Starch used for making modified starches comes from potatoes, cereals (like corn or maize), or other sources like tapioca. Manufacturers use various processes to modify the starch chemically, but the overall process is the same: the native starch is treated with chemicals and processing aids, washed, dried, ground, sieved, and packaged. Percentages mentioned in the following paragraphs refer to the dry weight of the starch.
Oxidised starch (E 1404)
Native starch is mixed with a base to make it slightly alkaline, and then treated with sodium hypochlorite to create oxidised starch. The extent of oxidation is determined by measuring the fluidity or viscosity. After the reaction is complete, the excess hypochlorite is neutralized, and the starch granules are washed, dewatered, and dried. Even though hypochlorite is used to create this modified starch, it is sometimes referred to as “chlorinated” starch, even though it does not contain any chlorine in its structure.
When making oxidised starch, four types of oxidation can occur. The first type leads to uronic acids by oxidizing primary hydroxyl groups at the C-6 position. The content of carboxyl groups is limited to ≤ 1.1% by Commission Regulation (EU) No 231/2012. The second type involves oxidizing secondary hydroxyls into ketone groups. In the third type, the glucopyranose ring breaks between C-2 and C-3, and the aldehydic is oxidized into carboxyl groups at C-2 and C-3. The fourth type is minor and involves oxidation of the end groups. According to JECFA (1975b), oxidised starches typically contain 1% (w/w) of carboxyl and 0.5% (w/w) of keto groups.
Monostarch phosphate (E 1410)
Monostarch phosphate is a type of modified starch that is produced by reacting native starch with phosphoric acid. The reaction can be carried out using different methods such as wet, semidry, or dry processes, with temperature and pH being important parameters. In the wet process, the phosphating agent is added to an aqueous starch slurry, while in the semidry or dry processes, native starch is mixed with the phosphating agent and heated. The resulting product is then filtered and dried. Monostarch phosphate is a phosphate ester in which one hydroxyl group of the starch molecule is esterified by phosphoric acid to form the monoester.
Distarch phosphate (E 1412)
Distarch phosphate (E 1412) is created by treating a mixture of native starch and either sodium trimetaphosphate or phosphorus oxychloride under alkaline conditions to achieve cross-linking. The reacted starch is then recovered, washed, dehydrated, and dried. The maximum amount of sodium trimetaphosphate used is limited to 1%, or up to 0.1% for phosphorus oxychloride. In the first process, one phosphate link is formed per approximately 620 glucopyranose units, while in the second process, the maximum number of phosphate bridges could reach one per 100 glucopyranose units.
Phosphated distarch phosphate (E 1413)
Phosphated distarch phosphate (E 1413) is a modified starch made from high-amylose corn starch. In its production, an aqueous starch slurry is treated with a combination of reagents used to make monostarch phosphate (E 1410) and distarch phosphate (E 1412) under alkaline conditions. After cross-linking and phosphorylation are achieved, the modified starch is recovered by neutralization, washing with water, and drying.
Acetylated Distarch Phosphate (E 1414)
Acetylated distarch phosphate is a modified starch used in food production. The manufacturing process involves treating native starch with sodium trimetaphosphate or phosphorous oxychloride under alkaline conditions, followed by esterification with either acetic anhydride or vinyl acetate. The resulting modified starch is recovered through neutralization, washing, dewatering, and drying. The production typically involves using up to 0.1% phosphorus oxychloride and 5% acetic anhydride. When it comes to food safety, the free and combined phosphate levels must not exceed 0.04% for distarch phosphate made from cereal starch other than wheat and 0.14% for that made from potato and wheat starch.
Acetylated starch (E 1420)
Acetylated starch (E 1420) is made by treating a mixture of native starch and water with either acetic anhydride or vinyl acetate. The esterification process is done at a certain pH level and temperature. The modified starch is then recovered by neutralization, washing, dewatering, and drying. The percentage of acetic anhydride or vinyl acetate used varies, but must not exceed certain limits (JECFA, 1982f; Xie et al., 2005; Wurzburg, 2006).
Acetylated distarch adipate (E 1422)
Acetylated distarch adipate (E 1422) is made by treating native starch with a mix of adipic anhydride and acetic anhydride in water, under mildly alkaline conditions. Once the desired degree of cross-linking and acetylation is achieved, the reaction is stopped with acid, and the modified starch is washed, dewatered, and dried. The amount of adipic cross-links is limited to about 1 in every 1,000 glucopyranose units, which is less than 0.09% adipyl groups (JECFA, 1982b; Wurzburg, 2006).
Hydroxypropyl starch (E 1440)
Hydroxypropyl starch (E 1440) is made by treating a mixture of native starch and water with up to 10% propylene oxide and sodium hydroxide. The reaction usually takes place at a temperature between 38-52°C for about 24 hours, with the addition of sodium sulfate to prevent starch granules from swelling. The resulting starch is then modified by oxidation, bleaching, or acid treatment. Once modified, the starch is neutralized with acid, washed, and dried.
Hydroxypropyl distarch phosphate (E 1442)
Hydroxypropyl distarch phosphate (E 1442) is made by treating native starch with sodium trimetaphosphate or phosphorus chloride and then adding propylene oxide. After the right amount of cross-linking and etherification, the modified starch is recovered by neutralizing with acid, washing, dewatering, and drying. The amount of sodium trimetaphosphate used is limited to 1%, and the amount of free and combined phosphate can’t exceed 0.04-0.14% depending on the type of starch used.
Starch sodium octenyl succinate (E 1450)
Starch sodium octenyl succinate (E 1450) is made by mixing a slurry of natural starch with octenyl-succinic anhydride and a mild base, while keeping the pH at 7.0 or higher. The resulting modified starch has around one octenyl monosuccinate group for every 50 anhydroglucose units. After the right amount of modification is achieved, the modified starch is recovered by neutralisation with acid, washing with water, and then dried.
Acetylated oxidised starch (E 1451)
Acetylated oxidised starch (E 1451) is made in two steps. First, native starch is treated with sodium hypochlorite in water at low temperature, and the excess hypochlorite is removed. In the second step, the oxidised starch is esterified with acetic anhydride. After this, the modified starch is neutralised with acid, washed thoroughly with water, dewatered and dried to create the final product.
Starch aluminium octenyl succinate (E 1452)
Starch aluminium octenyl succinate (E 1452) is made by mixing native starch with a small amount of octenyl-succinic anhydride in water, with a bit of alkaline substance. After the right amount of octenyl groups have been added, aluminium sulfate is added to the mixture. The modified starch is then recovered by washing it with water, removing the water, and drying it (Documentation provided to EFSA n. 1; Wurzburg, 2006).