Effect of magnesium salt concentration in water-in-oil emulsions on the physical properties and microstructure of tofu

AbstractFreezing can enhance the storage time of liquid egg products, but egg yolk undergoes an irreversible textural and structural change when it is cooled to –6 °C. In this study, the effects of different salt concentrations on the physical properties of frozen-thawed egg yolk were investigated.The pasteurised liquid egg yolk (LEY) was treated with 4, 5, and 6% of NaCl before freezing and it was stored at –18 °C for 4 weeks. The colour, pH, and rheological characteristics (firmness, consistency, cohesiveness, and index of viscosity) of yolk samples were evaluated before and after freezing.Salt treatment resulted in preventing gelation, with decreasing firmness, consistency and viscosity compared to control samples. The pH of all yolk samples increased during frozen storage. The lightness value decreased in treated samples and increased in the control sample after freezing.The results indicated that the applied salt concentrations could inhibit protein aggregation of LEY induced by freezing during the storage period. At least 5% salt concentration could reduce effectively the changes in rheological properties.

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Influence of Emulsifiers on Physical Properties of Oil/Water Emulsions Containing Ostrich Oil

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.777.592 ◽

2018 ◽

Vol 777 ◽

pp. 592-596

Author(s):

Juthaporn Ponphaiboon ◽

Sontaya Limmatvapirat ◽

Chutima Limmatvapirat

Keyword(s):

Zeta Potential ◽

Physical Properties ◽

Droplet Size ◽

Emulsion Stability ◽

Tween 80 ◽

High Viscosity ◽

Soy Lecithin ◽

Oil Emulsion ◽

Oil Water ◽

Oil Emulsions

The fabrication of oil/water (O/W) emulsions in order to prepare the spray-dried encapsulated bioactive ostrich oil emulsions can be useful for increasing stability of commercial products. In this study, O/W emulsions were stabilized with mixed emulsifiers (Span and Tween) or soy lecithin. The effects of emulsifiers on the physical properties of emulsions containing ostrich oil were investigated. Results showed that the addition of a mixture of Span and Tween emulsifiers at concentrations between 5 and 15% w/w reduced the droplet size of the emulsions but did not decrease the zeta potential in the emulsion system. The smallest droplet size of 5.01±0.43 μm was obtained from the emulsion containing 15% w/w mixture of Span 20 and Tween 80. The zeta potential values of all emulsions containing a mixture of Span and Tween emulsifiers in the concentration range of 5 to 20% w/w were between-23 and-55 mV. In addition, the viscosity of these emulsions increased with increases in the concentrations of both emulsifiers. The stable 20% w/w ostrich oil emulsion stabilized with 15% w/w Span 20/Tween 80 presented viscosity equal to 69.56±1.82 cP. For 10% w/w ostrich oil emulsions stabilized with lecithin, the droplet size and zeta potential of the emulsions tended to decrease with increasing lecithin concentrations. An emulsion containing 10% w/w lecithin exhibited the smallest droplet size (3.93±0.11 μm). The zeta potential values of all emulsions composed of 1-15% w/w lecithin were between-33 and –66 mV and the viscosity of these emulsions increased with increases in the concentrations of lecithin. The stable 10% w/w ostrich oil emulsion stabilized with 10% w/w lecithin exhibited a high viscosity of 172.50±1.01cP. In summary, 10% w/w lecithin provides better emulsion stability than 15% w/w Span 20/Tween 80. These results therefore reveal important parameters for the fabrication of stable O/W emulsions containing ostrich oil.

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