Unit 3: Food Preservation

Table of Contents

Basic Concepts of Food and Nutrition

Classification of Food and Nutrients

Classification of Food

Foods can be classified in several ways:

  • By Origin: Plant-based (cereals, fruits) vs. Animal-based (meat, dairy).
  • By Chemical Composition: Carbohydrates (rice), Proteins (pulses), Fats (oils), Vitamins & Minerals (vegetables).
  • By Function:
    • Energy-giving: Carbohydrates, Fats.
    • Body-building: Proteins.
    • Protective/Regulating: Vitamins, Minerals.

Classification of Nutrients

  1. Macronutrients: Needed in large quantities.
    • Carbohydrates: Main source of energy.
    • Proteins: For growth, repair, and enzymes.
    • Fats (Lipids): Stored energy, insulation, hormone production.
  2. Micronutrients: Needed in small quantities.
    • Vitamins: For metabolic regulation (e.g., A, B, C, D).
    • Minerals: For structure and regulation (e.g., Ca, Fe, I).
  3. Water: Essential for all bodily functions.

Food Preservation: Principles and Methods

Definition, Objectives, and Principles

  • Definition: The science of treating and handling food to stop or greatly slow down spoilage (loss of quality, edibility, or nutritive value) caused by microorganisms or chemical changes.
  • Objectives:
    1. To prevent microbial spoilage.
    2. To increase the shelf-life of food.
    3. To retain the nutritional value, texture, and flavor.
    4. To make seasonal foods available year-round.
  • Principles:
    1. Asepsis: Preventing contamination (keeping microbes out).
    2. Inhibiting Microbes: Slowing or stopping the growth of microbes (e.g., by refrigeration, drying, or adding acid/sugar).
    3. Killing Microbes: Destroying microorganisms (e.g., by heating/canning, irradiation).

Different Methods of Food Preservation

  • Refrigeration/Freezing: Low temperature slows down microbial growth and enzyme activity.
  • Canning (Heating): Food is sealed in cans and heated to high temperatures (Pasteurization or Sterilization) to kill microbes.
  • Drying/Dehydration: Removing water (lowering water activity) inhibits microbial growth. (e.g., dried fruit, milk powder).
  • Use of Sugar (Sugaring): High sugar concentration (as in jams) draws water out of microbes by osmosis, killing them.
  • Use of Salt (Salting/Curing): High salt concentration (as in pickles, cured meat) acts by osmosis, just like sugar.
  • Use of Acid (Pickling): Low pH (high acidity) (e.g., using vinegar) inhibits the growth of most microbes.
  • Smoking: The smoke contains chemicals (like formaldehyde) that act as preservatives and the heat dries the food.
  • Chemical Preservatives: Using food additives (see Unit 4).

Preserved Products

This section covers common food products made using preservation techniques.

Product Type/Composition/Manufacture Nutritional Aspects/Uses
Jam Made from fruit pulp, sugar, and pectin. Boiled to a thick consistency. High in sugar (energy), source of fruit fiber. Used as a spread.
Jelly Made from fruit juice (strained, no pulp), sugar, and pectin. Boiled to a clear, firm gel. High in sugar, but less fiber than jam. Used as a spread.
Marmalade A jelly-like product that contains suspended slices of citrus fruit peel (e.g., orange). Similar to jam/jelly, but with added fiber and flavor from the peel.
Sauces Thick liquid (e.g., tomato sauce, soy sauce) made from fruits/vegetables, often with vinegar, spices, and sugar. Used as a condiment to add flavor, moisture, and appeal to food.
Pickles Preserved in a high-acid (vinegar) or high-salt (brine) solution. Can be fermented. Low in calories, can be a source of probiotics (if fermented). High in sodium.
Squashes Concentrated syrup made from fruit juice, sugar, and water. Must be diluted to drink. Source of sugar (energy). Nutritional value depends on fruit juice content.
Syrups A thick, viscous liquid consisting primarily of a solution of sugar in water. (e.g., maple syrup, corn syrup). Used as a sweetener, topping. Very high in calories from sugar.

Food Standards

These are quality marks and regulatory bodies in India to ensure the quality and safety of food products.

  • ISI Mark: (Indian Standards Institution, now under BIS - Bureau of Indian Standards). A standard of quality for industrial products, including some food processing equipment and additives.
  • Agmark: (Agricultural Mark). A certification mark for agricultural products, assuring they conform to a grade standard. (e.g., for spices, ghee, flour).
  • FPO Mark: (Fruit Products Order). A mandatory mark for processed fruit products (jams, juices, pickles) to ensure quality and hygiene.
  • MPO Mark: (Meat Food Products Order). A mandatory mark for processed meat and fish products.
  • PFA: (Prevention of Food Adulteration Act, 1954). The former primary law in India to prevent the adulteration of food.
  • FSSAI: (Food Safety and Standards Authority of India, 2006). The modern, overarching authority that has replaced the PFA and FPO/MPO. FSSAI is now the single reference point for all food safety standards and regulations in India.