Sweet potatoes are cheaper than other crops as a starch source,
yet this abundant resource is still not properly utilised. The preparation
of sweet potato foods has several drawbacks. Discolouration
is a major problem in the quality of the products and arises from
two different sources. The first is the formation of brown discolouration
caused by the oxidase reaction of polyphenol groups by enzymes;
the second is the non-enzymatic browning (at high
temperatures) that results when reducing sugars condense with
amino groups (Utomo, Cheman, Rahman, & Saad, 2005). Several
methods have been developed to eliminate enzymatic discolouration.
Hoover and Miller (1973) used sodium acid pyrophosphate
blanch treatment to eliminate browning. Olorunda and Kitson
(1977) eliminated discolouration in chips prepared from white
flesh potatoes by dipping them in sodium sulphite