MADURACION FRUTAS

Introduction to Fruit Maturation

Overview of the Maturation Process

• The life cycle of fruit consists of three main periods: growth, maturation, and senescence. This is illustrated in a developmental graph presented at the beginning.

• Growth involves cellular division leading to an increase in fruit size, while maturation begins before growth ends and continues until the fruit softens, transitioning into senescence.

Changes During Maturation

• Maturation is crucial as it brings about significant changes in appearance, flavor, and texture that enhance consumer appeal. These transformations are both physical and biochemical.

• As fruits mature (e.g., bananas), they undergo color changes, texture modifications, and alterations in taste and aroma that make them more attractive to consumers. However, once peak maturity is reached, degradation of these organoleptic qualities begins rapidly.

Types of Maturation

Physiological vs Organoleptic Maturity

• Two types of maturation are identified: physiological maturity (occurs before cellular growth ends) and organoleptic maturity (when fruits develop desirable sensory characteristics for consumption). Physiological maturity ensures seeds are ready for propagation.

• Organoleptic maturity transforms physiologically mature but non-edible tissue into visually appealing and palatable fruit; this process starts towards the end of physiological maturation. Maximum organoleptic quality is achieved during this phase.

Harvesting Considerations

• The gap between physiological and organoleptic maturity is termed the "harvest window." If harvested too late after reaching organoleptic maturity, fruits may become overly soft with unpleasant flavors and shorter post-harvest life.

Changes During Fruit Ripening

Color Changes

• A key change during ripening includes pigment modification leading to color changes due primarily to decreased chlorophyll levels while other pigments like flavonoids or anthocyanins increase (e.g., blueberries). This shift enhances visual appeal for consumers.

• The color of fruit skins serves as a quality indicator influencing consumer acceptance; thus monitoring pigment content during ripening is essential for assessing readiness for consumption.

Starch Degradation

• Another significant change during ripening involves starch degradation; starch content decreases over time as it undergoes hydrolysis into simpler sugars which contribute to sweetness in ripe fruits. This process can be tracked through graphical representation showing starch levels declining with maturation progress.

Understanding Fruit Ripening and Its Chemical Changes

The Role of Sugars in Fruit Sweetness

• The breakdown of long-chain carbohydrates leads to an increase in simple sugars such as fructose, glucose, and sucrose, enhancing the sweetness of fruits like bananas and apples.

• Enzymes like alpha-amylase and beta-amylase, along with maltases, facilitate the conversion of starch into simple sugars during ripening.

Changes in Acidity During Ripening

• As fruits mature, there is a decrease in organic acids; for instance, malic acid predominates in ripe apples while tartaric acid is found in grapes.

• The overall acidity decreases due to the oxidation of acids during respiration, leading to a shift from high acidity and low sugar concentration at the start of ripening to higher sugar levels as maturity progresses.

Texture Modification Through Pectin Degradation

• A significant change during ripening is the softening of fruit texture caused by the degradation of protopectin into soluble pectin through enzymatic action.

• This transformation results in a softer fruit texture that can be measured using devices like texture meters or penetrometers.

Synthesis of Volatile Compounds Contributing to Aroma

• During ripening, various low molecular weight volatile compounds are synthesized (e.g., esters, alcohols), which contribute significantly to the characteristic aroma of fruits.

• Not all volatiles impact aroma equally; key compounds known as "impact volatiles" play crucial roles—like butyl acetate in apples or isoamyl acetate in bananas.

Distinction Between Odor and Aroma Perception

• It’s important to differentiate between odor (perceived through nasal inhalation) and aroma (detected via retro-nasal pathways after tasting).

• The term "aroma" encompasses a combination of olfactory and gustatory properties experienced during tasting but should not be confused with basic odor perception.

Respiration and Ripening in Fruits

Metabolic Activity Post-Harvest

• Fruits continue to respire and develop metabolic activity after being harvested, utilizing energy from sugars and other substrates like organic acids, proteins, and lipids. This process results in the formation or elimination of carbon dioxide and water vapor.

Changes During Maturation

• As fruits mature, their respiration patterns change significantly. The consumption of oxygen and production of carbon dioxide during respiration can be graphically represented, showing a decrease in respiratory intensity as growth progresses.

Climacteric vs Non-Climacteric Fruits

• Two types of fruits are identified based on their respiration patterns: climacteric fruits exhibit a climacteric peak in respiratory activity at physiological maturity, while non-climacteric fruits show a gradual decline without such a peak. Examples include apples (climacteric) versus cherries (non-climacteric).

Importance of Climacteric Peak

• The climacteric peak is associated with significant organoleptic changes during ripening. Climacteric fruits can be harvested at physiological maturity and will continue to ripen post-harvest, which helps prevent losses due to short storage life. In contrast, non-climacteric fruits must remain on the plant until fully ripe.

Ethelene Production and Its Effects

• Ethylene gas is produced naturally during fruit respiration; climacteric fruits produce it in larger quantities during the climacteric peak through autocatalytic processes. Ethylene acts as a phytohormone that enhances maturation but also triggers senescence post-maturation. Factors like high temperatures and mechanical damage increase ethylene synthesis.

Controlling Ethylene Levels

• Managing ethylene levels is crucial since excess accumulation can accelerate ripening leading to over-ripening or spoilage (e.g., "one rotten apple spoils the bunch"). Low oxygen concentrations and refrigeration help maintain low ethylene levels around mature fruits while controlled exposure can expedite uniform ripening for market readiness.