exam for processing

• Water comprises 76-95% of the total chemical component of perishable crops.
• Carbohydrates in perishable crops are the main sources of energy.
• Lipids in perishable crops are water-insoluble organic molecules that can be extracted from cells and tissues.
• Physiological Disorders:

  • Temperature-induced disorders include chilling injury in mango and pineapple, manifested as brown irregular specks or spots and browning at the inner tissue near the core respectively
  • Anoxia-induced disorder like internal breakdown of mango results in high respiration rate, low ethylene production, altered enzyme activity, and damaged membrane leading to abnormal softening and incomplete hydrolysis of starch
• Physiological disorder due to physical injury:

  • Oleocellosis of citrus results in discoloration of the rind due to the release of oil cells in the hypodermis
  • Sleepiness of carnation results in the rolling of petals
  • Russeting of lettuce leads to reddish discoloration of the rib
  • Bent neck of roses is a physiological disorder resulting in the bending of the stem immediately below the flower
• Moisture loss-induced physiological disorder:

  • Vascular streaking of cassava involves the formation of a ring of blue-black or brownish tissue along the vascular bundle
  • Finger drop where fingers prematurely separate from the pedicel due to several physiological changes
• Bases of Postharvest Technologies:

  • Physical Characteristics:
  • Size: weight or dimension of a commodity measured using weighing scales, measuring aids, or machine vision equipped with cameras
  • Shape: general outline or profile of a commodity determined by chartered standards, comparison with geometric shapes, or shape descriptors
  • Volume: space occupied by a commodity determined by water displacement method, weighing in air and water, or correlation with major dimensions
  • Density and Specific Gravity: weight of a commodity divided by its volume, determined by water displacement or weighing in air and water
  • Surface Area: area occupied by the peel, leaf, or floral parts when laid out on a flat surface, determined by planimetric method or correlation with major dimensions
• Transmittance:

  • It is the fraction of radiation that is not reflected and goes through an object's surface, determined by manual devices, spectroscopy, and image processing
  • Applications include detection of injuries, prediction of constituent levels
• Specific heat is the heat-absorbing capacity of a material at a constant pressure, defined as the quantity of energy required to raise the temperature of a unit mass by 1 K
• Acoustic response deals with the transmission of mechanical waves through mediums like fruit or vegetables, affecting characteristics as the wave encounters tissue boundaries
• Ultrasonic transmission involves sound waves above human hearing range, useful for non-destructive evaluation of internal quality in samples like detecting internal discontinuities
• Methods of determining ultrasonic transmission:

  • Ultrasonic emitter: produces pulses that travel through a sample, altered by internal conditions and analyzed by computer
  • Application: non-destructive evaluation of internal quality, detecting internal defects like hollow heart in potatoes
• Reaction to electromagnetic radiation includes X-ray and radio frequency methods for non-destructive quality evaluation of produce, with applications in detecting insect pests and physiological studies
• Electrical conductivity (EC) measures a material's ability to conduct electric current, influenced by factors like moisture content and ion concentration, often used as an indicator of overall quality and freshness of fruits and vegetables
• Dielectric properties describe how a material responds to an applied electric field, influenced by factors like water content and composition, used in non-destructive evaluation of fruit quality to assess attributes like moisture content and firmness
• Impedance measures a material's opposition to the flow of alternating current, useful for evaluating internal structure and physiological characteristics of fruits and vegetables
• Capacitance is a material's ability to store electrical charge, influenced by factors like distance between electrodes and dielectric constant, providing information about produce composition and structure for quality assessment
• cellulose imparting strength and form.
• Phenolics -compound with either one or many OH groups.
• Tannin –make unripe fruit to have chalky biting taste.
•   Lignin-high molecular weight phenolic.
• Suberin formed during the self-healing of wounded tissues of harvested root crops.
• Organic acid -intermediate compounds produced during metabolism of carbohydrates.
• It consist of citric acid, malic acid, tartaric acid, oxalic acid, and ascorbic acid.
• • common acid present in fresh produce
• Common acids present in fresh produce

  
  

  1.Citric acid- predominant in citrus fruit and tomato

  2.Malic acid- abundant in banana and mango; predominant acid in eggplant, melon, carrot, lettuce, celery, and onion

  3.Tartaric acid- tamarind and grapes

  4.Oxalic acid- carambola (balimbing), amaranth (kulitis), bilimbi (camias), storage roots, stem and leaves of taro(gabi) and chayote

  5.Ascorbic acid or Vitamin C-present in almost all fruits and vegetables. It easily responds to environmental changes.
• Lipids -water-insoluble organic molecules that can be extracted from cells and tissue
• Waxes -complex mixture of  long-chain hydrocarbons, alcohol, ketones, fatty acids.
• Enzymes important in fresh produce:

  • Cellulase: breaks down and degrades cellulose in biological materials
  • Polygalactunonase and pectin methylesterase: responsible for breaking down pectin
  • Amylase: breaks up starch molecules
  • Lipoxygenase: in the presence of oxygen, breaks down the lipid component of cell membranes, forming oxygenated lipids
  • Polyphenol oxydase: responsible for enzyme-mediated browning reaction in the presence of phenolics and oxygen
  • 1-aminocyclopropane-1-carboxylic (ACC) acid synthase and AC oxidase: control the production of ethylene inside tissues
  • Chlorophyllase: responsible for the breakdown of chlorophyll
• pigments - confer color to commodities.
• chlorophyll - Green, blue green, yellow green in most commodities.
• Carotene - Orange of carrots, yellow oranges of squash, yellow of pineapple, mango.
• Lycopene - Red in tomatoes and watermelon.
• The faster the respiration is, the shorter the postharvest life.
• Classification of produce according to respiration patterns:

  Climacteric  – commodity exhibits an increase or burst in respiration rate at a certain period during ripening.

  Non-climacteric – commodity shows a continuously declining rate of respiration from maturation to the end of senescence.
• Conditions that slow down respiration •Low temperature – the single most important factor in controlling the rate of respiration

  •Low O2 and high CO2 – example: controlled atmosphere technologies
• Transpiration - is the water evaporation process from plant organs.
• Conditions causing high rates of transpiration Low relative humidity (RH) – the lower the RH of the air, the faster the rate of transpiration

  High temperature – the higher the temperature, the higher the moisture loss

  High wind velocity during transport – wind removes the moisture on the surface of drawing more moisture from the cells
• Ethylene – colorless and odorless gaseous compound.
• Classification of produce according to ethylene production and commodity response

  1.Stage of maturity – immature commodities produce higher amounts of ethylene

  2.Physiological state- ripening commodities produce more ethylene than unripe ones.

  3.Environmental conditions- high temperature and the presence of

  4.Stress and mechanical damage- any stress can increase ethylene production of ethylene