Post harvest Technology

Definition of the post harvest technology is preservation, conservation, quality control, processing, packaging, storage, distribution,marketing and utilization to meet the food and nutritional requirements consumers.

Durable crops VS Perishable crops

Durable crops	Perishable crops
Low moisture content	High moisture content
low rate respiration	high respiration rate
small unit size	large unit size
small rate of heat generation	high rate of heat generation.
Hard texture	Soft texture
stable with the natural shelf-life several years	few days
losses mainly by external agents (molds, insects)	losses mainly by bacteria and fungi.

Importance of minimizing post harvest losses

1. Nutritional advantage
2. Economical advantage – waste of food give economic loss.
3. Cost effective – food amount can be increased without using extra land, energy, water.
4. Environmental friendly – reduce the environmental pollution.
5. Consumer satisfaction

Different causes of postharvest food losses

Primary causes

• Biological and microbiological by insects, pests, animals and microorganisms
• chemical and biochemical browning, rancidity, enzymatic changes,
• Mechanical – abrasion, bruising, crushing,
• physical – temperature, relative humidity, air speed,
• physiological – senescence, other respiratory and transpiratory
• psychological – personal or religious reasons.

Secondary causes

• improper harvesting and handling
• inadequate storage facilities, inadequate transportation
• inadequate refrigeration
• Improper environmental and storage conditions

Biological factors

• Respiration
• Ethylene production
• Compositional changes
• Growth and development
• Transpiration
• Physiological breakdown: Chilling injuries

Environmental factors

• Temperature
• Relative humidity
• Atmospheric composition
• Light

Socio economic factors

• Inadequate marketing system
• Inadequate transport facilities
• Government regulations and legislations
• Unavailability of needed tools and equipment
• Lack of information
• Poor maintenance.

How temperature effecting the post harvest losses.

Temperature is the single most important factor in maintaining quality after
harvest. (Prusky, 2011)

Low temperature prevent

• aging due to ripening, softening, and textural and color changes undesirable metabolic changes and respiratory heat production
• moisture loss and the wilting that results spoilage due to invasion by bacteria, fungi, and yeasts
  undesirable growth, such as sprouting of potatoes

Chilling injuries

This happen when the crop is exposed to the temperature below their normal storage condition. the Both time and temperature are involved. same crop are chilling sensitive the just above the freezing point. smoe crop are chilling sensitive the stored at 10⁰C -12⁰C.

Symptoms of the chilling injuries

• Browning
• Necrosis
• rots
• water soaking

Characters of the correct maturity

• Time – recorded from the flowering to harvesting
• Physical properties – size, shape, weight, colour,
• Chemical properties – sugar : acid ratio, starch content, oil content

Important of the identification of the correct maturity

• Ensure the sensory quality(flavor, colour, aroma) nutrient quality
• Ensure the adequate post harvesting shelf life.
• Facilities scheduling time for harvesting, marketing, packaging
• Improve the productivity

Curing

Principle is development of the corky tissue. crops are store for a long period, it should be immediately started after the harvesting. Bulb crops, tuber crops, root crops are mainly used. fresh friut and vegetables are can not be curing.

Type of curing – Field, shed, controlled indoor systems.

Advantages of curing – increased the storage life, low rate of water loss, improved the quality of the foods( appearance, healed wounded)

Sorting – Contamination, sensing, insect damage, broken skin foods are removed from the harvest grade the harvest according to their quality level.

Cleaning – washing, brushing, sanitation, to remove the debris, contamination, chemicals.

Sanitizers should be approved for use for the crops, should be standard concentrations.

Use HOCL ,hydrogen peroxides as sanitizations agents

Post harvest treatments.

Physical treatments

• Heat treatments
• Edible coating
• Irradiation

Chemical treatments

• Antimicrobial and browning agents
• Nitric oxide
• Sulphur dioxide

Gaseous treatments

• Ozone
• Ethylene
• Control atmosphere
• Modified atmosphere

Physical method – Heat treatments

Hot water dip, saturated water vapour heat, hot dry air

Benefits of heat treatments

• Reduction in chilling injury
• Delay of ripening processes by heat inactivation enzymes
• Killing of critical insect contaminations
• Controlling the onset of fungal decay

Bananas have been dip treated in water at 50°C for 20 min, Fruits and vegetables should not be handled
Cool water showers or forced cold air produce to return their optimum temperature the treatment. hot water treatments are very effective against the Penicillium, Rhizopus, Botrytis

Applications

• Preserve the colour of asparagus, green beans, kiwi, celery
• increases the longevity of fruits plums, grapes
• To firm potatoes, tomatoes, carrots and strawberries

Limitation

• Some fruits are not sensitive to high temperature (leman,oranges,pears)
• High energy cost and added labour

Physical method – Edible coating

A thin layers of external coatings is applied to the surface of fresh produce. edible coat including aloe vera, polyvinyl acetate, mineral oils

Benefits of the edible coating

• Minimize moisture loss during postharvest storage
• Provide the gas barrier, slows down respiration, enzymatic oxidation.
• Maintain the fruit structure and integrity, amd protect against the mechanical damages.

• Typical shelf life is 2 – 4 weeks at 2 to 4°C
• Waxing can increase shelf life to 1 to 2 months

Applications

• Waxing of immature fruit and vegetables such as cucumbers
• mature fruit vegetables such as eggplant,
• fruits such as apples and peaches

Limitation

• High cost
• lack of edible coat producing material

Physical method – Irradiation

Irradiation can neutralize pest and food safety problems by inhibiting the cellular reproduction.

• Low doses of irradiation (less than 1 kGy) – disrupt the cellular activity and inhibit the sprouting, delay senescence.
• Medium doses (1–10 kGy) – reduce microbial loads
• High doses (more than 10 kGy) – kill a broad spectrum of fungi and bacteria spp. and pests (Mahajan et al., 2014)

Chemical treatments – Nitric oxide

Nitric oxide (NO) is a highly reactive free radical gas, act as a multifunctional signalling molecules in many physiological process such as fruit ripening and senescence. Endogenous NO concentration deceased with maturation and the senescence.

Benefits

• Delay the climacteric phase of the many tropical fruits, reduce ethylene production, reduce ethylene production, delay fruit ripening.

Application

• NO fumigation in combination with cold storage. (apple, banana, kiwifruit,mango)

Limitation

• Depends upon the development of a smart carrier/ controlled release system for NO

Chemical treatments – Sulphur dioxide

Sulphur dioxide is mainly used as prevent decay during the storage. It is used as a fumigant or water spray. Rhizopus, Botrytis, Aspergillus

Limitations

• The SO₂ concentration necessary to inhibit fungal growth may induce injuries in grape fruits and stems
• Sulfite residues cause health risk for some individuals
• Firming of the texture of some fruit species (pomaces)
• Incomplete de-sulphiting and incomplete re-colouring of red fruits.

Gaseous treatments – Controlled Atmosphere storage (CAS)

CAS is referred as monitoring and adjusting the CO₂ and O₂ in the stores at the optimum storage temperature.

Benefits

• Delay senescence (reduction of the ethylene action at less oxygen and high carbon dioxide)
• Reduction in chilling injury of avocado
• Insect control
• CO₂ at 10–15% inhibits development Botrytis rots

Limitation

• Irregular ripening of fruits, such as banana, mango due to exposure to O₂ level below 2% and CO₂ higher than 5% more than one month
• foul odours at very low O₂ concentrations due to anaerobic respiration
• Increased susceptibility to decay when insufficient O₂ or too-high CO₂ concentrations
• High capital investments.

Gaseous treatments – Modified atmosphere packaging (MAP)

Any deviation of the regular atmosphere is know as modified atmosphere. Products are packaging in the plastic film bags.

Passive MAP

• Involves the use of packaging materials that have different levels of gas permeability to create a modified atmosphere around the product. The packaging material selectively allows the passage of oxygen, carbon dioxide, and water vapor through its pores, creating an environment that reduce the respiration rate and microbial growth of the product. It does not involve active control of the atmosphere.

Active MAP

• Active control of the atmosphere surrounding the product. The gas composition is modified using gas flushing systems or vacuum packaging. Automated systems to monitor and maintain the desired gas concentrations.

Cooling of Fruits and Vegetables

Cooling and Pre cooling

Pre-cooling is the rapid removal field heat from the freshly harvested crops before they are transported or stored. pre cooling and cooling both delay respiration, transpiration, enzymatic activity

Temperate produce should be preferably pre-cooled to 0–2°C
Tropical and subtropical should be cooled to 10–15°C.

Cooling and Pre cooling methods.

• room cooling
• forced air cooling
• hydro cooling
• vacuum cooling

• top icing, package icing
• liquid nitrogen cooling
• dry-ice cooling

Room cooling

A simple room cooler consists of an insulated room with refrigeration system and fans for air circulation. Relative humidity should be at 90%-95%, best for non perishable fruit and durable fruits

Forced-Air Cooling

Specifically designed to promote faster cooling times. Forced circulation air flow through the containers rather than around them, Important to have properly designed ventilation ports in the container that allow.

Hydrocooling

Hydro-cooling makes use of water as the cooling medium. Produce itself is either immersed in a tank or showered with a spray of cold water, Both the produce and containers must be water tolerant. Water is treated with chlorine for sanitation purposes. The product must be tolerant for low level of chlorine.

Contact Icing

Product filled containers using various forms of ice. slurry ice (liquid ice), Liquid ice is injected in the container and has better contact with the produce than the other forms.

Transport of packages

Main object: Deliver perishable products thousands of miles away without loss of fresh and quality. product mesu be kept as cool as possible, kept dry

• An open air vehicle can be loaded in such a way that air can pass through the load, and provide some cooling of the produce as the vehicle moves

• Travelling during cooler hours (night and early morning) can reduce the heat load
• Refrigerated transport is highly recommended for most perishable horticultural produce
• Loads must be stacked to enable proper air circulation to carry away heat from the produce
• Adequate levels of ventilation of contents with minimum wasted space
• Packages should be strong enough to protect contents

Causes of loss

• Mechanical damage – produce during loading and unloading, Vibration (shaking) of the vehicle, Packages stacked too high
• Overheating – not only external agent heat also generated from the package itself. Natural breakdown and decay, and increases the rate of water loss. Causes of overheating use close vehicles without ventilation. inadequate ventilation of the packages, expose to sunlight during transportation.
• Packages should not be stacked higher than the maximum recommended by the maker,otherwise bottom layers may collapse under the weight of those

Packaging Technology of fruits and vegetables

Main purpose of packaging

• prevent microbial and chemical contaminations
• Reduce vibration and mechanical damages
• Reduce exposure to oxygen, water, vapour and light.

Common methods of packaging

Field packaging – Products are placed in fibreboard boxes or wooden crates after harvesting in the field.

Shed packaging – Process of sorting and packing harvested crops before they are taken to the market or storage.

Common types of packaging practiced on commercial and experimental scales

• Volume fill – produce is placed by hand or machine into the packaging container until it reaches the desired capacity, weight, or count. This is commonly used for vegetables, fruits, and cut flowers
• Place pack – Produce is wrapped and placed in the container in a way that maximizes the net weight, amount of pack
• Consumer pack or prepack – Small amounts of fruits or vegetables are packed, weighed
• Modified atmosphere packaging

Importance of quality of the packaging materials

• Biodegradability
• variety
• sales application – high quality graphics, multi colour printing, distinctive lettering and logos boots sales appeal

References

• Elansari, A. M., Fenton, D. L., & Callahan, C. W. (2019). Precooling. Postharvest Technology of Perishable Horticultural Commodities, 161–207. https://doi.org/10.1016/b978-0-12-813276-0.00006-7
• Cooling methods | Cooling and storage | Postharvest fundamentals | Postharvest Management of Vegetables. (n.d.). Cooling Methods | Cooling and Storage | Postharvest Fundamentals | Postharvest Management of Vegetables. https://www.postharvest.net.au/postharvest-fundamentals/cooling-and-storage/cooling-methods/
• https://www.fao.org/3/ae075e/ae075e13.htm. (n.d.). https://www.fao.org/3/ae075e/ae075e13.htm
• Hydro Cooling – Cold Logic. (n.d.). Cold Logic. https://coldlogic.com.au/hydro-cooling/
• Prusky, D. (2011, November 15). Reduction of the incidence of postharvest quality losses, and future prospects. Food Security, 3(4), 463–474. https://doi.org/10.1007/s12571-011-0147-y
• Mahajan, P. V., Caleb, O. J., Singh, Z., Watkins, C. B., & Geyer, M. (2014, June 13). Postharvest treatments of fresh produce. Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, 372(2017), 20130309. https://doi.org/10.1098/rsta.2013.0309
• Mahajan, P. V., Caleb, O. J., Singh, Z., Watkins, C. B., & Geyer, M. (2014, June 13). Postharvest treatments of fresh produce. Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, 372(2017), 20130309. https://doi.org/10.1098/rsta.2013.0309