End-reducing sugars

Eldredge, E. P, Holmes, Z. A., Mosley, A. R., Shock, C. C., Stieber, T. D. (1996). Effects of transitory water stress on potato tuber stem-end reducing sugar and fry color. American Potato Journal, 73, 517-530. 

Another form of post-translational modification that may add carbohydrate to a polypeptide is non-enzymatic glycation. This reaction occurs between the reducing ends of sugar molecules and the amino groups of proteins and peptides. See Section 2.1 in this chapter for further details and the reaction sequence behind this modification. 

In some instances, reducing sugars are present that can be reductively aminated without prior periodate treatment. A reducing end of a monosaccharide, a disaccharide, or a polysaccharide chain may be coupled to a diamine by reductive amination to yield an aminoalkyl derivative bound by a secondary amine linkage (Figure 1.96). Also see Section 4.6, this chapter, for an extensive discussion on carbohydrate modification techniques. 

Figure 9.48 A cyanine dye containing a hydrazide group can be used to label glycans at their reducing end or other reducing sugars, forming a hydrazone linkage. Glycoproteins also can be labeled after periodate oxidation to form aldehyde groups.

The tuber samples should be selected at random and be representative of the entire batch in question. The samples should be evaluated for specific gravity and graded for size and absence of external and internal defects. A sub-sample should be Ified and if the fry color is not satisfactory, a reducing sugar evaluation should be made and the strategies for storage and end use followed as recommended above. The appearance and size of tubers are important to the user, and cleaning, uniformity of shape and size, depth of eyes, flesh color, and peel are very important in terms of... 

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