Ultrasonic Modification of Starch Granules Slurries
Starch is easily extractable from native sources, such as potato, maize or corn. Modification of starch is necessary to improve the physical and chemical properties. Hielscher ultrasonic reactors promote physical, chemical, and enzymatic modification of starch that leads to better functional properties for the use in food and non-food industries.
For most commercial applications starches must be modified chemically or physically to enhance their positive attributes or to minimize their defects. Ultrasonication is a highly effective means for the physical, chemical, and enzymatic modification of starches. Hielscher ultrasonic devices transfer highly intense ultrasonic waves into starch slurries. The resulting ultrasonic cavitation promotes:
- deagglomeration and dispersion
- mechanical degradation and disruption
- granule penetration and swelling
- mass transfer
- radical formation
- chemical reactivity
- heating
Chemical Modification of Starch
Ultrasonic cavitational disruption of the granule associated with higher facility for liquid entrance in the starch granule leads to improvements in the reaction kinetics for esterification, etherification, hydroxypropylation or oxidation and acid modification of starch polymers. Hielscher ultrasonic reactors are designed for a continuous inline processing. Higher reaction rates lead to increased reaction kettle capacity.
Alkaline Starch Modification
For the production of many commercial starch derivatives, reactive, organic reagents are added to aqueous starch slurries while controlling alkalinity and temperature. The esterification of starches is generally performed at pH 7 to 9. A pH of 11 to 12 is commonly used for the etherification of starches. Typical process temperatures are approximately 60°C. Without sonication, the degree of substitution of commercial starches is often less than 0.2. Ultrasonication assists the substitution resulting in a more cold-water-soluble starch.
Acidic Starch Modification
The reaction of a granular starch slurry with dilute hydrochloric or sulfuric acid at 40 to 60°C leads to fluidity starches or thinned starches. These partially depolymerized starches produce products that generate less viscosity. Starch octenylsuccinates are partially depolymerized to allow a higher solids content to be used while spray drying of encapsulated products. Ultrasonication during mild acid hydrolysis can dissociate the nanoparticle aggregates that form during the hydrolysis. This increases the yield of starch nanoparticles.
Amylopectin Molecule
Slurry Neutralization
After the process, the reaction slurry is neutralized, e.g. by adding hydrochloric or sulfuric acid after alkaline processing.
Starch Washing
Water washing, such as countercurrent washing in hydrocyclones, follows the neutralization of the modified starch slurries. At this stage, ultrasonication assists the washing and rinsing of the individual starch particles. The ultrasonic cavitation disperses starch granule agglomerates and increases mass transfer at the boundary layer between starch granules and the aqueous phase.
Starch Filtration and Drying
Hielscher ultrasonic devices are used ultra-filtration or nano-filtration processes as well as subsequent spray drying.
Physical Modification of Starch (Mechanical)
Physical modification of starches does not involve the use of chemicals. Yet, ultrasonication results in changes in the starch molecular structure followed by variations in physicochemical properties and functionality. The violent cavitational shear forces distort the crystalline region in starch granules. Polymer chains near the collapsing microbubbles are caught in a high gradient shear field that leads to the breakage of macromolecular C-C bonds, and the formation of long chain radicals. SEM pictures of sonicated starch granules show mechanical damages, such as fissures, depressions, and pitting. This results in a higher water absorption capacity, higher swelling power, and increased solubility. This effect is better for higher sonication amplitudes. Therefore, probe sonication is much more effective for starch modification than bath type sonication. Intense ultrasonic processing shows more disrupted granules when compared with native or heat-treated starch.
Ultrasonically OSA-Esterified Starches
Ultrasonically OSA-esterified starches demonstrated higher degree of substitution (DS) and reaction efficiency (RE), coupled with minor yet beneficial morphological changes that may expand their functionality in food systems. Sonication enhances the reaction rate and efficiency without altering the starch’s molecular structure, thus preserving its desirable properties for food applications.
These results suggest that ultrasonically-assisted esterification could represent a green technology, offering an energy-efficient, time-saving approach for starch modification. The potential for scaling sonciation-assisted esterification could revolutionize the modification process for starches in food science, aligning with sustainable production goals and broadening the applications of esterified starches in the industry.
Read more about ultrasonically esterified OSA-starch!
SEM micrographs for: (a) unsonicated, (b) 20min sonicated, (c) 40min. sonicated, (d) 60min sonicated wheat starch granules.
Study and images: ©Majzoobi et al., 2015
Ultrasonication can lower the beginning of the gelatinization temperature significantly. Starch gels prepared from sonicated starch granules present a higher hardness and higher values of adhesiveness and cohesiveness when compared with native starch. Adhesiveness, cohesiveness, springiness, and gumminess increase significantly with ultrasonic modification of starch.
Ultrasonication uses much less energy input and stressful processing conditions than conventional starch modification procedures. Hielscher Ultrasonics supplies high power ultrasonic reactors for commercial processing.
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Starch Use
Modified starch is used in wide range of food and non food applications. Starch octenylsuccinates are an important stabilizer of oil-in-water emulsions. In papermaking cationic starches improve wet and dry strength, stabilize emulsions and act as a surface sizing agents. Many wet-end additive systems incorporate inorganic microparticles (colloidal silica, bentonite) and synthetic polymers with modified starch. Other uses include starch latex dispersions or granular starch as a filler for polymers.
Scientific Articles about Ultrasonically Assisted Starch Modification
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- S. Manchun, J. Nunthanid, S. Limmatvapirat and P.Sriamornsak (2012): Effect of Ultrasonic Treatment on Physical Properties of Tapioca Starch, in: Advanced Materials Research Vol. 506 (2012) pp 294-297. [PDF]
- Anet Rezek Jambrak, Zoran Herceg, Drago Šubaric, Jurislav Babic, Mladen Brncic, Suzana Rimac Brncic, Tomislav Bosiljkov, Domagoj Cvek, Branko Tripalo, Jurica Gelo (2010): Ultrasound effect on physical properties of corn starch, in: Carbohydrate Polymers 79 (2010) 91–100.
- Herceg I.L., Jambrak A.R., Šubarić D., Brnčić M., Brnčić S.R., Badanjak M., Tripalo B., Ježek D., Novotni D., Herceg Z. (2010): Texture and pasting properties of ultrasonically treated corn starch, in: Czech J. Food Sci., 28: 83–93. [PDF]
- D. Knorr, B. I. O. Ade-Omowaye and V. Heinz (2002): Nutritional improvement of plant foods by non-thermal processing, in: Proceedings of the Nutrition Society (2002), 61, 311–318. [PDF]
Frequently Asked Questions
What are Native Starch Sources?
Starch comes from various native sources, such as: maize, waxy maize, high-amylose maize, tapioca, potato, wheat, rice, waxy rice, pea (smooth pea, wrinkled pea) sago, oat, barley, rye, amaranth, sweet potato, oat, cereal, cow cockle, quinoa, lentil, navy bean, sorghum, arrowroot or cassava.
What is Modified Starch?
Modified starch is a starch that has been physically, enzymatically, or chemically altered to enhance its performance in food and industrial applications. These modifications improve properties such as solubility, viscosity, gelation, and stability under various conditions, like heat or acidic environments. Commonly derived from natural sources like corn, potato, and tapioca, modified starches are used as thickeners, stabilizers, and emulsifiers to improve texture and shelf life in processed foods, pharmaceuticals, and other products.
What is the Difference between Modified Starch and OSA-Starch?
Modified starch refers to starch that has been altered in various ways—physically, enzymatically, or chemically—to improve its functional properties, such as thickening, gelling, or stabilizing in different conditions. These modifications make it suitable for diverse applications in food, pharmaceuticals, and industrial products.
OSA-starch, or octenyl succinic anhydride starch, is a specific type of chemically modified starch created by attaching octenyl succinic anhydride groups to the starch molecule. This modification imparts unique emulsifying properties, making OSA-starch particularly effective in stabilizing oil-in-water emulsions. While modified starch generally enhances basic properties like viscosity or stability, OSA-starch is specially tailored to provide emulsification capabilities, making it popular in products like salad dressings, sauces, and beverages where stable emulsions are essential. Read more about ultrasonically esterified OSA starch!