTHER CARBOHYDRATES IN THE FOOD INDUSTRY; Advances in Chemistry; American Chemical Society: Washington, DC, 1955.

ADVANCES

68

IN

CHEMISTRY SERIES

recently indicated to be of importance to an explanation of nonenzymatic browning i n sugar-protein systems (10,11). In spite of the complexity of these reactions, whatever has been learned of their chemistry and of the conditions that accelerate or retard them w i l l be directly applicable i n the production of the very large volume of candies i n which proteins are used. Theories of these reactions and proposed mechanisms are still open to question, but the large amount of experimental work being done to prove or dis prove the theories has already provided very many empirical observations that can be used to devise better candy cooking procedures.


Applications to Caramel Production

These complex reactions and further degradation of the i n i t i a l products are not always undesirable. Caramels provide the principal example of candies i n which such changes are deliberately produced, their flavor and color being dependent upon the interaction of sugars and proteins. The object is to develop the most attractive color and desirable flavor, while retaining suitable consistency or texture. There is considerable latitude for v a r i a t i o n i n reaction conditions to produce the various grades of caramels, r a n g i n g from the short, grained types approaching the con sistency of fudge to very smooth and "chewy" candies. I n any case, top quality products are obtained only through control of the extent of reaction, which is still attained by t r i a l and error methods and subjective examination of the results. A t tempts to use the latest equipment for high speed, continuous cooking by which the heating time is greatly reduced have not been successful i n producing caramels, because reaction does not proceed sufficiently f a r to develop typical caramel flavor and color. F r o m leads obtained by experiments i n simple systems containing p a i r s of i n dividual sugars and amino acids, the investigation of reactions of proteins w i t h more complex sugar mixtures has developed considerable evidence that condensation of sugar aldehyde groups with basic nitrogen of protein provided by lysine, arginine, and other basic amino acids is involved. T h i s is currently the best available ex planation of at least the i n i t i a l stages of the process. The reaction of glucose w i t h casein, the protein of milk, has been studied by P a t t o n et al. (18), who found considerable decrease i n the amounts of lysine and arginine i n the hydrolyzates ob tained after reaction under their conditions. Reaction of casein w i t h a variety of sugars was found by Lewis and L e a (15) to result i n the loss of variable amounts of amino nitrogen, depending upon the p a r t i c u l a r sugar used. T h i s immediately suggests a basis for the addition of p a r t i c u l a r sugars to caramel where i t is desired to promote more extensive reaction, and formulation entirely w i t h other less reactive sugars when the quality desired calls for minimum alteration of the ingredients. Literature Cited

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13) (14) (15) (16) (17) (18) (19)

A m a d o r i , M., Atti accad. nazl. Lincei, [6] 9, 68 (1929). A m b l e r , J. Α., Mfg. Confectioner, 7, N o . 1, 17 (1927). A m b l e r , J. Α., and B y a l l , S., Ind. Eng. Chem., Anal. Ed., 7, 168 (1935). Danehy, J. P . , and P i g m a n , W . W., Advances in Food Research, 3, 241 (1951). Ibid., p. 248. E n g l i s , D . T., and H a n a h a n , D . J., J. Am. Chem. Soc., 67, 51 (1945). Gélis, Α., Ann. chim., [3] 57, 234 (1859). Gélis, Α., Compt. rend., 45, 590 (1857). Gottfried, J. B . , and B e n j a m i n , D . G., Ind. Eng. Chem., 44, 141 (1952). Gottschalk, Α., Biochem. J., 52, 455 (1952). Hodge, J. E., and R i s t , C. E., J. Am. Chem. Soc., 75, 316 (1953). J o r d a n , S., and L a n g w i l l , Κ. E . , "Confectionery A n a l y s i s and Composition," Chicago, M a n u f a c t u r i n g Confectioner, 1946. Joszt, Α., and M o l i n s k i , S., Biochem. Z., 282, 269 (1935). K a l y a n a s u n d a r a m , Α., and Rao, D . L. N., Sugar, 46, N o . 3, 40 (1951). L e w i s , V. M., and L e a , C. H., Biochim. et Biophys. Acta, 4, 532 (1950). L o b r y d e B r u y n , C. Α., and van Ekenstein, W . Α., Rec. trav. chim., 14, 156, 203 (1895) ; 15, 92 (1896). Mathews, J. Α., and Jackson, R. F., Bur. Standards J. Research, 11, 619 (1933). P a t t o n , A. R., Hill, E. G., and Foreman, Ε. M., Science, 107, 623 (1948). Pictet, Α., and Andrianoff, N., Helv. Chim. Acta, 7, 703 (1924). In USE OF SUGARS AND OTHER CARBOHYDRATES IN THE FOOD INDUSTRY; Advances in Chemistry; American Chemical Society: Washington, DC, 1955.

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(20) (21) (22) (23) (24) (25)

CONFECTIONERY

69

Pictet, Α., and M a r f o r t , Α., Ibid., 6, 129 (1923). Pictet, Α., and Strieker, P . , Ibid., 7, 708 (1924). Pucherna, J., Z. Zuckerind. Cechoslovak Rep., 55, 14 (1930). Singh, B . , Dean, G . R., and Cantor, S., J. Am. Chem. Soc., 70, 517 (1948). Wolfrom, M. L., and B l a i r , M. G . , Ibid., 70, 2406 (1948). Zerban, F . W . , "Color Problem i n Sucrose Manufacture," Sugar Research Foundation, Technol. Rept. Ser., 2, 2-5, B i b l . refs. 2-20 (1947). 1953.


RECEIVED July 10,

In USE OF SUGARS AND OTHER CARBOHYDRATES IN THE FOOD INDUSTRY; Advances in Chemistry; American Chemical Society: Washington, DC, 1955.

Sugar in Confectionery

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