FOOD2000 Chap.5 Fruit and Vegetable Physiology and Ripening
Fruit and Vegetable Physiology and Ripening
Harvested fruit and vegetables remain living tissues. Their respiration, ethylene responses, pigment changes, cell-wall modification, water loss and reserve metabolism continue to shape quality after harvest. This chapter distinguishes climacteric from non-climacteric behaviour without turning the categories into absolute rules.
It uses causal chains to connect physiological change with colour, firmness, flavour and storage decisions. Harvest maturity, cultivar and exposure conditions are retained in comparisons so one visible sign does not stand in for overall ripening state.
What this chapter covers
- 01
Living tissue after harvest
- 02
Respiration and metabolic demand
- 03
Ethylene production and response
- 04
Climacteric and non-climacteric patterns
- 05
Pigment, flavour and cell-wall changes
- 06
Ripening, senescence and quality windows
Worked example · free
Interpret an ethylene exposure
- +1Identify ethylene exposure as the treatment rather than assuming contamination.
- +1Connect ethylene signalling with coordinated ripening responses.
- +1Link cell-wall and pigment changes to softer texture and altered colour.
- +1Propose separation, ventilation or atmosphere management and monitor the relevant quality measures.
Key terms
- Respiration
- Metabolic oxidation that supplies energy and continues after harvest while substrates and oxygen remain available.
- Ethylene
- A gaseous plant hormone that regulates many ripening and senescence responses.
- Climacteric
- A ripening pattern associated with a characteristic respiratory rise and often strong ethylene regulation.
- Senescence
- Progressive loss of cellular organisation and function as living tissue ages.
Fruit and Vegetable Physiology and Ripening FAQ
Why does produce keep changing after harvest?
Harvest separates tissue from the plant but does not immediately stop cellular metabolism. Respiration, water loss, enzyme activity, pigment turnover and hormone responses continue. Their rates depend on commodity, maturity and environment, so postharvest quality must be managed as a changing biological system.
Does non-climacteric mean no response to ethylene?
No. Climacteric classification describes a broad ripening pattern, not a rule that every non-climacteric tissue is insensitive to ethylene. Responses differ among commodities and attributes. State the observed or taught response and avoid using the category to claim that no physiological effect is possible.
How are softening and colour change explained?
Softening commonly reflects changes in cell-wall polymers and tissue structure, while colour change can involve chlorophyll loss and synthesis or exposure of other pigments. Both may accompany ripening, but they are distinct processes and should be measured with appropriate texture and colour methods.
Why is harvest maturity important to later quality?
Postharvest handling can slow or coordinate change, but it cannot recreate developmental capacity that was absent at harvest. Produce harvested too immature may change colour without developing expected flavour or texture, while overmature produce may deteriorate rapidly. Compare lots only after recording maturity indicators, cultivar and harvest conditions.
Storage recommendations should therefore begin with the incoming physiological state rather than treating every fruit as equivalent.
Exam move
Draw causal chains for three commodities from maturity state through respiration or ethylene response to pigment, texture and flavour outcomes. Compare climacteric and non-climacteric patterns while writing one caution against treating either as absolute. For every postharvest symptom, name a physiological mechanism, an observable measure and one management action that follows from the mechanism.
Start with a living-tissue budget. After harvest, photosynthetic input largely stops while respiration continues to consume reserves and release carbon dioxide, water and heat. Add arrows for water loss, membrane change, pigment turnover, cell-wall modification and aroma development. Use the map to explain why a commodity can look acceptable at one moment yet be moving rapidly toward senescence.
Construct paired profiles for a climacteric and a non-climacteric fruit. Mark harvest maturity, expected respiration pattern, ethylene role and which attributes can continue developing after removal from the plant. Then add exceptions and limits so the categories do not become absolute claims about every tissue response.
Practise deciding whether ethylene exposure should be encouraged, avoided or monitored for a named commodity and marketing goal. Separate maturity from ripeness in your notes. Maturity concerns developmental readiness, while ripeness is the condition associated with desirable eating attributes. A fruit harvested too immature may not develop expected flavour even if colour changes later.
Create observation sets containing colour, firmness, soluble solids, acidity, aroma and mass loss. Interpret disagreements between them instead of compressing them into one freshness score. For mechanisms, write four-step chains: treatment or signal, cellular or biochemical response, measurable quality attribute and management consequence. Apply this to warming, low oxygen, bruising and ethylene.
For each chain, name one confounder such as cultivar, initial maturity, sample position or storage duration. End with a commodity comparison grid and a short recommendation for harvest timing and storage. Your conclusion should specify the commodity, maturity state, exposure conditions and evidence to monitor, because a generic instruction to keep produce fresh does not reveal which physiological process is being controlled.
