Sucrose, heating

It has been shown also that the concentration of sucrose is a critical factor and that to obtain the highest yields very dilute solutions are necessary. Thus Fig. 1 shows the relative yields at different concentrations of sucrose heated with hydrobromic acid, all experiments being carried out under similar conditions. The highest yield of levulinic acid, weighed as crude material, was 79% of the theoretical and was obtained when the concentration of sucrose was 3%. Ploetz has also used the hydrobromic acid method to make levulinic acid and records a yield of 69% of the theoretical from crude sugar, 75% from glucose and 64 % from starch. 

Fig. 2 illustrates CL spectra of sucrose heated at 80 °C in both a nitrogen and oxygen atmosphere. All the saccharides produced a CL peak in the range of 350-370 nm probably due to excited carbonyl compounds and at 620-640 nm due to singlet... 

Table 7.5 Time Needed to Reach a Burn-off of Approximately 23% in the Activation of Nitrogen-Containing Carbonized Sucrose (Heat-Treated at 1373 K) with CO2 at 1123 K...

Hydrolysis by acids. Sucrose is readily hydrolysed by dilute acids. Dissolve 0 5 g. of sucrose in 5 ml. of water, add 2 ml. of dil. H2SO4 and heat in a boiling water-bath for 5 minutes. Cool and show that the solution has reducing properties, and will form glucosazone. Note that the excess of acid must be neutralised before carrying out the reduction tests. 

Saccharin. Sacchatin [81-07-2] C H NO S, which is approximately 300 times as sweet as sucrose ia coaceatratioas up to the equivaleat of a 10% sucrose solutioa, has beea used commercially as a nonnutritive sweeteaer siace before 1900, predomiaanfly ia carboaated soft drioks, tabletop sweeteaers, and dietetic foods marketed primarily to diabetics. In 1977, the FDA proposed a ban on sacchatin because of its association with bladder cancer ia laboratory animals. At the time, it was the only commercially available nonnutritive sweetener, and pubflc outcry led to a delay of the ban, which was officially withdrawn ia 1991. Instead, the FDA required that warning labels be placed on all foods that contained the iagredient. Although sacchatin is heat stable, the pubflc debate over its safety, as well as the fact that approximately one-third of the population perceives it to have a bitter aftertaste, has limited its use. 

The Provesteen process, developed by Phillips Petroleum Company, employs a proprietary 25,000-L continuous fermentor for producing Hansenu/a jejunii the sporulating form of C. utilis from glucose or sucrose at high cell concentrations up to 150 g/L. The fermentor is designed to provide optimum oxygen and heat transfer (69,70). 

Spray Drying. Spray-dry encapsulation processes (Fig. 7) consist of spraying an intimate mixture of core and shell material into a heated chamber where rapid desolvation occurs to thereby produce microcapsules (24,25). The first step in such processes is to form a concentrated solution of the carrier or shell material in the solvent from which spray drying is to be done. Any water- or solvent-soluble film-forming shell material can, in principle, be used. Water-soluble polymers such as gum arable, modified starch, and hydrolyzed gelatin are used most often. Solutions of these shell materials at 50 wt % soHds have sufficiently low viscosities that they stiU can be atomized without difficulty. It is not unusual to blend gum arable and modified starch with maltodextrins, sucrose, or sorbitol. 

Sugar is destroyed by pH extremes, and inadequate pH control can cause significant sucrose losses in sugar mills. Sucrose is one of the most acid-labile disaccharides known (27), and its hydrolysis to invert is readily catalyzed by heat and low pH prolonged exposure converts the monosaccharides to hydroxymethyl furfural, which has appHcations for synthesis of glycols, ethers, polymers, and pharmaceuticals (16,30). The molecular mechanism that occurs during acid hydrolysis operates, albeit slowly, as high as pH 8.5 (18). 

Alkaline Degradation. At high pH, sucrose is relatively stable however, prolonged exposure to strong alkaU and heat converts sucrose to a mixture of organic acids (mainly lactate), ketones, and cycHc condensation products. The mechanism of alkaline degradation is uncertain however, initial formation of glucose and fructose apparendy does not occur (31). In aqueous solutions, sucrose is most stable at —pH 9.0. 

A chlorination process (20,21,44—46) converts sucrose into sucralose [56038-13-2] (4,l, 6 -trichloro-4,l, 6 -trideoxy-galactosucrose), a heat-stable, noncariogenic, noncaloric, high intensity sweetener. Sucralose is approved for food use in Canada, Australia, and Russia. It is not yet approved for use in the United States. 

High test molasses is not a residual material, but cane juice, sometimes partly clarified, concentrated by evaporation, with at least half its sucrose hydrolyzed to invert (glucose and fmctose) by heating at the low juice pH (5.5). 

Raw juice is heated, treated sequentially with lime (CaO) and carbon dioxide, and filtered. This accomplishes three objectives (/) microbial activity is terminated (2) the thin juice produced is clear and only lightly colored and (J) the juice is chemically stabilized so that subsequent processing steps of evaporation and crystalliza tion do not result in uncontrolled hydrolysis of sucrose, scaling of heating surfaces, or coprecipitation of material other than sucrose. 

Acesulfame-K is a white crystalline powder having a long (six years or more) shelf life. It readily dissolves in water (270 g/L at 20°C). Like saccharin, acesulfame-K is stable to heat over a wide range of pH. At higher concentrations, there is a detectable bitter and metallic off-taste similar to saccharin. Use of the sodium salt of feruHc acid [437-98-4] (FEMA no. 3812) to reduce the bitter aftertaste of acesulfame-K has been described (64). The sweetness potency of acesulfame-K (100 to 200x, depending on the matching sucrose concentration) (63) is considered to be about half that of saccharin, which is about the same as that of aspartame. 

In the confectionery industry, com symps are used extensively in nearly every type of confection, ranging from hard candy to marshmallows. In hard candies, which are essentially soHd solutions of nearly pure carbohydrates, com symp contributes resistance to heat discoloration, prevents sucrose crystallization, and controls hygroscopicity, viscosity, texture, and sweetness. Maltose symps, high conversion symps, and acid-converted symps (36 and 42 DE) are used for this appHcation. 

Heats of dehydration per mole of water vapor are (74) decahydrate to pentahydrate, 54.149 kj (12.942 kcal), and decahydrate to tetrahydrate, 54,074 kj (12.924 kcal). Borax stored over a saturated sucrose-sodium sucrose—sodium chloride solution maintains exacdy 10 moles of water and can thus be used as an analytical standard. Commercial borax tends to lose water of crystallisation if stored at high temperature or ia dry air. 

Caramel. Officially, the color additive caramel is the dark brown Hquid or soHd material resulting from the carefully controlled heat treatment of the following food-grade carbohydrates dextrose, invert sugar, lactose, malt symp, molasses, starch hydrolysates and fractions thereof, or sucrose. Practically speaking, caramel is burned sugar. 

Optimum toxin production was found in a stirred, aerated culture medium consisting of potato infusion and sucrose after 3 to 5 days growth. The toxin was adsorbed on charcoal from the culture filtrate and eluted with chloroform. The red-brown residue remaining after evaporation showed little or no absorption in the carbonyl region of the infrared and only weak absorption in the ultraviolet. However, on mild treatment with acid, base, or heat two carbonyl peaks appeared at 1715 and 1685 cm.-1 in the infrared and at 266 mft in the ultraviolet (3). 

E5.4 The apparent molar heat capacity of sucrose (2) in water (1) is given as a function of the molality, m by the expression... 

Similar anomalous distributions are observed in other thermal product mixtures. A commercial soft caramel made by heating sucrose and 0.1% acetic acid to 160°C contained 18% of a mixture of di-D-fructose dianhydrides.94 fi-D-Fru/-1,2 2,1 - 3-D-Fru/(now assigned as a-D-Fru/-l,2 2,l -a-D-Fru/83), ot-D-Fru/-1,2 2,1 -p-D-Fru/(5), ot-D-Frup-1,2 2,l -0-D-Fnjp (4), ot-D-Fru/-l,2 2,1 - 3-D-Frup (1), and p-D-Fru/-l,2 2,3 - 3-D-Fru/ (2) were found in the ratio 4 12 1 6 2. The first three of these, constituting 68% of the mixture, are considered to be kinetic products. The authors commented on this, but did not offer any explanation. Notice, however, that the preparation of such commercial caramels commences with heating of an acidic aqueous solution of sucrose, which almost certainly results in hydrolysis. Hence, the final dianhydrides are probably derived from the reaction of fructose, rather than sucrose. 

Fig. 40.—Inactivation of Binding of [ C]Sucrose to Taste Papillae by Heating in Boiling...

Dehydration of the core by means of concentrated sucrose solution also results in heat resistance. 

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