Starch Sweetener Syrups

Chemistry.

Glucose is formed in plants from carbon dioxide absorbed from the air using sun light as energy source. Part of the glucose is polymerised into long chains of glucose and stored as starch in granules as a reserve. In spring starch is broken down again to support new growth.

This break down of starch can be imitated in a our factories by applying acid or enzymes to cooked starch. The way we do it cause the starch to hydrolyse into a variety of mixtures of glucose and intermediates and the way we characterise these various mixtures is by its DE number. DE means Dextrose Equivalent. The analytical procedure measures reducing end groups and attach a DE of 100 to pure glucose (glucose = dextrose) and a DE of 0 to pure starch.

Only glucose solution of high DE can crystallise easily and yield a product in powder or granular form. A most popular crystallised product is dextrose monohydrate with applications in medicine and used in chewing tablets by people doing sport. Dextrose monohydrate is pure glucose. A less purified product known as Total Sugar is produced by instant crystallising a 97 DE syrup leaving no hydrol (mother liquor) to dispose off.

Standard Acid converted 42 DE Syrup.

Lowering the DE, the syrup loose gradually its tendency to crystallise and below approximately 45 DE the syrup can be evaporated into a stable, non-crystallising and auto sterile liquid. These qualities are one of the reasons behind the success and wide spread use of the standard 42 DE syrup. Starch is hydrolysed by acid or enzymes to 40 - 42 DE and evaporated to a viscous liquid with a dry matter of 80% - 84%.

This standard product has a bland sweet taste, stores and ship well in drums or tank lorries. It find applications in canned fruit preserves, ice cream, bakery products, jam, soft drinks, candy and all kinds of confectionery. Large quantities are also used as a booster in the fermentation of alcohol The relative sweetness of 42 DE to sucrose is 40 - 45%.

High quality starch is supplied either as a slurry from a starch factory or a slurry of approximately 21 oBe is prepared from ordinary native dried starch. Acid - preferably hydrochloric acid, HCl is added to the slurry in order to acidify before cooking. The acidified slurry is heated to the desired temperature by injecting steam of 9 bar.

The liquefaction temperature is kept for a few minutes. The degree of liquefaction (hydrolysis) is controlled by the temperature in the holding zone. The acid is neutralised and the hydrolysate enters a cyclone - via a back pressure valve - where the hydrolysate is flashed down to atmospherical pressure. The crude hydrolysate is refined by means of activated carbon in order to remove discoloration from the interaction of protein and other starch constituents during hydrolysation.

Filter aid is added as body feed and the filtered off on a filter press. The purified hydrolysate passes a check filter and the water clear hydrolysate is evaporated until the dry substance reaches 80 - 84 %. From the evaporator the final product can be drummed off. Dependent on raw material and end product requirements various filtration steps and deionization etc. may be added to the process

Enzymes as catalysts.

The acid catalyst allows the manufacture of intermediate conversion products ranging from 35 - 55 DE. Intermediate and higher conversion products for special purposes can also be made by substituting acid with enzymes - typically in a two step process. For the first step, the liquefaction, termostable a-amylase or acid is used. After cooling and pH adjustment a saccharification enzyme like amyloglucosidase is applied.

Except for a different holding time the processes are in principles identical regardless of catalyst. However, enzymes and acid breaks down starch differently resulting in different sugar composition for identical DE, but it is possible to work around that problem and even produce the classic 42 DE syrup by an all-enzyme process only. With enzymes it is possible to produce syrups with DE from 28 and up to 98. Glucose syrups may be grouped according to the degree of conversion:

Conversion Groups

Conversion	DE
Low	20-38
Intermediate	38-58
High	58-73
Very high	73

Glucose Composition

DE	28	38	42	63	98
Catalyst	A/E	A	A	A/E	E
Glucose	5	12	18	37	96
Maltose	8	10	13	34	2
Maltotriose	16	10	12	16	1
Higher sugars	71	68	57	13	1

A=Acid E=Enzyme A/E=Acid liquefaction plus enzyme saccharification

High DE syrups are intermediates for fructose syrup, sorbitol, and many fermentation products and find uses in beverages, foods etc. Glucose syrup and maltose syrup are referred to as wort syrups in breweries, where they substitute malt improving capacity, adjusting protein, taste, mouthfeel etc.

Sugar confections will either pickup or lose moisture to the atmosphere, depending on the external conditions to which they are subjected. Therefore the water activity of the sweetener is an important property. This value is known as the equilibrium relative humidity (ERH).

Water Activity of Sweeteners

Syrup	Conversion	Solids	Water Acitity
42 DE	A	75	0.81
		80	0.77
		85	0.70
60 DE	A/E	75	0.78
		80	0.71
		85	0.64
94 DE	E	74	0.72
High Fructose	E	70	0.76
Liquid Sucrose		67	0.85

HFSS.

High Fructose Starch-based Syrups are produced from refined very high DE glucose syrups. An enzymatic process using isomerase fixated on a resin facilitates the conversion of glucose to fructose. By using more resin columns in parallel the enzyme activity is completely exhausted before a refill.

The isomerase catalyses the formation of 42% fructose in equilibrium with glucose. This syrup may be refined and evaporated as such and it is an excellent all-purpose sweetener.

In order to obtain a more perfect match with sucrose based liquid sugar (cane and beet sugar) the fructose content has to be increased to 55% by enrichment. A stream of HFSS-42 is fractionated. Previous attempts to do this by crystallisation have never gained industrial acceptance. The fractionation is done more elegantly by chromatography. By auto-matically switching the injection point an endless ring column is simulated and the HFSS-42 is fractionated in fructose and glucose. Water or condensate is used to eluate the column. The fructose fraction is backmixed with the HFSS-42 to make up an HFFS-55. In this way a perfect match with traditional sucrose based liquid sugar is obtained. The HFSS-55 finds widespread use as sweetener in soft drinks.

The fructose fraction from the chromatographic column can of course be refined and evaporated to a syrup separately as HFSS-90 finding applications in low calorie foods.

Demineralisation throughout the HFSS-process and precautions against de-cross-linking by oxygen extends the lifetime of the resins. An HFSS-section should preferably run continuously non-stop.

Starch & Sweetener Process Flow Chart in Principle

Corn ↓	Cassava Potato ↓	Native Starch ↓
Cleaning
Steeping	Washing
Milling	Rasping
Separation	Extraction
Concentration
Refining		Slurry preparation
Purified starch milk
		Prepara tion	Liquefaction
			Saccharification
			Refining
			Ion exchange
		Reaction	Hydrolysate
				Evaporation
				Crystal lisation	Hydro genation	Isomerisation
				Separa tion		Refining
		Finishing				Ion exchange
						Evapora tion
						Enrich ment
					Ion exchange
Drying					Evaporation
Granular Starch Products			Hydrolysed Starch products
Native Corn Starch	Native Tuber Starch	Modified Starch	Malto dextrin	Dextrose Mono hydrate	Sorbitol	HFSS 55	HFSS 42	High DE Glucose syrup	Glucose syrup

adapted from international starch institute