title: Application of Iron Oxide as a pH-dependent Indicator for Improving the Nutritional Quality.
abstract: Acid food indicators can be used as pH indicators for evaluating the quality and freshness of fermented products during the full course of distribution. Iron oxide particles are hardly suspended in water, but partially or completely agglomerated. The agglomeration degree of the iron oxide particles depends on the pH. The pH-dependent particle agglomeration or dispersion can be useful for monitoring the acidity of food. The zeta potential of iron oxide showed a decreasing trend as the pH increased from 2 to 8, while the point of zero charge (PZC) was observed around at pH 6.0-7.0. These results suggested that the size of the iron oxide particles was affected by the change in pH levels. As a result, the particle sizes of iron oxide were smaller at lower pH than at neutral pH. In addition, agglomeration of the iron oxide particles increased as the pH increased from 2 to 7. In the time-dependent aggregation test, the average particle size was 730.4 nm and 1,340.3 nm at pH 2 and 7, respectively. These properties of iron oxide particles can be used to develop an ideal acid indicator for food pH and to monitor food quality, besides a colorant or nutrient for nutrition enhancement and sensory promotion in food industry.
authors.affiliation: Department of Food Science and Technology, Sejong University, Seoul 05006, Korea .
authors.forename: Xiangpeng
authors.identifier: 0000-0002-2545-9753
authors.initials: X
authors.lastname: Meng
authors.affiliation: Department of Food Science and Technology, Sejong University, Seoul 05006, Korea .
authors.forename: Jina
authors.identifier: 0000-0002-7729-2625
authors.initials: J
authors.lastname: Ryu
authors.affiliation: School of Food Science, Kyungil University, Gyeongsan 38428, Korea .
authors.forename: Bumsik
authors.identifier: 0000-0001-8793-7696
authors.initials: B
authors.lastname: Kim
authors.affiliation: Department of Food Science and Technology, Sejong University, Seoul 05006, Korea .
authors.forename: Sanghoon
authors.identifier: 0000-0003-0664-3173
authors.initials: S
authors.lastname: Ko
keywords: Acid food indicator; Iron oxide; Particle; pH