W. M. Doane

Structure and morphology of baked starch foams

Baked starch foams were characterized by several physical methods in order to better understand the relationship between process parameters and starch foam structure. In this process, a thin-walled object such as a plate is formed by heating a starch batter inside a closed mould. Normal corn and potato starches are gelatinized by this treatment but some swollen granules remain. The foams have a dense outer skin and a less dense interior with large, mostly open cells. Overall foam density and strength increase with increasing starch concentration, molecular weight and amylose content. Foam flexibility tends to increase with decreasing density. Plates made from tuber starches such as potato have lower densities and higher flexibilities than those made from cereal starches such as corn. Starch foams are useful as disposable food packaging and serving articles which can be composted after use.

A facile route to trans cyclic carbonates of sugars

Abstract Five-membered, cyclic carbonates are formed when vicinal trans -hydroxyl groups in D -glucopyranosides are treated with ethyl chloroformate in the presence of triethylamine. With these reagents, methyl 4,6- O -benzylidene-α- D -glucopyranoside 2,3-carbonate ( 2 ), methyl 2,6-di- O -(methylsulfonyl)-α- D -glucopyranoside 3,4-carbonate ( 5 ), and methyl 4- O -(ethoxycarbonyl)-6- O -( p -tolylsulfonyl)-α- D -glucopyranoside 2,3-carbonate ( 8 ) were prepared. In contrast, when pyridine is the base present, only acyclic carbonates are formed.

Amylose content of starch controls the release of encapsulated bioactive agents

Abstract Controlled release of the herbicide butylate [ S -ethyl bis(2-methylpropyl) carbamothioate] from a non-chemically modified starch matrix has been achieved. Steam injection cooking of cornstarch or mixtures of starches with varying amylose content, followed by active agent addition, drying and grinding yields encapsulated products showing controlled slow release of active agent. As the amylose content increases, the rate of release decreases due to the ability of amylose to retrograde (starch chain association). As the amylose content is reduced to about 10% the efficiency of active agent encapsulation nears 100%. Encapsulated products consisting only of starch and an active agent should be useful in a variety of applications, i.e. food, feed or agriculture.

Reaction of starch with carbohydrate trans-carbonates☆

Abstract Mono- and poly-saccharides possessing certain substituted, vicinal, trans-hydroxyl groups are readily substituted onto starch. Such substitution occurs when a trans-fused, cyclic carbonate derivative of the saccharide is added to starch in the presence of a basic catalyst. Excellent yields of products result on addition of methyl 4,6-O-benzylidene-α- d -glucopyranoside 2,3-carbonate (or 2,3-thionocarbonate), and methyl 2,6-di-O-(methylsulfonyl)-α- d -??? 3,4-carbonate to starch in the presence of triethylamine. ??? of degree of substitution (DS) 0.40 and dextran carbonate of Ds 0.31 ??? with starch under various conditions, in the presence of different catalysts, to give ??? corresponding polysaccharide copolymers.

Factors affecting release of butylate from calcium ion-modified starch-borate matrices

Abstract Controlled release of the herbicide butylate [S-ethyl-bis(2-methylpropyl) carbamothioate] from a starch-borate matrix was modified by incorporating calcium chloride during the matrix-forming step. The addition of calcium chloride, known to be a starch-complexing agent, before borate addition caused the release of butylate to be slower than with borate alone. Varying the amounts of calcium chloride added gave a series of products with different butylate release rates. Varying the pH during product preparation also influenced butylate release. Re-evaluation of butylate release after storing the products for several months indicated the starch had undergone additional retrogradation, since butylate release decreased by 10–30% over that measured originally. Drying freshly prepared samples in an oven (130°C for 90 min) vs air drying (25° C for 24 h) causes a moderate slowing of butylate release. The ability to vary herbicide release rates will serve as a basis for producing starch-encapsulated herbicides for particular end uses.

CHEMICALS FROM STARCH

Publisher Summary Starch is a prime candidate for use as a raw material because it is available at a low cost and can be converted into a variety of useful monomeric and polymeric products by chemical and biochemical means. This chapter emphasizes the promising applications of starch-derived products. It describes the techniques for fermenting starch to various chemicals. The production of some industrial-grade ethanol from natural products is an example of the rising trend toward fermentation biosynthesis. Although starch is being considered for the production of alcohol and hydrocarbons as a direct replacement for petroleum, any such conversions are accompanied by drastic mass losses due to the elimination of CO2 and H2O. Several polyhydroxy compounds have been developed from starch for industrial applications that are less expensive than comparable products made from petroleum.

2,3-thionocarbonate and 2,3-carbonate derivatives of D-glucopyranosides

Abstract A unique sugar derivative, methyl 4,6- O -benzylidene-α- D -glucopyranoside 2,3-thionocarbonate, which contains a trans -fused ring-structure, was prepared in good yield by rearrangement of bis(methyl 4,6- O -benzylidene-2- O -thiocarbonyl-α- D -glucopyranoside) disulfide. The thionocarbonate was converted into the novel methyl 4,6- O -benzylidene-α- D -glucopyranoside 2,3-carbonate in 93% yield by treatment with silver nitrate. By following the same reaction sequence, 2,3-thionocarbonate and 2,3-carbonate groups were introduced into 6- O -tritylamylose. The rearrangement of bis( O -thiocarbonyl) disulfide derivatives provides a new route for the synthesis of carbohydrate thionocarbonates and carbonates previously unavailable.

Ring-opening reactions of trans-carbonates and thionocarbonates

Abstract The reaction of methyl 4,6- O -benzylidene-α-D-glucopyranoside 2,3-carbonate ( 1 ) and the corresponding 2,3-thionocarbonate ( 2 ) with various nucleophines was investigated. Under proper conditions, 1 and 2 reacted with methanol, benzyl alcohol, α-toluenethiol, ammonia, piperidine, and glycine to give the corresponding 2- O -and 3- O -carbonyl and thiocarbonyl adducts, which were obtained in crystalline form. In each reaction product the 2-isomer was preponderant.

Starch Xanthide Reinforced Styrene-Butadiene Rubber: Compounding To Reduce Water Sensitivity

ONV~NTI©NAL RUBBERS SLOWLY absorb water during prolonged water immersion by a complex process involving both reversible and irreversible mechanisms without reaching a swelling equilibrium [1, 2} . Usually water absorption is of little consequence, but it can be deleterious for rubber articles with thin cross-sections or acute profiles, especially if they are made from inherently watersensitive elastomers or if they contain water-sensitive components [1, 2) . The rate and extent of water absorption by starch xanthide reinforced articles depend on their size and shape and on frequency and duration of water immersion [3, 4] . For starch xanthide reinforced rubbers, the effect of 90 days’ water immersion is completely reversible by drying, even for specimens with large surface-tovolume ratios [4]. Our previous studies showed that the rate of water absorption could be greatly reduced by increasing the extent of crosslinkage of the starch xanthide, by improving adhesion between starch and rubber phases and by adding carbon black or other fillers [3, 4]. Both resorcinol-formaldehyde (RF) and an aminosilane coupling agent were effective in reducing swelling rates when incorporated in small proportions. However, each interfered with normal vulcanization; RF decreased and the aminosilane increased cure rates [4]. Accordingly, compounding was studied in more detail to find combinations of RF, aminosilane, and fillers that would reduce

O-(alkyl- and aryl-oxythiocarbonyl) sugar derivatives☆

Abstract Bis(1,2:5,6-di- O -isopropylidene-3- O -thiocarbonyl-α- d -glucofuranose) disulfide ( 1 ) in pyridine undergoes a fragmentation reaction when treated with excess methyl, ethyl, propyl, or butyl alcohols, or phenol, to give the corresponding O -oxythiocarbonyl derivatives ( 2 – 6 ). A faster reaction and higher yield result when iodine is included in the pyridine solution. The oxythiocarbonyl compounds are stable when distilled (near 190°) under diminished pressure. Selective, acid hydrolysis of 3- O -(ethoxythiocarbonyl)-1,2:5,6-di- O -isopropylidene-α- d -glucofuranose ( 3 gave 3- O -(ethoxythiocarbonyl)-1,2- O -isopropylidene-α- d -glucofuranose ( 10 ), which rearranged, on standing in triethylamine, to 1,2- O -isopropylidene-α- d -glucofuranose 5,6-thionocarbonate ( 12 ). Oxidation of 3 with lead tetraacetate or silver nitrate gave the corresponding 3- O -ethoxycarbonyl derivative ( 8 ), whereas reduction of 3 with Raney nickel gave 3- O -(ethoxymethylene)-1,2:5,6-di- O -isopropylidene-α- d -glucofuranose ( 11 ).