European Starch Industry Association (AAF) recommends that modified starches should not be stored for longer than 2 years due to the possibility of increased moisture content leading to impaired physical properties. However, under proper storage conditions such as keeping the original packaging unopened in a dry place at room temperature, the typical shelf-life of modified starches is 5 years. The stability of modified starches is supported by a lack of known relevant degradation or reaction products, a history of use for over 20 years, and the chemical nature of the additives. Stability is further supported by:
- The impact of chemical changes on the properties of the material is well known.
- The degree of chemical modification is legally limited to the minimum required for specific food applications, and is typically low.
- The efficacy of modified starches is evident by their ability to maintain their intended function in various foods.
Native starches have limitations for food applications due to their physical and chemical properties, including poor solubility and high hydrophilicity. Modified starches are altered to improve their functional properties for specific food uses by modifying the chemical and physical characteristics of the native substances, and the extent of modification required is generally low. Grain size also affects reactivity, with larger grains being more susceptible to modification. Modified starches are used in many food applications because of their superior properties compared to native starches.
Modified starches can be created not only through chemical reactions but also by physically weakening or degrading the crystalline structure of native starches. These physical modifications can make the starch swell in cold or lukewarm water, eliminating the need to cook the starch. It’s also possible to subject chemically modified starches to physical modifications.
Starch pastes need to have certain rheological properties to work as thickeners or gelling agents. Acetylated starch has a lower pasting temperature than the native version, according to Berski et al. (2011).
Microwave processing can change the way starch gelatinizes, which is an important function. The effect of microwaves causes structural changes to the starch that decrease its viscosity.
Sun et al. (2016) studied the interactions between starches and casein in a simulated yoghurt environment. They found that the interactions were different for modified starches than for native starches. Phosphate starch had close electrostatic adhesion to casein, while hydroxypropyl starch interacted through hydrogen bonds and steric stabilisation. Starch ester of octenyl succinate was both hydrophilic and hydrophobic, and was adsorbed with casein by steric stabilisation, increasing the structure tightness.