HORMA - 303
Postharvest Technology For Fruit Crops
Postharvest Technology For Fruit Crops
UNIT IV: Processing, Preservation & Value Additio
📚 Contents
1. Packing Methods and Transport
A. Packing Methods
Packaging is the "Silent Salesman." It protects the produce and aids in marketing.
- Functions of Packaging:
Protection: From physical damage (cuts/compression) and environmental factors (sun/rain).
Containment: Holds units together for easy handling.
Identification: Labeling (Variety, Grade, Origin). - Types of Packaging Materials:
Corrugated Fiber Board (CFB) Boxes: The most common modern package. Made of Kraft paper with fluting (wavy layer) for cushioning. Advantages: Lightweight, recyclable, printable, good cushioning. Ventilation: Must have 2–5% area as vent holes for airflow.
Wooden Crates: Traditional but declining use. Disadvantages: Heavy, destroys forests, bruises fruit (rough surface).
Plastic Crates: Reusable, rigid, easy to clean (washable). Good for local transport (field to packhouse).
Flexible Films / Net Bags: Polyethylene bags (consumer packs) or Nylon nets (for hard fruits like Citrus/Coconut). - Cushioning Materials: Used to fill empty spaces and absorb shock.
Old: Straw/Grass (High risk of infection/heat buildup).
Modern: Paper shavings, molded paper pulp trays (for eggs/apples), bubble wrap, foam nets (individual fruit sleeves for Papaya/Apple).
B. Transport
Transportation connects the production center (Farm) to the consumption center (Market).
- Modes of Transport:
Road (Trucks): Most common in India. Flexible but prone to vibration damage. Refrigerated trucks ("Reefer Vans") are essential for cold chain.
Rail: Efficient for bulk transport over long distances (e.g., Banana from South to North India). Ventilated wagons are used.
Air: Expensive. Used only for high-value, highly perishable exports (e.g., Mango, Strawberry, Cherry).
Sea: Slowest but cheapest. Used for massive international trade (e.g., Apple, Banana, Citrus). Requires Refrigerated Containers (Reefers).
2. Principles and Methods of Preservation
Definition: Preservation involves treating food to stop spoilage caused by microorganisms, enzymes, or chemical reactions, extending its shelf life.
Principles of Preservation (The 3 Main Pillars)
- Prevention or Delay of Microbial Decomposition:
Asepsis: Keeping out microorganisms (hygiene).
Filtration: Removing germs (used in clear juices/wine).
Anaerobic Conditions: Sealing food to cut off Oxygen (Canning). - Killing Microorganisms:
Heat: Pasteurization (kills pathogens) or Sterilization (kills all microbes).
Radiation: Using UV or Gamma rays. - Prevention or Delay of Self-Decomposition:
Blanching: Kills enzymes (like peroxidase) to prevent browning.
Antioxidants: Prevents oxidation (e.g., Vitamin C).
Methods of Preservation (Summary)
- Drying/Dehydration: Removal of moisture to a level (usually < 5%)
- Low Temperature: Freezing (-18°C) stops microbial growth (though it doesn't kill them).
- High Temperature: Canning/Bottling.
- Preservatives:
Class I (Natural): Sugar, Salt, Vinegar, Spices, Oil.
Class II (Chemical): KMS (Potassium Metabisulphite) and Sodium Benzoate.
3. Food Processing: Canning
Definition: Canning (or Appertization) is a method of preserving food by sealing it in airtight containers and applying heat to kill microorganisms.
Steps in Canning (Flow Chart)
- Selection: Choose firm, ripe, sound fruits.
- Sorting & Grading: Remove damaged fruit; sort by size for uniform cooking.
- Washing: Remove dirt/spray residues.
- Peeling/Coring/Pitting: Removing skin/seeds (e.g., Lye peeling for peaches, hand peeling for mango).
- Blanching: Dipping in boiling water for 2-5 mins.
Purpose: Inactivates enzymes, removes air from tissues, cleans fruit. - Filling: Putting fruit into cans (leaving head space of 0.3–0.5 cm).
- Syruping/Brining: Adding liquid medium.
Syrup (Sugar solution): For Fruits (usually 20–55° Brix).
Brine (Salt solution): For Vegetables (approx 2%).
Temp: Added boiling hot (79–82°C). - Exhausting: Crucial Step. Heating the open can to remove air (Oxygen).
Purpose: Prevents corrosion of tin (pinholes), preserves Vitamin C, prevents bursting during processing. - Sealing (Double Seaming): Hermetically (airtight) closing the lid.
- Processing (Thermal Treatment): Heating the sealed can to kill bacteria.
Fruits (Acidic, pH < 4.5): Processed in Boiling Water (100°C).
Vegetables (Non-acidic, pH > 4.5): Processed in Autoclave/Pressure Cooker (115–121°C) to kill Clostridium botulinum spores. - Cooling: Immediately cooling cans to 39°C to stop cooking (prevents "stack burn").
- Storage: In a cool, dry place.
4. Fruit Juices and Beverages
Beverages are classified based on their Fruit Juice content and Total Soluble Solids (TSS/Sugar). The FPO (Fruit Products Order) specifications are standard.
A. Unfermented Beverages
- Fruit Juice: 100% pure juice (natural TSS). No added sugar/water.
- RTS (Ready-to-Serve): Drinkable immediately.
Juice: Min 10%.
TSS: Min 10%.
Example: "Maaza" or "Frooti" type drinks. - Nectar: Thicker than RTS, contains pulp.
Juice: Min 20%.
TSS: Min 15%.
Example: Mango Nectar. - Squash: Concentrated; must be diluted with water before drinking.
Juice: Min 25%.
TSS: Min 40–50%.
Contains preservative (KMS or Benzoate).
Example: Orange Squash, Lemon Squash. - Cordial: Clarified squash (sparkling clear, no pulp/cloudiness).
Juice: Min 25%.
TSS: Min 30%.
Example: Lime Cordial. - Syrup: Synthetic or fruit-based concentrate used for flavor.
Juice: Variable (Synthetic syrups have 0%).
TSS: High (Min 65%).
5. Jams, Jellies, and Marmalades
These are high-sugar products where sugar acts as a preservative (by osmosis).
A. Jam
Definition: Prepared by boiling fruit pulp with sugar to a thick consistency.
FPO Standard:
Fruit content: Min 45%.
TSS (Final Sugar): Min 68%.
Preparation: Fruit pulp + Sugar + Pectin + Acid → Boil until thick.
Example: Mixed Fruit Jam, Apple Jam.
B. Jelly
Definition: Prepared by boiling clear fruit extract (strained juice, no pulp) with sugar and pectin. It should be transparent and hold its shape (tremble like a solid).
FPO Standard: Same as Jam (45% fruit extract, 65-68% TSS).
- Essential Constituents for Jelly:
Pectin (1%): The gelling agent. (Guava and Sour Apple are rich in pectin).
Sugar (60-65%): Gives structure.
Acid (pH 3.2): Essential for gel formation. - Test for End Point:
Sheet Test: Dip a spoon in boiling jelly and let it drip. If it drops as a "sheet" or flake (not individual drops), it is done.
Temperature Test: Boiling point reaches 105°C.
C. Marmalade
A fruit jelly containing suspended peel (shreds) of the fruit.
Usually made from Citrus fruits (Orange/Lemon).
Structure: Clear jelly background + Bitter-sweet peel shreds.
6. Pickles
Definition: Preservation of food in common salt, vinegar, oil, or spices.
Principles of Pickling:
- Salt Curing (Salting): Salt (15–20%) draws water out of the vegetable/fruit (osmosis), making it unavailable for bacteria.
- Acidification: Vinegar (Acetic acid, 2–3%) lowers pH below 4.5, inhibiting bacteria.
- Oil Layer: Oil floats on top, creating an anaerobic seal (no oxygen) that prevents mold/yeast growth.
Types:
- Fermented Pickles: Bacteria (Lactic acid bacteria) ferment sugars to produce acid naturally (e.g., Sauerkraut, Olive).
- Non-Fermented Pickles: Acid/Salt/Oil is added directly (e.g., Indian Mango pickle, Lime pickle).
7. Candies (Preserves)
Definition: A fruit impregnated with sugar syrup until the sugar concentration in the tissue is high enough to prevent spoilage.
Process (Osmotic Dehydration):
- Preparation: Fruit (Aonla, Karonda, Ginger, Citrus peel) is punctured or pricked.
- Blanching: Softens tissue.
- Syrup Treatment:
Start with low strength syrup (e.g., 40% sugar).
Boil daily and increase syrup strength progressively (40 → 50 → 60 → 70 → 75 °Brix).
Reason: Gradual increase prevents the fruit from shrinking/shriveling (plasmolysis). - Drying: The impregnated fruit is drained and dried.
- Glazing: Sometimes coated with sugar crystals.
Difference between Candy and Preserve (Murabba):
- Candy: Dry product (syrup is drained off).
- Preserve (Murabba): Wet product (fruit remains suspended in thick syrup).
📚 References
Srivastava, R.P. & Kumar, S. (2002). Fruit and Vegetable Preservation: Principles and Practices. International Book Distributing Co. (Standard text for this unit).
Bhutani, R.C. (2003). Fruit and Vegetable Preservation. Biotech Books.
Ranganna, S. (1997). Hand Book of Analysis and Quality Control for Fruit and Vegetable Products. Tata McGraw-Hill.
Chadha, K.L. (Ed.). Advances in Horticulture. Vol IV.