Food Analysis: Moisture and Ash Determination
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Questions and Answers

What is the term commonly used to describe the dry matter that remains after moisture removal?

total solids

In which of the following products is moisture used as a quality factor to prevent sugar crystallization?

  • Dried milks
  • Spices and herbs
  • Jams and jellies (correct)
  • Dehydrated vegetables
  • Compositional standards specify that cheddar cheese must have more than 39% moisture.

    False

    The ______________ method involves heating the sample under specified conditions to calculate moisture content.

    <p>oven drying</p> Signup and view all the answers

    Match the forms of water in foods with their descriptions:

    <p>Free water = Water that retains its physical properties and acts as a dispersing agent for colloids. Adsorbed water = Water held tightly in cell walls or protoplasm and tightly held to proteins. Water of hydration = Water bound chemically, such as lactose monohydrate or salts like Na2SO4 · 10H2O.</p> Signup and view all the answers

    What is the term commonly used to refer to the dry matter that remains after moisture removal from a food product?

    <p>total solids</p> Signup and view all the answers

    Which of the following products is NOT mentioned as being affected by moisture content in the content provided?

    <p>Frozen meats</p> Signup and view all the answers

    Moisture content is not relevant in the quality of jams and jellies.

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

    In the oven drying method, the sample is heated under specified conditions, and the loss of weight is used to calculate the ____________ content of the sample.

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

    Match the state of water in food products with the correct description:

    <p>Free water = Acts as a dispersing agent for colloids and a solvent for salts Adsorbed water = Held tightly in cell walls or protoplasm Water of hydration = Bound chemically to certain components</p> Signup and view all the answers

    Study Notes

    Importance of Moisture Assay

    • Moisture content is a quality factor in the preservation of some products and affects stability.
    • Moisture content is important for food processors as water is an inexpensive filler.
    • Examples of products where moisture content is important:
      • Dehydrated vegetables and fruits
      • Dried milks
      • Powdered eggs
      • Dehydrated potatoes
      • Spices and herbs
      • Jams and jellies
      • Sugar syrups
      • Prepared cereals
      • Concentrated milks
      • Liquid cane sugar and liquid corn sweetener
      • Dehydrated products
      • Concentrated fruit juices
      • Cheddar cheese
      • Enriched flour
      • Pineapple juice
      • Glucose syrup

    Forms of Water in Foods

    • Water exists in three states in food products:
      • Free water: retains its physical properties and acts as the dispersing agent for colloids and the solvent for salts.
      • Adsorbed water: held tightly or occluded in cell walls or protoplasm and is held tightly to proteins.
      • Water of hydration: bound chemically, e.g., lactose monohydrate.

    Oven Drying Method

    • The sample is heated under specified conditions, and the loss of weight is used to calculate the moisture content.
    • Various oven methods are approved by AOAC International for determining the amount of moisture in many food products.
    • The time required may be from a few minutes to over 24 hours.
    • Moisture removal is sometimes best achieved in a two-stage process.
    • Particle size, distribution, sample size, and surface area during drying influence the rate and efficiency of moisture removal.

    Calculation

    • The percentage of moisture is calculated as: % Moisture (wt/wt) = × 100
    • Where W1 = initial weight of empty crucible + rod (+ sand), W2 = weight of crucible + food + rod (+ sand) before drying, W3 = final weight of crucible + food + rod (+ sand) after drying.
    • % Total solids = 100 - % Moisture

    Microwave Analyzer

    • Microwave moisture analysis is a precise and rapid technique that allows for in-process adjustments of the moisture content in food products before final packaging.
    • A particular microwave moisture/solids analyzer is specified in the AOAC International procedures for total solids analysis of processed tomato products and moisture analysis of meat and poultry products.
    • Considerations when using a microwave analyzer:
      • The sample must be of a uniform, appropriate size to provide for complete drying under the conditions specified.
      • The sample must be centrally located and evenly distributed, so some portions are not burned and other areas are underprocessed.
      • The amount of time used to place an appropriate sample weight between the pads must be minimized to prevent moisture loss or gain before weight determination.

    Infrared Drying

    • No additional information provided.

    Physical Methods

    • Refractometry: can be used to determine moisture in liquid sugar products and condensed milks.
    • Freezing Point: can be used to determine the concentration of solutes in a solution.

    How to Select a Method of Analysis

    • Understand the principle of different methods.
    • Consider the nature of the sample: some foods contain volatiles that are lost at high temperatures, and some foods have constituents that undergo chemical reactions at high temperatures to generate or utilize moisture or other compounds.

    Ashing

    • Ashing is an important first step in proximate or specific mineral analysis.
    • Ash refers to the inorganic (mineral) residue remaining after the combustion or complete acid-facilitated oxidation of organic matter in food.
    • Definitions:
      • Dry ashing: uses a muffle furnace capable of maintaining temperatures of 500–600 °C.
      • Wet ashing: uses strong acids, oxidizing agents, or combinations thereof to chemically oxidize and remove organic substances.

    Ashing Process

    • Suggestions to accelerate incineration:
      • High-fat samples should be extracted prior to ashing.
      • Glycerin, alcohol, and hydrogen can be used to accelerate ashing.
      • Samples such as jellies may require mixing with cotton wool to avoid spattering.
      • Salt-rich foods may require a separate ashing of water-insoluble components and salt-rich water extract.
      • An alcoholic solution of magnesium acetate can be added to accelerate ashing of cereals.

    Importance of Moisture Assay

    • Moisture content is a quality factor in the preservation of some products and affects stability.
    • Moisture content is important for food processors as water is an inexpensive filler.
    • Examples of products where moisture content is important:
      • Dehydrated vegetables and fruits
      • Dried milks
      • Powdered eggs
      • Dehydrated potatoes
      • Spices and herbs
      • Jams and jellies
      • Sugar syrups
      • Prepared cereals
      • Concentrated milks
      • Liquid cane sugar and liquid corn sweetener
      • Dehydrated products
      • Concentrated fruit juices
      • Cheddar cheese
      • Enriched flour
      • Pineapple juice
      • Glucose syrup

    Forms of Water in Foods

    • Water exists in three states in food products:
      • Free water: retains its physical properties and acts as the dispersing agent for colloids and the solvent for salts.
      • Adsorbed water: held tightly or occluded in cell walls or protoplasm and is held tightly to proteins.
      • Water of hydration: bound chemically, e.g., lactose monohydrate.

    Oven Drying Method

    • The sample is heated under specified conditions, and the loss of weight is used to calculate the moisture content.
    • Various oven methods are approved by AOAC International for determining the amount of moisture in many food products.
    • The time required may be from a few minutes to over 24 hours.
    • Moisture removal is sometimes best achieved in a two-stage process.
    • Particle size, distribution, sample size, and surface area during drying influence the rate and efficiency of moisture removal.

    Calculation

    • The percentage of moisture is calculated as: % Moisture (wt/wt) = × 100
    • Where W1 = initial weight of empty crucible + rod (+ sand), W2 = weight of crucible + food + rod (+ sand) before drying, W3 = final weight of crucible + food + rod (+ sand) after drying.
    • % Total solids = 100 - % Moisture

    Microwave Analyzer

    • Microwave moisture analysis is a precise and rapid technique that allows for in-process adjustments of the moisture content in food products before final packaging.
    • A particular microwave moisture/solids analyzer is specified in the AOAC International procedures for total solids analysis of processed tomato products and moisture analysis of meat and poultry products.
    • Considerations when using a microwave analyzer:
      • The sample must be of a uniform, appropriate size to provide for complete drying under the conditions specified.
      • The sample must be centrally located and evenly distributed, so some portions are not burned and other areas are underprocessed.
      • The amount of time used to place an appropriate sample weight between the pads must be minimized to prevent moisture loss or gain before weight determination.

    Infrared Drying

    • No additional information provided.

    Physical Methods

    • Refractometry: can be used to determine moisture in liquid sugar products and condensed milks.
    • Freezing Point: can be used to determine the concentration of solutes in a solution.

    How to Select a Method of Analysis

    • Understand the principle of different methods.
    • Consider the nature of the sample: some foods contain volatiles that are lost at high temperatures, and some foods have constituents that undergo chemical reactions at high temperatures to generate or utilize moisture or other compounds.

    Ashing

    • Ashing is an important first step in proximate or specific mineral analysis.
    • Ash refers to the inorganic (mineral) residue remaining after the combustion or complete acid-facilitated oxidation of organic matter in food.
    • Definitions:
      • Dry ashing: uses a muffle furnace capable of maintaining temperatures of 500–600 °C.
      • Wet ashing: uses strong acids, oxidizing agents, or combinations thereof to chemically oxidize and remove organic substances.

    Ashing Process

    • Suggestions to accelerate incineration:
      • High-fat samples should be extracted prior to ashing.
      • Glycerin, alcohol, and hydrogen can be used to accelerate ashing.
      • Samples such as jellies may require mixing with cotton wool to avoid spattering.
      • Salt-rich foods may require a separate ashing of water-insoluble components and salt-rich water extract.
      • An alcoholic solution of magnesium acetate can be added to accelerate ashing of cereals.

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    Description

    This quiz covers the importance of moisture assay in food products, including the economic significance of water content and its impact on food manufacturing. Learn about the analytical procedures involved in determining moisture levels and total solids in food.

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