Stabilisation of oil-in-water emulsions with non-chemical modified gelatinised starch

In this research, stabilisation of oil-in-water emulsions with non-chemically modified gelatinised starch is presented. Thus far only octenyl succinic anhydride (OSA) modified gelatinised starch has been known to adsorb at emulsion droplet interfaces, acting as emulsifiers. Screening a range of commercially available food starches revealed that a non-waxy rice starch, a waxy rice starch and the waxy maize starch PRIMA600 showed oil-in-water emulsifying ability following gelatinisation. The microstructure of emulsions formulated with 20% oil and 1% starch was stable for at least 3 months. Thermal, crystallinity and molecular property analyses as well as amylose and protein content revealed no obvious link to this property. Nevertheless, this research has provided the food industry with exciting results for the formulation of clean label emulsions. Moreover, it presents a concept for oral release food emulsions with destabilisation via salivary amylase digestion of the stabilising starch emulsifier.

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Non-chemically modified gelatinised starches screened for emulsifier functionality.

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High shear overhead processing of oil-in-water emulsions.

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A waxy & non-waxy rice & waxy maize starch adsorbed at oil droplets, others did not.

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Not related to thermal, crystallinity & molecular properties, amylose, protein.

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Functionality as clean label emulsifier clearly demonstrated.

Molecular fractionation of starch by density-gradient ultracentrifugation

Amylose and amylopectin in corn and potato starches were fractionated by centrifugation at 124,000g for 3-72 h at 40 degrees C in a gradient media, Nycodenz, based on their sedimentation rate differences. The fractions were collected from a centrifuge tube, and then analyzed by the phenol-sulfuric acid method and iodine-binding test. Amylopectin, a large and highly branched starch molecule, migrated faster than amylose and quickly reached its isopycnic point with a buoyant density of about 1.25 g/mL, exhibiting a sharp and stable carbohydrate peak. Amylose, which is a relatively small and linear molecule, however, migrated slowly in a broad density range and continued moving to higher density regions, eventually overlapping with amylopectin peak as the centrifugation continued. This could indicate that the buoyant density of amylose is similar to that of amylopectin. Under centrifugal conditions of 3 h and 124,000g, amylose and amylopectin molecules were clearly separated, and the presence of intermediate starch molecules (11.5 and 7.7% for corn and potato starch, respectively) was also observed between amylose and amylopectin fractions. The amylose content of corn and potato starches was 22.6 and 21.1%, respectively, based on the total carbohydrate analysis after the ultracentrifugation for 3 h. In alkaline gradients (pH 11 or 12.5), the sedimentation rate of starch molecules and the buoyant density of amylopectin were reduced, possibly due to the structural changes induced by alkali.

Rapid analysis of starch, amylose and amylopectin by high-performance size-exclusion chromatography

Starch components, amylose and amylopectin, were analyzed by high-performance size-exclusion chromatography. These two-components were separated using a two-column system (E-Linear and E-1000) and dimethyl sulphoxide as the mobile phase. The void volume (V0 = 2.22 ml) was measured using tobacco mosaic virus. Column calibration was accomplished with dextrans of known average molecular weight (Mw range = 10,100-2,000,000). The elution volume of amylopectin (Ve = 2.5 ml) indicated that this starch component was fractionated on the column system despite its very large molecular size. Standard curves were prepared from various mixtures of purified corn and wheat amylose and amylopectin. From the linear relationships obtained, the percentages of both components in corn and wheat starches were determined. The method developed proved useful to monitor the purity of amylose and amylopectin preparations, and to estimate rapidly the amylose:amylopectin ratio of starch samples.