Fruit Maturity & Quality

• Maturity includes maturity indices in fruits and vegetables, and maturity and harvesting indices.

Maturity

• It is the full development stage of tissues in fruits and vegetables that happens before ripening starts.
• The fruit receives regular nutrients from the plant during maturation.
• A mature abscission or corky layer at the stem's base halts nutrient inflow causing fruits to depend on their reserves.
• Storage life and fruit quality are influenced by the stage of maturity at harvest.
• Early harvested fruits may lack flavor and fail to ripen.
• Late picked fruits may be fibrous or have a very short shelf life
• Maturity is categorized in two ways: physiological maturity and horticultural maturity.

Horticultural or Commercial Maturity

• Horticultural maturity is the development stage when plant parts possess desired characteristics by consumers.
• This depends on intended use as seen with papayas and jackfruit.

Physiological Maturity

• It is the end of development stage, where products have the ability to ripen normally after harvest.

Maturity and Shelf Life

• Quality is best when harvested at a more mature and ripe stage.
• Shelf life increases when harvested at unripe stages.
• Lower maturity leads to fruit that never ripens, shrivels, exhibit poor flavor, leads to no repeat buys, and have a long shelf life.
• Higher maturity includes more decay, better flavor, produce that is too soft, bruises easily, with a short shelf life.

Maturity Indices

• Maturity indices are equivalent to harvest indices for the purposes of sensory and nutritional quality.
• Maturity indicies assure adequate shelf life.
• Maturity indicies facilitate marketing standards and productivity.

Developmental Continuum

• Growth -> Maturation -> Physiological Maturity -> Ripening -> Senescence.
• Fruits such as cucumber, beans, and sweet corn go through the Growth and Maturation faze.
• Fruits such as carrots, onions, and potatoes go through Physiological Maturity,.
• Fruits such as apples, bananas, melons, pears, and tomatoes go through Ripening/Senescence.

Types of Maturity Indices

• Visual Indices include Shape and Color.
• Physical Indices include Firmness, Acoustic sound test, and Specific gravity.
• Chemical Indices include Total soluble solids and Titrable acidity.
• Calculated Indices include Calender dates, Days after full bloom, and Heat Units.
• Physiological Method includes Respiration rate, Ethylene peak, and Volatile production.

Size and Shape

• Fruit shape serves to ascertain maturity as seen with mangos(fullness of cheeks) and bananas(angular shape becomes more round)

Colour

• Color can be an indication of maturation
• Colorimeters can be used

Firmness

• Middle lamella dissolves during maturity leading to soft fruit.
• Penetrometers measure the pressure to force a plunger inside the fruit tissue, measured in pounds or kilograms force Common fruits:
  • Apple
  • Pear
  • Plum
  • Guava
  • Kinnow

Accoustic/ Sound Tests

• Tapping immature and ripened fruit with finger knuckles generates sounds of varying quality.
• Ripe fruits produce dull sound.
• Examples: Watermelon and Jackfruit

Specific gravity

• Specific gravity is the ratio of a substance to a reference substance.
• As fruits mature their specific gravity increases which, is useful for grading fruits according to maturity.
• When placed in a tank full of water more mature fruits sink, while less mature fruits float.
• Specific gravity = weight of fruits and vegetables in air / weight of fruits and vegetables in water.

Total Soluble Solids

• Starch breaks down into sugars as fruit grows, ripening and sugar content measurement provides a measure of maturity.
• Measurements are taken by a Brix refractometer.
• Measurements are of the refractive index of fruit juice.
• Readings can range from 0-32°B, 28-62°B, to 56-90°B.

Titratable Acidity

• Titratable acidity (TA) determined by titrating a known volume of juice with 0.1N NaOH to end point.
• Milliliters of NaOH needed are used to calculate the TA.
• The TA expressed as percent malic, citric or tartaric acid is calculated:
• TA = ml NaOH x N (NaOH) x acid meq. Factor* x 100 / Juice titrated
• Citric (0.0064) - Berries, citrus fruits, pineapple
• Malic (0.0067) - Apple, pear, peach, tomato
• Tartaric (0.0075) - Grape

Days after full bloom

• Useful guide to harvest when seasonal variation in climate is small
• Works when the blooming period is short
• This is reliable but varies from year to year and location to location.
• Optimum harvest date predicted by night temperature correction for 15 days after full bloom, correcting 1 day in the standard figure for every 10°F variation from average night temperature.
• Mango requires 110-125 days (Var. alphanso and Pairi).
• Banana requires : 99-107 days (Dwarf Cavendish).

Heat Units

• All plants have a tolerable growth temperature range; faster ripening or earlier harvest occurs at higher temperatures.
• If everything else is equal, the time a fruit takes to fully develop depends on the surrounding temperature.
• This may be expressed in degree-hours or degree-days
• Degree-hour measures the accumulated heat unit equivalent to a crop's exposure to one degree above a reference temperature for one hour.
• Degree-day measures the accumulated heat unit equivalent to a crop's exposure to one degree above a reference temperature for one day.
• The formula to use for to measure General heat units= (Actual temperature-Reference temperature) x time.
• Heat units are used for planning, planting, harvesting, and factory programs. Used for corn, peas and tomato for processing

Respiration Rate

• Particularly useful in climacteric fruits as there is a sharp increase in respiration rate.
• Helpful to pin pointing the most appropriate time of harvest.
• Determination of respiration peak can help in determining the maturity of the product.

Ethylene Peak

• Climacteric fruits have an ethylene peak.
• This is helpful in determining the maturity stage for harvesting

Volatile Production

• Apple: Ethyl-2 -methyl butyrate
• Banana: Eugenol
• Grapefruit: Nootaketone
• Lemon: Citral
• Orange: Valencene

Maturity Indices Definition

• Maturity indices are signs indicating harvest readiness and are a basis for determining harvest date.
• Includes two types of indices: subjective and objective.

Subjective Maturity Indices

• Subjective indices are qualitative and rely on the senses for evaluation.
• Utilizes color, size, shape, sound, firmness, and juice content assessments.

Objective Maturity Indices

• Objective indices are quantitative.
• Includes measurable indices such as TSS, TA, starch content, oil content, firmness, dry matter, days after full bloom, heat degree day, respiration and ethylene production, and production of volatiles.

Recommended Features of Maturity Indices

• Simple, easy to carry out
• Uses Objective vs subjective indicators
• Related to quality and storage life –Represents a progressive change with maturity
• Permits prediction of maturity from year to year
• Inexpensive

Advantages of Maturity Estimation

• Preserves the product's quality
• Enhances produce freshness, appearance, and elegance
• Improves the storage life of produce
• Facilitates management of ripening and senescence by hastening or delaying harvesting
• Enables extended utilization of produce
• Supports long-distance transportation of produce
• Maximizes returns

Limitations of Maturity Indices

• Limitations include: Soil conditions, nutrition, irrigation
• Season, climate position on the plant, pruning or other cultural & management practices, and variety
• Table Examples of maturity measures of fruits & vegetables

Explore the relationship between fruit maturity at harvest and its shelf life. This includes the primary physiological changes during maturation as fruit detaches from the plant. Also covered are the visual indicators of fruit maturity.