This presentation covers the key concepts and practical applications of maturity indices in fruits and vegetables. Understanding the correct stage of harvest is essential for optimizing quality, minimizing post-harvest losses, and ensuring marketability. The slides detail physiological and horticultural maturity, types of indices, and specific examples for major crops, providing a comprehensive guide for students and professionals in horticulture and postharvest technology.
Introduction to Maturity Indices
- Maturity indices are signs or measurements indicating readiness for harvest.
- Correct harvest stage ensures optimal quality, shelf life, and market value.
- Improper timing leads to poor flavor, texture, and increased post-harvest losses.
- India loses 25–30% of produce due to improper harvest timing.
Definitions: Maturity and Ripening
- Maturity: Stage when fruit/vegetable is fully developed and can ripen normally.
- Ripening: Qualitative changes after maturity making produce edible.
- Harvesting at correct maturity is crucial for quality and storage.
Types of Maturity
- Physiological maturity: End of development; ability to ripen after harvest (mainly for fruits).
- Horticultural (Commercial) maturity: Stage preferred by consumers; depends on intended use.
- Climacteric fruits: Harvest at mature but unripe stage.
- Non-climacteric fruits: Harvest at ripe stage.
Importance of Maturity Indices
- Ensure sensory and nutritional quality.
- Provide adequate shelf life and facilitate marketing.
- Help standardize harvest timing and improve productivity.
- Balance between shelf life and eating quality.
Types of Maturity Indices
- Subjective (Qualitative): Color, size, shape, firmness, aroma, sound.
- Objective (Quantitative): TSS, acidity, starch content, oil content, firmness, dry matter, days after bloom, heat units, respiration, ethylene production.
Visual and Physical Indices
- Size and shape: Final size/shape indicates maturity (e.g., mango cheeks, banana angularity).
- Color: Loss of green or development of characteristic color.
- Firmness: Softening indicates maturity (measured by penetrometer).
- Specific gravity: Increases with maturity; used for grading.
Chemical and Calculated Indices
- Total Soluble Solids (TSS): Measured by refractometer; indicates sugar content.
- Titratable acidity (TA): Determined by titration; used with TSS for sugar-acid ratio.
- Calendar date/days after full bloom: Useful where climate is stable.
- Heat units: Degree-days required for maturity.
Physiological and Other Indices
- Respiration rate: Climacteric rise indicates harvest time in some fruits.
- Ethylene evolution: Peaks at maturity in climacteric fruits.
- Volatile production: Specific aroma compounds signal maturity (e.g., apple, banana).
Characteristics of Good Maturity Indices
- Simple, easy, and inexpensive to use.
- Objective and related to quality and storage life.
- Show progressive change with maturity.
- Allow prediction from year to year.
Limitations of Maturity Indices
- Affected by soil, nutrition, irrigation, climate, and variety.
- Position on plant and cultural practices influence indices.
- Visual indices may mislead due to environmental variation.
Maturity Indices: Major Fruits (Examples)
Mango
- Peel color change on shoulders.
- Tapka method: natural fruit drop.
- Specific gravity: 1.01–1.02.
- Days from fruit set to maturity.
Banana
- Disappearance of angularity; round fingers.
- Pulp:peel ratio 1.2–1.6; pH 5.2–5.6.
- Harvest at 75–80% maturity for distant markets.
Guava
- Color change from dark to light green.
- Specific gravity ~1.0.
- 17–20 weeks from fruit set to maturity.
Maturity Indices: Other Fruits
Grape
- TSS: 16–24% (variety-dependent).
- Peel color, pulp texture, flavor, easy berry separation.
Papaya
- Skin color change at apex or yellow streaks.
- Latex becomes watery.
Pineapple
- 25% surface yellow for local market.
- Flattened eyes, TSS:acid ratio 21–27.
Jackfruit
- Dull, hollow sound when tapped.
- Spines widely spaced, aromatic odor.
Maturity Indices: Citrus, Pomegranate, Sapota, and Others
Citrus
- Rind color change (species-specific).
- TSS:acid ratio (e.g., sweet orange 8.5–8.9).
- Minimum juice content standards.
Pomegranate
- 135–170 days after anthesis.
- Peel color change, hard rind, metallic sound.
Sapota
- Dull orange/potato color, minimal latex.
- Disappearance of brown scaly surface.
Maturity Indices: Temperate and Other Fruits
Apple
- TSS, color change, firmness, ease of separation.
- Iodine test for starch breakdown.
Strawberry
- 2/3 to 3/4 red color for local markets.
Peach/Plum
- Days from full bloom, size, firmness, color, sugar:acid ratio.
Ber, Date Palm, Litchi, Fig, Custard Apple, Aonla
- Color change, TSS, acid ratio, specific gravity, days after pollination, sound, texture, and aroma as indices.
Maturity Indices in Vegetables: General Principles
- Physiological maturity: Maximum growth and development.
- Commercial maturity: Stage required by market; varies by crop and edible part.
- Harvest timing affects marketability, storage, and quality.
Maturity Indices: Vegetable Examples (I)
Cauliflower
- Curds 4–8 in. diameter, compact, white, smooth.
Cabbage
- Heads hard and solid, uniform color.
Broccoli
- Dark green, compact head, before yellow flowers appear.
Brussels Sprouts
- Sprouts 1–1.5 in. diameter, firm.
Maturity Indices: Vegetable Examples (II)
Tomato
- Harvested from mature green to fully red, depending on market.
Eggplant
- Glossy, purplish-black or white color, 6–8 in. diameter.
Beans
- Pods filled with seeds, green, not yellowing.
Okra
- Pods 3–5 in. long, tender.
Maturity Indices: Vegetable Examples (III)
Onion
- Bulbs 2–4 in. diameter, tops fall over and dry.
Peas
- Pods fully developed, seeds not more than half full size.
Pepper
- Firm, crisp, full-sized; color depends on cultivar.
Potato
- Harvest when plants yellow and die down; avoid sun exposure.
Maturity Indices: Vegetable Examples (IV)
Pumpkin/Squash
- Full size, firm, glossy rind, ground spot cream to orange.
Cucumber
- Bright deep green, 2–3 in. long, before yellowing.
Watermelon
- Dull sound when thumped, yellow ground spot, brown tendrils.
Muskmelon
- Stem slips easily, netting rounded, flesh color change.
Maturity Indices: Root and Leafy Vegetables
Carrot
- Roots 1 in. diameter, dark tops.
Turnip
- Roots 2–3 in. diameter, tops 3–5 in. long.
Radish
- Roots 1 in. diameter, shoulders visible, avoid over-maturity.
Spinach
- Leaves 4–6 in. long, harvested at base.
Summary and Key Points
- Maturity indices are essential for optimal harvest timing and quality.
- Indices vary by crop, variety, and intended use.
- Combination of visual, physical, chemical, and physiological indices is best.
- Proper harvest reduces losses and improves marketability.
Objective Questions
Q1. Which of the following is a subjective maturity index for fruits?
A. TSS/TA ratio
B. Colour
C. Specific gravity
D. Heat units
Answer: B
Q2. What is the recommended TSS percentage for harvesting Thompson seedless grapes?
A. 12-14%
B. 16-18%
C. 20-22%
D. 24-26%
Answer: C
Q3. Which instrument is used to measure the firmness of fruits like apple and pear?
A. Refractometer
B. Penetrometer
C. Colorimeter
D. Hygrometer
Answer: B
Q4. For bananas intended for long distance transport, at what maturity percentage should they be harvested?
A. 60-65%
B. 70-75%
C. 75-80%
D. 90-100%
Answer: C
Q5. Which of the following is NOT a reliable maturity index for sapota?
A. Dull orange peel colour
B. Increase in milky latex content
C. Disappearance of brown scaly material
D. Light yellow streak after scratching
Answer: B
Q6. In citrus fruits, which ratio is preferred as a maturity index for sweet oranges?
A. 5.5 to 6.0
B. 8.5 to 8.9
C. 10.5 to 13.0
D. 12.1 to 14.1
Answer: B
Q7. Which method is used to determine the total soluble solids (TSS) in fruit juice?
A. Penetrometer
B. Titration with NaOH
C. Refractometer
D. Colorimeter
Answer: C
Q8. What is the main maturity index for harvesting muskmelons?
A. Colour change of rind
B. Stem slips easily from fruit
C. Firmness of flesh
D. TSS/acid ratio
Answer: B
Q9. Which of the following is a calculated maturity index?
A. Colour development
B. Days after full bloom
C. Firmness
D. Aroma production
Answer: B
Q10. For cauliflower, when should the curds be harvested?
A. When curds are 1-2 inches in diameter
B. When curds are 4-8 inches in diameter and compact
C. When outer leaves turn yellow
D. When curds start to loosen
Answer: B