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Postharvest > Post-harvest behaviour of different crop categories > Flashcards

Post-harvest behaviour of different crop categories Flashcards

1
Q

Please give a categorization of crops by region?

A
  1. Fruits from temperate zone:
    pome fruits (pip fruits), stone fruits (drupes), small fruits, berries
  2. Subtropical fruits:
    citrus fruit, avocado, persimmon, pomegranate
  3. Tropical:
    banana, mango, papaya, pineapple others: passion fruit, lychee, rambutan,…
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2
Q

Please give a categorization crops by their ripening behaviour?

A

1. CLIMACTERIC FRUITS (apple, pear, apricot, peach, plum, kiwi, avocado..)

  • mature (fully developed) fruits ripen also after beeing separated by the originating plant
  • Ethylene production during ripening
  • Influence of ethylene on ripening process

2. NON-CLIMACTERIC FRUITS (berries, grape, cherry, citrus, pineapple, lychee, pomegranate)

  • the ripening is not continued after separation from the originating plant
  • Very low ethylene production
  • Ripening processes not influenced by ethylene

The optimal ripening stage for maintaining quality after harvest == compromise between: highest possible quality and best storage potential

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3
Q

What are negative quality effects influenced by ethylen?

A
  1. Decay: fresh produce and flower bulbs
  2. Russet spotting: leafy vegetables and eggplants Yellowing: cucumbers, broccoli and brussel sprouts Odor: garlic and onions
  3. Wilting: vegetables and cut flowers
  4. Scald and loss of crunch apples
  5. Rind breakdown: citrus
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4
Q

Whats is the categorization of crops according to their potential post-harvest life-span?

A
  1. Lowest temperature tolerated
  2. Longest life-span at ideal temperature
  3. Metabolic activity and fruit development duration
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5
Q

What are post harvest factors for quality degradadtion?

A
  1. Metabolic stress (Senescence, Physiological disorders)
  2. Transpiration (Water loss, weight loss, profit loss, quality loss)
  3. Mechanical injuries (Wounds)
  4. Microorganisms (facilitated by senescence, physiological disorders, wounds, hygen)
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6
Q

What are the HACCP Principles?

A
  1. Hazard assessment (all steps reg. biol., chem., physical. hazards)
  2. Defining Critical Control Points (where lack of control results in unacceptable risk)
  3. Compilation of Specifications (critical values and tolerances)
  4. Development of Procedures for monitoring & testing
  5. Creation of Amendment procedures
  6. Documentation: functionality of HACCP,
  7. Verification: operationality HACCP reg. whole process
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7
Q

What should the HACCP outcomes be?

A
  1. Surveillance of hazards and health risks
  2. Improvement of processes
  3. Control on product outage
  4. Waste reduction
  5. Cost reduction
  6. Consumer trust
  7. HACCP demand to supplier
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8
Q

How can we define quality?

A

Quality = Fulfillment of Expectations

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9
Q

What are the main post harvest quality criteria for consumer?

A
  1. Appearance- size, color, shape
  2. Freshness & perfection- Ripeness, Mechanical injuries
  3. Texture (The mouthfeel)- Firmness, Crunchiness, Juiciness, Mealiness
  4. Flavour- Taste+Aroma
  5. Nutritional value- Not instantly recognizable
  6. Safety/hygiene- Pesticide residues, Microbial contaminations
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10
Q

What are the two main post harvest losses?

A
  1. Quantitative losses (shrivelling, rots, mechanical injuries, physiological disorders)
  2. Qualitative losses (loss of taste, aroma, acidity, sweetness, color change, texture changes, nutritional value)
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11
Q

What are the main quality management systems?

A

1. Quality Assurance (QA)

  • intentional Planning of all quality- and safety-related activities
  • continuous Monitoring and Evaluating of all product related procedures and processes

2. Quality Control (QC)

  • Definition of Quality and Safety
  • by assessing: well defined criteria or specifications
  • Integration of preventive measures is encouraged
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12
Q

What are the HACCP critical points in post harvest?

A

1. pH/organic acids

  • C. botulinum > pH 4.5 or > 3 °C
  • Yeasts, fungi < pH 4.5

2. Respiration vs. storeability

  • Apple @25°C 5xhigher as @ 5°C
  • Bruising increases respiration
  • *3. Harvest moment
    4. Post-harvest handling**
  • Bruising, wounds, cold chain, storage conditions

5. Hygiene and sanitation

  • staff, equipment, rooms, container
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13
Q

What are the factors that contribute to post harvest physiological disorders?

A
  1. Developmental stage (under developed)
  2. Agronomical conditions (crop density)
  3. Nutritional supply
  4. Meteorological conditions
  5. Pedoclimatic conditions (soil, site)
  6. Storage conditions
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14
Q

What are common post harvest disorders and how are they expressed?

A
  1. Un-ripe: common scald
  2. Advanced ripeness: internal flesh browning, Jonathan-Spot
  3. Over-ripe: senescent scald, break down
  4. Too low temperature: flesh browning, soft scald, chilling injury
  5. CA (extreme O2/CO2): skin-, flesh-discoloration, tissue deformation, flavour change
  6. Developmental disorders: bitter pit, water core
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15
Q

How can the superficial sclad be prevented in post-harvest?

A

1. Lowest possible O2-level

  • Purging, hypobaric storage
  • DCA: dynamically controlled atmosphere)

2. Antioxidants treatment

  • Diphenylamine
  • Ethoxyquine

3. Alpha-farnesene elimination

  • accumulation in ‘oil’ films

4. Ethylene-inhibition

  • 1-methylcyclopropene (1-MCP)
  • CO -shock
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16
Q

What are the causes for bitter pit?

A
  1. Lower calyx: lowest Ca supply
  2. K/Ca (N/Ca) ratio too high
  3. Ca-deficiency -> cell walls
  4. Water core sometimes before necroses
  5. Involvement of carbohydrate metabolism
  6. Browning phenoloxidases
17
Q

How can bitter pit be prevented?

A

1. Forecasting-Methods

  • Fruit mineral analyses (K/Ca ratio > 25)
  • 2-Chlorethanphosphonsäure -> Ethylen → symptoms
  • Mg-infiltration → symptoms

2. Prevention

  • Pre-harvest: good supply with nutrients, irrigation
  • Pre-harvest: additional Ca foliar nutrition
  • Post-harvest: Ca dipping
18
Q

What is bitter pit?

A
  1. Dark-green to brown, bitter spots in the fruit flesh
  2. necroses (3-10 mm)
  3. deep corky pits
  4. Mainly around the calyx
19
Q

What is internal flesh browning?

A
  1. All disorders regarding the inner fruit tissues
  2. By: low temperatures
  3. By: anaerobic processes -> toxic compounds
  4. Browning ist the result of cell damage

Influencing factors:

  1. Over-ripeness: high metabolic activity, senescence
  2. Oversize: weak cell cohesion/structure, little cations
  3. High rainfall
  4. high N, little Ca
  5. low crop load
20
Q

What are the most important storage factors?

A
  1. Temperature
  2. Air recirculation
  3. Air humidity
  4. Air composition (CA)
21
Q

What are the main functions of the storage factor temperature?

A
  1. Temperature influences mainly: speed and intensity of metabolism
  2. Cooling= Heat removal
  3. Aim: Max. ripening inhibition WITHOUT physiological disorders
  4. Rapid cooling (e.g. pears) Stepwise cooling
22
Q

What are the main functions of the storage factor air recirculation?

A
  1. Uniform distribution of: Temperature, Humidity and other atmosphere components (organ. compounds)
  2. Heat distributive processes: Convection, Radiation, Ventilation
  3. Avoid water loss
  4. Avoid air stratification
  5. Parameters: Air recirculation number and Air velocity
23
Q

What are the main functions of the storage factor air humidity?

A
  1. Prevent weight loss through water evaporation (ca. 5percent due to respiration and ca. 95 due to transpiration)
  2. No transpiration at RH>98 percent- equilibrium between turgor of the fruit and partial preassure gradient of the air
  3. Transpiration influenced by: Specific permeability of the fruit, Developing stage, Maturity stage, Storage conditions
  4. Problem: Too high RH= Accumulation of phytotoxic metabolites (ethanol) and risk of pyhsiological disorders (internal browning or sclad)
  5. Ideal RH between 92-98% = min. weight loss and no free water on fruits
24
Q

What are potential ways to passively control transpiration?

A
  • COATINGS with: mineral oil, wax, polymers

But: uncontrollable interactions with respiration and Additional costs

  • Advantage: senescence delay
25
Q

What are the main functions of the storage factor controlled atmosphare (CA)?

A
  1. Delay of ripening processes by partial inhibition respiratory activity
  2. By modification of atmoshpere composition: Decrease of O2>
  3. CA conditions reduce: Organic Acid conversion, Mitochondria activity (respiration) and Ethylene turnover
26
Q

What are the effects of a controlled atmosphere on fruit?

A

CA delays:

  1. Chlorophyll-degradation
  2. Pectin degradation
  3. Org. acid degradation
  4. Starch, sugar, protein degradation
  5. Activation of climacteric metabolism
  6. Ethylene, VOCs (aroma)
27
Q

What are potential problems related to CA storage and how can they be prevented?

A

Induced fruit damage:

  1. Phytotoxicity
  2. skin injuries
  3. cavities formation (Pyruvat)
  4. internal tissue browning

Prevention:

  1. automated gas control
  2. additional gas checking/calibrating
  3. fruit checking
  4. additional analytics, alarm sensors
  5. post-storage
28
Q

What is dynmaic CA?

A
  1. The atmospheric composition is not static anymore , i.e. set at specific, ‘optimal’, constant gas levels
  2. But dynamically modified according to the plant product´s physiological stage and current its requiremnts
  3. CA levels respond to actual fruit needs
29
Q

What do the right DCA conditions depend upon?

A
  1. Cultivar
  2. Maturity
  3. Seasonal quality variation
  4. Location influence
  5. Ripening during storage
30
Q

Why does DCA focus on achieving LOL (lowest O2 level)?

A
  1. Slows down the aerobic respiratory metabolism
  2. Inhibits oxidative processes
  3. Reduceds respiratory driven catabolism
  4. Reduces ethylene related ripening processes
  5. Reduces physiological disorders
31
Q

Explain the LOL value and draw the graph?

A
  1. The LOL represents the O2 level where respiration changes: from predominantely aerobic to fermentative
  2. The Fermentation Threshold (FT): The O2 level at which fermentation is induced
  3. The Anaerobic Compensation Point (ACP): The O2 concentration at which the CO2 evolution is minimum
  4. The Respiratory Quotient Breaking Point (RQB): the increase of RQ in response to lowering the O2
  5. The respiratory quotient RQ is the ratio of CO2 respired over O2 consumed.
32
Q

How are the O2 levels dinamically controlled?

A
  1. A Chlorophyll Fluorescence (CF) sensor responds to low O2 levels with fluorescence spike signals
  2. Large surface measurement on the fruit skin
  3. Non-destructive
  4. Always on same sample
  5. Real-time monitoring
  6. Frequent, rapid and robust measurements
  7. Not averaging the response from whole room/fruit content, instead giving a sample specific signal
33
Q

What are the ways of action of 1-MCP (1-Methylcyclopropen)

A
  1. Influences the ripening hormon ethylene by binding at the ethylene receptors of the cell membrane
  2. Inhibits the signalling by exogenous ethylene
  3. Inhibits the production of endogenous ethylene
34
Q

What´s the difference between desease and disorder?

A
35
Q

What different types of controlled atmosphere?

A
36
Q

How can we reduce the effects of Ethylen?

A
  1. 1-MCP
  2. Scrubbers
  3. Temperature

Postharvest (2 decks)

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