Antimicrobial Preservatives and Agents
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Questions and Answers

Which characteristic is NOT essential for a preservative to function effectively?

  • High toxicity (correct)
  • Stability to heat and storage
  • Acceptable taste, odor, and color
  • Effective against microbial growth

    • Which of the following antimicrobial agents is primarily an antifungal?

  • Benzoic acid (correct)
  • Phenol
  • Formaldehyde
  • Chlorhexidine

    • What property must a preservative exhibit to penetrate bacteria effectively?

  • Unionized state (correct)
  • High molecular weight
  • High cost
  • Insolubility in water

    • Which of the following is a quaternary ammonium compound used as an antimicrobial agent?

    <p>Benzalkonium chloride</p> Signup and view all the answers

    Why should a preservative not bind to other components of an emulsion?

    <p>To ensure stability and efficacy</p> Signup and view all the answers

    Which of the following methods can prevent autoxidation?

    <p>Using a free radical chain breaker</p> Signup and view all the answers

    Which of the following is a suitable example of an antioxidant for oral use products?

    <p>L-tocopherol</p> Signup and view all the answers

    What type of physical instability involves the merging of droplets in an emulsion?

    <p>Coalescence</p> Signup and view all the answers

    Which of the following options is NOT a type of physical instability of emulsions?

    <p>Agglomeration</p> Signup and view all the answers

    Which antioxidant is known for its bitter taste and is used in pharmaceuticals and cosmetics?

    <p>Gallic acid</p> Signup and view all the answers

    What is the primary cause of creaming in an emulsion?

    <p>Differences in density between dispersed droplets and the continuous phase</p> Signup and view all the answers

    What does the phenomenon of creaming visually manifest as?

    <p>A separation of layers with different color shades</p> Signup and view all the answers

    How is creaming classified in terms of reversibility?

    <p>As a reversible process that can be mitigated by agitation</p> Signup and view all the answers

    What size of droplets may settle preferentially during creaming?

    <p>Droplets larger than 1 mm</p> Signup and view all the answers

    What is the main characteristic of the protective sheath surrounding oil globules during creaming?

    <p>An emulsifier that stabilizes the droplets</p> Signup and view all the answers

    What determines the reversibility of flocculation?

    <p>Chemical nature of emulsifier</p> Signup and view all the answers

    Which factor contributes to the extent of flocculation of globules?

    <p>Viscosity of the external medium</p> Signup and view all the answers

    What is a consequence of having uniform sized globules in an emulsion?

    <p>Prevention of flocculation</p> Signup and view all the answers

    How can charge on the globule surface be increased?

    <p>By using an ionic emulsifying agent</p> Signup and view all the answers

    What effect does increasing the viscosity of the external medium have on flocculation?

    <p>It prevents flocculation</p> Signup and view all the answers

    What is a characteristic of cationic surfactants?

    <p>They are quaternary ammonium compounds.</p> Signup and view all the answers

    Which of the following is classified as an anionic surfactant?

    <p>Soaps</p> Signup and view all the answers

    Which natural hydrocolloid can be derived from plant sources?

    <p>Polysaccharides</p> Signup and view all the answers

    What role do semi-synthetic surfactants play in emulsions?

    <p>They provide a protective sheath around droplets.</p> Signup and view all the answers

    Which of the following encompasses both animal and plant-derived emulsifying agents?

    <p>Natural surface active agents</p> Signup and view all the answers

    What is the definition of an emulsion?

    <p>A stable system of two immiscible liquid phases with one phase dispersed as droplets.</p> Signup and view all the answers

    What is the role of the emulsifying agent in an emulsion?

    <p>To stabilize the dispersion of immiscible liquids.</p> Signup and view all the answers

    In an emulsion, what is referred to as the internal phase?

    <p>The dispersed phase consisting of small liquid globules.</p> Signup and view all the answers

    Which phase is known as the external phase in an emulsion?

    <p>The liquid phase where the dispersed phase is suspended.</p> Signup and view all the answers

    What distinguishes an emulsion from a suspension?

    <p>Emulsions contain immiscible liquid phases while suspensions have solid particles.</p> Signup and view all the answers

    What are emulsifying agents primarily used for in an emulsion?

    <p>To prevent the coalescence of globules</p> Signup and view all the answers

    Which process is NOT involved in how emulsifying agents stabilize emulsions?

    <p>Improvement of solubility</p> Signup and view all the answers

    Which of the following is a pharmaceutical requirement for emulsifying agents?

    <p>Should be colorless and odorless</p> Signup and view all the answers

    What is one of the mechanisms through which an emulsifying agent provides stability to an emulsion?

    <p>By forming a rigid interfacial film</p> Signup and view all the answers

    Which type of additive is specifically categorized as an emulsifying agent?

    <p>Auxiliary emulsifiers</p> Signup and view all the answers

    Which of the following is a component of colloidal clays?

    <p>Bentonite</p> Signup and view all the answers

    What is the primary use of methyl cellulose in emulsions?

    <p>Hydrophilic thickening agent</p> Signup and view all the answers

    Which product is considered a lipophilic thickening agent for lotions?

    <p>Glyceryl mono stearate</p> Signup and view all the answers

    Which of the following is classified as a metallic hydroxide?

    <p>Aluminum hydroxide</p> Signup and view all the answers

    What happens to stearic acid when it is reacted with alkali?

    <p>It forms a true emulsifier</p> Signup and view all the answers

    Which of the following is NOT one of the main methods by which emulsification can be carried out?

    <p>Hot Water Method</p> Signup and view all the answers

    What are the physical parameters that affect emulsion stability?

    <p>Method of incorporation of the phases</p> Signup and view all the answers

    Which energy supply method is NOT commonly used in emulsification processes?

    <p>Compression</p> Signup and view all the answers

    How many parts of gum are used in the 4:2:1 method of emulsification?

    <p>1 part</p> Signup and view all the answers

    Which of the following factors does NOT directly affect droplet size distribution in emulsions?

    <p>Phase color</p> Signup and view all the answers

    What is the primary characteristic of the internal phase in an emulsion?

    <p>It consists of small globules of a liquid.</p> Signup and view all the answers

    What role does the emulsifying agent play in an emulsion?

    <p>It stabilizes the emulsion by reducing surface tension.</p> Signup and view all the answers

    Which phase is known as the external or continuous phase in an emulsion?

    <p>The medium in which the droplets are dispersed.</p> Signup and view all the answers

    What typically happens to an unstable emulsion over time?

    <p>It begins to separate slowly.</p> Signup and view all the answers

    Why are two immiscible liquids unable to form a stable emulsion without an emulsifying agent?

    <p>They create a solid state upon contact.</p> Signup and view all the answers

    Study Notes

    Antimicrobial Preservatives

    • Must be less toxic, stable to heat and storage, chemically compatible, reasonably priced, and have acceptable taste, odor, and color.
    • Effective against bacterial, yeast, and fungal contaminants.
    • Should remain available in both oil and aqueous phases at effective concentrations.
    • Must be unionized for bacterial penetration and not bind to other emulsion components.

    Examples of Antimicrobial Agents

    • Acids: Benzoic acid serves as an antifungal agent.
    • Aldehydes: Formaldehyde demonstrates broad-spectrum antimicrobial properties.
    • Phenolics: Include phenol, cresol, and propyl p-hydroxy benzoate; effective against a range of microbials.
    • Quaternary Compounds: Chlorhexidine and salts, benzalkonium chloride, and cetyl trimethyl ammonium bromide, all exhibiting broad-spectrum efficacy.
    • Mercurials: Phenyl mercuric acetate, also broad-spectrum.

    Antioxidants

    • Autoxidation is a free radical reaction that can be mitigated by removing oxygen, using free radical chain breakers, or employing reducing agents.
    • Notable examples include gallic acid, ascorbic acid, and L-tocopherol, suitable for pharmaceuticals and cosmetics with minimal taste alteration.

    Stability of Emulsion

    • Physical instabilities include coalescence, flocculation, creaming, and phase inversion.
    • Creaming: Movement of dispersed droplets due to density differences, reversible through agitation.
    • Larger droplets (>1mm) may settle under gravity.

    Emulsions: Definition and Components

    • Thermodynamically unstable systems comprising two immiscible liquid phases, stabilized by emulsifying agents.
    • Composed of an internal phase (dispersed droplets) and external phase (continuous medium).

    Flocculation

    • Initial stage leading to instability, characterized by neighboring droplets forming colonies without clear visibility.
    • Depends on chemical nature of emulsifiers, phase volume ratio, and presence of electrolytes.
    • Uniform globule size distribution helps prevent flocculation by minimizing surface charge interactions and increasing viscosity.

    Classification of Surfactants

    • Cationic: Quaternary ammonium compounds.
    • Nonionic: Polyoxyethylene derivatives, sorbitan fatty acid esters.
    • Anionic: Soaps (monovalent, polyvalent), sulfates, sulfonates.

    Semi-Synthetic and Natural Surface Active Agents

    • Hydrocolloid emulsifying agents that form protective films around droplets, impart charge to disperse droplets, and increase system viscosity.
    • Semisynthetic examples: sodium carboxymethyl cellulose; natural examples include plant polysaccharides and animal proteins like gelatin.

    Additives for Emulsion Formulation

    • Antimicrobial Preservatives: Protect formulations from microbial growth.
    • Emulsifying Agents: Prevent coalescence, stabilize emulsions by reducing interfacial tension and forming mechanical barriers.

    Classification of Additives

    • Emulsifying Agents: Substances added to enhance stability and prevent coalescence.
    • Auxiliary Emulsifiers: Additional stabilizing agents like cetyl alcohol and glyceryl mono stearate.

    Key Emulsification Points

    • Internal phase: Dispersed liquid (discontinuous).
    • External phase: Dispersion medium (continuous).
    • Stability of emulsions contingent upon emulsifying agent efficacy and system viscosity.

    Extemporaneous and Large Scale Methods

    • Emulsification techniques include dry gum, wet gum, Forbes bottle, and auxiliary methods.
    • Physical factors affecting stability include emulsifier location, phase incorporation methods, and cooling rates.
    • Energy for emulsification can be supplied through heat, homogenization, or agitation.

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    Description

    This quiz explores the characteristics and examples of antimicrobial preservatives, including their effectiveness against various microbial contaminants. It covers different types of antimicrobial agents such as acids, aldehydes, phenolics, and quaternary compounds, as well as their applications in food preservation.

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