James N. BeMiller

Location of sites of reaction within starch granules

ABSTRACT To observe granular reaction patterns within modified starch granules, starch derivatives were converted to thallium(I) salts and viewed by scanning electron microscopy compositional backscattered electron imaging. Observation of phosphorylated potato and sorghum starches and a hydroxypropyl analog of waxy maize starch revealed that granular patterns of reaction were influenced by both starch and reagent types. In waxy maize and sorghum starches, flow of reagent into the granule matrix occurred from channels (laterally) and cavities (from the inside outward). In potato starch granules, which do not possess channels, reagent diffused inward through exterior granule surfaces. Phosphoryl chloride (highly reactive) reacted to a large extent at granule surfaces, while the propylene oxide analog (less reactive) appeared to diffuse into the granule matrix prior to reacting.

Characterization of hydroxypropylated potato starch

Unmodified and modified (hydroxypropylated) potato starch were fractionated on a size-exclusion column to obtain amylose and amylopectin fractions. The molar substitution (MS) of modified whole starch was determined to be 0.099, of amylopectin, 0.096, and of amylose, 0.113. The location and distribution of modifying groups on amylopectin and amylose were determined by enzyme-catalyzed hydrolysis, using various combinations of isoamylase, β-amylase, α-amylase and amyloglucosidase, and comparing elution profiles of unmodified and modified amylopectin and amylose digests by size-exclusion chromatography. It was confirmed that amylose was modified to a greater extent than amylopectin, and that further modification of amylopectin occurred close to branch points, probably because amorphous regions are more accessible to the modifying reagent. It was also evident that amylose, likewise, was not uniformly modified.

One Hundred Years of Commercial Food Carbohydrates in the United States

Initiation and development of the industries producing specialty starches, modified food starches, high-fructose sweeteners, and food gums (hydrocolloids) over the past century provided major ingredients for the rapid and extensive growth of the processed food and beverage industries. Introduction of waxy maize starch and high-amylose corn starch occurred in the 1940s and 1950s, respectively. Development and growth of the modified food starch industry to provide ingredients with the functionalities required for the fast-growing processed food industry were rapid during the 1940s and 1950s. The various reagents used today for making cross-linked and stabilized starch products were introduced between 1942 and 1961. The initial report of enzyme-catalyzed isomerization of glucose to fructose was made in 1957. Explosive growth of high-fructose syrup manufacture and use occurred between 1966 and 1984. Maltodextrins were introduced between 1967 and 1973. Production of methylcelluloses and carboxymethylcelluloses began in the 1940s. The carrageenan industry began in the 1930s and grew rapidly in the 1940s and 1950s; the same is true of the development and production of alginate products. The guar gum industry developed in the 1940s and 1950s. The xanthan industry came into being during the 1950s and 1960s. Microcrystalline cellulose was introduced in the 1960s. Therefore, most carbohydrate food ingredients were introduced in about a 25 year period between 1940 and 1965. Exceptions are the introduction of maltodextrins and major developments in the high-fructose syrup industry, which occurred in the 1970s.

Physical Modification of Starch

Abstract Physical modifications of starches are starch property modifications imparted by physical treatments that do not result in any chemical modification of the starch other than limited glycosidic bond cleavages. Thermal treatments include those that produce pregelatinized and granular cold-water-swelling starches, heat-moisture treatment, annealing, microwave and other heating of “dry” starch, and “osmotic pressure treatment.” Nonthermal treatments include sonication, milling, static ultrahigh (high hydrostatic) pressure treatments, use of high-pressure homogenizers, pulsed electric field, freezing and thawing, and freeze-drying.