Sugar systems

Gonera, A. and Comillion, P. 2002. Gelatinization of starch/gum/sugar systems studied by using DSC, NMR, and CSLM. Starch/Starke 54, 508-516. 

Lopez-Driez, E.C., Bone, S. (2000). An investigation of the water-binding properties of protein + sugar systems. Physics in Medicine and Biology, 45, 3577-3588. 

The kinetic-acetonation procedure previously reported,107 employing alkyl isopropenyl ethers in N,N-dimethylformamide, and applied to the common pentoses and hexoses, has been extended to various hexuloses, oligosaccharides, and other sugar systems.108 Maltose gave the 4, 6 -monoacetal, isolated as the crystalline hexaacetate, on treatment with isopropenyl methyl ether inN,N-dimethylformamide in the presence of p-toluenesulfonic acid. 

This work has shown that in acyclic sugar systems the planar zigzag arrangement is the favored conformation in solution unless such an arrangement would lead to parallel 1,3-interaction between substituent groups, in which case the molecule adopts a sickle conformation to alleviate this interaction. 

Pyrazines are formed from many amino acid-sugar systems by the condensation of a-diketones arising from sugar fragmentation with amino acids via Strecker degradation and ammonia or amino acids. 

Fewer solubilities are recorded for ethanol-sugar systems. Trey80 found the solubility of D-glucose in ethanol to be 0.25% w/v at 20°... 

It is this variability, often uncontrolled, that leads to problems in controlling nucleation in food systems. Even in relatively pure systems, like carefully controlled supersaturated sugar systems, nucleation may occur over a very wide time span. For example, van Hook and Frulla (1952) found that identical supersaturated sucrose samples held at the same temperature nucleated over a very wide time span, with some crystallizing as quickly as 3 hours while other samples took over a day to nucleate. 

Levenson and Hartel (2005) studied nucleation of amorphous sugar systems (sucrose and com syrup mixtures) at temperatures above Tg, and compared Equation... 

The transition temperatures of carbohydrates and proteins are significantly affected by water. It is often reported that an increase in water content results in a substantial decrease in transition temperatures (Slade and Levine 1995). For example, the glass transition of dehydrated food solids decreases as a result of water sorption (i.e., water uptake from its surroundings) and their properties may change from those of the glassy solid to viscous liquids or syrup (e.g., sugar systems) or leathery material (e.g., protein systems) in an isothermal process. 

Lau, C.K., and Diekinson, E. (2004). Structural and rheological properties of aerated high sugar systems eontaining egg albumen. J. Food Set. 69, E232-E239. 

The effect of sugar cn toted yields of pyrazlnes was also investigated. In the lysine-sugar systems, total yield was greatest with the pentose, ribose, with 20 ppm total pyrazlnes produced. Glucose resulted in 13 ppm, versus fructose with 5.7 ppm total pyrazlnes. With a ragine, the effect of hexoses cn... 

Formation of a new stereogenic carbon center during the addition of a dialkyl phosphite to the C - C double bond of a sugar system usually proceeds with high stereoselectivity. For example, methyl 4,6-0-benzylidcnc-2,3-dideoxy-3-nitro-/ -D-criv/ ro-hex-2-cnopyranosidc reacts with dialkyl phosphites in the presence of catalytic amounts of triethylumine to give preferentially the 3-nitro-2-phosphono- /wo derivatives 1714. 

Aromatic Claisen rearrangements in 2,3-unsaturated sugar systems are useful for the stereo-controlled synthesis of aryl-branched sugars [87] (O Scheme 20). The a-anomer 97 is much less reactive in comparison to the /3-anomer 99. This thermal rearrangement is carried out by refluxing in iV,iV-diethylaniline. The efficiency of the reaction is almost independent of the nature of the p-substituent in the phenyl group. 

In search for the key intermediates to meat flavor development in heated cysteine-sugar systems, it was found that in addition to thiazolidine derivatives also the tetrahydro-l,4-thiazine derivatives are being formed. These tetrahydro-l,4-thiazines, which are the cyclic form of Amadori compounds of cysteine, have excellent meat flavor precursor properties and are likely to play a prominent part in meat flavor development. Another major pathway to meat flavor development is the reaction of cysteine with the Amadori compounds of other amino acids. Model experiments showed that both pathways are probably of about equal importance for flavor development in boiled meat and process flavorings, this in spite of the low reactivity of cysteine with sugars. It seems that the first pathway is general-acid-catalyzed by the other amino acids, whereas the second pathway is inhibited by cysteine. 

Figure 2. Proposed mechanisms of thiazolidine and tetrahydro-1,4-thicaine formation in cysteine-sugar systems (on the analogy of Kallen (9) and Hodge...

Figure 3. Browning in cysteine-sugar systems in dilute aqueous medium (74-79% water) at 90 °C. a equimolar mixtures of cysteine and sugar, b equimolar mixtures of cysteine, sugar andNaOH (5).

Maximizing flavor yields in cysteine-sugar systems... 

One of the major problems encountered in maximizing the flavor yields from cysteine-sugar systems is the high instability of the thiols diat are generated. The thiols do not only react with melanoidins but also widi each other (6, 2S). The result is that the characteristic meaty flavor disappears and a rubbery off-flavor is formed. Since the rates of the second-order reactions between the thiols are proportional to the square of the thiol concentrations, it is clear that products... 

Mazzobre, M.E, Longinotti, M.E, Corti, H.R., and Buera, M.P. Effect of the salts on the properties of aqueous sugar systems, in relation to biomaterial stabilization. 1. Water sorption behaviour and ice crystallisation/melting. Cryobiology, 43,199, 2001. 

The CV for dihydrocinchonidine adsorption on Pt(976) is identical to that for its adsorption on Pt(976) (Figure 2). The absence of an adsorption rate differentiation in this system, viewed alongside the presence of a reaction differentiation in the Pt/sugar system, suggests that molecular recognition in these chiral systems may require relatively weak interactions, and that perhaps the cinchona alkaloids are too strongly adsorbed to show delicate chiral-chiral interactions under these conditions. 

---