Modified tuber starches as potential stabilizer for food-grade Pickering emulsions

The application of modified tuber starches in particle-stabilized emulsions was studied to obtain surfactant-free emulsions, called Pickering emulsions. Three different starches, namely, potato (P), sweet potato (S) and tapioca (T) starches were modified using dry-heat treatment (HD, 120°C, 150 mins), hydrothermal treatment (HM, 50°C, 30 mins), OSAmodification (OSA, 2.9%) and hydroxypropylation (HP, 2 mL of 20% propylene oxide) before being used as stabilizer for stabilizing emulsion. The physicochemical properties of the starches and the characteristics of the stabilized emulsion were studied. Potato OSAtreated starch (POSA) had significantly higher degree of substitution (DS) (DS = 0.0154) than SOSA (DS = 0.0081) and TOSA (DS = 0.0083). For the starches undergone treatment of hydroxypropylation, SHP had the highest molar substitution (MS) value of 0.20, followed by PHP (0.11) and THP (0.10). The amylose content of starches reduced significantly after all modifications (HD, HM, OSA, and HP). All OSA-treated starch (POSA, SOSA, and TOSA) had higher fat binding capacity compared to their native and starches that modified using different treatments (HD, HM, and HP). Based on the emulsification index values and optical microscopic images, all starch particles were able to stabilize emulsions except for SC, SHM, TC, and THM. Optical microscopic images showed that the starch particles accumulated and formed a densely packed layer at the oilwater interface. At the starch concentration of 400 mg/mL oil, emulsion stabilized by dryheated potato starch and all hydroxypropylated-starch-stabilized emulsions had a high emulsification index value of 1. Significantly highest viscosity was noticed from the emulsion stabilized by POSA. Overall, by comparing the physico-chemical properties of the modified starches and the characteristics of emulsions stabilized, potato OSA-treated starch (POSA) had the best emulsifying ability.

Outstanding Characteristics of Thai Non-GM Bred Waxy Cassava Starches Compared with Normal Cassava Starch, Waxy Cereal Starches and Stabilized Cassava Starches

Waxy cassava roots of nine varieties successfully developed in Thailand by a non-genetic modification (non-GM), conventional breeding method were used for extracting starches and their starch physico-chemical properties were evaluated and compared with normal cassava starches, commercial waxy starches (i.e., waxy maize starch and waxy rice starch) and commercial stabilized starches (i.e., acetylated starch and hydroxypropylated starch). All waxy cassava varieties provided starches without amylose while normal cassava starches contained 18%–20% amylose contents. As determined by a Rapid Visco Analyzer (RVA) at 5% (dry basis), waxy cassava starches had the highest peak viscosity and the lowest setback viscosity. Cooked paste of waxy cassava starches had the greatest clarity and stability among all starches during storage at 4 ℃ for 7 days as evidenced by its high light transmittance (%T) at 650 nm. No syneresis was detected in waxy cassava starch gels after subjecting to four freeze-thaw cycles (4 weeks) indicating high potential use of waxy cassava starches, free from chemicals, to replace stabilized starches as thickening and texturing agents in food products.

Evaluation of Effects of Increasing Molar Substitution of Hydroxypropylene on Physicochemical, Functional and Morphological Properties of Starch from Water Yam (Dioscorea Alata)

Amidst rising demand for modified starch, hydroxypropylated derivatives from water yam, an underutilized tropical botanical source remains unexplored. The objective of this work therefore is to extract starch from water yam, modify same by hydroxypropylation and determine their physicochemical, functional and morphological characteristics. Extraction of starch was carried out by blending peeled water yam previously soaked in 0.2%(w/v) NaHSO3 solution and filtering the resulting slurry. The filterate was next suspended in 0.2% NaOH solution, allowed to sediment and the supernatant oven-dried (400C) for 24 hrs. The dried product was subjected to hydroxypropylation (HP) (propylene oxide 4-12%/100g starch) and extent of molar substitution (MS) determined. The native and Hydroxypropylated starch (HPS) were evaluated for physicochemical, functional and morphological characteristics following standard methods. Pasting properties were analysed using Rapid Visco Analyzer (RVA) and elucidation of inherent functional groups was carried out by analyzing the FTIR Spectrum. Starch yield of 84.2% (dry wt. basis) and molar substitution (0.0024-0.05) of HPS were established. Bulk density increased (0.4988-0.6005g/cm3) with MS. There was significant (p=0.05) increase in the degree of Whiteness (W) (42.4-63.6%). Although granule size reduction was evident (33.88-33.43µm), hydroxypropylation did not affect their morphology. There was decline in concentrations of crude protein (0.18-0.01%), ash (1.35-0.34%) and amylose (44.19-37.48%) as MS rose. In contrast, there was significant (p=0.05) increase in water (1.76-2.66g/g) and oil absorption capacities (0.72-1.42g/g), swelling power (1.54-4.19g/g) and solubility (3.17-5.84g/g) at 500C. Freeze thaw cycles showed marked reduction in syneresis (10.3-1.09%) as MS increased. Peak Viscosity, pasting temperature and peak time of the HPS ranges were 297.83-583.6, 81.9-86.40C, and 4.5-7.0 mins respectively. FTIR band spectra indicated the presence of hydroxypropyl substituent groups in the modified starch. Hydroxypropylated starch (from water yam) at different molar substitution has been characterised and its properties established with strong potentials for wider applications in food systems.