Related Experiment Video
Updated: Jun 8, 2026
08:05
Staining the Cytoplasmic Ca2+ with Fluo-4/AM in Apple Pulp
Published on: November 6, 2021
Calcium and pH influence on orange juice cloud stability.
Lindsey Ellerbee1, Louise Wicker
1Department of Food Science and Technology, University of Georgia, Athens, GA 30602, USA.
Journal of the Science of Food and Agriculture
|September 21, 2010
Summary
Ammonium oxalate prevents citrus juice clarification by inhibiting calcium pectate cross-bridges. Cloud stability depends on particle size, pH, and non-covalent interactions, not just electrostatic attraction.
Area of Science:
- Food Science
- Biochemistry
Background:
- Citrus juice clarification is a quality defect linked to pectin methylesterase (PME) activity.
- Cloud stability is influenced by PME, calcium chelation, and physical interactions of cloud components.
Purpose of the Study:
- Evaluate cloud stability and physical properties of citrus juice.
- Investigate the effect of ammonium oxalate (AO) and pH on juice clarification.
Main Methods:
- Assessed cloud stability and physical properties of pulp-free juice.
- Utilized particle size analysis and zeta potential measurements.
- Compared juice samples with and without AO at pH 4.0 and pH 5.5 over 3 weeks.
Main Results:
- Only the sample without AO at pH 4.0 clarified within 3 weeks.
- Samples at pH 4.0 had larger particle sizes and less negative zeta potential than those at pH 5.5.
- Cloud particle size fluctuated before clarification, increasing then decreasing.
Conclusions:
- Ammonium oxalate prevented clarification by inhibiting calcium pectate cross-bridges.
- Cloud particle interactions involve non-covalent, non-electrostatic forces beyond electrostatic attraction and calcium binding.
- pH and storage time significantly affect particle size and cloud stability.
Related Concept Videos
04:01Factors Affecting Solubility
Compared with pure water, the solubility of an ionic compound is less in aqueous solutions containing a common ion (one also produced by dissolution of the ionic compound). This is an example of a phenomenon known as the common ion effect, which is a consequence of the law of mass action that may be explained using Le Chȃtelier’s principle. Consider the dissolution of silver iodide:
01:19Ionic Strength: Effects on Chemical Equilibria
The addition of an inert ionic compound increases the solubility of a sparingly soluble salt. For example, adding potassium nitrate to a saturated solution of calcium sulfate significantly enhances the solubility of calcium sulfate. Le Châtelier's principle cannot predict this shift in the equilibrium. Instead, this could be explained in terms of changes in the effective concentration of the ions in solution in the presence of added inert salt.
In this solution, the primary cation—the calcium...
In this solution, the primary cation—the calcium...
03:38Polyprotic Acids
Acids are classified by the number of protons per molecule that they can give up in a reaction. Acids such as HCl, HNO3, and HCN that contain one ionizable hydrogen atom in each molecule are called monoprotic acids. Their reactions with water are:
00:53Extraction: Effects of pH
Consider a neutral form of an amine, B, with a partition coefficient, K, in a liquid mixture containing organic and aqueous phases. The pH of the aqueous phase affects the charge on acidic and basic solutes, and the charged form is usually more soluble in the aqueous phase. Suppose the conjugate acid form of the amine is soluble only in the aqueous phase while the base form is soluble in both phases. Then the distribution coefficient, D, can be given as the ratio of amine concentration in the...
01:17Colloids and Suspensions
Children at play often make suspensions such as mixtures of mud and water, flour and water, or a suspension of solid pigments in water known as tempera paint. These suspensions are heterogeneous mixtures composed of relatively large particles visible to the naked eye or seen with a magnifying glass. They are cloudy, and the suspended particles settle out after mixing. The suspended particles in a suspension settle out after some time of mixing. The separation of particles from a suspension is...
03:22Colloids
Children at play often make suspensions such as mixtures of mud and water, flour and water, or a suspension of solid pigments in water known as tempera paint. These suspensions are heterogeneous mixtures composed of relatively large particles that are visible to the naked eye or can be seen with a magnifying glass. They are cloudy, and the suspended particles settle out after mixing. On the other hand, a solution is a homogeneous mixture in which no settling occurs and in which the dissolved...