Certain food additives commonly used in flour products also have a plasticization effect on product shelf life regarding retrogradation. Sucrose, sorbitol, glycerol, citric acid, and acetic acid at 25, 25, 25, 0.5, and 0.5%, respectively, were added to two different starch gel systems: slurry (high‐amylose rice flour gel) and dough (waxy rice flour dough). All plasticizers increased gelatinization temperature, decreased enthalpy (ΔH), and promoted a more homogeneous system. Sucrose had the greatest effect on gelatinization increase. Rice dough was more susceptible to plasticizers, resulting in higher moisture content and a more amorphous structure. Retrogradation was highly positively correlated with amylose content, moisture retention, ratio of protons of water/starch, and previous occurrence of retrogradation. Moisture retention was increased in plasticizer‐added samples, especially waxy rice dough. Over a longer storage period, sucrose and sorbitol showed an antiplasticization effect in waxy rice flour dough, but glycerol and acid caused higher retrogradation in high‐amylose rice flour gel.
The concentrations effects of sugars (trehalose and allose) and oils (canola and coconut oil) on the characteristics of rice starch suspension and mechanical properties of rice starch film were studied. The samples were prepared using 3% (w/w) rice starch, with 10% or 30% (w/w) sugar (trehalose or allose) added and 10% or 30% (w/w) oil (canola or coconut). The droplet size of the film suspension increased with increasing oil concentration both in trehalose and allose, which blended with oil. The flow behavior of the film suspensions showed shear-thinning behavior as calculated by the Power Law model. The apparent viscosity tended to increase with the addition of sugar and oil. The breaking stress of the films blended with sugar and oil was less than that of control. On preparation day and after 7 days' storage, the breaking strain tended to increase more with the addition of coconut oil than with that of canola oil. However, breaking stress and breaking strain decreased after 28 days' storage. Adding sugar had correlation with mechanical properties whereas adding oil had correlation with film suspension characteristics, allowed the sugar and oil to interact and inhibited starch chain mobility due to concentration, sugar type, and oil type.
The effect of some sugars (maltose, sucrose, and d-allulose) on different starch sources (normal corn, normal rice, waxy corn and waxy rice) to produce edible film was studied. Films were prepared using 3% (w/w) starch and 20% (w/w) sugar as a plasticizer. The relative crystallinity of films increased with addition of sugars and extended storage. The thickness of films was increased with addition of sugar. The morphology of films surface became homogeneous with sugars. Sugars decreased breaking stress and increased breaking strain immediately after preparation and during storage. The flow behavior of all the starch film suspensions showed shear-thinning properties determined using the Power law model. The apparent viscosity of the suspensions changed during the drying process resulting from the added sugar and starch type. Adding sugar as a plasticizer showed different effects on the crystallization, the thickness, the morphology of the film surface, the mechanical properties of the film and the flow behavior during drying. Both types of sugar and starch that could interact and inhibited starch chain mobility due to size of sugar, hydroxyl group, and hydrogen bond.
The characteristics of rice starch film blended with sucrose, maltose, and trehalose at concentrations of 0%, 10%, 20%, or 30% (w/w of the starch weight) were investigated. Relative crystallinity (RC) of the rice starch film as determined by X‐ray increased with increasing sucrose concentration and the RC tended to decrease with an increasing concentration of maltose and trehalose. RC was inhibited by adding sugar in the order of trehalose, maltose, and sucrose after 28 days storage. The rice starch film with 30% added sugar showed a homogeneous matrix and a lower frequency chemical shift of the proton OH group as determined on the day of preparation; however, the film with 30% added maltose cracked after 28 days storage. Adding sugar as a plasticizer affected the properties of the rice starch film by concentration and type of sugar because of the hydroxyl groups of the sugar.Practical ApplicationDisaccharides, such as sucrose, maltose, and trehalose, could be used as a plasticizer in a rice starch film system. The sugar conformation might be one factor for selecting the sugar to use for starch film system. Trehalose might improve film properties by inhibiting recrystallization after storage.
The esterified maltodextrins (EMs) are prepared by enzymatic esterification of maltodextrin DE of 16 with three fatty acids (C‐10, C‐12, and C‐16). Three EMs are maltodextrin decanoate (DE16_D), maltodextrin laurate (DE16_L), and maltodextrin palmitate (DE16_P). Their surface‐active properties and anti‐microbial activities are investigated with various concentrations (0–20% (w/w)). All EMs exhibit surface activity that depends on the chain length of the fatty acid. The anti‐microbial activities of EMs and native maltodextrin are evaluated against Escherichia coli, a Gram‐negative bacterium, and Staphylococcus aureus a Gram‐positive bacterium. DE16_L is the most effective at retarding E. coli growth. The minimum inhibitory concentration (MIC) of DE16_L is 5% (w/w). Cell numbers of E. coli tend to decrease as the concentration increases for native maltodextrin, DE16_D, and DE16_L. On the other hand, DE16_P enhances the available cells of E. coli and S. aureus as concentration increases. EMs and native maltodextrin do not clearly retard the growth of S. aureus. This investigation indicates that the chain length of the fatty acid and the concentration of EMs affects their anti‐microbial ability.
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