Honey ketose

D-fructose, C HijOo. Crystallizes in large needles m.p. 102-104 C. The most eommon ketose sugar. Combined with glucose it occurs as sucrose and rafftnose mixed with glucose it is present in fruit juices, honey and other products inulin and levan are built of fructose residues only. In natural products it is always in the furanose form, but it crystallizes in the pyranose form. It is very soluble in... 

The approximate proportions of these sugars in the oligosaccharide fraction (3.65%) of the honey were maltose, 29.4 kojibiose, 8.2 turanose, 4.7 isomaltose, 4.4 sucrose, 3.9 ketose band (mixture... 

D-Fructose (Fru), a ketose that is a close structural and metabolic relative of D-glucose. It occurs in honey and fruit juices in free form, in the disaccharide sucrose (table sugar) as a 5-membered furanose ring, and in other oligosaccharides and polysaccharides. 

In all three the carbonyl group is at C-2, which is the most common case for naturally occurring ketoses. D-Ribulose is a key intermediate in photosynthesis, the process by which energy from sunlight drives the formation of D-glucose from carbon dioxide and water. L-Xylulose is a product of the abnormal metabolism of xylitol in persons who lack a particular enzyme. D-Fructose is the most familiar ketose it is present in fruits and honey and is sweeter than sucrose. 

Glucose and fructose are structural isomers— they both have the same formula (C6H12O6), but they have different structures. Fructose is a ketose, a sugar that is a ketone. Since fructose has six carbon atoms, it is a ketohexose. Fructose, often called fruit sugar, is in many fruits and vegetables and is a major component of honey. 

Ketoses can be formed from each of the aldoses, and aldoses can be formed from ketoses by isomerization of the carbons at positions 1 and 2 (see reactions 1.6 and 1.7 in Chapter 1). A naturally occurring ketose that was first isolated from honey was d fructose (see Chapter 2). It can be formed by isomerization of either D-glucose or D-mannose (see reaction 1.7 in Chapter 1). Other ketoses can be formed from other aldoses. They are usually named by replacidng -ose with -ulose at the end of the name of the sugar from which they are formed. Thus,... 

D-Pructose, fruit sugar, or Icevulose, accompanies glucose in fruits, flowers, and their product, honey. It is obtained also from the hydrolysis of fructosides, the chief of which is sucrose, and from the polysaccharide, inulin. It crystallises with difficulty in fine, colourless needles, m.p. 110° C. Fructose differs from the other three fermentable hexoses in being a keto-sugar, or ketose, and in being tovo-rotatory, [a]j, = — 92 0°. It is much sweeter and more reactive than glucose. 

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