INTRODUCTION - CORN INDUSTRY

The natural sugar extracted from cane is sucrose. It has been the traditional sweetener since the dawn of civilization. The increasing demand for the sugar rising trend in its prices the world over has drawn the attention of the scientists to develop alternative sources of sugars. Semi synthetic sugars like dextrose in crystal form and glucose syrups have been commercially produced from starch since the beginning of this century.

In India the raw material, starch is mainly obtained from different crops like corn, wheat, tapioca, potato. The north India corn and wheat are the crops where as South India Tapioca is the major crop for the production of the starch.

Corn Product: The corn grown in the field is retained on the field by farmer for animal feeding. The major product sold from the field of the corn is again used for the production of animal feed and other industrial products.

The use for dry milling process of the corn is mainly for the production of corn meal and breakfast cereal. The distilling industry also uses corn.

The wet milling process industry uses corn for the production of starch, syrup, dextrose, refined corn oil and feed products..

The major product from the wet milling is starch. The further processing of the starch by isolation and washing usually contains less than 0.3 % protein, less than 0.1 % ash, and about 0.6 % total fat. The bulk is present as free fatty acids complexes with amylose fractions.

STARCH PRODUCTS

Starch may be marked in an unmodified form after drying or it may modified by variety of chemical and / or physical means prior to sale.

Starch can be partially hydrolysed with acid or enzymes or combinations to produce corn syrup. Starch can be completely hydrolysed for the production of crystalline dextrose. Starch obtained from the wet milling of corn normally contains substantially less than 0.1 % nitrogen containing substituent group.

MANUFACTURING PROCESS

In the manufacturing of the liquid glucose or dextrose monohydrate, 30 % hydrochloric acid is being used for the hydrolysis of the starch. The starch source may be corn (maize), potato, wheat or tapioca.

The starch is first liquefied by heat treatment or by enzyme pretreatment or by both treatment in sequence while being heated.

The first step of this process is effected by gelatinizing an appropriate starch source. The thinned starch i s then converted into a converter juice and treated with soda ash to a breakpoint pH. This process removes the scum. The filtered liquid is pretreated with powdered activated carbon (PAC) for colour removal.

Carbon treatment before deionization is extensively practiced in the purification of starch hydrolysate. This practice is beneficial in removing resin foulants. Hence it extends resin's useful life.

This is further passed through ion exchange resin units of STRONG ACID CATION & WEAK BASE ANION resin beds for ash removal. The ion exchange treated feed solution after evaporation gives 87º DS liquid glucose.

BENEFITS OF ION EXCHANGE TREATMENT

• Removal of alkaline earth salts like CaCl₂ , MgSO₄, NaCl
• Removal of ionizable organic salts.
• Nitrogenous compounds polypeptides and amino acids.
• Coloured products derived from Millard reaction and hydroxy methyl furfural (HMF) which causes colour to develop during storage, in particular at higher temperature.

ION EXCHANGE PROCESS FOR THE DEASHING OF DEXTROSE

Ion exchange technology has made slow but steady progress in the sugar refining industry around the world. In many respects the progress made in sugar refining has rivaled that made in water treatment.

Presently the sugar juices and syrups are being softened  (calcium removal), decolourized, deionized by means of ion exchange.

Powdered activated carbon treatment before the processing of liquefied starch is carried out in the purification starch hydrolysate. This practice is beneficial in removing resin foulants thereby extending ion exchange resin life.

The ion exchange system comprises of STRONG ACID CATION EXCHANGE RESIN and WEAK BASE ANION EXCHANGE RESIN UNITS.The process for the removal of the dissolved mineral impurities (ash) by ion exchange resins can be generalized as follows:

Ion exchange process involves two stages of demineralization.

The first stage involves the removal of cationic impurities (decationization) with the help of strong acid cation exchange resin.

The second stage is removal of the anionic counterparts using weakly basic macroporous resin.